Prof. Anna Vašků1
Přednášky
Zubní lékařství
Embryolog
Patofyziologie II- jaro 2023
Patofyziologie sepse, septický šok
ZLE – jaro 2023
Prof. Anna Vašků2
History
̶ Over the past 30 years, attempts to treat the “cytokine storm” of sepsis have universally failed to
improve outcomes. In addition, no single biological response modifier has been approved by the FDA
for treating sepsis. However, the “Surviving Sepsis Campaign” initiated in 2002 promotes earlier
recognition of sepsis and implementation of best practices that, as now recognized, results in lower inhospital
mortality for patients with sepsis . Unfortunately, similar to trauma, improved early survival has
led to a new patient phenotype described as chronic critical illness (CCI). The definition of CCI includes
ICU length of stay (LOS) greater than or equal to 14 days with evidence of persistent organ dysfunction.
According to this definition, approximately 40% of sepsis patients progress to CCI .
Prof. Anna Vašků3
Prof. Anna Vašků4
Sepsis
̶ is a severe illness caused by an aberrant host response to infections, and it is
associated with acute organ failure and a high mortality risk. Although there has
been a global improvement in clinical outcomes as a result of improved
treatment practices resulting from the dissemination and implementation of the
Surviving Sepsis Campaign guidelines over the preceding decades, mortality
rates remain unacceptably high, ranging from 25 to 30 percent for sepsis and 40
to 50 percent in cases of septic shock, with country-specific variations.
Moreover, many sepsis survivors have long-term physical and cognitive
impairments as well as higher death rates than the general population.
Zhang T, Yu-Jing L, Ma T. Role of regulation of PD-1 and PD-L1 expression in sepsis. Front Immunol. 2023 Mar 9;14:1029438
Sepsis
̶ is characterized by dysregulation and overactivation of host-protective innate
immunity
̶ Host immune responses to pathogens depend on the magnitude of the physiologic
insult. Highly virulent pathogens and host immune impairment may potentiate the
host’s vulnerability to sepsis.
̶ Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated
host response to an infection. An overactivated or a dysregulated innate immune
response to infection can result in tissue damage, cellular compromise, and
molecular dysregulation that lead to organ dysfunction and failure.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků5
Prof. Anna Vašků6
Sepsis
̶ is a severe illness caused by an aberrant host response to infections, and it is
associated with acute organ failure and a high mortality risk. Although there has
been a global improvement in clinical outcomes as a result of improved
treatment practices resulting from the dissemination and implementation of the
Surviving Sepsis Campaign guidelines over the preceding decades, mortality
rates remain unacceptably high, ranging from 25 to 30 percent for sepsis and 40
to 50 percent in cases of septic shock, with country-specific variations.
Moreover, many sepsis survivors have long-term physical and cognitive
impairments as well as higher death rates than the general population.
Zhang T, Yu-Jing L, Ma T. Role of regulation of PD-1 and PD-L1 expression in sepsis. Front Immunol. 2023 Mar 9;14:1029438
„THE SYSTEMIC inflammatory response syndrome“
(SIRS)
• Klinická manifestace nespecifického zánětu,
významná příčina morbidity a mortality a
vedoucí příčina smrti na jednotkách intenzivní
péče.
• SIRS může být iniciován mnoha příčinami,
včetně infekce, závažnost kolísat až k život
ohrožujícímu stavu.
Prof. Anna Vašků7
Závažné poškození nebo infekce
• Závažné poškození nebo infekce začínají tím, že jsou rozpoznány
alarminy, které se primárně skládají z mikrobiálních produktů a
poškozené tkáně.
• Vrozený imunitní systém na základě vrozených rekogničních receptorů
(PRRs – „pattern recognition receptors“) rozpoznává cizí antigeny a
poškozené buňky. PRRs jsou exprimovány na mnoha buněčných liniích
(myeloidní, endoteliální a epiteliální).
• PRRs detekují konzervované mikrobiální komponenty zvané
„pathogen-associated molecular patterns (PAMPs)“, stejně jako
hostitelské molekuly derivované z poškozených buněk, známě jako
„damage-associated molecular patterns (DAMPs)“.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků8
PRRs
•PRRs zahrnují Toll-like receptory (TLRs), C-type lectin
receptory (CLRs), nucleotide-binding oligomerization
domain (NOD)-like receptors (NLRs), retinoic-acidinducible
gene-I (RIG-I)-like receptors (RLRs) a
receptor pro získané produkty glykaces (RAGE).
•Velký počet, diverzita a redundance se uplatňují v
rámci optimalizace imunitní odpovědi.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků9
PRRs
•Na základě rozpoznání hostitelských PAMPs
nebo DAMPs PRRs iniciují komplexní soubor
signálních událostí , které indukují hostitelskou
obranyschopnou odpověď. Jedná se o
povolávání a fosforylaci intracelulárních
intermediálních látek, což vede částečně k
aktivaci genů okamžité odpovědi.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků10
PRRs
• PRRs aktivace a následná signalizace vede k nespecifickým i pro
patogen specifickým buněčným odpovědím, které mají zajistit
eliminaci stresorů nebo prevenci jejich uplatnění. Těmito stresory jsou
mikrobiální infekce nebo tkáňové poškození.
• Suprese mikrobiální replikace, invaze Mb do tkání a diseminace z místa
infekce zahrnují mnoho buněk vrozeného imunitního systému: neutrofily
(PMNs), monocyty/makrofágy (Mφ), dendritické buňky (DCs), natural
killer (NK) buňky a innate lymphoid cells (ILCs) . Tyto buňky hrají
klíčovou roli v časné zánětlivé odpovědi.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků11
Pattern-recognition receptor pathways for damage-associated molecular patterns (DAMPs) and
pathogen-associated molecular patterns (PAMPs). AGEs, advanced glycosylation end products;
HMGB, high-mobility group box; ATP, adenosine triphosphate; RNA, ribonucleic acid; DNA,
deoxyribonucleic acid; LPS, lipopolysaccharide; RAGE, receptor for advanced glycation end
products; NLR, nucleotide-binding oligomerization domain-like receptors; TLR, toll-like receptors; CLR,
C-type lectin receptors; RLR, retinoic-acid-inducible gene-I-like receptors; NF-kB, nuclear factor
kappa-light-chain-enhancer of activated B cells; IL, interleukin; TNF, tumor necrosis factor.
Prof. Anna Vašků12
Toll-like receptory (TLRs)
•Zatím u člověka známo 13 různých TLRs.
•Některé exprimovány na plasmatické mebráně
buněk (TLRs 1, 2, 4, 5, 6) jako konstantní součást
lokálního prostředí
•Jiné jsou v endosomálních kompartmentech (TLRs 3,
7, 8, 9, 11, 12, 13), kde vnímají signály nebezpečí pro
hostitele, mikrobiální proteiny a nukleové kyseliny.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků13
TLRs
• TLRs na plasmatických mebránách detekují vnější
mikrobiální komponenty a cirkulující signály poškození, jako
jsou lipopolysacharidy (LPS), fosfolipidy, zymosan, flagellin,
peptidoglycan, S100A8/9 a „endogenous high-mobility
group box (HMGB)“ nukleární proteiny z buněk
poškozených distresem.
• Cytoplasmatické TLRs detekují virové nebo mikrobiální
nukleové kyseliny a mitochondriální nukleové kyseliny
asociované se poškozením buňky.
• TLRs hrají centrální roli v iniciaci vrozené imunitní odpovědi
ve spolupráci s jinými PRRs prostřednictvím různých i
přesahujících se „pathways“.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků14
Prof. Anna Vašků15
Zánět a získaná imunita
̶ Tradičně se vrozená imunitní odpověď definovala jako rychlá a nespecifická, bez
schopnosti propisovat zkušenost do imunologické paměti. Dnes už víme, že některé
buňky vrozené imunity jsou epigeneticky reprogramovány („imprinted“) minulými
zkušenostmi. Tyto „trénované“ buňky vrozené imunity vykazují změněné prozánětlivé
odpovědi při následném kontaktu s patogenem. Tato vlastnost se klasicky
přisuzovala antigenně specifickým paměťovým T a B lymfocytům. Během opakovaně
vyvolané odpovědi paměťové B a T lymfocyty rychle odpovídají proliferací s
produkcí efektorových cytokinů a prováděním dalších efektorových funkcí. Často
přehlíženou efektorovou funkcí paměťových CD4 a CD8 T lymfocytů je podpora
prozánětlivého prostředí v místě infekce, která odráží primární zkušenost. Tato
zánětlivá odpověď podmíněná pamětí spolu se sekundárními funkcemi
efektorových T-lymfocytů má za následek lepší kontrolu a rychlejší řešení infekce i
tkáňového poškození, které je s touto infekcí spojeno.
Prof. Anna Vašků16
SIRS (Systemic Inflammatory Response Syndrome) is based on the presence of two out of four criteria: fever (> 38.0 °C) or hypothermia (< 36.0 °C), tachycardia
(> 90 beats/min), tachypnea (> 20 breaths/min), leukocytosis (> 12 × 109/L), or leucopenia (< 4 × 109/L)
CARS (compensatory anti-inflammatory response) occurs with SIRS. CARS is regarded as a delayed response to SIRS, but some authors argue that it occurs at the
same time SIRS begins. CARS is clinically expressed as hypothermia, leukopenia, and failure to clear infection
MODS (multiple organ dysfunction syndrome) is defined as the failure of two or more organ systems in the acutely ill patient
PICS (persistent inflammation-immunosuppression catabolism syndrome). PICS is proposed as a diagnosis for patients who have a prolonged stay in the ICU
(intensive care units) with manageable organ dysfunctions, with protein catabolism, poor nutritional status, poor wound healing, immunosuppression, and recurrent
infections. They also typically develop decubitus ulcers and tend to suffer from increased levels of pain, dyspnea, fatigue, and delirium.
Inflammation volume 41, pages1115–1127 (2018)
PICS
̶ We believe that individuals who experience a morbid post-ICU hospital course are developing a
new syndrome, termed the persistent inflammation, immunosuppression, and catabolism
syndrome (PICS).
̶ Emerging evidence indicates that the pathogenesis of PICS involves chronic low-grade
inflammation, suppressed host protective immunity, and loss of lean tissue.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků17
Prof. Anna Vašků18
PICS -criteria
• ICU stay ≥ 10 days
- Persistent inflammation
- C-reactive protein concentration > 150 μg/dl
- Retinol binding protein concentrations < 10 μg/dl
• Immunosuppression
- Total lymphocyte count < 800/mm3
• Catabolic state
- Serum albumin concentrations < 3.0 g/dl
- Creatinine height index < 80%
- Weight loss > 10% or BMI < 18 during the current hospitalization
Inflammation volume 41, pages1115–1127 (2018)
Severe injury or infection
̶ Severe injury or infection leading to CCI and PICS begins
with the recognition of alarmins, primarily consisting of
microbial products and damaged tissue.
̶ The innate immune system relies on germ line-encoded
pattern-recognition receptors (PRRs) to sense components
of foreign pathogens and damaged cells to mount hostprotective
responses.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků19
Severe injury or infection
̶ These PRRs are expressed on a variety of host cells, including
cells of myeloid, endothelial, and epithelial lineages. These
PRRs detect conserved microbial components called
pathogen-associated molecular patterns (PAMPs) as well as
host molecules derived from damaged cells, known as
damage-associated molecular patterns (DAMPs).
Front Immunol. 2018; 9: 595.Prof. Anna Vašků20
Pattern-recognition receptor pathways for damage-associated molecular patterns (DAMPs) and pathogenassociated
molecular patterns (PAMPs). AGEs, advanced glycosylation end products; HMGB, highmobility
group box; ATP, adenosine triphosphate; RNA, ribonucleic acid; DNA, deoxyribonucleic acid;
LPS, lipopolysaccharide; RAGE, receptor for advanced glycation end products; NLR, nucleotide-binding
oligomerization domain-like receptors; TLR, toll-like receptors; CLR, C-type lectin receptors; RLR,
retinoic-acid-inducible gene-I-like receptors; NF-kB, nuclear factor kappa-light-chain-enhancer of activated
B cells; IL, interleukin; TNF, tumor necrosis factor.
Prof. Anna Vašků21
Type of infection
̶ Most of the sepsis patients had bacterial infections.
̶ Patients with viral infection commonly, but not always, have
considerably lower serum pre-CT values. This probably is related
to the lower incidence of associated severe systemic inflammation
in viral infection.
Prof. Anna Vašků22
Neutrophil Priming and NETs in Sepsis
̶ PMNs exist in three states: resting, primed and activated. PMNs
shift from a resting state in the circulation to an activated state at
the site of infection via several priming stimuli, including cytokines,
LPS, and C5a.
̶ During sepsis, excessive priming of PMNs can cause excessive
production of ROS, which are released into the nearby
environment, resulting in tissue damage.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků23
Neutrophil Priming and NETs in Sepsis
̶ Priming of the neutrophil respiratory burst is believed to be involved in the
pathophysiology of the acute respiratory distress syndrome. In addition, NETs
can harm the host during sepsis. Although NET formation can help eradicate
a wide range of pathogens in the early phase of the infection, the generation
of excessive amounts of NETs, as well as impairment of their degradation by
extracellular DNAases within the bloodstream, can damage tissues and
endothelia . This can induce diffuse thrombosis and lead to DIC and acute
organ injury. Also, extracellular histones released by excessively
accumulated NETs are cytotoxic to endothelial and epithelial cells.
Prof. Anna Vašků24
NETosis
̶ Stimulated PMNs could release extracellular nucleic acids decorated with histones
and granular proteins capable of entrapping exogenous bacteria.
̶ Suicidal vs. vital NETosis
Prof. Anna Vašků25
Vital NETosis allows PMNs to maintain
conventional host defensive functions.
(A) Conventional neutrophil host response
incudes the recruitment cascade,
emigration, chemotaxis, phagocytosis,
and microbial killing.
(B) Vital NETosis aids in containing local
infections, such as gram-positive cellulitis,
by allowing PMNs to rapidly release NETs
and continue to chemotax and
phagocytose live bacteria. Additionally,
the live NET-releasing PMNs are able to
maintain their membrane integrity,
thereby imprisoning the captured
bacteria.
(C) Intravascular NET release optimizes the
capture of both bacteria and viruses
within the blood stream. Intravascular
NETosis may also contribute to
immunothrombosis.
Blood. 2013 Oct 17;122(16):2784-94
Prof. Anna Vašků26
Coagulation in Sepsis
̶ Although the activation of the coagulation cascade is protective in reducing the dissemination of
invading pathogens through fibrin deposition, overactivation of coagulation and subsequent
microthrombus formation may lead to disseminated intravascular coagulation (DIC) which can reduce
microcirculation and oxygen delivery to tissues . This can result in multiple organ failure. The
prevalence of DIC in severe sepsis has been reported to be as high as 47% . During sepsis-induced
activation of coagulation, the function of anticoagulant pathways such as antithrombin, activated protein
C, and TF pathway inhibitor (TFPI) can be impaired. These impairments lead to increased fibrin
formation and insufficient fibrinolysis, which results in microvascular thrombus.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků27
Platelets
Platelet activation within the sites of bacterial infection
also provides a first line of defense against pathogenic
microbial agents . Although activated platelets can have
bactericidal activity through platelet secretion, platelets
contribute more to bactericidal activity by forming
platelet-bound bacteria bundles, which boost the activity
of professional phagocytes such as PMNs and Mφs .
TLRs and the complement system seem to contribute to
coagulation and thrombosis.
Front Immunol. 2018; 9: 595.Prof. Anna Vašků28
Complement Activation in Sepsis
̶ The complement system is activated during sepsis, resulting in increased levels of C3a, C4a,
and C5a in plasma. Excessive amounts of these anaphylatoxins can lead to adverse
systemic consequences through several mechanisms, including, but not limited to,
hemodynamic instability and impaired oxygen delivery.
̶ In the complement system, C5a is the most powerful inflammatory mediator, and the C5a–
C5aR interaction can induce various biological responses. In acute sepsis, C5a plays a
central role in the production of both inflammatory and anti-ILCs. In addition, the excessive
generation of C5a results in the aggravation of the cardiovascular system as well as paralysis
of crucial neutrophil functions, such as chemotaxis, respiratory burst, and phagocytosis.
Moreover, C5a regulates the host reaction to sepsis.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků29
MDSCs in Sepsis
̶ Myeloid-derived suppressor cell expansion is thought to be primarily mediated by the Janus
kinase protein family leading to the activation of transcription 3 (STAT3). Activation is a
second step dependent primarily on NF-κB activation through the MyD88 pathway. Several
inflammatory mediators, such as IL-6, G-CSF, GM-CSF, and VEGF, are involved in the latter
pathway .
̶ Following activation, MDSCs produce multiple mediators such as ROS, inducible nitric oxide
synthase, arginase-1, TGF-β, and IL-10 that suppress T-effector and NK cell proliferation and
activation, preferentially induce Th2 polarization.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků30
Microbiom during sepsis
̶ In sepsis, several changes occur in gut physiology and immunity, including loss of gut
motility, increased bowel wall permeability, and apoptosis of intestinal epithelium due to
extrinsic factors (e.g., antibiotics, opiates, and parental and enteral nutrition) and intrinsic
factors (e.g., inflammation and increased bowel wall permeability).
̶ These changes may result in the alternation of the microbiota composition, overgrowth of
pathogenic microbes, and loss of commensal organisms .
̶ In patients with the systemic inflammatory response syndrome, there is a loss of diversity in
gut microbiota, which is associated with an increased incidence of bacteremia and an
increased mortality.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků31
Prof. Anna Vašků32
Prof. Anna Vašků33
Schematic Diagram of the Role of MAMPs in Metabolic Diseases.
Upon the overload of nutrients and their metabolites, levels of MAMPs, such as OxLDLs, FFAs, glucose, AGEs, and cholesterol crystals, are significantly increased.
These MAMPs are sensed by PRRs, leading to the initiation of metaflammation that is associated with the pathogenesis and development of various metabolic
diseases. Abbreviations: AGEs, advanced glycation end products; FFAs, free fatty acids; MAMPs, metabolism-associated molecular patterns; OxLDL, oxidized lowdensity
lipoproteins; PRR, pattern recognition receptor.
Wang X, Wang Y, Antony V, Sun H, Liang G. Metabolism-Associated Molecular Patterns (MAMPs). Trends Endocrinol
Metab. 2020 Oct;31(10):712-724
Prof. Anna Vašků34
Prof. Anna Vašků35
To the previous figure: The production and types
of MAMPs and their role in sepsis
̶ When the metabolic balance is broken, the metabolic disorders will lead to a decrease in repair
ability of the body. Meanwhile, metabolic disorders can cause extensive cell damage in the body
tissues. Cell damage leads to increased levels of endogenous danger signaling molecules (DAMPs),
including FFAs, AGEs, glucose, cholesterol crystal, and mtDNA, which are closely related to metabolic
disorders and are defined as MAMPs. MAMPs can be recognized by PRRs and activate
proinflammatory signaling pathways to promote the release of proinflammatory mediators. In
addition, pathogenic substances such as LPS can also be recognized by PRRs and further activate the
proinflammatory signaling pathway to cause the formation and deterioration of sepsis. Sepsis further
enhances catabolism and increases MAMPs’ levels in turn. With the development of SIRS, the
inflammatory process becomes uncontrollable, and the organ function and coagulation function
become abnormal. Finally, these disorders cause the formation of MODS.
̶ MAMPs, metabolism-associated molecular patterns; FFAs, free fatty acids; AGEs, advanced glycation
end products; mtDNA, mitochondrial DNA; PRRs, pattern recognition receptors; SIRS, systemic
inflammatory response syndrome; MODS, multiple organ dysfunction syndromes.
Prof. Anna Vašků36
Zhu XX, Zhang WW, Wu CH, Wang SS, Smith FG, Jin SW, Zhang PH. The Novel Role of Metabolism-Associated
Molecular Patterns in Sepsis. Front Cell Infect Microbiol. 2022 Jun 2;12:915099.
Prof. Anna Vašků37
To the previous figure: Relationship between high
glucose (HG) and sepsis
̶ Sepsis can stimulate the hypothalamus to increase the secretion and release of CRH. Meanwhile, CRH
promotes the synthesis and release of ACTH from the pituitary gland, and ACTH in turn stimulates
the adrenal cortex to secrete cortisol, which can lead to an increase in blood glucose. Sepsis can also
stimulate macrophages to secrete large amounts of IL-6, TNF-α, and other proinflammatory
mediators. These proinflammatory mediators can disrupt the signaling of the insulin transduction
pathway, and it is a major cause of insulin resistance in the host. Insulin resistance can further
exacerbate HG in turning. Glucose is recognized by TLRs in a variety of tissue cells and activates
NLRP3 inflammasomes that can cleave pro-caspase-1 into activated caspase-1 to induce
inflammation. Activated caspase-1 processes pro-IL-1β and pro-IL-18 to form mature IL-1β and IL-18,
promoting the development of inflammation in sepsis.
HG, high glucose; CRH, corticotropin-releasing hormone; ACTH, adrenocorticotropic hormone; IL,
interleukin; TNF, tumor necrosis factor; TLRs, Toll-like receptors.
Zhu XX, Zhang WW, Wu CH, Wang SS, Smith FG, Jin SW, Zhang PH. The Novel Role of MetabolismAssociated
Molecular Patterns in Sepsis. Front Cell Infect Microbiol. 2022 Jun 2;12:915099.
Sepsis
̶ Sepsis-3 defines sepsis as a “life-threatening organ dysfunction caused by a dysregulated host response to
infection” and septic shock as “subset of sepsis in which underlying circulatory and cellular/metabolic
abnormalities are profound enough to substantially increase mortality
̶ The host “resists” invading pathogen by mounting a systemic inflammatory response in innate immune
cells such as macrophages and monocytes that produce pro-inflammatory cytokines, chemokines, and
coagulation cascade within minutes. Further fuel to the fire of pro-inflammatory response is added by the
activated pro-coagulant factors such as thrombin, Factor X, tissue factor via PAR1 signaling.
̶ However, hyperinflammation cannot be sustained, as it also attacks the host tissue and organs
indiscriminately. The hyperactive immune cells transition to a deactivation/tolerance state also known as
a “hypoinflammatory” and immunosuppressive phenotype. This phase is characterized by increased antiinflammatory
cytokine expression and decreased pro-inflammatory mediators biomarked by endotoxin
tolerance.
Innate Immun. 2019 Apr 18:1753425919842320.
doi: 10.1177/1753425919842320.
Prof. Anna Vašků38
Immune response in sepsis: immune response in sepsis transitions from
hyperinflammatory to a hypoinflammatory phase followed by resolution.
Hyperinflammatory phase of immune cell activation is characterized by endotoxin
responsive state with cytokine storm is cytotoxic to immune and other organ cells.
Hypoinflammatory phase is characterized by endotoxin tolerance and
immunosuppression. Hyper- and hypoinflammatory phases are associated with profound
departure from homeostasis. Restoration of homeostasis is achieved during the
resolution phase of sepsis.
Innate Immun. 2019 Apr 18:1753425919842320. doi:
10.1177/1753425919842320.
Prof. Anna Vašků39
Prof. Anna Vašků40
Lancet. 2018 Jul 7;392(10141):75-87
Prof. Anna Vašků41
Organ dysfunction during sepsis
̶ In the intensive care unit (ICU), organ dysfunction is
scored according to the sequential organ failure
assessment (SOFA) score and Marshall Multiple Organ
Dysfunction Score (MMODS), among others.
̶ They score for dysfunction in respiratory, cardiovascular,
hepatic, hematologic, neurologic, and renal systems. As
the score increases, so does the mortality. Both the SOFA
score and MMODS are very sensitive but not specific for
organ failure.
Prof. Anna Vašků42
Operationalization of Clinical Criteria Identifying Patients With Sepsis and Septic Shock The baseline Sequential [Sepsisrelated]
Organ Failure Assessment (SOFA) score should be assumed to be zero unless the patient is known to have
preexisting (acute or chronic) organ dysfunction before the onset of infection. qSOFA indicates quick SOFA; MAP, mean
arterial pressure.
Singer M, Deutschman CS, Seymour CW et al. The Third
International Consensus Definitions for Sepsis and Septic Shock
(Sepsis-3). JAMA. 2016 Feb 23;315(8):801-10.
Septic shock - pathophysiology
̶ vasodilation
̶ increased permeability of blood vessels
̶ hypovolemia
̶ ventricular dysfunction – decreased cardiac output
Critical Care Clinics ; Volume 34, Issue 1, January 2018, Pages 43-61
Prof. Anna Vašků43
Prof. Anna Vašků44
Sepsis and cardiac dysfunction
̶ Sepsis is now defined as life-threatening organ dysfunction caused by a dysregulated host response to infection.
Septic shock occurs when circulatory, metabolic and cellular abnormalities are profound and is defined by a
requirement for vasopressor support and persistent hyperlactataemia in the absence of hypovolaemia. Septic shock
is classically a form of distributive shock, in which cardiac output is elevated or normal, hypotension results from
vasodilatation, and organ dysfunction is attributable, at least in part, to that hypotension, with a contribution from the
maldistribution of blood flow with centralization of it.
̶ Historically, cardiac systolic performance was assumed to be normal in patients with sepsis because cardiac output
was high. However, a series of landmark studies in the mid-1980s challenged this view. A radionucleotide
angiographic study demonstrated a subgroup of patients with sepsis in whom left ventricular (LV) ejection fraction
(EF) was decreased. The absence of myocardial lactate production, noted in blood sampled from the coronary sinus,
excluded myocardial ischaemia as a cause of this LV dysfunction. Although LV systolic dysfunction should have
resulted in a substantially decreased cardiac output, concurrent LV dilatation resulted in a preserved stroke volume,
provided that fluid resuscitation was adequate. Paradoxically, patients with reversible decreases in EF had better
outcomes than those without a decreased EF.
Nature Reviews Cardiology volume 18, pages424–434 (2021)
Prof. Anna Vašků45
Potential pathophysiological implications of systolic dysfunction and
downregulation of mitochondrial function in sepsis-induced cardiomyopathy.
1-methyl- 4-phenyl-1, 2, 3, 6tetrahydropyridine
= neurotoxin
Prof. Anna Vašků46
Pathophysiology of sepsis
̶ Immune activation in response to the offending organisms is
initiated when microbial pathogen-associated molecular patterns
are recognized by cellular pattern-recognition receptors
̶ Neutrophils, macrophages and T cells release pro-inflammatory
cytokines and other mediators
̶ Counter-regulatory responses can lead to a subsequent hypoinflammatory
state
̶ The precise mechanisms of cell injury and sepsis-induced organ
dysfunction are incompletely understood
̶ Vascular dysfunction is predominantly microvascular
Septic shock - pathophysiology
̶ Disequilibrium between necessities of tissues and possibilities of cardiovascular
system
̶ Loss of reactivity of smooth muscle cells of vessels (ischemia?) leading to
vasodilation
̶ SNS activation: catocholamines levels in blood are extremely high; they reflect
severity of septic state
̶ RAS system activation
̶ Deficiency of vasopressin?
̶ Critical Care Clinics ; Volume 34, Issue 1, January 2018, Pages 43-61
Prof. Anna Vašků47
Summary
̶ Sepsis is associated with alterations in immune effector cells including defects in antigen presentation,
quantitative and qualitative alternation in neutrophils, defective NK cell-mediated immunity, defective T
and B cell-mediated immunity, relative increases in regulatory T cells (Tregs), an increased expression
of PD-1/PD-L1
̶ Programmed Cell Death Protein 1 (PD-1) plays a vital role in inhibiting immune responses and
promoting self-tolerance through modulating the activity of T-cells, activating apoptosis of antigenspecific
T cells and inhibiting apoptosis of regulatory T cells.
̶ Programmed Cell Death Ligand 1 (PD-L1) is a trans-membrane protein that is considered to be a coinhibitory
factor of the immune responses, decreased immunoglobulin levels, hypercytokinemia, and
complement consumption.
Front Immunol. 2018; 9: 595.
Prof. Anna Vašků48
Prof. Anna Vašků49
Overview of the PD-1 and PD-L1
checkpoints and signaling pathways
associated with them.
The presentation of antigen by MHC on
APCs to the TCR complex on T cells
activates T cells via the Zap70 and
ERK/MAPK signaling pathways. CD28 on
T cells binds to CD80/86 on APCs to
provide co-stimulatory signals. PD-1/PDL
and CTLA-4 signaling suppress the AKT
signaling pathway to limit T cell
activation. CTLA-4 suppresses the AKT
pathway directly by recruiting PP2A,
while PD-1 signaling includes SHPmediated
regulation of Zap20 and the
PI3K/AKT signaling pathway. Green lines
indicate stimulatory messages, while red
lines represent inhibitory ones. ITSM and
ITIM are intracellular domains of
immunological checkpoints that are
responsible for intracellular signaling..
APC, antigen presenting cell; TCR, T cell receptor; MHC, major histocompatibility complex;
PD-1, programmed death-1; CTLA4, cytotoxic T lymphocyte antigen-4; ZAP70, zeta chain of
T cell receptor associated protein kinase 70; PI3K, phosphoinositide 3 kinase; PP2A,
protein phosphatase 2A; ERK, extracellular signal-regulated kinase; MAPK, mitogen
activated protein kinase; AKT, protein kinase B; ITIM, immunoreceptor tyrosine-based
inhibition motif; ITSM, immunoreceptor tyrosine-based motif; SHP, Src homology region 2
domain-containing phosphatase
Zhang T, Yu-Jing L, Ma T. Role of regulation of PD-1 and PD-L1 expression in sepsis. Front Immunol. 2023 Mar 9;14:1029438.
Prof. Anna Vašků50
Biomarkers of sepsis
̶ Procalcitonin (PCT) is a prohormone of calcitonin and in healthy individuals PCT is produced in thyroid C cells, from a calcitonin
gene-related peptide I (CALC-1) located on chromosome 11. The mRNA product is known as preprocalcitonin. It is further modified
to 116-amino acid procalcitonin, and all the PCT formed in thyroid C cells is converted to calcitonin, so no PCT is released into the
circulation and its level in healthy subjects is very low (0.05 ng mL-1). During systemic infection PCT is produced mainly by two
alternative mechanisms: the direct pathway induced by lipopolysaccharide (LPS) or other toxic metabolites from microbes and the
indirect pathway induced by various inflammatory mediators such as IL-6, tumor necrosis factor-α (TNF-α), etc. The increase of PCT
was observed in 3–4 hours after intravenous injection of endotoxin and was maintained for 24 hours in healthy volunteers. The
measurement of PCT helps to guide and shorten the antibiotic therapy in septic patients, but recent studies showed that use of PCT
did not affect the frequency of diagnostic or therapeutic procedures. Additionally, the cut-off range of PCT concentration for sepsis
confirmation depends on clinical settings, source of infection and co-morbidities.
C-reactive protein level may be increased during both infectious or non-infectious processes and in contrast to PCT, the hepatic
synthesis of CRP starts 6 to 8 hours after onset and peak concentrations are reached between 36 to 50 hours after infection has
started. The half-life of CRP is 19 hours and it is cleared by the liver.
Interleukin-6 belongs to the group of pro-inflammatory cytokines. Similarly to TNF-α and IL-1 it is an endogenous pyrogen but in
contrast to them it has a longer half-life. The synthesis of IL-6 is regulated by various factors, including endotoxin, which stimulates
its formation in monocytes and fibroblasts as well as glucocorticoids which inhibit its formation. The highest level is achieved most
often in 2-3 hours after stimulation with endotoxin. IL-6 is considered as useful in septic patients but increase of its level is not
specifically linked to infectious conditions.
Prof. Anna Vašků51
Schematic depiction of the PD-1/PD-L1
related immune cell dysfunction.
The interaction between PD-1 and PD-L1
impairs T cell function and myeloid cell
function.
Antibodies against these inhibitory molecules
restore the immune system’s function and
boost resistance to infection in patients
suffering from sepsis. The up arrow
represents an increase, whereas the down
arrow denotes a decrease.
PD-1, programmed cell death-1; PD-L1,
programmed cell death ligand-1; IFN-γ,
interferon-gamma; IL-2, interleukin-2; IL-6,
inerleukin-6.
Also non-immune cells, such as the lung, liver, kidney, colon, small intestine, and tissue endothelial cells
express PD-L1. Therefore, PD-1/PD-L1 signaling has been associated with organ damage induced by sepsis.
Zhang T, Yu-Jing L, Ma T. Role of regulation of PD-1 and PD-L1 expression in sepsis. Front Immunol. 2023 Mar 9;14:1029438.
Prof. Anna Vašků
52
Sepsis, septic shock, and sepsis-associated
encephalopathy biomarkers.
The infection triggers a cascade of
signaling pathways that activate several
transcription factors and promote
proinflammatory mediators such as acutephase
proteins, cytokines, chemokines,
and antimicrobial peptides necessary to
eliminate the invading pathogens. The
unbalanced host immune response
triggers vascular endothelial damage,
increasing gut and BBB permeability,
culminating in organ dysfunction.
Zhang T, Yu-Jing L, Ma T. Role of regulation of PD-1 and PD-L1
expression in sepsis. Front Immunol. 2023 Mar 9;14:1029438
Ang-2 (angiopoietin-2), APP (acute phase proteins), aPPT (activated partial thromboplastin), AST (astrocytes), AT (antithrombin), BBB
(blood–brain barrier), C5aR (complement component 5a receptor), CD (cluster of differentiation), CD14-ST (soluble subtype of CD14),
CRP (C reactive protein), DAMPs (damage-associated molecular patterns), GFAP (glial fibrillary acidic protein), HMGB-1 (high mobility
group box 1), ICAM-1 (intercellular adhesion molecule 1), I-FABP (intestinal fatty acid binding protein), LBP (lipopolysaccharide binding
protein), mHLA-DR (monocytic human leukocyte antigen DR), Mo (macrophage), NFL (neurofilament light), NSE (neuron specific
enolase), NT-proBNP (N-terminal pro-brain natriuretic peptide), OCLN (occludin), OLG (oligodendrocyte), PAMPs (pathogen-associated
molecular patterns), PCT (procalcitonin), PMNL (polymorphonuclear leukocytes), PT (prothrombin), PTX-3 (pentraxin-3), S100B
(calcium-binding protein B), sFlt-1 (soluble fms-like tyrosine kinase 1), suPAR (soluble form of the urokinase plasminogen activator
receptor), TNFR (tumor necrosis factor receptor type), TREM-1 (triggering receptor expressed on myeloid cells 1), VCAM-1 (vascular
cell adhesion molecule 1), ZO-1 (zonula-occluden 1)
Prof. Anna Vašků53
Key points
• Procalcitonin is a biomarker generally elevated in bacterial
infections but not viral.
• Procalcitonin guidance may aid physicians in modestly reducing
antibiotic use in critically ill patients.
• However, impact in settings with low baseline antibiotic use may be
muted, and effect on antibiotic resistance is unclear.
• As with all tests, procalcitonin will require extensive observational
and interventional studies to best determine its role.
Thank you for your attention
Prof. Anna Vašků54