Blood platelets in the development of sepsis, septic shock and multiple organ failure syndrome

Participation of blood platelets in the development of sepsis is clearly illustrated by hemocoagulation disorders and frequently observed thrombocytopenia. In the patients with sepsis, thrombocytopenia develops rapidly, with minimal platelet counts registered on the fourth day of observation, after which the platelet counts usually rise. Continuous thrombocytopenia and absence of a relative increase in platelets are considered predictors of patient death. The mechanisms of thrombocytopenia developing in sepsis are quite diverse, but the processes in periphery are prevailing, e.g., the so-called “platelet consumption” which is determined by their activation, chemotaxis and isolation in the microvasculature. Recently, a mechanism has been identified for the accelerated removal of platelets with desialized surface glycoproteins from the circulation. Sialidases, also known as neuraminidases, are widely present in viruses and bacteria, and pharmacological inhibition of sialidases is able to withstand thrombocytopenia in the infectious process. The key role of platelets in the development of septic shock was revealed. Sequestration of platelets in the microvessels of the lungs and brain (manifesting as thrombocytopenia) is accompanied by rapid serotonin release, thus underlying the main clinical manifestations, e.g., decreased blood pressure, heart rate and increased capillary permeability. To counteract sharp release of this mediator, pharmacological attempts are made to inhibit the SERT transporter by means of selective serotonin reuptake inhibitors. Blood platelets are key participants in the pathogenesis of multiple organ failure syndromes, such as acute renal damage, acute respiratory distress syndrome, myocardial dysfunction, and sepsis-associated encephalopathy. To restore impaired vascular permeability in these conditions, in particular, sepsis-associated encephalopathy, a pharmacological S1P receptor mimetic is under study. The review specifies possible pathogenetically significant targets that can be used to perform pharmacological correction of conditions associated with sepsis and concomitant thrombocytopenia

IL-2 and regulation of stress hormones and BDNF neurotropic factor levels after experimental traumatic brain injury (TBI)

Experimental traumatic brain  injury  (TBI)   causes  a  stable  stress  response   and  changes   the expression  of various cytokine genes and neurotrophic factors.  The goal of this study was to reveal changes  in the  levels of the  corticosterone and  testosterone hormones and  the  BDNF cytokine in blood  serum,  as well as the expression  of the BDNF gene in hypothalamus in order  to determine the opportunity of correcting the TBI damage  with rIL-2. We used a rat model  of “dropping load”:  mild TBI was caused  by falling of the 115 g load from the height  of 80 cm,  or 120 cm to produce a moderate-degree trauma. After TBI (immediately, or 72 hours  later), the  rats were injected daily with recombinant human interleukin-2 (Roncoleukin) at a dose of 30 μg/kg, a total  of 3 injections. Control animals  (also with TBI)  received  0.15 M NaCl  injections. Blood serum  concentrations of corticosterone, testosterone, and  BDNF were measured with ELISA  tests.  BDNF gene expression in hypothalamus was measured using RT-PCR. Results: the experiments showed a relationship between  hormone concentrations and severity of head injury. In mild TBI,  blood corticosterone levels reached a peak  2 hours  after the  injury, while in moderate TBI,  the  peak  concentration of corticosterone was lower, being delayed  in time  (after  24 hours). Corticosterone and  testosterone concentrations changed reciprocally in the both groups of injured  animals. With injection of rIL-2 in both groups,  corticosterone and testosterone levels were significantly  increased. On  day 7 after  TBI,  the  BDNF level in blood  serum  was decreased, but it was raised  in experimental group  that  received  rIL-2. On day 7, the increase  of BDNF gene expression  in hypothalamus was more  pronounced, when  rIL-2 was administered at 72 hours  after  the  head  injury.  The revealed  positive  association of BDNF levels and  glucocorticoid hormones after  mild  TBI,  like as possible coordination of these  parameters with rIL-2 injection after experimental moderate TBI  provides  a reason  to assume  that  the favorable  impact of rIL-2 on the CNS  recovery  after TBI is, in part,  mediated by the mutual modulating interaction of BDNF and glucocorticoid hormones

BLOOD PLATELETS AS ACTIVATORS AND REGULATORS OF INFLAMMATORY AND IMMUNE REACTIONS. PART 2. THROMBOCYTES AS PARTICIPANTS OF IMMUNE REACTIONS

Thrombocytes keep a leading role in conjugating thrombosis, inflammation and congenital immune responses. The platelets provide stable adhesion and interaction with immune cells. Activated platelets express CD40L (CD154), a membrane glycoprotein of tumor necrosis factor (TNF) family. Hence, the platelets are the main source of sCD40L in blood plasma. Platelet CD154 may interact with CD40 receptor on endothelial cells, causing an inflammatory response, and enhancing production of immunoglobulins by B-lymphocytes. Membrane and soluble CD154 of platelets combined with other signals can induce maturation and activation of dendritic cells (DC). The platelets possess functional receptors, e.g., TLR2, TLR4, TLR7 and TLR9 they also bear Fc-receptors, including FcγRIIA, FcεRI and FcαRIA. FcγRIIA on platelets mediate protection against bacteria. Cross-linking of FcαRI on platelets results in production of prothrombotic and pro-inflammatory mediators such as tissue factor and IL-1β. Activation of platelets via FcεR1 causes release of chemokine RANTES and serotonin, which contribute to the pro-inflammatory response of other immune cells. Platelets possess receptors for activated complement components and its fragments (CR2, CR3, CR4, C1q, C1 inhibitor and factors D and H). Activated platelets trigger the complement system through the release of protein kinases and ATP, and also by phosphorylation of C3 and C3b. α-granules of platelets contain chemokines which represent the most numerous group of antimicrobial proteins of platelets (kinocidins), and there is an antimicrobial protein of the defensin family – hBD-1 in the cytoplasm of platelets. Ligand and receptor of the TNF superfamily (TRAIL and LIGHT), the SDF-1 chemokine (CXCL12), the IL-1βinterleukins, IL-8 and the soluble IL-6 receptor (sRIL-6) are recognized as platelet products belonging to the family of cytokines and their receptors. The HMGB-1 protein classified as an inflammatory cytokine, is expressed by activated platelets and causes formation of the extracellular traps by neutrophils. Platelets produce numerous growth factors, including EGF-α and EGF-β1, EGF-β2, TGF-α and TGF-β1, TGF-β2, PDGF, HGF, FGF-β, IGF, pro- and antiangiogenic factors, e.g., VEGF-F and angiopoietins Ang-1 and Ang-2. Fulfillment of immune functions by the platelets is carried out by their interaction with leukocytes, which are attracted to the site of infection and inflammation and retained during the development of an “immune thrombus” under conditions of high shear stress. Platelets can not only maintain and guide the immune response, but also initiate these events. They are able to present the antigen in the context of MHC class I molecules, and activate naїve CD8+ T lymphocytes. Potential consequences of platelet interaction with neutrophils, monocytes, dendritic cells and lymphocytes are discussed in the review article

BLOOD PLATELETS AS ACTIVATORS AND REGULATORS OF INFLAMMATORY AND IMMUNE REACTIONS. PART 1. BASIC CHARACTERISTICS OF PLATELETS AS INFLAMMATORY CELLS

Platelets are the smallest blood cells, and yet their total volume and surface area exceed those of all types of leukocytes combined. Platelets are produced by the bone marrow megakaryocytes and megakaryocytes in the lung microvessels. Approximately 50% of all platelets are produced in the lungs, which makes it possible to characterize them as the main site for the production of platelets. In small circuit of blood circulation, there are approximately 30% more platelets than in large circuit. This “excess” of platelets is necessary for the stabilization of the endothelial barrier of the lung vessels regulated by the platelet mediator sphingosine-1-phosphate, a regulator of tight junctions of endothelial cells. The circulating platelets have an amazing ability to “bud” new pro- and pre-platelets, giving rise to new platelets. The removal of platelets from circulation proceeds via their phagocytosis by spleen macrophages (if platelets are covered with IgG or are bound to immune complexes), or Kupffer liver cells and hepatocytes (if platelets have incomplete glycans or desialated proteins). In homeostatic conditions, most of the platelets are removed in liver. Platelet clearance in bacterial infections and sepsis is accelerated because of the activity of bacterial sialidases. Recognition of desialized platelet structures is carried out by the liver cells through the Asgr receptor. Despite DNA absence, the platelets are able to synthesize proteins at mRNAs that are present in majority of platelets. Activation of platelets leads to aggregation and exocytosis of the granule contents, and production of immunomodulating molecules. However, activation of platelets may be incomplete and has various consequences. In a non-classical activation model, platelets can release microparticles that contain about 600 different proteins. About 75% of microparticles in the blood of healthy donors are derived from platelets. Like as immune system cells, platelets are activated by numerous endogenous ligands (alarms), including ADP and ATP, which bind to purinergic receptors P2Y1, P2Y12 andP2X1. Platelets accumulate and retain 99% of the serotonin stored in the body. The platelets contribute to induction of inflammation by releasing proinflammatory cytokines, chemokines, and lipid mediators. In addition, platelets are the source of enzymes that accomplish the capacities of neutrophils and endothelium for production of anti-inflammatory lipid mediators that contribute to tissue repair following acute phase of inflammation

Pathogenetic and Prognostic Significance of Thrombocytopenia in Patients With Necrotizing Soft Tissue Infections

Necrotizing soft tissue infection (NSTI) is a severe surgical infection which can result in sepsis and septic shock when generalized.The aim of the study was to determine the frequency of thrombocytopenia in patients with generalized NSTI, the factors promoting its development, and its association with septic shock.Materials and Methods. We examined 129 patients with NSTI treated between 09.2015 and 12.2019 at St. George Hospital in St. Petersburg, Russia. Surgical treatment, hematological and biochemical examinations, and bacteriological analysis of blood and wound discharge were performed in each patient. The studied group included 22 patients with systemic inflammatory reaction syndrome, 63 patients with sepsis, and 44 patients with septic shock.Results. We found a decrease in platelet count in NSTI patients with septic shock as early as on the first day of the disease and its further decrease within the next 3 days, with the mean platelet volume (MPV) increasing during the same period and significantly exceeding that in patients with sepsis and systemic inflammatory response syndrome. In NSTI patients with thrombocytopenia on admission, we found a significant correlation between the platelet count and the percentage of segmented neutrophils (r=0.349; P<0.001; n=40). The maximum incidenсe of septic shock was observed in patients infected with Klebsiella pneumoniae (13 out of 19, 65%). These patients had the highest MPV but did not develop thrombocytopenia. Maximum frequency of thrombocytopenia and elevation of MPV and platelet distribution width (PDW) was found in patients with NSTI and underlying chronic viral hepatitis C. However, the relative frequency of septic shock in these patients was not increased.Conclusion. The development of septic shock in NSTI is associated with a specific platelet activation patter

Патогенетическое и прогностическое значение тромбоцитопении у пациентов с некротизирующими инфекциями мягких тканей

Necrotizing soft tissue infection (NSTI) is a severe surgical infection which can result in sepsis and septic shock when generalized.The aim of the study was to determine the frequency of thrombocytopenia in patients with generalized NSTI, the factors promoting its development, and its association with septic shock.Materials and Methods. We examined 129 patients with NSTI treated between 09.2015 and 12.2019 at St. George Hospital in St. Petersburg, Russia. Surgical treatment, hematological and biochemical examinations, and bacteriological analysis of blood and wound discharge were performed in each patient. The studied group included 22 patients with systemic inflammatory reaction syndrome, 63 patients with sepsis, and 44 patients with septic shock.Results. We found a decrease in platelet count in NSTI patients with septic shock as early as on the first day of the disease and its further decrease within the next 3 days, with the mean platelet volume (MPV) increasing during the same period and significantly exceeding that in patients with sepsis and systemic inflammatory response syndrome. In NSTI patients with thrombocytopenia on admission, we found a significant correlation between the platelet count and the percentage of segmented neutrophils (r=0.349; P<0.001; n=40). The maximum incidenсe of septic shock was observed in patients infected with Klebsiella pneumoniae (13 out of 19, 65%). These patients had the highest MPV but did not develop thrombocytopenia. Maximum frequency of thrombocytopenia and elevation of MPV and platelet distribution width (PDW) was found in patients with NSTI and underlying chronic viral hepatitis C. However, the relative frequency of septic shock in these patients was not increased.Conclusion. The development of septic shock in NSTI is associated with a specific platelet activation patternНекротизирующая инфекция мягких тканей (НИМТ) — тяжелая хирургическая инфекция, при генерализации которой часто развивается сепсис и септический шок.Цель исследования — определить частоту тромбоцитопении у больных с генерализованными формами НИМТ, факторы, способствующие ее развитию и связь с развитием септического шока.Материал и методы. Обследовали 129 больных c НИМТ, лечившихся с 09.2015 по 12.2019 гг. в больнице Св. Великомученика Георгия Санкт-Петербурга. Всем пациентам провели хирургическое лечение, лабораторное гематологическое и биохимическое обследование и бактериологическое исследование крови и отделяемого из раны. Всего больных с синдромом системной воспалительной реакции было 22, с сепсисом — 63, септическим шоком — 44 человека.Результаты. Выявили снижение количества тромбоцитов у больных НИМТ с септическим шоком уже в первые сутки заболевания и дальнейшее его снижение в течение 3-х дней, причем средний объем тромбоцитов (MPV) в эти же сроки возрастал и существенно превосходил таковой у больных с сепсисом и синдромом системной воспалительной реакции. У больных НИМТ, имевших при поступлении тромбоцитопению, выявили статистически значимую корреляцию количества тромбоцитов с долей сегментоядерных нейтрофилов (r=0,349; р<0,001; n=40). Максимальную частоту септического шока отметили у больных, инфицированных Klebsiella pneumoniaе (13 из 19, 65%). У этих больных тромбоциты имели наибольший MPV, однако тромбоцитопения не развивалась. Максимальную частоту тромбоцитопении, увеличение MPV и анизоцитоз (относительную ширину распределения тромбоцитов по объему — PDW) выявили у больных с развитием НИМТ на фоне хронического вирусного гепатита С. Однако, сравнительная частота развития септического шока у этих больных не была повышена.Заключение. Развитие септического шока при НИМТ обусловлено определенным типом активации тромбоцито

Тромбоциты при инвазивном аспергиллезе: роль в патогенезе и иммунной защите

Invasive aspergillosis (IA) is a serious disease, with mortality rate up to 80%. A. fumigatus is an angiovasive pathogen, fragments of its hyphae can detach and circulate in the bloodstream. Platelets are activated by surface structures, metabolites and soluble fungal complexes, resulting in adhesion to conidia and fungal hyphae. The melanin and hydrophobin contained in the conidia, as well as the galactosaminogalactan contained in the hyphae and the glyphotoxin secreted by the hyphae, suppress phagocytic cells, but activate the platelets. Activated platelets show direct antifungal activity by releasing microbicidal proteins and serotonin. In addition to direct antifungal effect, platelets form an interactive network with cellular components of the immune system and a complement system, increasing the response of neutrophils and monocytes. In the presence of platelets, the efficacy of antimycotics is greatly enhanced. The adverse effects of platelet activation in IA are associated with clinical conditions such as hemoptysis, pulmonary hemorrhage and infarctions of various organs. Another danger associated with IA is the development of thrombocytopenia. Thrombocytopenia is defined as an independent risk factor of mortality in IA in oncohematological patients after allogeneic transplantation of hematopoietic stem cells. Numerous evidences of the important role of platelets in protection from A. fumigatus suggest that the study of the number and functional state of platelets will provide a new data, which will help develop new methods for prediction and treatment of IA.Инвазивный аспергиллез – тяжелое заболевание, при котором летальность может достигать 80%. Aspergillus fumigatus – самый частый возбудитель заболевания, ангионвазивный патоген, фрагменты гифов которого могут циркулировать в кровотоке. Тромбоциты активируются поверхностными структурами, метаболитами и растворимыми грибковыми комплексами, после чего наблюдается их адгезия к конидиям и гифам гриба. Содержащиеся в конидиях меланин и гидрофобин, а также содержащийся в гифах галактозаминогалактан и секретируемый гифами глиотоксин подавляют фагоцитирующие клетки, но активируют тромбоциты. Активированные тромбоциты проявляют прямую противогрибковую активность путем высвобождения микробицидных белков и серотонина, а также формируют интерактивную сеть с клеточными компонентами иммунной системы и системой комплемента, увеличивая ответ нейтрофилов и моноцитов. В присутствии тромбоцитов существенно усиливается эффективность антимикотиков. Неблагоприятные эффекты активации тромбоцитов при инвазивном аспергиллезе связаны с развитием легочного кровотечения и инфарктов различных органов. Другой опасностью, связанной с инвазивным аспергиллезом, является развитие тромбоцитопении. Тромбоцитопения определена как независимый фактор риска летальности при инвазивном аспергиллезе у онкогематологических больных после аллогенной трансплантации гемопоэтических стволовых клеток. Изучение количества и функционального состояния тромбоцитов позволит создать новые методы прогнозирования и лечения инвазивного аспергиллеза

CT-IGFBP-4 as a novel prognostic biomarker in acute heart failure

Aims Insulin-like growth factor binding protein-4 (IGFBP-4) fragments have been shown to predict the risk of major adverse cardiovascular events, including segment-elevation myocardial infarction, in patients with acute coronary syndrome. We evaluated the prognostic value of the carboxy-terminal fragment of IGFBP-4 (CT-IGFBP-4) for all-cause mortality in emergency room patients with acute heart failure (AHF). Methods and results CT-IGFBP-4, N-terminal pro brain natriuretic peptide (NT-proBNP), and C-reactive protein (CRP) were measured at admission from the lithium-heparin plasma of 156 patients with AHF. All-cause mortality was recorded for 1 year. Receiver operator characteristic (ROC) curves, Kaplan-Meier, and Cox proportional hazard ratio analyses were performed to evaluate the prognostic value of the various clinical variables, CT-IGFBP-4, NT-proBNP, CRP, and their combinations. During 1 year of follow-up, 52 (33.3%) patients died. CT-IGFBP-4 only weakly correlated with NT-proBNP (Pearson correlation coefficient r = 0.16, P = 0.044) and did not correlate with CRP (r = 0.08, P = 0.35), emphasizing the different nature of these biomarkers. The receiver operator characteristic area under the curve (ROC AUC) of CT-IGFBP-4 for the prediction of all-cause mortality (0.727) was significantly higher than that of NT-proBNP (0.680, P = 0.045) and CRP (0.669, P = 0.016). The combination of CT-IGFBP-4, NT-proBNP, and CRP predicted mortality significantly better (ROC AUC = 0.788) than any of the biomarkers alone (P <0.01 for all). The addition of CT-IGFBP-4 to a clinical prediction model that included age, gender, systolic blood pressure, creatinine, and sodium levels, as well as the history of previous heart failure, coronary artery disease, and hypertension significantly improved the mortality risk prediction (ROC AUC 0.774 vs. 0.699, P = 0.025). Cox hazard analysis indicated that elevated CT-IGFBP-4 was independently associated with 1 year mortality (hazard ratio 3.26, P = 0.0008) after adjustment for age, gender, history of previous heart failure, coronary artery disease, hypertension, chronic kidney failure, history of diabetes, heart rate, haemoglobin, plasma sodium, NT-proBNP, CRP, cystatin C, and elevated cardiac troponin I or T. Patients with increased levels of either two or three of the biomarkers CT-IGFBP-4, NT-proBNP, and CRP had significantly higher mortality risk (adjusted hazard ratio 10.04, P <0.0001) than patients with increased levels of one or none of the biomarkers. Conclusions CT-IGFBP-4 was independently associated with all-cause mortality in patients with AHF. Compared with single biomarkers, the combination of CT-IGFBP-4, NT-proBNP, and CRP improved the prediction of all-cause mortality in patients with AHF.Peer reviewe

Adenosine-regulated mechanisms in the pathogenesis of ventilation disorders in patients with pulmonary tuberculosis

Uncovering involvement of the purinergic system in the pathogenesis of ventilation disorders (VD) may provide additional information about the pathophysiological mechanisms leading to the development of VD in pulmonary tuberculosis (PT). The aim was to identify a relationship between the parameters of adenosine metabolism, inflammatory response and altered ventilation metabolism in PT patients. Materials and methods. Obstructive and mixed PT patients were assigned to subgroups with/without VD for assessing adenosine deaminase activity (ADA-1, 2) in serum, mononuclear cells, neutrophils; ecto-5’-nucleotidase (ecto-5’-NT); CD26 (dipeptidyl peptidase-4, DPP-4), phagocyte oxidative burst measured by NO generation. Results. PT patients showed decreased ADA-1 and CD26 (DPP-4), but increased ADA-2. Elevated intracellular adenosine concentration was found in mononuclear cells in patients lacking VD, whereas patients with mixed and obstructive VD — had it in neutrophils. Mononuclear cells of patients with PT lacking VD as well as with obstructive VD type had decreased NO3– concentration. Neutrophil hyperactivity was recorded in all groups of PT patients. Patients with PT lacking VD as well as with mixed VD type showed that the parameters of external respiration were associated with activity of extra-/intracellular ADA, whereas obstructive VD was caused by excessive formation of serum adenosine. Changes in respiratory function in PT were associated with decreased level of serum NO radicals, impaired nitrogen-dependent bactericidal phagocyte activity, and overproduced neutrophil oxygen radicals. Conclusion. Purinergic regulation is involved in regulating inflammatory and compensatory processes in PT patients as well as impaired ventilation efficiency. The most severe respiratory disorders observed in PT patients with mixed VD type are associated with the most prominent changes in nucleotidase activity, particularly ecto-ADA-2 and DPP-4/CD26

Immunomodulating effects of antitumor drugs Bruton tyrosine kinase inhibitors and the possibility of their use in allergic and infectious diseases

Bruton's tyrosine kinase (BTK) inhibitors represent a class of drugs that have demonstrated their efficacy and safety in patients with chronic lymphocytic leukemia and non-Hodgkin's lymphomas who were considered refractory to any previously used type of therapy. BTK plays a key role in all stages of B lymphocyte development, but in recent years, there have been data indicating that BTK is also involved in the activation of myeloid cells.The aim of this study is to analyze and systematize all published materials on the immunomodulatory effects of BTK inhibitors (ibrutinib, acalabrutinib, etc.).A systematic review of the scientific literature was performed using a step-by-step search process in electronic databases (PubMed, Web of Science, ScienceDirect, and Scopus). The following keywords were used in the database search: “CLL”, “BTK”, “ibrutinib”, “COVID-19”, “allergy”, “inflammation.” The search for studies was conducted from the time of the first BTK inhibitor drug (ibrutinib) appearance in 2009 until December 2022.The results of the study on the influence of BTK inhibitors on the functional state of B and T lymphocytes, neutrophils, and monocytes/macrophages are presented. The immunomodulatory effects of ibrutinib on adaptive and innate immune system cells, including CD4+ and CD8+T lymphocytes and NK cells, are described. Since BTK inhibitors alter the functional activity of phagocytic cells and the ratio of T cell populations, there is a suggestion about the possibility of using these drugs for the treatment of other nosological forms, not only B cell malignancies, which is currently being studied in clinical trials. Data on the use of BTK inhibitors to combat hyperacute inflammation and to suppress allergic reactions, including anaphylaxis, are summarized. In addition, the expediency of short-term use of BTK inhibitors to reduce the risk of side effects during oral immunotherapy and for desensitization to drugs is discussed.The presented data indicate that BTK inhibitors are promising drugs with immunomodulatory effects. However, BTK inhibitors need to increase selectivity to reduce off-target effects on other kinases