The pathophysiologic role of myocardial depressant factor as a mediator of circulatory shock

Burn Shock and Resuscitation: Review and State of the Science

Burn shock and acute fluid resuscitation continue to spark intense interest and debate among burn clinicians. Following a major burn injury, fluid resuscitation of burn shock is life-saving, but paradoxically can also be a source of increased morbidity and mortality because of the unintended consequence of systemic edema formation. Considerable research over the past two decades has been devoted to understanding the mechanisms of edema formation, and to develop strategies to curb resuscitation fluids and limit edema development. Recognition of burn endotheliopathy - injury to the endothelium's glycocalyx layer- is one of the most important recent developments in our understanding of burn shock pathophysiology. Newer monitoring approaches and resuscitation endpoints, along with alternative resuscitation strategies to crystalloids alone, such as administration of albumin, or plasma, or high dose ascorbic acid, have had mixed results in limiting fluid creep. Clear demonstration of improvements in outcomes with all of these approaches remains elusive. This comprehensive review article on burn shock and acute resuscitation accompanies the American Burn Association's State of the Science meeting held in New Orleans, LA on November 2-3, 2021 and the Proceedings of that conference published in this journal.

Proton pump inhibitors interfere with the anti-tumor potency of RC48ADC

Antibody-drug conjugates (ADCs) are a promising modality for cancers, but the interaction between them and proton pump inhibitors (PPIs), the common adjuvant drugs for cancer treatment, has not been understood. Here, the interactions between PPIs and RC48ADC, a novel HER2-targeting ADC, were quantified in vitro. CCK-8 assay showed that RC48ADC displayed a significant inhibitory effect on the proliferation of SK-BR-3, NCI-N87 and SK-OV-3 cells with the IC₅₀ values of 4.91 ± 1.15 ng/mL, 14.54 ± 0.85 ng/mL and 11.28 ± 0.68 ng/mL respectively. PPIs alone had no significant anti-tumor effect in the dose range of 1.37-1000 ng/mL. When used together, PPIs inhibited the anti-tumor activity of RC48ADC in a dose-dependent manner. And 1000 ng/mL (~Cmax) PPIs significantly recovered RC48ADC-inhibited cell proliferation by (32.85 ± 2.81) % (p < 0.05). However, cimetidine, a non-PPIs gastric acid secretion inhibitor, had no significant inhibitory effect on RC48ADC. Furthermore, omeprazole, rather than cimetidine, significantly reduced the activity of vacuolar H⁺-ATPase and Cathepsin B compared with the control cells. These results, if confirmed in vivo, indicate that PPIs are antagonists of RC48ADC, even all ADCs, appearing to be due to inhibition of vacuolar H⁺-ATPase activity. Moreover, cimetidine combined with ADCs instead of PPIs can prevent an adverse drug interaction.

Cardiac Dysfunction in Severely Burned Patients: Current Understanding of Etiology, Pathophysiology, and Treatment

Patients who experience severe burn injuries face a massive inflammatory response resulting in hemodynamic and cardiovascular complications. Even after immediate and appropriate resuscitation, removal of burn eschar and covering of open areas, burn patients remain at high risk for serious morbidity and mortality. As a result of the massive fluid shifts following the initial injury, along with large volume fluid resuscitation, the cardiovascular system is critically affected. Further, increased inflammation, catecholamine surge, and hypermetabolic syndrome impact cardiac dysfunction, which worsens outcomes of burn patients. This review aimed to summarize the current knowledge about the effect of burns on the cardiovascular system.A comprehensive search of the PubMed and Embase databases and manual review of articles involving effects of burns on the cardiovascular system was conducted.Many burn units use multimodal monitors (e.g., transpulmonary thermodilution) to assess hemodynamics and optimize cardiovascular function. Echocardiography is often used for additional evaluations of hemodynamically unstable patients to assess systolic and diastolic function. Due to its noninvasive character, echocardiography can be repeated easily, which allows us to follow patients longitudinally.The use of anabolic and anticatabolic agents has been shown to be beneficial for short- and long-term outcomes of burn survivors. Administration of propranolol (non-selective β-receptor antagonist) or oxandrolone (synthetic testosterone) for up to 12 months post-burn counteracts hypermetabolism during hospital stay and improves cardiac function.A comprehensive understanding of how burns lead to cardiac dysfunction and new therapeutic options could contribute to better outcomes in this patient population.

Therapeutic approaches targeting renin-angiotensin system in sepsis and its complications

Sepsis, caused by the inappropriate host response to infection, is characterized by excessive inflammatory response and organ dysfunction, thus becomes a critical clinical problem. Commonly, sepsis may progress to septic shock and severe complications, including acute kidney injury (AKI), acute respiratory distress syndrome (ARDS), sepsis-induced myocardial dysfunction (SIMD), liver dysfunction, cerebral dysfunction, and skeletal muscle atrophy, which predominantly contribute to high mortality. Additionally, the global pandemic of coronavirus disease 2019 (COVID-19) raised the concern of development of effectve therapeutic strategies for viral sepsis. Renin-angiotensin system (RAS) may represent as a potent therapeutic target for sepsis therapy. The emerging role of RAS in the pathogenesis of sepsis has been investigated and several preclinical and clinical trials targeting RAS for sepsis treatment revealed promising outcomes. Herein, we attempt to review the effects and mechanisms of RAS manipulation on sepsis and its complications and provide new insights into optimizing RAS interventions for sepsis treatment.

The effect of hypothalamic peptides, neurohormone C and proline-rich peptide-1on the Ca2+-handling system in heartin pathophysiological conditions

Atthe Institute of Biochemistry named after H. Buniatyan we discovered and studied hypothalamic peptides with coronary dilatory and antioxidant activities:neurohormone C (NC) and proline-rich peptide-1 (PRP-1). Both NC and PRP-1 exhibit cardioprotective effects, in part by restoring the calcium affinity for calcium-binding membrane proteins in cardiomyocytes. This affinity is diminished in the sarcoplasmic reticulum and mitochondriawith myocardial damage, heart failure, pancreatic necrosis and crush syndrome caused by isoproterenol. The peptides can also destroy the four detected toxic peptides and myocardial depressant factor, and protect against ischemia-reperfusion injury. Further studies of these peptides may be promising for the treatment of patients at high risk of cardiovascular disease, regardless of pathology.

Current Status of Septic Cardiomyopathy: Basic Science and Clinical Progress

Septic cardiomyopathy (SCM) is a complication that is sepsis-associated cardiovascular failure. In the last few decades, there is progress in diagnosis and treatment despite the lack of consistent diagnostic criteria. According to current studies, several hypotheses about pathogenic mechanisms have been revealed to elucidate the pathophysiological characteristics of SCM. The objective of this manuscript is to review literature from the past 5 years to provide an overview of current knowledge on pathogenesis, diagnosis and treatment in SCM.

Pancreatic Blood Flow with Special Emphasis on Blood Perfusion of the Islets of Langerhans

The pancreatic islets are more richly vascularized than the exocrine pancreas, and possess a 5- to 10-fold higher basal and stimulated blood flow, which is separately regulated. This is reflected in the vascular anatomy of the pancreas where islets have separate arterioles. There is also an insulo-acinar portal system, where numerous venules connect each islet to the acinar capillaries. Both islets and acini possess strong metabolic regulation of their blood perfusion. Of particular importance, especially in the islets, is adenosine and ATP/ADP. Basal and stimulated blood flow is modified by local endothelial mediators, the nervous system as well as gastrointestinal hormones. Normally the responses to the nervous system, especially the parasympathetic and sympathetic nerves, are fairly similar in endocrine and exocrine parts. The islets seem to be more sensitive to the effects of endothelial mediators, especially nitric oxide, which is a permissive factor to maintain the high basal islet blood flow. The gastrointestinal hormones with pancreatic effects mainly influence the exocrine pancreatic blood flow, whereas islets are less affected. A notable exception is incretin hormones and adipokines, which preferentially affect islet vasculature. Islet hormones can influence both exocrine and endocrine blood vessels, and these complex effects are discussed. Secondary changes in pancreatic and islet blood flow occur during several conditions. To what extent changes in blood perfusion may affect the pathogenesis of pancreatic diseases is discussed. Both type 2 diabetes mellitus and acute pancreatitis are conditions where we think there is evidence that blood flow may contribute to disease manifestations. © 2019 American Physiological Society. Compr Physiol 9:799-837, 2019.

Imbalance of autonomic nervous systems involved in ventricular arrhythmia after splenectomy in dogs

The role of cardiac autonomic modulation on ventricular arrhythmia, known as ventricular premature complexes (VPC), after splenectomy was investigated. Twelve dogs undergoing splenectomy were divided into 2 groups: low VPC (<1,000/day, n=6) and high VPC groups (≥1,000/day, n=6). Electrocardiograph recording was performed prior to (D0), during the first three days (D1-3) and on day 9 (D9) after surgery. Arrhythmic indices, T_peak-T_end, corrected QT interval and short-term variability of QT interval as well as heart rate variability (HRV) were evaluated. Plasma concentrations of norepinephrine (NE) and epinephrine (E) were measured. In the high VPC group, the occurrences of VPC were significantly increased (P<0.05) after surgery, and reached the levels higher than those in the low VPC group. For the arrhythmic indices, only Tp-Te in the high VPC group increased significantly (P<0.05) after surgery. For HRV analysis, enhancement of both time and frequency domains were found postoperatively in both groups. On D2, however, the high VPC group showed significantly lower total power and high frequency with higher low to high frequency ratio (P<0.05) than the low VPC group. Plasma NE concentration significantly increased in the high VPC group after surgery. Dogs in the high VPC group had shorter survival time than those in the low VPC group. In conclusion, dogs with imbalance cardiac autonomic modulation accompanied with high circulating NE concentration after splenectomy are prone to ventricular arrhythmia, which leads to short survival time.

Serine protease inhibition reduces post-ischemic granulocyte recruitment in mouse intestine

Proteases and proteinase-activated receptor (PAR) activation are involved in several intestinal inflammatory conditions. We hypothesized that serine proteases and PAR activation could also modulate the intestinal injury induced by ischemia-reperfusion (I-R). C57Bl/6 mice were subjected to 90 minutes of intestinal ischemia followed or not by reperfusion. Sham-operated animals served as controls. After ischemia, plasma and tissue serine protease activity levels were increased compared to the activity measured in plasma and tissues from sham-operated mice. This increase was maintained or further enhanced after 2 and 5 hours of reperfusion, respectively. Trypsin (25 kDa) was detected in tissues both after ischemia and 2 hours of reperfusion. Treatment with FUT-175 (10 mg/kg), a potent serine protease inhibitor, increased survival after I-R, inhibited tissue protease activity, and significantly decreased intestinal myeloperoxidase (MPO) activity and chemokine and adhesion molecule expression. We investigated whether serine proteases modulate granulocyte recruitment by a PAR-dependent mechanism. MPO levels and adhesion molecule expression were significantly reduced in I-R groups pre-treated with the PAR(1) antagonist SCH-79797 (5 mg/kg) and in Par(2)(-/-)mice, compared, respectively, to vehicle-treated group and wild-type littermates. Thus, increased proteolytic activity and PAR activation play a pathogenic role in intestinal I-R injury. Inhibition of PAR-activating serine proteases could be beneficial to reduce post-ischemic intestinal inflammation.

Pressor effects of the alpha 2-adrenoceptor agonist B-HT 933 in anaesthetized and haemorrhagic rats: comparison with the haemodynamic effects of amidephrine

1. Blood pressure responses to single and multiple bolus doses of the alpha 2-adrenoceptor agonist B-HT 933 were analysed in intact anaesthetized rats which were either normotensive or hypotensive as a result of haemorrhage. Single bolus doses of B-HT 933 in normotensive rats induced a fall in blood pressure, whilst further doses induced dose-dependent pressor responses which were inhibited by the alpha 2-adrenoceptor antagonist yohimbine and unaffected by the alpha 1-adrenoceptor agonist prazosin. In the haemorrhagic, hypotensive animals, single bolus doses of B-HT 933 induced immediate dose-dependent pressor responses; the maximum pressor responses to the bolus of B-HT 933 and its ED50 values were the same in both the normotensive and hypotensive, haemorrhagic animals. 2. Cardiac output, its distribution and tissue blood flows were determined with tracer microspheres in intact anaesthetized normotensive and haemorrhagic, hypotensive rats during depressor (normotensive) and pressor (normotensive and hypotensive) responses to B-HT 933. Haemodynamics were also determined during pressor responses to the alpha 1-adrenoceptor agonist amidephrine. 3. In control normotensive rats, a single dose of B-HT 933 (1 mg kg-1) reduced blood pressure by reducing cardiac output (through a decrease in heart rate). It increased the fractional distribution of cardiac output to the spleen and stomach, reduced it to the heart and liver and reduced cardiac and hepatic blood flow. A further dose of B-HT 933 (1 mg kg-1 bolus followed by 100 micrograms min-1 infusion) increased blood pressure by increasing total peripheral resistance, which was accompanied by decreased proportions of cardiac output passing to the heart, liver and testes. There was also increased fractional distribution of cardiac output to the lungs, spleen, kidneys and stomach but blood flows through the liver and testes were reduced. Amidephrine (6 micrograms kg-1 bolus followed by 0.5 micrograms min-1 infusion) increased blood pressure by increasing cardiac output through an increased stroke volume. It increased cardiac output distribution to the kidneys and brain, increasing blood flow through the heart, lungs, brain, testes, epididimides, skin and large intestine. 4. Haemorrhage caused a fall in blood pressure which resulted from decreased total peripheral resistance and cardiac output (the latter due to decreases in both heart rate and stroke volume). It reduced the proportion of cardiac output distributed to the lungs, spleen, kidneys, testes and pancreas/mesentery and decreased blood flow through these organs as well as through the heart, liver, brain, epididimides, skin and the gastrointestinal tract.4

Hemodynamics and coagulation in experimental auxiliary liver transplantation during fulminant hepatic failure

In pigs, ischemic liver cell necrosis was induced by 6 hours' occlusion of the hepatic artery and the portal vein 3 days after construction of a side-to-side portacaval shunt and division of the hepatic ligaments. Two thirds of the liver of an MLC-compatible donor was heterotopically transplanted 13 hours (group I), and 3 hours (group II) after induction of liver failure. In group I (N = 11), three animals died of liver failure before or shortly after induction of anesthesia. Of the remaining pigs, two animals survived more than 2 weeks. In group II (N = 10), intraoperative hypotension was prevented by reduction of the interval between liver failure and transplantation and by thermodilution catheter monitored fluid replacement. A significant decrease in cardiac output and an increase of pulmonary and systemic vascular resistance were observed during auxiliary partial liver transplantation (APLT). In the immediate postoperative period, six pigs died of deficiencies in hemostasis that were caused by consumptive coagulopathy related to severe host liver damage rather than fibrinolysis. Two pigs in group II survived in good condition 12 and 42 days after APLT. In the longer surviving pigs of both groups, either the graft or the host liver recovered. Processes that might be responsible for the observed hemodynamic changes and coagulation disorders are discussed. These results indicate that APLT is technically feasible in severely ill pigs with acute hepatic failure.

A circulating myocardial depressant substance in humans with septic shock. Septic shock patients with a reduced ejection fraction have a circulating factor that depresses in vitro myocardial cell performance

We have previously described a subpopulation of patients with septic shock who had a reversible depression of radionuclide-determined left ventricular ejection fraction (EF). To investigate the mechanism of this myocardial depression, an in vitro model of mammalian myocardial cell performance was established employing primary spontaneously beating rat myocardial cells. The contraction of a single cardiac cell was quantitated by recording the changes in area occupied by the cell during contraction and relaxation. In 20 septic shock patients during the acute phase, the mean left ventricular EF was decreased (mean = 0.33, normal mean = 0.50), and serum obtained during this acute phase induced a mean (+/- standard error of the mean) 33 +/- 4% decrease in extent and 25 +/- 4% decrease in velocity of myocardial cell shortening during contraction (P less than 0.001). In contrast, serum obtained from 11 of these same patients before shock (n = 2) or after recovery (n = 9) of the left ventricular EF (mean = 0.50) showed a return toward normal in extent and velocity of shortening (P less than 0.001). Sera from 17 critically ill nonseptic patients, from 10 patients with structural heart disease as a cause for a depressed EF, and from 12 healthy laboratory personnel, induced no significant changes in in vitro myocardial cell performance. In 20 patients during the acute phase of septic shock, the decreased EF in vivo demonstrated a significant correlation (r = +0.52, P less than 0.01) with a decrease in the extent of myocardial cell shortening in vitro. The quantitative and temporal correlation between the decreased left ventricular EF and this serum myocardial depressant substance argues for a pathophysiologic role for this depressant substance in producing the reversible cardiomyopathy seen during septic shock in humans.