Nitric oxide synthase is downregulated, while haem oxygenase is increased, in patients with septic shock

Cardiovascular Responses During Sepsis

Sepsis is the life-threatening organ dysfunction arising from a dysregulated host response to infection. Although the specific mechanisms leading to organ dysfunction are still debated, impaired tissue oxygenation appears to play a major role, and concomitant hemodynamic alterations are invariably present. The hemodynamic phenotype of affected individuals is highly variable for reasons that have been partially elucidated. Indeed, each patient's circulatory condition is shaped by the complex interplay between the medical history, the volemic status, the interval from disease onset, the pathogen, the site of infection, and the attempted resuscitation. Moreover, the same hemodynamic pattern can be generated by different combinations of various pathophysiological processes, so the presence of a given hemodynamic pattern cannot be directly related to a unique cluster of alterations. Research based on endotoxin administration to healthy volunteers and animal models compensate, to an extent, for the scarcity of clinical studies on the evolution of sepsis hemodynamics. Their results, however, cannot be directly extrapolated to the clinical setting, due to fundamental differences between the septic patient, the healthy volunteer, and the experimental model. Numerous microcirculatory derangements might exist in the septic host, even in the presence of a preserved macrocirculation. This dissociation between the macro- and the microcirculation might account for the limited success of therapeutic interventions targeting typical hemodynamic parameters, such as arterial and cardiac filling pressures, and cardiac output. Finally, physiological studies point to an early contribution of cardiac dysfunction to the septic phenotype, however, our defective diagnostic tools preclude its clinical recognition. © 2021 American Physiological Society. Compr Physiol 11:1605-1652, 2021.

Invited review: Compartmentalization of the inflammatory response in sepsis and SIRS

Sepsis and systemic inflammatory response syndrome (SIRS) are associated with an exacerbated production of both pro- and anti-inflammatory mediators that are mainly produced within tissues. Although a systemic process, the pathophysiological events differ from organ to organ, and from organ to peripheral blood, leading to the concept of compartmentalization. The nature of the insult ( e.g. burn, hemorrhage, trauma, peritonitis), the cellular composition of each compartment ( e.g . nature of phagocytes, nature of endothelial cells), and its micro-environment ( e.g. local presence of granulocyte-macrophage colony stimulating factor [GM-CSF] in the lungs, low levels of arginine in the liver, release of endotoxin from the gut), and leukocyte recruitment, have a great influence on local inflammation and on tissue injury. High levels of pro-inflammatory mediators ( e.g. interleukin-1 [IL-1], tumor necrosis factor [TNF], gamma interferon [IFN-γ], high mobility group protein-1 [HMGB1], macrophage migration inhibitory factor [MIF]) produced locally and released into the blood stream initiate remote organ injury as a consequence of an organ cross-talk. The inflammatory response within the tissues is greatly influenced by the local delivery of neuromediators by the cholinergic and sympathetic neurons. Acetylcholine and epinephrine contribute with IL-10 and other mediators to the anti-inflammatory compensatory response initiated to dampen the inflammatory process. Unfortunately, this regulatory response leads to an altered immune status of leukocytes that can increase the susceptibility to further infection. Again, the nature of the insult, the nature of the leukocytes, the presence of circulating microbial components, and the nature of the triggering agent employed to trigger cells, greatly influence the immune status of the leukocytes that may differ from one compartment to another. While anti-inflammatory mediators predominate within the blood stream to avoid igniting new inflammatory foci, their presence within tissues may not always be sufficient to prevent the initiation of a deleterious inflammatory response in the different compartments.

Anti-cancer Effect and Underlying Mechanism(s) of Kaempferol, a Phytoestrogen, on the Regulation of Apoptosis in Diverse Cancer Cell Models

Phytoestrogens exist in edible compounds commonly found in fruits or plants. For long times, phytoestrogens have been used for therapeutic treatments against human diseases, and they can be promising ingredients for future pharmacological industries. Kaempferol is a yellow compound found in grapes, broccoli and yellow fruits, which is one of flavonoid as phytoestrogens. Kaempferol has been suggested to have an antioxidant and anti-inflammatory effect. In past decades, many studies have been performed to examine anti-toxicological role(s) of kaempferol against human cancers. It has been shown that kaempferol may be involved in the regulations of cell cycle, metastasis, angiogenesis and apoptosis in various cancer cell types. Among them, there have been a few of the studies to examine a relationship between kaempferol and apoptosis. Thus, in this review, we highlight the effect(s) of kaempferol on the regulation of apoptosis in diverse cancer cell models. This could be a forecast in regard to use of kaempferol as promising treatment against human diseases.

Gene polymorphisms in the heme degradation pathway and outcome of severe human sepsis

Heme and its breakdown products CO, Fe, and bilirubin are being recognized as signaling molecules or even therapeutic agents, but also exert adverse effects when released at high concentrations. Manipulating the pathway confers protection in rodent sepsis models via both control of free heme and formation of its first and higher-order products. Thus, regulatory elements present in human heme oxygenase 1 (HMOX1) and biliverdin reductases (BLVRA/B) genes might impact outcome. We tested whether a highly polymorphic (GT)n microsatellite and single-nucleotide polymorphisms in HMOX1 and BLVRA/B genes are associated with outcome of sepsis. Two cohorts (n = 430 and 398 patients) with severe sepsis were screened for single-nucleotide polymorphisms and/or the microsatellite by fragment length analysis and genotyping techniques. Heme oxygenase 1 plasma levels were determined in additional patients with severe sepsis (n = 92) by enzyme-linked immunosorbent assay. Based on mean Sepsis-related Organ Failure Assessment scores, patients homozygous for rs2071746 A allele or medium length (GT)n microsatellites of HMOX1 showed higher 28-day mortality (P = 0.047 and P = 0.033) in one cohort compared with other genotypes, whereas 90-day mortality rates showed no association. The T allele was less frequently observed in both cohorts than would be expected according to Hardy-Weinberg equilibrium. Heme oxygenase 1 plasma levels were elevated in septic patients, independent of the genotype. Single-nucleotide polymorphisms within BLVRA/B showed no association with outcome. Short (GT)n repeats that are in linkage disequilibrium with the T allele of rs2071746 in HMOX1 are associated with favorable outcome, whereas no association with gene variants of BLVRA/B, involved in the generation of higher-order metabolites, was noticed.

Augmentation of platelet and endothelial cell eNOS activity decreases sepsis-related neutrophil-endothelial cell interactions

NO is an important mediator of microvascular patency and blood flow. The purpose of this study was to examine the role of enhanced eNOS activity in attenuating sepsis-induced neutrophil-endothelial cell interactions. Microslides coated with human umbilical vein endothelial cells were stimulated with plasma from patients with septic shock. Neutrophil and platelets from control subjects were also stimulated with plasma from patients in septic shock and perfused over stimulated endothelial cells. l-Arginine (LA) with and without NG-monomethyl l-arginine (LNMMA), a nonselective NOS inhibitor, and N-(3-(aminomethyl) benzyl acetamide) ethanimidamide dihydrochloride (1400W), a highly selective iNOS inhibitor, were added to the septic plasma. The number of neutrophils adherent to endothelial cells, neutrophil rolling velocity, and the number of neutrophil aggregates were determined. Cell activation and the formation of platelet-neutrophil aggregates were assessed by flow cytometry. Separate experiments were done with isolated platelets using platelet aggregometry. l-Arginine significantly decreased sepsis-related neutrophil adhesion and aggregation and increased rolling velocity. The addition of LNMMA to LA and cell suspensions reversed the effects of LA on these parameters, whereas the addition of 1400W had no effect on LA-related changes. Platelet-neutrophil aggregation, platelet aggregation, platelet activation, and neutrophil activation induced by septic plasma were also significantly decreased by LA. Again, the addition of LNMMA reversed the effects of LA on these parameters, whereas 1400W had no effect on LA-related changes. These data suggest that enhancement of platelet and endothelial cell eNOS activity decreases sepsis-induced neutrophil-endothelial cell interactions and may play a role in maintaining microvascular patency in septic shock.

Carbon monoxide in sepsis

Despite modern practices in critical care medicine, sepsis or systemic inflammatory response syndrome remains a leading cause of morbidity and mortality in the intensive care unit. Thus, the need to identify new therapeutic tools for the treatment of sepsis is urgent. In this context, carbon monoxide has become a promising therapeutic molecule that can potentially prevent uncontrolled inflammation in sepsis. In humans, carbon monoxide arises endogenously from the degradation of heme by heme oxygenase enzymes. Both endogenously synthesized and exogenously applied carbon monoxide can exert antiinflammatory and antiapoptotic effects in cells and tissues. Based on these properties, carbon monoxide, when applied at low concentration, conferred protection in a variety of cellular and rodent models of sepsis, and furthermore reduced morbidity and mortality in vivo. Therefore, application of carbon monoxide may have a major impact on the future of sepsis treatment. This review summarizes evidence for salutary effects of carbon monoxide in sepsis of various organs, including lung, heart, kidney, liver, and intestine, and discusses the potential translation of the data into human clinical trials.

[Carbon monoxide--poison or potential therapeutic?]

Carbon monoxide (CO) is much more than just a toxic gas. Carbon monoxide is produced endogenously by the enzyme heme oxygenase and has important functions under physiological and pathophysiological conditions. Recent studies suggested antioxidative, anti-inflammatory, antiproliferative, anti-apoptotic, and vasodilating characteristics. Regarding clinically-relevant diseases in anesthesiology and critical care medicine, such as adult respiratory distress syndrome (ARDS), sepsis, or during organ transplantation, cytoprotective properties have been demonstrated by low-dose CO in experimental models. In view of a potential CO application in future human studies, this review discusses what is known to date about CO as it relates to functional, protective and toxic aspects.

Role of heme-oxygenase pathway on vasopressin deficiency during endotoxemic shock-like conditions

The septic shock is characterized by decrease in median arterial pressure; many researchers have been related a deficiency in vasopressin release during the septic shock. Lipopolysaccharide administration is used to induce septic shock model in animals. We investigated the heme-oxygenase (HO) inhibition during the endotoxemic shock-like conditions. The LPS administration induced a significant decrease in MAP (-15.4 +/- 1.2 mmHg at second hour, -25.8 +/- 8.7 mmHg at fourth hour, and -22.3 +/- 8.6 mmHg at sixth hour) with a concomitant increase in heart rate (486.3 +/- 55.0, 531.8 +/- 53.8, and 510.0 +/- 55.3 bpm, respectively), a significant decrease in diuresis (from 1.1 +/- 0.7 to 0.4 +/- 0.3/100g body weight at fourth hour), and a transitory decrease in body temperature (from 37.0 +/- 0.5 to 35.4 +/- 0.8 degrees C at second hour). An increase in plasma arginine vasopressin (AVP) concentration (from 3.2 +/- 0.9 to 19.0 +/- 5.7 pg/mL at the first hour) occurred in these animals and was present for 2 h after LPS administration, returning close to basal levels thereafter and remaining unchanged until the end of the experiment. When LPS was combined with the i.c.v. administration of HO inhibitor, we observed a sustained increase in plasma AVP concentration, attenuation in the drop of MAP, and increase in antidiuresis induced by LPS treatment. These data suggest that central HO pathway may activate a control mechanism that attenuates AVP secretion during endotoxemia and may consequently regulate the MAP and diuretic output.

Upregulation of Renal Inducible Nitric Oxide Synthase during Human Endotoxemia and Sepsis Is Associated with Proximal Tubule Injury

The incidence and the mortality of septic acute kidney injury are high, partly because the pathogenesis of sepsis-induced renal dysfunction is not clear. The objective of this study was to investigate the upregulation of renal inducible nitric oxide synthase (iNOS) in human endotoxemia and sepsis and the effect of NO on tubular integrity. Septic patients and endotoxemia that was induced by a bolus injection of 2 ng/kg Escherichia coli LPS in human volunteers were studied. In addition, the effect of co-administration of the selective iNOS inhibitor aminoguanidine was evaluated. The urinary excretion of the cytosolic glutathione-S-transferase-A1 (GSTA1-1) and GSTP1-1, markers for proximal and distal tubule damage, respectively, was determined. In septic patients, an almost 40-fold induction of iNOS mRNA in cells that were isolated from urine was found accompanied by a significant increase in NO metabolites in blood. The mRNA expression of iNOS was induced 34-fold after endotoxin administration. LPS-treated healthy volunteers showed a higher urinary excretion of NO metabolites compared with control subjects. Urinary NO metabolite excretion correlated with urinary GSTA1-1 excretion, indicating proximal tubule damage, whereas no distal tubular damage was observed. Co-administration of aminoguanidine reduced the upregulation of iNOS mRNA, urinary NO metabolite, and GSTA1-1 excretion, indicating that upregulation of iNOS and subsequent NO production may be responsible for renal proximal tubule damage observed.

Therapeutic applications of carbon monoxide-releasing molecules

Carbon monoxide (CO), which is formed in mammalian cells through the oxidation of haem by the enzyme haem oxygenase, actively participates in the regulation of key intracellular functions. Emerging evidence reveals that an increased generation of haem oxygenase-derived CO plays a critical role in the resolution of inflammatory processes and alleviation of cardiovascular disorders. The authors have identified a novel class of substances, CO-releasing molecules (CO-RMs), which are capable of exerting a variety of pharmacological activities via the liberation of controlled amounts of CO in biological systems. A wide range of CO carriers containing manganese (CORM-1), ruthenium (CORM-2 and -3), boron (CORM-A1) and iron (CORM-F3) are currently being investigated to tailor therapeutic approaches for the prevention of vascular dysfunction, inflammation, tissue ischaemia and organ rejection.

Enantiomers of higenamine inhibit LPS-induced iNOS in a macrophage cell line and improve the survival of mice with experimental endotoxemia

The importance of development of single enantiomers (optically pure isomers) of chiral molecules has been recognized and manifested in countless pharmaceutical and biological advancement. (RS)-(+/-)-Higenamine (racemic mixture), an active ingredient of Aconite tuber, has been shown to have antioxidant activity along with inhibitory action of iNOS expression in various cells. In the present study, the effects of each enantiomer of higenamine [(S)-(-)-higenamine and (R)-(+)-higenamine] were investigated in comparison with the effects of racemic mixture [(RS)-(+/-)-higenamine] on iNOS expression and NO production in RAW 264.7 cells activated with LPS. In addition, the effects of higenamine enantiomers on the survival rates were also investigated using mice, in which each test compound was injected (i.p.) 90 min prior to LPS. All three forms of higenamine inhibited iNOS expression and reduced NO production with IC50 of 26.2, 86.3, and 53.4 microM, for (S)-, (R)-, and (RS)-higenamine, respectively. (S)-higenamine also significantly reduced serum NOx level and increased survival rates in LPS-treated mice. In contrast, (R)-isomer only showed tendency to increase the survival rates which was not statistically significant when compared to LPS-treated controls. Taken together, it was concluded that (S)-higenamine may be more beneficial than (R)-enantiomer in diseases associated with iNOS over-expression, such as septic shock.