Nitric oxide in shock

Exploring the Pathophysiology of Long COVID: The Central Role of Low-Grade Inflammation and Multisystem Involvement

Long COVID (LC), also referred to as Post COVID-19 Condition, Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), and other terms, represents a complex multisystem disease persisting after the acute phase of COVID-19. Characterized by a myriad of symptoms across different organ systems, LC presents significant diagnostic and management challenges. Central to the disorder is the role of low-grade inflammation, a non-classical inflammatory response that contributes to the chronicity and diversity of symptoms observed. This review explores the pathophysiological underpinnings of LC, emphasizing the importance of low-grade inflammation as a core component. By delineating the pathogenetic relationships and clinical manifestations of LC, this article highlights the necessity for an integrated approach that employs both personalized medicine and standardized protocols aimed at mitigating long-term consequences. The insights gained not only enhance our understanding of LC but also inform the development of therapeutic strategies that could be applicable to other chronic conditions with similar pathophysiological features.

Nitric oxide in kidney transplantation

Kidney transplantation is the treatment of choice for patients with kidney failure. Compared to dialysis therapy, it provides better quality of life and confers significant survival advantage at a relatively lower cost. However, the long-term success of this life-saving intervention is severely hampered by an inexorable clinical problem referred to as ischemia-reperfusion injury (IRI), and increases the incidence of post-transplant complications including loss of renal graft function and death of transplant recipients. Burgeoning evidence shows that nitric oxide (NO), a poisonous gas at high concentrations, and with a historic negative public image as an environmental pollutant, has emerged as a potential candidate that holds clinical promise in mitigating IRI and preventing acute and chronic graft rejection when it is added to kidney preservation solutions at low concentrations or when administered to the kidney donor prior to kidney procurement and to the recipient or to the reperfusion circuit at the start and during reperfusion after renal graft preservation. Interestingly, dysregulated or abnormal endogenous production and metabolism of NO is associated with IRI in kidney transplantation. From experimental and clinical perspectives, this review presents endogenous enzymatic production of NO as well as its exogenous sources, and then discusses protective effects of constitutive nitric oxide synthase (NOS)-derived NO against IRI in kidney transplantation via several signaling pathways. The review also highlights a few isolated studies of renal graft protection by NO produced by inducible NOS.

Vascular Inflammatory Diseases and Endothelial Phenotypes

The physiological functions of endothelial cells control vascular tone, permeability, inflammation, and angiogenesis, which significantly help to maintain a healthy vascular system. Several cardiovascular diseases are characterized by endothelial cell activation or dysfunction triggered by external stimuli such as disturbed flow, hypoxia, growth factors, and cytokines in response to high levels of low-density lipoprotein and cholesterol, hypertension, diabetes, aging, drugs, and smoking. Increasing evidence suggests that uncontrolled proinflammatory signaling and further alteration in endothelial cell phenotypes such as barrier disruption, increased permeability, endothelial to mesenchymal transition (EndMT), and metabolic reprogramming further induce vascular diseases, and multiple studies are focusing on finding the pathways and mechanisms involved in it. This review highlights the main proinflammatory stimuli and their effects on endothelial cell function. In order to provide a rational direction for future research, we also compiled the most recent data regarding the impact of endothelial cell dysfunction on vascular diseases and potential targets that impede the pathogenic process.

Genes regulating oxidative-inflammatory response in circulating monocytes and neutrophils in septic syndrome

Despite significant progress in the past decades, sepsis still lacks a specific treatment. Under normal conditions, leucocytes play a critical role in controlling infection and it is suggested that their activity is impaired during sepsis which contribute to the dysregulation of immune reactions. Indeed, in response to infection, several intracellular pathways are affected mainly those regulating the oxidative- inflammatory axis. Herein, we focused on the contribution of NF-kB, iNOS, Nrf2, HO-1 and MPO genes in the pathophysiology of septic syndrome, by analyzing the differential expression of their transcripts in circulating monocytes and neutrophils, and monitoring the nitrosative/oxidative status in septic syndrome patients. Circulating neutrophils of septic patients displayed a significant overexpression of NF-kB compared to other groups. In monocytes, patients with septic shock expressed the highest levels of iNOS and NF-kB mRNA. However, genes involved in cytoprotective response had increased expression in patients with sepsis, in particular, the Nrf2 and its target gene HO-1. Moreover, patient monitoring indicates that the iNOS enzyme expression and NO plasma levels may play a role in assessing the severity of septic conditions. Overall, in either monocytes or neutrophils, we pointed out the major role of NF-κB and Nrf2 in the pathophysiological process. Therefore, therapies targeted to redox abnormalities may be useful for better management of septic patients.

Effect of Nitric Oxide Pathway Inhibition on the Evolution of Anaphylactic Shock in Animal Models: A Systematic Review

Simple Summary

Anaphylactic shock (AS) is the most serious consequence of anaphylaxis, with life-threatening sequelae including hypovolemia, shock, and arrhythmias. The literature lacks evidence for the effectiveness of interventions other than epinephrine in the acute phase of anaphylaxis. Our objective was to assess, through a systematic review, how inhibition of nitric oxide (NO) pathways affects blood pressure, and whether such blockade improves survival in AS animal models. AS was induced in all included studies after or before drug administration that targeted blockade of the NO pathway. In all animal species studied, the induction of AS caused a reduction in arterial blood pressure. However, the results show different responses to the inhibition of nitric oxide pathways. Overall, seven of fourteen studies using inhibition of nitric oxide pathways as pre-treatment before induction of AS showed improvement of survival and/or blood pressure. Four post-treatment studies from eight also showed positive outcomes. This review did not find strong evidence to propose modulation of blockade of the NO/cGMP pathway as a definitive treatment for AS in humans. Well-designed in vivo AS animal pharmacological models are needed to explore the other pathways involved, supporting the concept of pharmacological modulation.

Abstract

Nitric oxide (NO) induces vasodilation in various types of shock. The effect of pharmacological modulation of the NO pathway in anaphylactic shock (AS) remains poorly understood. Our objective was to assess, through a systematic review, whether inhibition of NO pathways (INOP) was beneficial for the prevention and/or treatment of AS. A predesigned protocol for this systematic review was published in PROSPERO (CRD42019132273). A systematic literature search was conducted till March 2022 in the electronic databases PubMed, EMBASE, Scopus, Cochrane and Web of Science. Heterogeneity of the studies did not allow meta-analysis. Nine hundred ninety unique studies were identified. Of 135 studies screened in full text, 17 were included in the review. Among six inhibitors of NO pathways identified, four blocked NO synthase activity and two blocked guanylate cyclase downstream activity. Pre-treatment was used in nine studies and post-treatment in three studies. Five studies included both pre-treatment and post-treatment models. Overall, seven pre-treatment studies from fourteen showed improvement of survival and/or arterial blood pressure. Four post-treatment studies from eight showed positive outcomes. Overall, there was no strong evidence to conclude that isolated blockade of the NO/cGMP pathway is sufficient to prevent or restore anaphylactic hypotension. Further studies are needed to analyze the effect of drug combinations in the treatment of AS.

Impaired Myocardial Mitochondrial Function in an Experimental Model of Anaphylactic Shock

Anaphylactic shock (AS) is associated with a profound vasodilation and cardiac dysfunction. The cellular mechanisms underlying AS-related cardiac dysfunction are unknown. We hypothesized that myocardial mitochondrial dysfunction may be associated with AS cardiac dysfunction. In controls and sensitized Brown Norway rats, shock was induced by ovalbumin i.v bolus, and abdominal aortic blood flow (ABF), systemic mean arterial pressure (MAP), and lactatemia were measured for 15 min. Myocardial mitochondrial function was assessed with the evaluation of mitochondrial respiration, oxidative stress production by reactive oxygen species (ROS), reactive nitrogen species (RNS), and the measurement of superoxide dismutases (SODs) activity. Oxidative damage was assessed by lipid peroxidation. The mitochondrial ultrastructure was assessed using transmission electronic microscopy. AS was associated with a dramatic drop in ABF and MAP combined with a severe hyperlactatemia 15 min after shock induction. CI-linked substrate state (197 ± 21 vs. 144 ± 21 pmol/s/mg, p < 0.05), OXPHOS activity by complexes I and II (411 ± 47 vs. 246 ± 33 pmol/s/mg, p < 0.05), and OXPHOS activity through complex II (316 ± 40 vs. 203 ± 28 pmol/s/mg, p < 0.05) were significantly impaired. ROS and RNS production was not significantly increased, but SODs activity was significantly higher in the AS group (11.15 ± 1.02 vs. 15.50 ± 1.40 U/mL/mg protein, p = 0.02). Finally, cardiac lipid peroxidation was significantly increased in the AS group (8.50 ± 0.67 vs. 12.17 ± 1.44 µM/mg protein, p < 0.05). No obvious changes were observed in the mitochondrial ultrastructure between CON and AS groups. Our experimental model of AS results in rapid and deleterious hemodynamic effects and was associated with a myocardial mitochondrial dysfunction with oxidative damage and without mitochondrial ultrastructural injury.

Pathophysiological, Cellular, and Molecular Events of the Vascular System in Anaphylaxis

Anaphylaxis is a systemic hypersensitivity reaction that can be life threatening. Mechanistically, it results from the immune activation and release of a variety of mediators that give rise to the signs and symptoms of this pathological event. For years, most of the research in anaphylaxis has focused on the contribution of the immune component. However, approaches that shed light on the participation of other cellular and molecular agents are necessary. Among them, the vascular niche receives the various signals (e.g., histamine) that elicit the range of anaphylactic events. Cardiovascular manifestations such as increased vascular permeability, vasodilation, hypotension, vasoconstriction, and cardiac alterations are crucial in the pathophysiology of anaphylaxis and are highly involved to the development of the most severe cases. Specifically, the endothelium, vascular smooth muscle cells, and their molecular signaling outcomes play an essential role downstream of the immune reaction. Therefore, in this review, we synthesized the vascular changes observed during anaphylaxis as well as its cellular and molecular components. As the risk of anaphylaxis exists both in clinical procedures and in routine life, increasing our knowledge of the vascular physiology and their molecular mechanism will enable us to improve the clinical management and how to treat or prevent anaphylaxis.

Key Message

Anaphylaxis, the most severe allergic reaction, involves a variety of immune and non-immune molecular signals that give rise to its pathophysiological manifestations. Importantly, the vascular system is engaged in processes relevant to anaphylactic events such as increased vascular permeability, vasodilation, hypotension, vasoconstriction, and decreased cardiac output. The novelty of this review focuses on the fact that new studies will greatly improve the understanding of anaphylaxis when viewed from a vascular molecular angle and specifically from the endothelium. This knowledge will improve therapeutic options to treat or prevent anaphylaxis.

Gases in Sepsis: Novel Mediators and Therapeutic Targets

Sepsis, a potentially lethal condition resulting from failure to control the initial infection, is associated with a dysregulated host defense response to pathogens and their toxins. Sepsis remains a leading cause of morbidity, mortality and disability worldwide. The pathophysiology of sepsis is very complicated and is not yet fully understood. Worse still, the development of effective therapeutic agents is still an unmet need and a great challenge. Gases, including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), are small-molecule biological mediators that are endogenously produced, mainly by enzyme-catalyzed reactions. Accumulating evidence suggests that these gaseous mediators are widely involved in the pathophysiology of sepsis. Many sepsis-associated alterations, such as the elimination of invasive pathogens, the resolution of disorganized inflammation and the preservation of the function of multiple organs and systems, are shaped by them. Increasing attention has been paid to developing therapeutic approaches targeting these molecules for sepsis/septic shock, taking advantage of the multiple actions played by NO, CO and H2S. Several preliminary studies have identified promising therapeutic strategies for gaseous-mediator-based treatments for sepsis. In this review article, we summarize the state-of-the-art knowledge on the pathophysiology of sepsis; the metabolism and physiological function of NO, CO and H2S; the crosstalk among these gaseous mediators; and their crucial effects on the development and progression of sepsis. In addition, we also briefly discuss the prospect of developing therapeutic interventions targeting these gaseous mediators for sepsis.

Disruption of Kidney-Immune System Crosstalk in Sepsis with Acute Kidney Injury: Lessons Learned from Animal Models and Their Application to Human Health

In addition to being a leading cause of morbidity and mortality worldwide, sepsis is also the most common cause of acute kidney injury (AKI). When sepsis leads to the development of AKI, mortality increases dramatically. Since the cardinal feature of sepsis is a dysregulated host response to infection, a disruption of kidney-immune crosstalk is likely to be contributing to worsening prognosis in sepsis with acute kidney injury. Since immune-mediated injury to the kidney could disrupt its protein manufacturing capacity, an investigation of molecules mediating this crosstalk not only helps us understand the sepsis immune response, but also suggests that their supplementation could have a therapeutic effect. Erythropoietin, vitamin D and uromodulin are known to mediate kidney-immune crosstalk and their disrupted production could impact morbidity and mortality in sepsis with acute kidney injury.

The 'cytokine storm': molecular mechanisms and therapeutic prospects

Cytokine storm syndrome (CSS) has generally been described as a collection of clinical manifestations resulting from an overactivated immune system. Cytokine storms (CSs) are associated with various pathologies, as observed in infectious diseases, certain acquired or inherited immunodeficiencies and autoinflammatory diseases, or following therapeutic interventions. Despite the role of CS in tissue damage and multiorgan failure, a systematic understanding of its underlying molecular mechanisms is lacking. Recent studies demonstrate a positive feedback loop between cytokine release and cell death pathways; certain cytokines, pathogen-associated molecular patterns (PAMPs), and damage-associated molecular patterns (DAMPs), can activate inflammatory cell death, leading to further cytokine secretion. Here, we discuss recent progress in innate immunity and inflammatory cell death, providing insights into the cellular and molecular mechanisms of CSs and therapeutics that might quell ensuing life-threatening effects.

Vasopressin and copeptin release during sepsis and septic shock

Sepsis is defined as a potentially fatal organ dysfunction caused by a dysregulated host response to infection. Despite tremendous progress in the medical sciences, sepsis remains one of the leading causes of morbidity and mortality worldwide. The host response to sepsis and septic shock involves changes in the immune, autonomic, and neuroendocrine systems. Regarding neuroendocrine changes, studies show an increase in plasma vasopressin (AVP) concentrations followed by a decline, which may be correlated with septic shock. AVP is a peptide hormone derived from a larger precursor (preprohormone), along with two peptides, neurophysin II and copeptin. AVP is synthesized in the hypothalamus, stored and released from the neurohypophysis into the bloodstream by a wide range of stimuli. The measurement of AVP has limitations due to its plasma instability and short half-life. Copeptin is a more stable peptide than AVP, and its immunoassay is feasible. The blood concentrations of copeptin mirror those of AVP in many physiological states; paradoxically, during sepsis-related organ dysfunction, an uncoupling between copeptin and AVP blood levels appears to happen. In this review, we focus on clinical and experimental studies that analyzed AVP and copeptin blood concentrations over time in sepsis. The findings suggest that AVP and copeptin behave similarly in the early stages of sepsis; however, we did not find a proportional decrease in copeptin concentrations as seen with AVP during septic shock. Copeptin levels were higher in nonsurvivors than in survivors, suggesting that copeptin may work as a marker of severity or sepsis-related organ dysfunction.

Vasopressor-Sparing Action of Methylene Blue in Severe Sepsis and Shock: A Narrative Review

Shock is a serious acute circulatory failure leading to inadequate oxygen delivery to the cells. Its treatment is mainly based on circulating fluid optimization, and vasopressors to provide an adequate mean arterial pressure and microcirculatory flow. Norepinephrine is the drug of choice, but high dosages may be responsible for several side effects, including increased myocardial oxygen consumption, dysrhythmias, and peripheral and organ ischemia. Moreover, some patients are “non-responders” to first-line norepinephrine treatment. Hence, other drugs have been proposed to reach and maintain the hemodynamic target. In general, they are described as catecholamine-sparing agents. Among others, the most used are vasopressin, corticosteroids, and angiotensin II. Methylene blue (MB) represents a further option, even though its use is still a topic of controversy. This review article tries to summarize what is known and unknown about the actions of MB in patients in shock. It reduces excessive production of nitric oxide via blockade of guanylate cyclase in shock states. At present, it appears the MB provides positive results in septic shock, if administered early. Further randomized controlled trials are warranted regarding its use to provide more precise indications to physicians involved in the treatment of such patients.

HDAC6 Mediates Macrophage iNOS Expression and Excessive Nitric Oxide Production in the Blood During Endotoxemia

Excessive nitric oxide (NO) production and NO-mediated nitrative stress contribute to vascular dysfunction, inflammation, and tissue injury in septic shock. New therapeutic targets are urgently needed to provide better control of NO level during septic shock. In the present study, we investigated the role of HDAC6 in the regulation of NO production and nitrative stress in a mouse model of endotoxin-induced septic shock. HDAC6 deficient mice and a specific HDAC6 inhibitor were utilized in our studies. Our data clearly indicate that HDAC6 is an important mediator of NO production in macrophages. HDAC6 mediates NO production through the regulation of iNOS expression in macrophages. HDAC6 up-regulates iNOS expression in macrophages by modulating STAT1 activation and IRF-1 expression. HDAC6 inhibition potently blocked endotoxin-induced STAT1 activation and iNOS expression in macrophages. Furthermore, HDAC6 contributes to excessive NO production and nitrotyrosine level in the blood and promotes iNOS expression in the lung tissues during septic shock. Our data reveal a novel HDAC6/STAT1/iNOS pathway that mediates excessive NO production and nitrative stress in septic shock.

Intravenous Arginine Administration Benefits CD4+ T-Cell Homeostasis and Attenuates Liver Inflammation in Mice with Polymicrobial Sepsis

This study investigated the effects of a single dose of arginine (Arg) administration at the beginning of sepsis on CD4+ T-cell regulation and liver inflammation in C57BL/6J mice. Mice were divided into normal control (NC), sham (SH), sepsis saline (SS), and sepsis Arg (SA) groups. An inducible nitric oxide (NO) synthase (iNOS) inhibitor was administered to additional sepsis groups to evaluate the role of NO during sepsis. Sepsis was induced using cecal ligation and puncture (CLP). The SS and SA groups received saline or Arg (300 mg/kg body weight) via tail vein 1 h after CLP. Mice were euthanized at 12 and 24 h post-CLP. Blood, para-aortic lymph nodes, and liver tissues were collected for further measurement. The findings showed that sepsis resulted in decreases in blood and para-aortic lymph node CD4+ T-cell percentages, whereas percentages of interleukin (IL)-4- and IL-17-expressing CD4+ T cells were upregulated. Compared to the SS group, Arg administration resulted in maintained circulating and para-aortic lymph node CD4+ T cells, an increased Th1/Th2 ratio, and a reduced Th17/Treg ratio post-CLP. In addition, levels of plasma liver injury markers and expression of inflammatory genes in liver decreased. These results suggest that a single dose of Arg administered after CLP increased Arg availability, sustained CD4+ T-cell populations, elicited more-balanced Th1/Th2/Th17/Treg polarization in the circulation and the para-aortic lymph nodes, and attenuated liver inflammation in sepsis. The favorable effects of Arg were abrogated when an iNOS inhibitor was administered, which indicated that NO may be participated in regulating the homeostasis of Th/Treg cells and subsequent liver inflammation during sepsis.

Bench to bedside review: therapeutic modulation of nitric oxide in sepsis-an update

Nitric oxide is a signalling molecule with an extensive range of functions in both health and disease. Discovered in the 1980s through work that earned the Nobel prize, nitric oxide is an essential factor in regulating cardiovascular, immune, neurological and haematological function in normal homeostasis and in response to infection. Early work implicated exaggerated nitric oxide synthesis as a potentially important driver of septic shock; however, attempts to modulate production through global inhibition of nitric oxide synthase were associated with increased mortality. Subsequent work has shown that regulation of nitric oxide production is determined by numerous factors including substrate and co-factor availability and expression of endogenous regulators. In sepsis, nitric oxide synthesis is dysregulated with exaggerated production leading to cardiovascular dysfunction, bioenergetic failure and cellular toxicity whilst at the same time impaired microvascular function may be driven in part by reduced nitric oxide synthesis by the endothelium. This bench to bedside review summarises our current understanding of the ways in which nitric oxide production is regulated on a tissue and cellular level before discussing progress in translating these observations into novel therapeutic strategies for patients with sepsis.

Fusigen Reduces Intracellular Reactive Oxygen Species and Nitric Oxide Levels

BACKGROUND/AIM

Oxidative stress caused by the production of excessive cellular reactive oxygen species (ROS) and high levels of nitric oxide contribute to several human pathologies. This study aimed to examine the anti-oxidant effects of fusigen, a compound produced from Aureobasidium melanogenum.

MATERIALS AND METHODS

Extracts of A. melanogenum were selected as a source for the isolation of fusigen. The anti-oxidant, nitric oxide suppression, as well as the free radical scavenging activities of fusigen were tested in BEAS-2B human bronchial epithelial cell line (BEAS-2B cells) and human dermal papilla cells (DP cells) using specific fluorescence dyes and flow cytometry analysis. Cell viability was determined by the MTT assay.

RESULTS

Fusigen did not exert cytotoxicity in the human normal BEAS-2B and DP cells at concentrations up to 100 μM. Fusigen decreased basal levels of cellular ROS, as well as the levels of ROS induced by hydrogen peroxide and ferrous ion enrichment. ROS decreasing effect was confirmed in DP cells. In addition, fusigen treatment suppressed intracellular NO levels in both BEAS-2B and DP cells.

CONCLUSION

The optimal process of production of purified fusigen from A. melanogenum was determined. Fusigen exhibited a low cytotoxic effect and the potential to suppress ROS and NO. These results demonstrated that fusigen may be used for the treatment or prevention of human diseases.

Anti-inflammatory activity of small-molecule antagonists of Toll-like receptor 2 (TLR2) in mice

Toll-like receptor 2 (TLR2) is currently investigated as a potential therapeutic target in diseases with underlying inflammation like sepsis and arthritis. We reported the discovery, by virtual screening and biological testing, of eight TLR2 antagonists (AT1-AT8) which showed TLR2-inhibitory activity in human cells (Murgueitio et al., 2014). In this study, we have deepened in the mechanism of action and selectivity (TLR2/1 or TLR2/6) of those compounds in mouse primary cells and in vivo. The antagonists reduced, in a dose-dependent way the TNFα production (e.g. AT5 IC₅₀ 7.4 μM) and also reduced the nitric oxide (NO) formation in mouse bone marrow-derived macrophages (BMDM). Treatment of BMDM with the antagonists showed that downstream of TLR2, MAPKs phosphorylation and IkBα degradation was reduced. Notably, in a mouse model of tri-acylated lipopeptide (Pam3CSK4)-induced inflammation, AT5 attenuated the TNFα and IL-6 inflammatory response. Further, the effect of AT5 in the stimulation of BMDM by the endogenous alarmin HMGB1 was investigated. Our results indicate that AT4-AT7 and, particularly AT5 appear as good starting points for the development of inhibitors targeting TLR2 in inflammatory disorders.

Evidence for a protective role for the rs805305 single nucleotide polymorphism of dimethylarginine dimethylaminohydrolase 2 (DDAH2) in septic shock through the regulation of DDAH activity

BACKGROUND

Dimethylarginine dimethylaminohydrolase 2 (DDAH2) regulates the synthesis of nitric oxide (NO) through the metabolism of the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA). Pilot studies have associated the rs805305 SNP of DDAH2 with ADMA concentrations in sepsis. This study explored the impact of the rs805305 polymorphism on DDAH activity and outcome in septic shock.

METHODS

We undertook a secondary analysis of data and samples collected during the Vasopressin versus noradrenaline as initial therapy in septic shock (VANISH) trial. Plasma and DNA samples isolated from 286 patients recruited into the VANISH trial were analysed. Concentrations of L-Arginine and the methylarginines ADMA and symmetric dimethylarginine (SDMA) were determined from plasma samples. Whole blood and buffy-coat samples were genotyped for polymorphisms of DDAH2. Clinical data collected during the study were used to explore the relationship between circulating methylarginines, genotype and outcome.

RESULTS

Peak ADMA concentration over the study period was associated with a hazard ratio for death at 28 days of 3.3 (95% CI 2.0-5.4), p < 0.001. Reduced DDAH activity measured by an elevated ADMA:SDMA ratio was associated with a reduced risk of death in septic shock (p = 0.03). The rs805305 polymorphism of DDAH2 was associated with reduced DDAH activity (p = 0.004) and 28-day mortality (p = 0.02). Mean SOFA score and shock duration were also reduced in the less common G:G genotype compared to heterozygotes and C:C genotype patients (p = 0.04 and p = 0.02, respectively).

CONCLUSIONS

Plasma ADMA is a biomarker of outcome in septic shock, and reduced DDAH activity is associated with a protective effect. The polymorphism rs805305 SNP is associated with reduced mortality, which is potentially mediated by reduced DDAH2 activity.

TRIAL REGISTRATION

ISRCTN Registry, ISRCTN20769191 . Registered on 20 September 2012.

Effects of Inducible Nitric Oxide Synthase Inhibition on Cardiovascular Risk of Adult Endotoxemic Female Rats: Role of Estrogen

Aim: Autonomic modulation responds to ovarian hormones and estrogen increases nitric oxide bioavailability. Also, females have minor susceptibility to sepsis and a higher survival rate. However, few studies have evaluated the role of estrogen in cardiovascular, autonomic, and oxidative parameters during initial endotoxemia and under inducible nitric oxide synthase (iNOS) inhibition in female rats.

Methods: Female wistar rats were subjected to ovariectomy and divided into three groups: OVX (ovariectomized), OVX+E (OVX plus daily estradiol) and SHAM (false surgery). After 8 weeks, mean arterial pressure (MAP) and heart rate (HR) were recorded in non-anesthetized catheterized rats, before and after intravenous LPS injection, preceded by S-methylisothiourea sulfate (SMT) injection, or sterile saline. Cardiovascular recordings underwent spectral analysis for evaluation of autonomic modulation. Two hours after LPS, plasma was collected to assess total radical-trapping antioxidant (TRAP), nitrite levels (NO2), lipoperoxidation (LOOH), and paraoxonase 1 (PON1) activity.

Results: Two hours after LPS, females treated with SMT presented a decrease of MAP, when compared to saline-LPS groups. At this same time, all SMT+LPS groups presented an increase of sympathetic and a decrease of parasympathetic modulation of HR. Two hours after saline+LPS, OVX presented decreased total radical-trapping antioxidant (TRAP) compared to SHAM. When treated with SMT+LPS, OVX did not altered TRAP, while estradiol reduced LOOH levels.

Conclusion: iNOS would be responsible for sympathetic inhibition and consumption of antioxidant reserves of females during endotoxemia, since iNOS is inhibited, treatment with estradiol could be protective in inflammatory challenges.

Prognostic value of the biomarkers serum amyloid A and nitric oxide in patients with sepsis

OBJECTIVE

Sepsis is a major cause of mortality among critically ill patients in the intensive care unit (ICU). Alterations in serum amyloid A (SAA) and nitric oxide (NO) levels have been associated with mortality in critically ill patients. In the present study, we investigated the predictive value of SAA and/or NO compared to traditional predictive markers such as C-reactive protein (CRP) and Acute Physiology and Chronic Health Evaluation II (APACHE II) score.

METHODS

100 adult patients with sepsis and 25 without sepsis were enrolled in a prospective, randomized study in our ICU. The APACHE II score was calculated, and their peripheral venous blood SAA, NO and CRP levels were evaluated on days 1, 3, and 7 after sepsis was diagnosed. The patients were sorted based on incidence of septic shock into septic shock (A) and non-septic shock (B) groups. Comparative analyses of altered levels of these indicators between the two groups were performed, and correlations between SAA, NO, and the more traditional APACHE II score were probed. Patients were sorted based on survival status into death (D) and survival (S) groups based on death endpoint within 28 days after admission.

RESULTS

We observed that the difference in APACHE II score, SAA and CRP levels were statistically significantly (p < 0.05) between groups A and B on days 1, 3 and 7 post-diagnosis, while inter-group NO level significantly differed (p < 0.05) on days 1 and 3 post-diagnosis, no apparent difference was observed on day 7 post-diagnosis. For groups D and S, SAA, CRP and NO levels significantly differed (p < 0.05) on days 3 and 7 post-diagnosis, with no apparent difference on day 1. APACHE II score was significantly different on day 7 (p < 0.05), however the difference on days 1 and 3 were non-significant. We also demonstrated a positive correlation between APACHE II scores, SAA levels on days 1, 3, and 7, as well as NO levels on days 1 and 3. In addition, for the D and S groups, SAA at all time points, NO on day 3 and CRP on day 7 positively correlated with increased death events.

CONCLUSION

The dynamic monitoring of SAA and NO serum levels with APACHE II scores better reflect the severity of sepsis than traditional indicators like CRP and may serve as independent prognosticators of sepsis in critically ill patients, shorten time to diagnosis confirmation and improve therapeutic decision-making.

Skin microcirculatory reactivity assessed using a thermal challenge is decreased in patients with circulatory shock and associated with outcome

Background

Shock states are characterized by impaired tissue perfusion and microcirculatory alterations, which are directly related to outcome. Skin perfusion can be noninvasively evaluated using skin laser Doppler (SLD), which, when coupled with a local thermal challenge, may provide a measure of microcirculatory reactivity. We hypothesized that this microvascular reactivity would be impaired in patients with circulatory shock and would be a marker of severity.

Methods

We first evaluated skin blood flow (SBF) using SLD on the forearm and on the palm in 18 healthy volunteers to select the site with maximal response. Measurements were taken at 37 °C (baseline) and repeated at 43 °C. The 43 °C/37 °C SBF ratio was calculated as a measure of microvascular reactivity. We then evaluated the SBF in 29 patients with circulatory shock admitted to a 35-bed department of intensive care and in a confirmatory cohort of 35 patients with circulatory shock.

Results

In the volunteers, baseline SBF was higher in the hand than in the forearm, but the SBF ratio was lower (11.2 [9.4–13.4] vs. 2.0 [1.7–2.6], p < 0.01) so we used the forearm for our patients. Baseline forearm SBF was similar in patients with shock and healthy volunteers, but the SBF ratio was markedly lower in the patients (2.6 [2.0–3.6] vs. 11.2 [9.4–13.4], p < 0.01). Shock survivors had a higher SBF ratio than non-survivors (3.2 [2.2–6.2] vs. 2.3 [1.7–2.8], p < 0.01). These results were confirmed in the second cohort of 35 patients. In multivariable analysis, the APACHE II score and the SBF ratio were independently associated with mortality.

Conclusions

Microcirculatory reactivity is decreased in patients with circulatory shock and has prognostic value. This simple, noninvasive test could help in monitoring the peripheral microcirculation in acutely ill patients.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0393-7) contains supplementary material, which is available to authorized users.

Comparison of Chemical Profiles, Anti-Inflammatory Activity, and UPLC-Q-TOF/MS-Based Metabolomics in Endotoxic Fever Rats between Synthetic Borneol and Natural Borneol

Natural borneol (NB, called “Bingpian”) is an important traditional Chinese medicine to restore consciousness, remove heat and relieve pain, all of which are inflammation-related diseases. Recently, due to the limited source of NB, synthetic borneol (SB) is widely used as a substitute for NB in clinics. However, little is known about the effects of SB instead of NB. Herein, the aim of the present study was to compare NB and SB on chemical profiles by gas chromatography-mass spectrometer (GC-MS) analysis, anti-inflammatory activity in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages, and ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) metabolomic approaches in endotoxic fever induced in rats. Results showed that, in total, 13 volatile components could be identified in NB and SB by GC-MS analysis, in which a significant difference between them still existed. The main constituents in SB were iso-borneol and borneol, while borneol contributes to 98.96% of the amount in NB. Additionally, both NB and SB exhibited remarkable anti-inflammatory effects to reduce the level of inflammatory factors including NO, TNF-α and IL-6 in LPS-induced RAW 264.7 macrophages, and lower the high body temperature in rats with endotoxic fever induced by LPS. Moreover, it seems that NB exhibited higher efficacy than SB. The unequal bioactive efficiency between NB and SB was also indicated by means of non-targeting metabolomics. Based on UPLC-Q-TOF/MS technology, 12 biomarkers in the serum of fever rats were identified. Pathway analysis revealed that the anti-fever effect of NB and SB was related to regulating the abnormal glycerophospholipid, linoleic acid and alpha-linoleic acid metabolism pathways in the fever model. Results indicated that there was still a great difference between NB and SB involving chemical constituents, anti-inflammation activity and the ability to regulate the abnormal metabolism pathways of the fever model. Certainly, further studies are warranted to better understand the replacement rationale in medicinal application.

Activation of mTOR/IκB-α/NF-κB pathway contributes to LPS-induced hypotension and inflammation in rats

Mammalian target of rapamycin (mTOR), a serine/threonine kinase plays an important role in various pathophysiological processes including cancer, metabolic diseases, and inflammation. Although mTOR participates in Toll-like receptor 4 signalling in different cell types, the role of this enzyme in sepsis pathogenesis and its effects on hypotension and inflammation in endotoxemic rats remains unclear. In this study we investigated the effects of mTOR inhibition on lipopolysaccharide (LPS)-induced changes on expressions and/or activities of ribosomal protein S6 (rpS6), an mTOR substrate, nuclear factor-κB (NF-κB) p65, inhibitor κB (IκB)-α, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 with production of nitric oxide, peroxynitrite, prostacyclin, and tumor necrosis factor (TNF)-α and activity of myeloperoxidase (MPO), which results in hypotension and inflammation. Injection of LPS (10mg/kg, i.p.) to male Wistar rats decreased blood pressure and increased heart rate that were associated with elevated nitrotyrosine, 6-keto-PGF_1α, and TNF-α levels and MPO activity, and increased expressions and/or activities of rpS6, NF-κB p65, iNOS, and COX-2 and decreased expression of IκB-α in renal, cardiac, and vascular tissues. LPS also increased serum and tissue nitrite levels. Rapamycin (1mg/kg, i.p.) given one h after injection of LPS reversed these effects of LPS. These data suggest that the activation of mTOR/IκB-α/NF-κB pathway associated with vasodilator and proinflammatory mediator formation contributes to LPS-induced hypotension and inflammation.

Diagnosis of anaphylactic death in forensics: Review and future perspectives

The diagnosis of anaphylaxis in a pre- or post-mortal phase involves the formulation of problems not yet solved by the international scientific literature, due to the complexity of pathogenic factors and pathophysiological processes that characterizes it. For forensic autopsies, further problems of differential diagnosis arise and often leave the forensic pathologist unable to express an opinion of certainty, as a result of lack of case history, circumstantial and autoptical-histopathological data. Nevertheless, in routine cases the postmortem diagnosis of anaphylactic death continues to be based on exclusion and circumstantial evidence. The author, after an extensive review of the literature relating to deaths from anaphylaxis of forensic pathological interest, and a discussion of the microscopical and biochemical findings, proposes a diagnostic protocol for forensic purposes and evaluates the diagnostic perspectives enabled by the newly available analytic techniques and markers. Maybe, the application of omics methodologies could help in the future for anaphylaxis diagnosis.

The neutrophil elastase inhibitor, sivelestat, attenuates sepsis-related kidney injury in rats

Sepsis-induced acute kidney injury (AKI) represents a major cause of mortality in intensive care units. Sivelestat, a selective inhibitor of neutrophil elastase (NE), can attenuate sepsis-related acute lung injury. However, whether sivelestat can preserve kidney function during sepsis remains unclear. In this study, we thus examined the effects of sivelestat on sepsis-related AKI. Cecal ligation and puncture (CLP) was performed to induce multiple bacterial infection in male Sprague-Dawley rats, and subsequently, 50 or 100 mg/kg sivelestat were administered by intraperitoneal injection immediately after the surgical procedure. In the untreated rats with sepsis, the mean arterial pressure (MAP) and glomerular filtration rate (GFR) were decreased, whereas serum blood urea nitrogen (BUN) and neutrophil gelatinase-associated lipocalin (NGAL) levels were increased. We found that sivelestat promoted the survival of the rats with sepsis, restored the impairment of MAP and GFR, and inhibited the increased BUN and NGAL levels; specifically, the higher dose was more effective. In addition, sivelestat suppressed the CLP-induced macrophage infiltration, the overproduction of pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1β, high-mobility group box 1 and inducible nitric oxide synthase) and serine/threonine kinase (Akt) pathway activation in the rats. Collectively, our data suggest that the inhibition of NE activity with the inhibitor, sivelestat, is beneficial in ameliorating sepsis-related kidney injury.

Hypoxia causes increased monocyte nitric oxide synthesis which is mediated by changes in dimethylarginine dimethylaminohydrolase 2 expression in animal and human models of normobaric hypoxia

BACKGROUND

Tissue hypoxia is a cardinal feature of inflammatory diseases and modulates monocyte function. Nitric oxide is a crucial component of the immune cell response. This study explored the metabolism of the endogenous inhibitor of nitric oxide production asymmetric dimethylarginine(ADMA) by monocyte dimethylarginine dimethylaminohydrolase 2(DDAH2), and the role of this pathway in the regulation of the cellular response and the local environment during hypoxia.

METHODS

Peritoneal macrophages were isolated from a macrophage-specific DDAH2 knockout mouse that we developed and compared with appropriate controls. Cells were exposed to 3% oxygen followed by reoxygenation at 21%. Healthy volunteers underwent an 8 h exposure to normobaric hypoxia with an inspired oxygen percentage of 12%. Peripheral blood mononuclear cells were isolated from blood samples taken before and at the end of this exposure.

RESULTS

Intracellular nitrate plus nitrite(NOx) concentration was higher in wild-type murine monocytes after hypoxia and reoxygenation than in normoxia-treated cells (mean(SD) 13·2(2·4) vs 8·1(1·7) pmols/mg protein, p = 0·009). DDAH2 protein was 4·5-fold (SD 1·3) higher than in control cells (p = 0·03). This increase led to a 24% reduction in ADMA concentration, 0·33(0.04) pmols/mg to 0·24(0·03), p = 0·002). DDAH2-deficient murine monocytes demonstrated no increase in nitric oxide production after hypoxic challenge. These findings were recapitulated in a human observational study. Mean plasma NOx concentration was elevated after hypoxic exposure (3·6(1.8)μM vs 6·4(3·2), p = 0·01), which was associated with a reduction in intracellular ADMA in paired samples from 3·6(0.27) pmols/mg protein to 3·15(0·3) (p < 0·01). This finding was associated with a 1·9-fold(0·6) increase in DDAH2 expression over baseline(p = 0·03).

DISCUSSION

This study shows that in both human and murine models of acute hypoxia, increased DDAH2 expression mediates a reduction in intracellular ADMA concentration which in turn leads to elevated nitric oxide concentrations both within the cell and in the local environment. Cells deficient in DDAH2 were unable to mount this response.

S-nitrosothiols dilate the mesenteric artery more potently than the femoral artery by a cGMP and L-type calcium channel-dependent mechanism

S-nitrosothiols (SNOs) are metabolites of NO with potent vasodilatory activity. Our previous studies in sheep indicated that intra-arterially infused SNOs dilate the mesenteric vasculature more than the femoral vasculature. We hypothesized that the mesenteric artery is more responsive to SNO-mediated vasodilation, and investigated various steps along the NO/cGMP pathway to determine the mechanism for this difference. In anesthetized adult sheep, we monitored the conductance of mesenteric and femoral arteries during infusion of S-nitroso-l-cysteine (L-cysNO), and found mesenteric vascular conductance increased (137 ± 3%) significantly more than femoral conductance (26 ± 25%). Similar results were found in wire myography studies of isolated sheep mesenteric and femoral arteries. Vasodilation by SNOs was attenuated in both vessel types by the presence of ODQ (sGC inhibitor), and both YC-1 (sGC agonist) and 8-Br-cGMP (cGMP analog) mediated more potent relaxation in mesenteric arteries than femoral arteries. The vasodilatory difference between mesenteric and femoral arteries was eliminated by antagonists of either protein kinase G or L-type Ca(2+) channels. Western immunoblots showed a larger L-type Ca(2+)/sGC abundance ratio in mesenteric arteries than in femoral arteries. Fetal sheep mesenteric arteries were more responsive to SNOs than adult mesenteric arteries, and had a greater L-Ca(2+)/sGC ratio (p = 0.047 and r = -0.906 for correlation between Emax and L-Ca(2+)/sGC). These results suggest that mesenteric arteries, especially those in fetus, are more responsive to SNO-mediated vasodilation than femoral arteries due to a greater role of the L-type calcium channel in the NO/cGMP pathway.

Two N-(2-phenylethyl)nitroaniline derivatives as precursors for slow and sustained nitric oxide release agents

Notwithstanding its simple structure, the chemistry of nitric oxide (NO) is complex. As a radical, NO is highly reactive. NO also has profound effects on the cardiovascular system. In order to regulate NO levels, direct therapeutic interventions include the development of numerous NO donors. Most of these donors release NO in a single high-concentration burst, which is deleterious. N-Nitrosated secondary amines release NO in a slow, sustained, and rate-tunable manner. Two new precursors to sustained NO-releasing materials have been characterized. N-[2-(3,4-Dimethoxyphenyl)ethyl]-2,4-dinitroaniline, C16H17N3O6, (I), crystallizes with one independent molecule in the asymmetric unit. The adjacent amine and nitro groups form an intramolecular N-H...O hydrogen bond. The anti conformation about the phenylethyl-to-aniline C-N bond leads to the planes of the arene and aniline rings being approximately perpendicular. Molecules are linked into dimers by weak intermolecular N-H...O hydrogen bonds such that each amine H atom participates in a three-center interaction with two nitro O atoms. The dimers pack so that the arene rings of adjacent molecules are not parallel and π-π interactions do not appear to be favored. N-(4-Methylsulfonyl-2-nitrophenyl)-L-phenylalanine, C16H16N2O6S, (II), with an optically active center, also crystallizes with one unique molecule in the asymmetric unit. The L enantiomer was established via the configuration of the starting material and was confirmed by refinement of the Flack parameter. As in (I), there is an intramolecular N-H...O hydrogen bond between adjacent amine and nitro groups. The conformation of the molecule is such that the arene rings display a dihedral angle of ca 60°. Unlike (I), molecules are not linked via intermolecular N-H...O hydrogen bonds. Rather, the carboxylic acid H atom forms a classic, approximately linear, O-H...O hydrogen bond with a sulfone O atom. Pairs of molecules related by twofold rotation axes are linked into dimers by two such interactions. The packing pattern features a zigzag arrangement of the arene rings without apparent π-π interactions. These structures are compared with reported analogues, revealing significant differences in molecular conformation, intermolecular interactions, and packing that result from modest changes in functional groups. The structures are discussed in terms of potential NO-release capability.

Local and systemic vasodilatory effects of low molecular weight S-nitrosothiols

S-nitrosothiols (SNOs) such as S-nitroso-L-cysteine (L-cysNO) are endogenous compounds with potent vasodilatory activity. During circulation in the blood, the NO moiety can be exchanged among various thiol-containing compounds by S-transnitrosylation, resulting in SNOs with differing capacities to enter the cell (membrane permeability). To determine whether the vasodilating potency of SNOs is dependent upon membrane permeability, membrane-permeable L-cysNO and impermeable S-nitroso-D-cysteine (D-cysNO) and S-nitroso-glutathione (GSNO) were infused into one femoral artery of anesthetized adult sheep while measuring bilateral femoral and systemic vascular conductances. L-cysNO induced vasodilation in the infused hind limb, whereas D-cysNO and GSNO did not. L-cysNO also increased intracellular NO in isolated arterial smooth muscle cells, whereas GSNO did not. The infused SNOs remained predominantly in a low molecular weight form during first-passage through the hind limb vasculature, but were converted into high molecular weight SNOs upon systemic recirculation. At systemic concentrations of ~0.6 μmol/L, all three SNOs reduced mean arterial blood pressure by ~50%, with pronounced vasodilation in the mesenteric bed. Pharmacokinetics of L-cysNO and GSNO were measured in vitro and in vivo and correlated with their hemodynamic effects, membrane permeability, and S-transnitrosylation. These results suggest local vasodilation by SNOs in the hind limb requires membrane permeation, whereas systemic vasodilation does not. The systemic hemodynamic effects of SNOs occur after equilibration of the NO moiety amongst the plasma thiols via S-transnitrosylation.

Inhibition of complement C3 might rescue vascular hyporeactivity in a conscious hemorrhagic shock rat model

BACKGROUND

Vascular hyporeactivity in severe hemorrhagic shock could induce refractory hypotension and is an important cause of death. The global acute inflammatory response induced in shock triggers the over-expression of reactive oxygen species, NO, ET1 and TNF-α, which play essential roles in the pathology of vascular hyporeactivity. This leads to a hypothesis that inhibition of the complement system, the mediator of the inflammatory cascade, might be a promising therapeutic exploration for vascular hyporeactivity.

METHODS

We use cobra venom factor (CVF) and the soluble form of CR1 (sCR1) which deplete or inhibit complement C3 respectively to examine its role in vascular hyporeactivity in a conscious hemorrhagic shock rat model.

RESULTS

We first confirmed the over-activation of C3 during shock and the down-regulation effects of CVF and sCR1 on C3. Then, both CVF and sCR1 could significantly mitigate the over-expression of serum NO, ET-1, TNF-α and reactive oxygen species. Finally, the vascular reactivity of superior mesenteric arteries (SMA) was examined in vitro, which confirmed the massive reduction of vascular reactivity in shock, which was significantly rescued by both CVF and sCR1.

CONCLUSIONS

Inhibition of C3 might improve the reactivity of SMA to norepinephrine during hemorrhagic shock possibly through the downregulation of NO, ET1, TNF-α and reactive oxygen radicals.

Nitric oxide inhibition strategies

Nitric oxide is involved in many physiologic processes. There are efforts, described elsewhere in this volume, to deliver nitric oxide to tissues as a therapy. Nitric oxide also contributes to pathophysiologic processes. Inhibiting nitric oxide or its production can thus also be of therapeutic benefit. This article addresses such inhibitory strategies.

Cardiovascular and pharmacological implications of haem-deficient NO-unresponsive soluble guanylate cyclase knock-in mice

Oxidative stress, a central mediator of cardiovascular disease, results in loss of the prosthetic haem group of soluble guanylate cyclase (sGC), preventing its activation by nitric oxide (NO). Here we introduce Apo-sGC mice expressing haem-free sGC. Apo-sGC mice are viable and develop hypertension. The haemodynamic effects of NO are abolished, but those of the sGC activator cinaciguat are enhanced in apo-sGC mice, suggesting that the effects of NO on smooth muscle relaxation, blood pressure regulation and inhibition of platelet aggregation require sGC activation by NO. Tumour necrosis factor (TNF)-induced hypotension and mortality are preserved in apo-sGC mice, indicating that pathways other than sGC signalling mediate the cardiovascular collapse in shock. Apo-sGC mice allow for differentiation between sGC-dependent and -independent NO effects and between haem-dependent and -independent sGC effects. Apo-sGC mice represent a unique experimental platform to study the in vivo consequences of sGC oxidation and the therapeutic potential of sGC activators.

Haem-free, NO-insensitive soluble guanylate cyclase (apo-sGC) generated during oxidative stress contributes to cardiovascular pathology. By generating and characterizing apo-sGC knock-in mice, Thoonen et al. provide a scientific ground for the therapeutic concept of sGC activators, and dissect the relevance of the NO-sGC axis.

Protective effects of Sparstolonin B, a selective TLR2 and TLR4 antagonist, on mouse endotoxin shock

Sepsis is characterized by an overwhelming systemic inflammation and multiple organ injury. Toll-like receptors (TLRs) 2 and 4 mediate these inflammatory responses. Sparstolonin B (SsnB), isolated from Chinese herb Scirpus yagara, is a new selective TLR2/4 antagonist. Herein, we report that SsnB inhibited the expression of various inflammatory mediators such as tumor necrosis factor (TNF-α), interleukin (IL)-1β, IL-6, and chemokine (C-C motif) ligand 2 (CCL-2) in lipopolysaccharide (LPS)- or Pam3csk4-stimulated macrophages. Moreover, in LPS-stimulated macrophages, the downregulation of peroxisome proliferator-activated receptor γ (PPAR-γ) was reversed by SsnB dose-dependently; and SsnB had synergistic inhibitory effects with rosiglitazone, a PPAR-γ agonist, on TNF-α and IL-6 expression in LPS-stimulated macrophages. The effects of SsnB were further evaluated in a mouse endotoxin shock model. When intraperitoneal injected in mice 2 days before or 1-2h after LPS challenge, SsnB attenuated the body temperature reduction and decreased the mortality. SsnB pre-treatment significantly suppressed LPS-induced increase of TNF-α and IL-6 in serum, lungs and livers, and substantially attenuated lung dysfunction in mice. In vivo toxicity test showed that at doses as high as 500 mg/kg, SsnB did not cause death of mice. These results suggest that SsnB protects mice against endotoxin shock by inhibiting production of multiple cytokines and lung dysfunction. In conclusion, our findings indicate that SsnB may be used in the prevention and treatment of endotoxin shock.

Cromoglycate, not ketotifen, ameliorated the injured effect of warm ischemia/reperfusion in rat liver: role of mast cell degranulation, oxidative stress, proinflammatory cytokine, and inducible nitric oxide synthase

Hepatic ischemia/reperfusion (ISCH/REP) is a major clinical problem that is considered to be the most common cause of postoperative liver failure. Recently, mast cells have been proposed to play an important role in the pathophysiology of ISCH/REP in many organs. In contrast, the role played by mast cells during ISCH/REP-induced liver damage has remained an issue of debate. This study aimed to investigate the protective role of mast cells in order to search for an effective therapeutic agent that could protect against fatal ISCH/REP-induced liver damage. A model of warm ISCH/REP was induced in the liver of rats. Four groups of rats were used in this study: Group I: SHAM (normal saline, intravenously [iv]); Group II: ISCH/REP; Group III: sodium cromoglycate + ISCH/REP (CROM + ISCH/REP), and Group IV: ketotifen (KET) + ISCH/REP (KET + ISCH/REP). Liver damage was assessed both histopathologically and biochemically. Mast cell degranulation was assessed histochemically. Lipid peroxidation (malondialdehyde [MDA]) as well as the levels of glutathione (GSH), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α), the formation of nitric oxide (NO), and the expression of inducible NO synthase (iNOS) were determined. The results of this study revealed increased mast cell degranulation in the liver during the acute phase of ISCH/REP. Moreover, CROM, but not KET, decreased the activity of alanine aminotransferase, aspartate aminotransferase, and lactic dehydrogenase and maintained normal liver tissue histology. Both CROM and KET protected against mast cell degranulation in the liver. In addition, both CROM and KET decreased IL-6 and TNF-α. However, CROM, but not KET, decreased MDA formation and increased GSH. Furthermore, KET, but not CROM, increased both NO formation and iNOS expression. In conclusion, this study clearly demonstrated mast cell degranulation in warm ISCH/REP in the liver of rats. More importantly, CROM, but not KET, ameliorated the effect of ISCH/REP-induced injury in rat liver. CROM may protect the liver through mast cell stabilization, inhibition of TNF-α, IL-6, MDA, and iNOS and increased GSH. KET may maintain ISCH/REP-induced liver injury through the NO/iNOS pathway.

Celastrol prevents circulatory failure via induction of heme oxygenase-1 and heat shock protein 70 in endotoxemic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Celastrol, a quinone methide extracted from the root of Tripterygium wilfordii Hook, possesses anti-oxidant and anti-inflammatory effects. Tripterygium wilfordii Hook is officially listed in the Chinese Pharmacopoeia and is used traditionally against rheumatoid arthritis, ankylosing spondylitis, and cancer. Furthermore, the circulatory protective effect of celastrol on an in vivo animal model of sepsis was investigated.

AIM OF THE STUDY

Sepsis is a systemic inflammatory disorder that increases tissue oxidative stress and leads to multiple organ injury. We evaluated the beneficial effects of celastrol on multiple organ failure induced by lipopolysaccharide (LPS) in rats.

MATERIALS AND METHODS

Celastrol (0.5 and 1.0 mg/kg, i.v.) was administered to anaesthetized rats 2 h before and 30 min after LPS challenge (10 mg/kg, i.v.). Eight hours later, cardiac and aortic protein expressions related to inflammatory responses, superoxide anion production, and reduced glutathione (GSH) level were measured.

RESULTS

Treatment with celastrol prevented circulatory failure (bradycardia and hypotension) 8h after LPS challenge. The plasma levels of ALT, LDH, TNF-α, and nitric oxide metabolites increased markedly during sepsis, which significantly reduced after celastrol treatments. Celastrol attenuated iNOS, TNF-α, NF-κB phospho-p65 expression, superoxide anion production, and caspase 3 activity in the cardiovascular system, all of which were markedly elevated after LPS challenge. Furthermore, celastrol induced HO-1 and HSP70 expressions increase in nuclear levels of Nrf2 and HSF-1, respectively, and increase cardiac GSH level 8h after LPS challenge.

CONCLUSION

Anti-inflammatory and anti-oxidant effects of celastrol contribute to prevent circulatory failure in sepsis. Induction of HO-1 and HSP70 by celastrol participates in these beneficial effects.

Abandon the mouse research ship? Not just yet!

Many preclinical studies in critical care medicine and related disciplines rely on hypothesis-driven research in mice. The underlying premise posits that mice sufficiently emulate numerous pathophysiologic alterations produced by trauma/sepsis and can serve as an experimental platform for answering clinically relevant questions. Recently, the lay press severely criticized the translational relevance of mouse models in critical care medicine. A series of provocative editorials were elicited by a highly publicized research report in the Proceedings of the National Academy of Sciences (PNAS; February 2013), which identified an unrecognized gene expression profile mismatch between human and murine leukocytes following burn/trauma/endotoxemia. Based on their data, the authors concluded that mouse models of trauma/inflammation are unsuitable for studying corresponding human conditions. We believe this conclusion was not justified. In conjunction with resulting negative commentary in the popular press, it can seriously jeopardize future basic research in critical care medicine. We will address some limitations of that PNAS report to provide a framework for discussing its conclusions and attempt to present a balanced summary of strengths/weaknesses of use of mouse models. While many investigators agree that animal research is a central component for improved patient outcomes, it is important to acknowledge known limitations in clinical translation from mouse to man. The scientific community is responsible to discuss valid limitations without overinterpretation. Hopefully, a balanced view of the strengths/weaknesses of using animals for trauma/endotoxemia/critical care research will not result in hasty discount of the clear need for using animals to advance treatment of critically ill patients.

Role of nitric oxide in development of centralization of blood circulation upon experimental hemorrhagic shock

Effects of a NO donor L-arginine and a non-selective NO-synthase inhibitor N(G)-nitro-Larginine methyl ester on BP, microcirculation, acid-base balance, and gas content of blood were examined on rat model of hemorrhagic shock; the substances were administered without infusion media before blood loss. Bloodletting was stopped after manifestation of marked microcirculation disorders. Inhibition of NO synthesis in response to blood loss resulted in pronounced centralization of blood circulation with microcirculation disturbances, which was accompanied by metabolic changes aggravating hemorrhagic shock. Administration of NO donor reduced the degree of circulation centralization, maintained vasodilatatory vascular tone and perfusion of vital organs, improved animal resistance to blood loss, and prolonged their lifespan. Enhanced NO generation after administration of NO donor promoted longer microcirculation maintenance, which suggests that the so-called basal level of NO is essential at early stages of hemorrhagic shock.

Renal histopathology during experimental septic acute kidney injury and recovery

OBJECTIVES

Our understanding of septic acute kidney injury is limited. We therefore assessed renal histopathological changes induced by septic acute kidney injury and their evolution during recovery.

DESIGN

Prospective experimental study.

SETTING

Physiology Research Institute.

SUBJECTS

Twenty-two Merino sheep.

INTERVENTION

We induced septic acute kidney injury by continuous i.v. infusion of Escherichia coli. We studied histology, immunohistochemistry, markers of apoptosis, and expression of nitric oxide synthase isoforms and hypoxia-inducible factor-1α. Analysis was performed on kidneys from normal sheep, sheep with septic acute kidney injury, and sheep after recovery from septic acute kidney injury.

MEASUREMENTS AND MAIN RESULTS

In normal, septic, and recovery sheep, respectively, serum creatinine was (median) 82 (interquartile range, 70-85), 289 (171-477), and 70 (51-91) μmol/L and renal blood flow was 270 ± 42, 653 ± 210, and 250 ± 49 mL/min. There were no histological differences between baseline, acute kidney injury, and recovery sheep. There was no evidence of macrophage or myofibroblast infiltration, no evidence of caspase-3 cleavage to suggest activation of apoptotic pathways, and no increase in neutrophil gelatinase-associated lipocalin to suggest tubular injury. Similarly, quantification of apoptosis revealed no differences between the normal and septic groups (normal: median, 3; interquartile range, 0-5 cells per visual field and septic acute kidney injury: median, 3.5; interquartile range, 0-8 cells per visual field; p = 0.618), but in the recovery group, there was increased apoptosis (median, 14; interquartile range, 4-34 cells per visual field; p = 0.002). Expression of all nitric oxide synthase subtypes increased significantly in the renal cortex during septic acute kidney injury but tended to decrease in the medulla. Medullary hypoxia-inducible factor gene expression decreased from 1.00 (95% CI, 0.74-1.36) to 0.26 (95% CI, 0.09-0.76) in recovery (p = 0.0106). Both inducible nitric oxide synthase and neuronal nitric oxide synthase expressions correlated with renal blood flow.

CONCLUSION

The lack of any tubular injury or increased apoptosis, the increased expression of all cortical nitric oxide synthase isoforms, and the link between inducible nitric oxide synthase and neuronal nitric oxide synthase with renal blood flow suggest in this experimental model that severe sepsis acute kidney injury can develop in the absence of histological or immunohistological changes and may be functional in nature.

Arginine and nitric oxide synthase: regulatory mechanisms and cardiovascular aspects

L-Arginine (L-Arg) is a conditionally essential amino acid in the human diet. The most common dietary sources of L-Arg are meat, poultry and fish. L-Arg is the precursor for the synthesis of nitric oxide (NO); a key signaling molecule via NO synthase (NOS). Endogenous NOS inhibitors such as asymmetric-dimethyl-L-Arg inhibit NO synthesis in vivo by competing with L-Arg at the active site of NOS. In addition, NOS possesses the ability to be "uncoupled" to produce superoxide anion instead of NO. Reduced NO bioavailability may play an essential role in cardiovascular pathologies and metabolic diseases. L-Arg deficiency syndromes in humans involve endothelial inflammation and immune dysfunctions. Exogenous administration of L-Arg restores NO bioavailability, but it has not been possible to demonstrate, that L-Arg supplementation improved endothelial function in cardiovascular disease such as heart failure or hypertension. L-Arg supplementation may be a novel therapy for obesity and metabolic syndrome. The utility of l-Arg supplementation in the treatment of L-Arg deficiency syndromes remains to be established. Clinical trials need to continue to determine the optimal concentrations and combinations of L-Arg, with other protective compounds such as tetrahydrobiopterin (BH4 ), and antioxidants to combat oxidative stress that drives down NO production in humans.

The protective action of ketanserin against lipopolysaccharide-induced shock in mice is mediated by inhibiting inducible NO synthase expression via the MEK/ERK pathway

Nitric oxide (NO) plays an important role in the pathogenesis of endotoxic shock. This work tested the hypothesis that ketanserin could attenuate endotoxic shock by inhibiting the expression of inducible NO synthase (iNOS). The results demonstrated that ketanserin could inhibit iNOS expression in the heart, lungs, liver, and kidneys and nitrate production in the serum upon endotoxic shock in mice. In RAW264.7 cells, ketanserin significantly inhibited the expression of iNOS and decreased the production of NO, TNFα, IL-6, and reactive oxygen species upon lipopolysaccharide (LPS) challenge. Ketanserin also increased the level of ATP and mitochondrial membrane potential in RAW264.7 cells upon LPS exposure. LPS-induced iNOS expression was inhibited by the 5-HT2A receptor antagonist ritanserin and not the α1 receptor antagonist prazosin. Knockdown of 5-HT2A receptor by siRNA abolished the inhibitory effect of ketanserin on the expression of iNOS. These results indicated that the inhibitory effect of ketanserin on the expression of iNOS is mediated by blocking the 5-HT2A receptor. Furthermore, ketanserin significantly inhibited the activation of ERK1/2 and NF-κB signal. Pretreatment with PD184352, a specific inhibitor of ERK1/2, blocked the inhibitory effect of ketanserin on the expression of iNOS and NO production, indicating a critical role for the MEK/ERK1/2 signaling pathway. Collectively, our findings indicate that inhibition of the expression of iNOS via the MEK/ERK pathway mediates the protective effects of ketanserin against LPS-induced shock in mice.