Sepsis alters myocardial and plasma concentrations of endothelin and nitric oxide in rats

Unraveling the immune response of the spleen in sepsis using green-synthesized silver nanoparticles from pomegranate peel extracts

Sepsis is a serious disease characterized by an inappropriate host response to infection, resulting in widespread inflammation and systemic organ failure. The aim of this research is to investigate the possibility of pomegranate peel-derived silver nanoparticles (PGNP) as a potential alternative therapy for sepsis. Characterization using transmission electron microscopy revealed 10-30 nm spherical nanoparticles. In a rat model of sepsis, PGNP treatment improved spleen health, histology, and immune response as compared with septic rats. In rats treated with PGNP during sepsis, significant alterations in oxidative stress markers (p < .01) were observed. These included elevated levels of glutathione (0.63 ± 0.08 mmol/mg protein), reduced concentrations of nitric oxide (8.7 ± 0.8 μ mol/mg protein) and malondialdehyde (2.2 ± 0.3 nmol/mg protein), as well as increased activity of superoxide dismutase (159 ± 33 U/mg protein). Following PGNP administration, gene expression analysis revealed a decrease in spleen IL-1β, IL-6, and TNF-α, highlighting its anti-inflammatory potential. Furthermore, PGNP effectively controlled apoptosis-related genes (Bax, Bcl-2, and Casp3), indicating its role in cellular survival pathways. This study sheds light on the immunological regulation of the spleen during sepsis using PGNP, demonstrating its potential as a new effective treatment approach. The study emphasizes the necessity of continuing to investigate and develop alternative medicines, particularly in light of antibiotic resistance and the global impact of sepsis. RESEARCH HIGHLIGHTS: The study explored the potential medicinal benefits of pomegranate peel-derived silver nanoparticles (PGNP) in the treatment of sepsis. PGNP suppressed pro-inflammatory cytokines and enhanced the immune response. The study recommends PGNP as a viable substitute treatment.

Effect of thymoquinone on sepsis-induced cardiac damage via anti-inflammatory and anti-apoptotic mechanisms

Objective

Sepsis is a systemic and deleterious host reaction to severe infection. Cardiac dysfunction is an established serious outcome of multiorgan failure associated with this condition. Therefore, it is important to develop drugs targeting sepsis-induced cardiac damage and inflammation. Thymoquinone (TQ) has anti-inflammatory, anti-oxidant, anti-fibrotic, anti-tumor, and anti-apoptotic effects. This study examined the effects of thymoquinone on sepsis-induced cardiac damage.

Methods

Male BALB/c mice were randomly segregated into four groups: control, TQ, cecal ligation and puncture (CLP), and CLP + TQ groups. CLP was performed after gavaging the mice with TQ for 2 weeks. After 48 hours, we estimated the histopathological changes in the cardiac tissue and the serum levels of cardiac troponin-T. We evaluated the expression of factors associated with inflammation, apoptosis, oxidative stress, and the PI3K/AKT pathway.

Results

TQ significantly reduced intestinal histological alterations and inhibited the upregulation of interleukin-6, tumor necrosis factor-α, Bax, NOX4, p-PI3K, and p-AKT. TQ also increased Bcl-2, HO-1, and NRF2 expression.

Conclusion

These results suggest that TQ effectively modulates pro-inflammatory, apoptotic, oxidative stress, and PI3K/AKT pathways, making it indispensable in the treatment of sepsis-induced cardiac damage.

Irisin Attenuates Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis in the H9C2 Cellular Model of Septic Cardiomyopathy through Augmenting Fundc1-Dependent Mitophagy

In the present study, we used lipopolysaccharide- (LPS-) stimulated H9C2 cardiomyocytes to investigate whether irisin treatment attenuates septic cardiomyopathy via Fundc1-related mitophagy. Fundc1 levels and mitophagy were significantly reduced in LPS-stimulated H9C2 cardiomyocytes but were significantly increased by irisin treatment. Irisin significantly increased ATP production and the activities of mitochondrial complexes I and III in the LPS-stimulated cardiomyocytes. Irisin also improved glucose metabolism and significantly reduced LPS-induced levels of reactive oxygen species by increasing the activities of antioxidant enzymes, glutathione peroxidase (GPX), and superoxide dismutase (SOD), as well as levels of reduced glutathione (GSH). TUNEL assays showed that irisin significantly reduced LPS-stimulated cardiomyocyte apoptosis by suppressing the activation of caspase-3 and caspase-9. However, the beneficial effects of irisin on oxidative stress, mitochondrial metabolism, and viability of LPS-stimulated H9C2 cardiomyocytes were abolished by silencing Fundc1. These results demonstrate that irisin abrogates mitochondrial dysfunction, oxidative stress, and apoptosis through Fundc1-related mitophagy in LPS-stimulated H9C2 cardiomyocytes. This suggests irisin is a potentially useful treatment for septic cardiomyopathy, though further investigations are necessary to confirm our findings.

Preclinical septic shock research: why we need an animal ICU

Animal experiments are widely used in preclinical medical research with the goal of disease modeling and exploration of novel therapeutic approaches. In the context of sepsis and septic shock, the translation into clinical practice has been disappointing. Classical animal models of septic shock usually involve one-sex-one-age animal models, mostly in mice or rats, contrasting with the heterogeneous population of septic shock patients. Many other factors limit the reliability of preclinical models and may contribute to preclinical research failure in critical care, including the host specificity of several pathogens, the fact that laboratory animals are raised in pathogen-free facilities and that organ support techniques are either absent or minimal. Advanced animal models have been developed with the aim of improving the clinical translatability of experimental findings. So-called animal ICUs refer to the preclinical investigation of adult or even aged animals of either sex, using—in case of rats and mice—miniaturized equipment allowing for reproducing an ICU environment at a small animal scale and integrating chronic comorbidities to more closely reflect the clinical conditions studied. Strength and limitations of preclinical animal models designed to decipher the mechanisms involved in septic cardiomyopathy are discussed. This article reviews the current status and the challenges of setting up an animal ICU.

Cerium oxide nanoparticle treatment ameliorates peritonitis-induced diaphragm dysfunction

The severe inflammation observed during sepsis is thought to cause diaphragm dysfunction, which is associated with poor patient prognosis. Cerium oxide (CeO2) nanoparticles have been posited to exhibit anti-inflammatory and antioxidative activities suggesting that these particles may be of potential use for the treatment of inflammatory disorders. To investigate this possibility, Sprague Dawley rats were randomly assigned to the following groups: sham control, CeO2 nanoparticle treatment only (0.5 mg/kg iv), sepsis, and sepsis+CeO2 nanoparticles. Sepsis was induced by the introduction of cecal material (600 mg/kg) directly into the peritoneal cavity. Nanoparticle treatment decreased sepsis-associated impairments in diaphragmatic contractile (P(o)) function (sham: 25.6±1.6 N/cm(2) vs CeO2: 23.4±0.8 N/cm(2) vs Sep: 15.9±1.0 N/cm(2) vs Sep+CeO2: 20.0±1.0 N/cm(2), P<0.05). These improvements in diaphragm contractile function were accompanied by a normalization of protein translation signaling (Akt, FOXO-1, and 4EBP1), diminished proteolysis (caspase 8 and ubiquitin levels), and decreased inflammatory signaling (Stat3 and iNOS). Histological analysis suggested that nanoparticle treatment was associated with diminished sarcolemma damage and diminished inflammatory cell infiltration. These data indicate CeO2 nanoparticles may improve diaphragmatic function in the septic laboratory rat.

Cecal inoculum peritonitis: An alternative model for sepsis vascular dysfunction study

AIMS

Sepsis is a life threatening condition that is characterized by the loss of vascular reactivity. The factor(s) responsible for the diminished vascular function seen in sepsis are not well understood. The purpose of this study was to characterize the vascular dysfunction from the rat cecal inoculum (CI) sepsis model using cecal ligation and puncture (CLP), and lipopolysaccharide (LPS) sepsis as reference models.

MATERIALS AND METHODS

Experiments were performed on isolated aorta from CI, CLP and LPS treated rats using a combination of pharmacological approaches.

KEY FINDINGS

Phenylephrine (PE)-induced aortic contraction was significantly decreased in each model (p<0.05) and not normalized by L-NAME or indomethacin. The vascular response elicited in the CI model for acetylcholine (Ach) was more similar to that seen in the CLP than the LPS model. The removal of the endothelial layer increased sensitivity to L-NAME (p<0.05) in aortae from CI group. Inhibition of the large conductance Ca(2+)/voltage sensitive K(+) (BKCa) channel did not normalize PE hyporesponsiveness but did abolish sepsis-induced contractile oscillation. Inhibition of the voltage dependent Kv1.5 channel was not able to reverse the vascular hyporesponsiveness, however, inhibition of the ATP dependent (KATP) channel inhibition partially restored the contractile response (p<0.05). Elevation of VCAM expression and aortic structural alternation were observed in each model.

SIGNIFICANCE

These results suggest that the CI model may be an additional tool that could be used to investigate the mechanisms of vascular hyporesponsiveness in sepsis.

Protective effect of total saponins of Aralia elata (Miq) Seem on lipopolysaccharide-induced cardiac dysfunction via down-regulation of inflammatory signaling in mice

TAS attenuates LPS-induced cardiomyocyte dysfunctionviadown-regulation of inflammatory signaling in mice.

Significant reversal of cardiac upregulated endothelin-1 system in a rat model of sepsis by landiolol hydrochloride

AIMS

Landiolol hydrochloride, an ultra-short-acting highly cardio-selective β-1 blocker, has become useful for various medical problems. Recent studies have demonstrated that co-treatment with landiolol protects against acute lung injury and cardiac dysfunction in rats of lipopolysaccharide (LPS)-induced systemic inflammation, and was also associated with a significant reduction in serum levels of the inflammation mediator HMGB-1 and histological lung damage. Endothelin (ET)-1, a potent vasoconstrictor, has been implicated in pathogenesis of sepsis and sepsis-induced multiple organ dysfunction syndrome. Here, we investigated whether landiolol hydrochloride can play important roles in ameliorating LPS-induced alterations in cardiac ET system of septic rats.

MAIN METHODS

Eight-week-old male Wistar rats were administered LPS only for 3 h and the rest were treated with LPS as well as with landiolol non-stop for 3 h.

KEY FINDINGS

At 3 h after LPS (only) administration, circulatory tumor necrosis factor (TNF)-α level, blood lactate concentration and percentage of fractional shortening of heart were significantly increased. In addition, LPS induced a significant expression of various components of cardiac ET-1 system compared to control. Finally, treatment of LPS-administered rats with landiolol for 3 h normalized LPS-induced blood lactate levels and cardiac functional compensatory events, without altering levels of plasma TNF-α and ET-1. Most strikingly, landiolol treatment significantly normalized various components of cardiac ET-1 signaling system in septic rat.

SIGNIFICANCE

Taken together, these data led us to conclude that landiolol may be cardio-protective in septic rats by normalizing the expression of cardiac vasoactive peptide such as ET, without altering the circulatory levels of inflammatory cytokines.

Myocardial dysfunction in sepsis: a large, unsolved puzzle

Sepsis has high incidence and mortality rates around the world. The role of cardiac depression in myocardial dysfunction during sepsis remains to be elucidated. This review attempts to summarize our understanding of the anatomical, histopathological, and pathophysiological mechanisms behind cardiac dysfunction. Biomarkers to detect cardiac depression have been used to recognize developing problems, but the actual impact of these tools remains unclear.

Modulation of myocardial mitochondrial mechanisms during severe polymicrobial sepsis in the rat

Background

We tested the hypothesis that 5-Hydroxydecanoic acid (5HD), a putative mitoK_ATP channel blocker, will reverse sepsis-induced cardiodynamic and adult rat ventricular myocyte (ARVM) contractile dysfunction, restore mitochondrial membrane permeability alterations and improve survival.

Methodology/Principal Findings

Male Sprague-Dawley rats (350–400 g) were made septic using 400 mg/kg cecal inoculum, ip. Sham animals received 5% dextrose water, ip. The Voltage Dependent Anion Channels (VDAC1), Bax and cytochrome C levels were determined in isolated single ARVMs obtained from sham and septic rat heart. Mitochondria and cytosolic fractions were isolated from ARVMs treated with norepinephrine (NE, 10 µmoles) in the presence/absence of 5HD (100 µmoles). A continuous infusion of 5HD using an Alzet pump reversed sepsis-induced mortality when administered at the time of induction of sepsis (−40%) and at 6 hr post-sepsis (−20%). Electrocardiography revealed that 5HD reversed sepsis-induced decrease in the average ejection fraction, Simpsons+m Mode (53.5±2.5 in sepsis and 69.2±1.2 at 24 hr in sepsis+5HD vs. 79.9±1.5 basal group) and cardiac output (63.3±1.2 mL/min sepsis and 79.3±3.9 mL/min at 24 hr in sepsis+5HD vs. 85.8±1.5 mL/min basal group). The treatment of ARVMs with 5HD also reversed sepsis-induced depressed contractility in both the vehicle and NE-treated groups. Sepsis produced a significant downregulation of VDAC1, and upregulation of Bax levels, along with mitochondrial membrane potential collapse in ARVMs. Pretreatment of septic ARVMs with 5HD blocked a NE-induced decrease in the VDAC1 and release of cytochrome C.

Conclusion

The data suggest that Bax activation is an upstream event that may precede the opening of the mitoK_ATP channels in sepsis. We concluded that mitoK_ATP channel inhibition via decreased mitochondrial membrane potential and reduced release of cytochrome C provided protection against sepsis-induced ARVM and myocardial contractile dysfunction.

Norepinephrine induces systolic failure and inhibits antiapoptotic genes in a polymicrobial septic rat model

AIMS

We examined the effect of norepinephrine (NE) infusion on left ventricular function and apoptotic genes during progression of polymicrobial sepsis.

METHODS

Male Sprague-Dawley rats (350-400 g) were made septic by intraperitoneal (i.p.) administration of 200mg/kg cecal inoculum. Sham animals received 5% dextrose water, i.p. Echocardiography was performed at baseline, 3 days and 7 days post-sepsis/sham. NE (0.6 μgkg(-1)h(-1)) was infused for 2h, before the end of day 3 of echocardiography. At the end of day 7, rats were euthanized and heart tissues harvested for isolation of total RNA. PCR was performed using RT(2) profiler™ PCR array PARN-012 (Rat apoptosis array; SuperArray, MD) using RT(2) Real-Time™ SYBR Green PCR master mix PA-012.

KEY FINDINGS

NE-infusion resulted in a significant decrease in the left ventricular ejection fraction (EF) (62.56±2.07 from the baseline 71.11±3.23, p<0.05) and fractional shortening (FS) (39.90±2.64 from the sham group 54.41±2.19, p<0.05) at 7 days post-sepsis, respectively. Super Array data revealed that during sepsis, tumor necrosis factor (TNF-α) (2.85±0.07 fold, p<0.0001), anti-apoptotic molecules, Prok2 (16.07±0.48 fold, p<0.0001) and interleukin-10 (IL-10) (23.5±0.57 fold, p<0.0001) were up regulated at day 1. At 7-days post-sepsis, CD40l g (2.49±0.54 fold, p<0.08) and Birc1b (17.8±0.58 fold, p<0.0001) were up regulated compared to the sham, 1 and 3-days post-sepsis groups.

SIGNIFICANCE

The data suggest that upregulation of a series of pro-apoptotic molecules could be responsible for systolic and diastolic dysfunction during 3 and 7 days post sepsis.

Sepsis worsening vascular hyporeactivity of the superior mesenteric artery in portal vein-ligated rats

BACKGROUND

Vascular hyporeactivity is observed in portal hypertensive animals and septic rats. The objective of this study was to investigate whether impairment of superior mesenteric artery vascular contractility in the portal hypertensive rat was further impaired after sepsis.

METHODS

Sepsis was induced by cecum ligation and puncture (CLP) in male portal hypertensive Sprague-Dawley rats that had been subjected to portal vein ligation (PVL) for 14 days. Hemodynamic studies, isolated vascular ring studies, microbiological studies, and plasma nitrite/nitrate measurements were performed 2, 6, and 18 hours after CLP. An additional group of PVL rats received prophylactic imipenem (10 mg intravenously for 1 hour) before CLP and then were studied 6 hours after CLP.

RESULTS

Mean arterial pressure and heart rate of PVL rats were significantly decreased shortly after CLP. CLP caused further nitric oxide production and vascular hyporesponsiveness 6 and 18 hours after CLP compared with the baseline portal hypertensive group. Vascular hyporeactivity was corrected by N-nitro-L-arginine methyl ester + 1400W (1400W is N-(3-(aminomethyl)benzyl)acetamidine hydrochloride, a selective inducible nitric oxide synthase inhibitor). Prophylactic imipenem did not alter nitric oxide production or vascular contractility after sepsis induced by CLP.

CONCLUSION

Our study showed that vascular contractility in portal hypertensive rats is further impaired soon after CLP-induced sepsis.

Contractile response of norepinephrine is modulated by caspase-3 in adult rat ventricular myocytes isolated from septic rat heart

Sepsis accounts for 50% of intensive care unit deaths due to cardiac dysfunction. The cellular mechanisms following norepinephrine (NE) during sepsis are undefined. Using a septic adult rat ventricular myocyte (ARVM) paradigm, we examined the molecular mechanism responsible for the blunted contractile response of NE. We tested the hypothesis that NE-induced increases in active caspase-3 contribute to sepsis-induced ARVM contractile dysfunction. Single ARVMs were isolated from hearts harvested from sham and septic male rats. The contractile properties and expression of caspase-3 cascade proteins were determined in ARVMs treated with NE with and without QVD-OPH, prazosin and atenolol to characterize the effect of NE on their mechanical properties. Septic ARVMs exhibited a significant decrease in peak shortening (PS) compared to sham ARVMs. The effect of NE on the PS of the sham ARVMs was more pronounced compared to the septic ARVMs, suggesting a blunted contractile response of NE. NE in the presence of QVD-OPH ameliorated the sepsis-induced decrease in PS at 18h but not at 1h, while the effect of NE on sepsis-induced contractile response remained unaffected at 18h by prazosin and atenolol. An up-regulated expression of caspase-3 in NE-treated septic ARVMs was reversed by QVD-OPH, as seen by the increased number of septic ARVMs exhibiting caspase-3 fluorescence. Transfection of ARVMs using caspase-3 siRNA blocked sepsis-induced up-regulation of caspase-3 and increased PS following NE treatment. These data suggest that caspase-3 inhibition ameliorated sepsis-induced decreased ARVM contractility and blocked the blunted contractile response of NE.

Sepsis-induced myocardial dysfunction

Despite the fact that septic patients exhibit altered cardiac function, it is not considered a major pathology during sepsis. Thus, the molecular mechanisms underlying sepsis-induced myocardial dysfunction have not been studied extensively. In a polymicrobial septic rat model, +dP/dt and -dP/dt on day 1 were not altered but found depressed later, i.e., at 3 and 7 days postsepsis. Diastolic dysfunction characterized by an elevation of the time constant of left ventricular relaxation, tau, was evident at 1, 3, and 7 days postsepsis. Recent data from our laboratory demonstrated that sepsis-induced cardiodynamic alterations correlated with upregulation of TNF receptor-associated death domain, Bax, Smac (both mitochondrial and cytosolic fractions), total nuclear factor kappaB expression, p38-mitogen-activated protein kinase and c-Jun N-terminal kinase phosphorylation, and cytochrome c levels in the rat heart at 3 and 7 days postsepsis. Data from various laboratories emphasized that molecular myocardial alteration, which occurs during early and late stages of sepsis, needs to be elucidated thoroughly. A poor understanding of myocardial signaling during early sepsis could be one of the main reasons for limited success of pharmacotherapeutic options for sepsis. We anticipate that an increased understanding of pathophysiological mechanisms leading to sepsis-induced myocardial dysfunction would generate new enthusiasm among various research groups in this area of research.

Sepsis and the heart

Sepsis is generally viewed as a disease aggravated by an inappropriate immune response encountered in the afflicted individual. As an important organ system frequently compromised by sepsis and always affected by septic shock, the cardiovascular system and its dysfunction during sepsis have been studied in clinical and basic research for more than 5 decades. Although a number of mediators and pathways have been shown to be associated with myocardial depression in sepsis, the precise cause remains unclear to date. There is currently no evidence supporting global ischemia as an underlying cause of myocardial dysfunction in sepsis; however, in septic patients with coexistent and possibly undiagnosed coronary artery disease, regional myocardial ischemia or infarction secondary to coronary artery disease may certainly occur. A circulating myocardial depressant factor in septic shock has long been proposed, and potential candidates for a myocardial depressant factor include cytokines, prostanoids, and nitric oxide, among others. Endothelial activation and induction of the coagulatory system also contribute to the pathophysiology in sepsis. Prompt and adequate antibiotic therapy accompanied by surgical removal of the infectious focus, if indicated and feasible, is the mainstay and also the only strictly causal line of therapy. In the presence of severe sepsis and septic shock, supportive treatment in addition to causal therapy is mandatory. The purpose of this review is to delineate some characteristics of septic myocardial dysfunction, to assess the most commonly cited and reported underlying mechanisms of cardiac dysfunction in sepsis, and to briefly outline current therapeutic strategies and possible future approaches.

THE EXTRACELLULAR CARDIAC PURINE METABOLOME IN SEPSIS

The total cardiac purine metabolome includes all of the adenine and guanine nucleoside and nucleosides and related molecules involved throughout the intracellular and extracellular compartments and various cell types in the heart. In considering purines as molecules involved in autocrine and paracrine communication, effective interstitial concentrations of the nucleoside adenosine, or purine metabolites, are of greatest interest. These molecules arise from the complex interactions between cardiac-specific cell types, including fibroblasts and myocytes, and noncardiac cells, such as tissue-resident macrophages and other immune cells that have vascular access. In the interstitial environment, adenosine can regulate vascular resistance, contractile function, and immunochemical interactions. The breakdown of purines can produce reactive oxygen species that also influence autocrine and paracrine interactions. A central enzyme in this paradigm, adenosine deaminase, is a pivotal molecule in regulating the balance between pro-inflammatory and anti-inflammatory signaling cascades. A new role for adenosine deaminase as an allosteric regulator of relevant membrane proteins has yet to be explored in the heart.

Distinct cardiodynamic and molecular characteristics during early and late stages of sepsis-induced myocardial dysfunction

We hypothesized that progressive decline in myocardial performance would correlate with upregulation of markers for apoptotic mechanisms following increased duration of polymicrobial sepsis in the rat. Male Sprague-Dawley rats (350-400 g) were randomized into sham, 1-, 3- and 7-day sepsis groups. Each septic rat received 200 mg/kg cecal inoculum intraperitoneally (i.p). The post-mortem analysis showed a severely inflamed peritoneum with the presence of pus in all septic animals that was directly proportional to the duration of sepsis. We observed 10, 33 and 42% mortality in the 1-, 3- and 7-day sepsis groups, respectively. Septic animals at 3 and 7 days exhibited an increased wet lung/total body weight and heart weight/total body weight. A significant increase in total cardiac troponin I (cTnI) and C Reactive Protein (CRP) and endothelin-1 (ET-1) was also observed with an increased duration of sepsis. Myocardial ET-1 concentration in the 7-day post-sepsis group was significantly elevated compared to the sham and 1-day post-sepsis groups. Sepsis also produced a significant decrease in the mean arterial pressure in the 7-day post-sepsis group and tachycardia in the 1-, 3-, and 7-day post-sepsis groups compared to the sham group. A significant prolongation of the left ventricular isovolumic relaxation rate constant, tau, and left ventricular end-diastolic pressure in the 1-, 3- and 7-day post-sepsis groups compared to the sham group was observed. In addition, a significant decrease in the rates of left ventricular relaxation (-dP/dt) and contraction (+dP/dt) in the 3- and 7-day post-sepsis groups compared to the sham and 1-day post-sepsis group was observed. Sepsis produced a significant upregulation in the expression of myocardial TRADD, cytosolic active caspase-3, the Bax/Bcl(2) ratio, and the mitochondrial release of cytochrome C in the 3- and 7-day post-sepsis groups. We observed a progressive increase in the number of TUNEL positive nuclei, cytosolic caspase-3 activation and co-localization of PARP in the nuclei at 1, 3 and 7 days post-sepsis. These data suggest that the progression of sepsis from 1 day to 3-7 days produce distinct cardiodynamic characteristics with a more profound effect during later stages. The sepsis-induced decline in myocardial performance correlates with the induction of myocardial apoptosis.

Role of protein C in renal dysfunction after polymicrobial sepsis

Protein C (PC) plays an important role in vascular function, and acquired deficiency during sepsis is associated with increased mortality in both animal models and in clinical studies. This study explored the consequences of PC suppression on the kidney in a cecal ligation and puncture model of polymicrobial sepsis. This study shows that a rapid drop in PC after sepsis is strongly associated with an increase in blood urea nitrogen, renal pathology, and expression of known markers of renal injury, including neutrophil gelatinase-associated lipocalin, CXCL1, and CXCL2. The endothelial PC receptor, which is required for the anti-inflammatory and antiapoptotic activity of activated PC (APC), was significantly increased after cecal ligation and puncture as well as in the microvasculature of human kidneys after injury. Treatment of septic animals with APC reduced blood urea nitrogen, renal pathology, and chemokine expression and dramatically reduced the induction of inducible nitric oxide synthase and caspase-3 activation in the kidney. The data demonstrate a clear link between acquired PC deficiency and renal dysfunction in sepsis and suggest a compensatory upregulation of the signaling receptor. Moreover, these data suggest that APC treatment may be effective in reducing inflammatory and apoptotic insult during sepsis-induced acute renal failure.

Tezosentan reduces the microvascular filtration coefficient in isolated lungs from rats subjected to cecum ligation and puncture

INTRODUCTION

We recently demonstrated that the non-selective endothelin-1 (ET-1) receptor blocker tezosentan antagonizes ovine acute lung injury (ALI) following infusion of endotoxin or ET-1 by reducing the enhanced lung microvascular pressure, although we could not exclude the possibility of a simultaneous decline in microvascular permeability. In the present study, our aim was to find out if tezosentan reverses the rise in microvascular filtration coefficient (Kfc) in rat lungs that have been isolated and perfused 12 h after cecum ligation and puncture (CLP) or infusion of ET-1.

METHODS

Wistar rats (n = 42) were subjected to CLP. Postoperatively, rats were randomized to a CLP group (n = 7) and a CLP + tezosentan group (n = 7); the latter received tezosentan 30 mg/kg. A sham-operated group (n = 5) underwent laparotomy without CLP. Twelve hours postoperatively, the lungs were isolated and perfused with blood from similarly treated rats that also were used to assess plasma concentration of ET-1 and protein kinase Calpha (PKCalpha) in lung tissue. Additionally, isolated blood perfused lungs from healthy rats were randomized to a control group (n = 8), an ET-1 group (n = 7) subjected to pulmonary arterial injection of ET-1 10 nM, and an ET-1 + tezosentan group (n = 7) that received tezosentan 30 mg/kg. All lung preparations received papaverine 0.1 microg/kg added to the perfusate for vasoplegia. Pulmonary hemodynamic variables, Kfc and lung compliance (CL) were assessed.

RESULTS

After CLP, the plasma concentration of ET-1 increased. Papaverine abolished the vasoconstrictor response to ET-1 and the pulmonary vascular pressures remained close to baseline throughout the experiments. Both CLP and injection of ET-1 caused significant changes in Kfc and CL that were prevented in tezosentan-treated rats. Compared to sham-operated animals, CLP increased the content of PKCalpha by 50% and 70% in the cytosolic and the membrane fractions of lung tissue homogenates, respectively. Tezosentan prevented the upregulation of PKCalpha in the membrane fraction.

CONCLUSION

In rat lungs isolated and perfused after CLP, tezosentan precludes both the increase in Kfc and the upregulation of PKCalpha in the membrane fraction of lung tissue.

Bigendothelin-1 (1-21) fragment during early sepsis modulates tau, p38-MAPK phosphorylation and nitric oxide synthase activation

Earlier we have demonstrated that inhibition of endothelin biosynthesis ameliorates endotoxemia-induced inducible nitric oxide synthase (iNOS) activation and phosphorylation of p38-mitogen activated protein kinase (pp38-MAPK). Therefore, in the present study, we tested the hypothesis that activation of endothelin (ET)-1 biosynthesis using bigET-1 during early sepsis would upregulate iNOS and affect myocardial function in the rat. Male Sprague-Dawley rats (350-400 g) were anesthetised using Nembutal (50 mg/kg, i.p.) and jugular vein, tail artery (Mean arterial pressure, MAP) and right carotid arteries (advanced to left ventricle, LV) were cannulated. The rats were randomly divided into saline-, bigET-1- and C-terminal fragment of bigET-1 (bigET-1(22-38))-treated groups. Sepsis was induced using i.p. injection of cecal inoculum obtained from a donor rat (200 mg/kg in 5 ml 5% sterile dextrose water, D5W). Sham animals received an i.p. injection of D5W (5 ml/kg). MAP and LVP were recorded and cardiodynamic parameters were calculated at 0, 2, 6, 12 and 24 h post sham or sepsis-induction. A significant elevation in LV isovolumic relaxation rate constant (tau), LV end diastolic pressure (LVEDP) and rate pressure product (RPP) was observed in vehicle-treated septic group at 24 h. BigET-1 significantly increased concentration of LV ET-1 both in sham and septic groups. BigET-1 elevated tau and LVEDP both in sham and septic animals as early as 12 h which persisted through 24 h. However, bigET-1(22-38) elevated LVEDP in septic group at 24 h but not in sham group. BigET-1 accentuated the levels of plasma nitric oxide byproduct (NOx) levels in both sham and septic animals at 6, 12 and 24 h. Sepsis increased myocardial iNOS at 24 h. BigET-1 significantly upregulated expression of myocardial iNOS and pp38-MAPK. The data suggest that increased substrate availability for ET-1 at the time of sepsis-induction contributes in diastolic dysfunction, iNOS activation and p38-MAPK phosphorylation.

Bigendothelin-1 via p38-MAPK-dependent mechanism regulates adult rat ventricular myocyte contractility in sepsis

We tested the hypothesis that exogenous administration of the ET-1 precursor, bigET-1, would regulate adult rat ventricular myocyte (ARVM) contractility in a p38-mitogen activated protein kinase (p38-MAPK)-dependent mechanism during sepsis. Ventricular myocytes from adult rat hearts (both sham and septic) were stimulated to contract at 0.5 Hz and mechanical properties were evaluated using an IonOptix Myocam system. Immunoblot analysis was used to determine the phosphorylation of p38-MAPK and extracellular signal-regulated kinase 1/2 (ERK1/2). ARVMs were treated with vehicle, bigET-1 and inhibitors for 24 h and then subjected to functional and biochemical estimations. Septic ARVM displayed a distorted cell membrane and irregular network within the cells along with increased cell contractility as evidenced by elevated peak shortening (PS), maximal velocity of shortening (+dL/dt) and relengthening (-dL/dt) in comparison to sham ARVM. BigET-1 treatment caused ARVM enlargement in both sham and sepsis groups. BigET-1 (100 nM) produced an increase in ARVM contractility in sham group as compared to vehicle treatment. However, septic ARVM treated with bigET-1 exhibited unaltered ARVM contractility, and upregulated ET(B) receptors as compared to respective sham group. BigET-1 increased the concentration of ET-1 and upregulated phosphorylation of p38-MAPK but not of ERK1/2 in sham and septic ARVM. Furthermore, inhibition of p38-MAPK by SB203580 (10 microM) increased ARVM contractility in sham but not in sepsis group. BigET-1 reversed SB203580-induced increase in PS in sham group but accentuated it in sepsis group. BigET-1 also reversed SB203580-induced inhibition of p38-MAPK phosphorylation in sham but not in septic ARVM. SB203580 pretreatment followed by bigET-1 administration significantly decreased p38-MAPK phosphorylation and downregulated ET(B) receptor expression as compared to bigET-1 treatment per se in sepsis group but not in sham. We concluded that a bigET-1-induced non-responsive effect on septic ARVM contractile function could be due to upregulation of p38-MAPK phosphorylation and ET(B) receptor expression.

Plasma endothelin-1 and clinical manifestations of neonatal sepsis

AIM

To determine whether plasma endothelin-1 (ET-1) relates to clinical manifestations of sepsis in the newborn, especially with systemic hypotension, acidosis, severe hypoxemia (which may represent pulmonary hypertension) and oliguria.

METHODS

Prospective study of 35 consecutive newborns with clinical sepsis: 22 with hemoculture-positive (HC+) sepsis and 13 hemoculture-negative (HC-). Plasma ET-1 concentrations were measured within 2 days of the diagnosis of sepsis. SNAP-II severity score was performed at the time of highest clinical severity.

RESULTS

Newborns with HC+ sepsis had higher plasma ET-1 concentrations and SNAP-II scores (especially PO 2 /FiO 2 ratio) than HC- septic children. Plasma ET-1 concentrations increased linearly with each item of the SNAP-II score, but only reached significant differences in lowest mean blood pressure (P=0.030), lowest pH (P=0.048), multiple seizures (P=0.010) and lowest urine output (P=0.013). Leukocyte count, immature/total neutrophil ratio and C-reactive protein value were not different. Each item of the SNAP-II score was independently related only to ET-1 level. Oliguria, acidosis and systemic hypotension were more correlated (R 2 >0.5).

CONCLUSIONS

Plasma ET-1 levels in neonatal sepsis are related to the severity of clinical manifestations, especially oliguria, acidosis and systemic hypotension.

Duration of streptozotocin-induced diabetes differentially affects p38-mitogen-activated protein kinase (MAPK) phosphorylation in renal and vascular dysfunction

BACKGROUND

In the present study we tested the hypothesis that progression of streptozotocin (STZ)-induced diabetes (14-days to 28-days) would produce renal and vascular dysfunction that correlate with altered p38- mitogen-activated protein kinase (p38-MAPK) phosphorylation in kidneys and thoracic aorta.

METHODS

Male Sprague Dawley rats (350-400 g) were randomized into three groups: sham (N = 6), 14-days diabetic (N = 6) and 28-days diabetic rats (N = 6). Diabetes was induced using a single tail vein injection of STZ (60 mg/kg, I.V.) on the first day. Rats were monitored for 28 days and food, water intake and plasma glucose levels were noted. At both 14-days and 28-days post diabetes blood samples were collected and kidney cortex, medulla and aorta were harvested from each rat.

RESULTS

The diabetic rats lost body weight at both 14-days (-10%) and 28-days (-13%) more significantly as compared to sham (+10%) group. Glucose levels were significantly elevated in the diabetic rats at both 14-days and 28-days post-STZ administration. Renal dysfunction as evidenced by renal hypertrophy, increased plasma creatinine concentration and reduced renal blood flow was observed in 14-days and 28-days diabetes. Vascular dysfunction as evidenced by decreased carotid blood flow was observed in 14-days and 28-days diabetes. We observed an up-regulation of inducible nitric oxide synthase (iNOS), prepro endothelin-1 (preproET-1) and phosphorylated p38-MAPK in thoracic aorta and kidney cortex but not in kidney medulla in 28-days diabetes group.

CONCLUSION

The study provides evidence that diabetes produces vascular and renal dysfunction with a profound effect on signaling mechanisms at later stage of diabetes.

Despite minimal hemodynamic alterations endotoxemia modulates NOS and p38-MAPK phosphorylation via metalloendopeptidases

In the present study, we hypothesized that endotoxemia produces metalloendopeptidase (MEPD)-dependent generation of endothelin-1 (ET-1) and alters NOS expression correlating with p38-mitogen-activated protein kinase (MAPK) phosphorylation in thoracic aorta. Male Sprague-Dawley rats (350-400 g) were subjected to two groups randomly; sham-treated (N = 10) and lipopolysaccharide (LPS)-treated (N = 10) (E. coli LPS 2 mg/kg bolus + 2 mg/kg infusion for 30 min). The animals in each group were further subdivided into vehicle and MEPD inhibitor phosphoramidon (1 mg/kg bolus, PHOS)-treated groups. LPS produces a significant decrease in mean arterial pressure (MAP) at 2 h post endotoxemia that was blocked by PHOS. PHOS attenuated LPS-induced increase in tumor necrosis factor-alpha (TNF-alpha) concentration at 2- and 24 h post-LPS administration. LPS significantly elevated plasma concentrations of ET-1 at 2- and 24 h post endotoxemia. An upregulated preproET-1 expression following both LPS and MEPD inhibition was observed in thoracic aorta at 2 h post treatment. PHOS effectively blocked conversion of preproET-1 to ET-1 in thoracic aorta locally at 24 h post treatment in endotoxic rats. PHOS inhibited LPS-induced upregulation of inducible NOS (iNOS), downregulation of endothelial NOS (eNOS) and elevation of NO byproducts (NOx) in thoracic aorta. PHOS also blocked LPS-induced upregulated p38-MAPK phosphorylation in thoracic aorta at 24 h post endotoxemia. The data revealed that LPS induces MEPD-sensitive inflammatory response syndrome (SIRS) at 2- and 24 h post endotoxemia. We concluded that inhibition of MEPD not only decreases the levels of ET-1 but also simultaneously downregulates protein expression of iNOS and phosphorylated p38-MAPK while increasing eNOS in thoracic aorta during SIRS in endotoxemia. We suggest that MEPD-dependent ET-1 and NO mechanisms may be involved in endotoxemia-induced altered p38-MAPK phosphorylation.

Endothelin-1 Receptor Antagonist BQ123 Prevents Pulmonary Artery Hypertension Induced by Low Ambient Temperature in Broilers

Evidence has indicated that endothelin-1 is related to the pathogenesis of hypertension. To characterize the role of endothelin-1 (ET-1) in the development of pulmonary hypertension syndrome in broilers, the blockade effect of ETA receptor (ET(A)) antagonist, BQ123, on blood pressure in experimental models of pulmonary hypertension was examined. Birds were locally anesthetized and instrumented with venous catheters for pulmonary arterial pressure (PAP) and right ventricular pressure (RVP), followed by packed cell volume (PCV) and Ascites heart index (AHI) measured, after exposed to low ambient temperature for 7 or 14 d. In treated groups, BQ123 (0.4 or 2.0 microg each time, 2 times a day), administered in abdominal cavities for 7 or 14 d during birds kept in low ambient temperature, prevented both PAP and RVP increasing, especially the high dose BQ123 lowered PAP and RVP to normotensive levels as that in control under normal temperature, whereas significant increases (p<0.05) were found in the two parameters of broilers in both untreated and saline treated group under low ambient temperature compared with those of birds in control. Furthermore, there was also a reduction in low ambient temperature-induced right ventricular hypertrophy in the groups administered BQ123. The preventive effect of BQ123 suggests that ET-1 is associated with the development of broilers' pulmonary hypertension, which leads to the development of ascites, and BQ123 can prevent the occurrence of pulmonary hypertension.

Left ventricular mitogen activated protein kinase signaling following polymicrobial sepsis during streptozotocin-induced hyperglycemia

We hypothesized that sepsis during hyperglycemia would activate left ventricular (LV) mitogen activated protein kinase (MAPK) signaling mechanisms and modulate generation of endothelin-1 (ET-1) and nitric oxide (NO) that can contribute to the progression of LV dysfunction. A single injection of streptozotocin (STZ, 60 mg/kg, via tail vein) was used to produce type 2 diabetes in male SD rats. Polymicrobial sepsis and sham-sepsis were induced using single i.p. injection of cecal inoculum and sterile 5% dextrose water, respectively, on the 13th and 27th day following STZ injection. Both 2-week (2-wk) and 4-wk diabetes groups were associated with hyperglycemia and weight loss. LV end diastolic pressure (LVEDP) was significantly increased in 4-wk diabetes but not in 2-wk diabetes group. Plasma concentration of tumor necrosis factor-alpha (TNF-alpha) was significantly increased in 4-wk diabetes+sepsis group as compared to sham, 2-wk diabetes+sepsis and sepsis groups. Elevated plasma and LV ET-1 and NO byproducts (NOx) along with LV preproET-1 and inducible nitric oxide synthase (iNOS) protein expression were observed in 4-wk but not in 2-wk diabetes group. Sepsis further elevated LV iNOS and preproET-1 in 4-wk diabetes group. Up-regulated phosphorylation of LV p38-MAPK, extracellular signal-regulated kinase 1/2 (ERK1/2) and heat shock protein-27 (Hsp27) was observed in 4-wk diabetes group. Sepsis caused a factorial increase in LV p38-MAPK and Hsp27 phosphorylation and iNOS up-regulation but not ERK1/2 following progression from 2-wk to 4-wk diabetes. The study provides evidence that sepsis up-regulated LV iNOS, p38-MAPK phosphorylation and elevated LVEDP during 4-wk diabetes. We concluded that sepsis contributes in the development of LVEDP dysfunction and alteration in signaling mechanisms depending upon the progression from 2-wk to 4-wk diabetes in the rat.

Science review: natriuretic peptides in critical illness

The present review will cover the mechanisms of release and the potential pathophysiological role of different natriuretic peptides in critically ill patients. By focusing on the cardiovascular system, possible implications of natriuretic peptides for diagnosis and treatment will be presented. In critical illness such as sepsis, trauma or major surgery, systemic hypotension and an intrinsic myocardial dysfunction occur. Impairment of the cardiovascular system contributes to poor prognosis in severe human sepsis. Natriuretic peptides have emerged as valuable marker substances to detect left ventricular dysfunction in congestive heart failure of different origins. Increased plasma levels of circulating natriuretic peptides, atrial natriuretic peptide, N-terminal pro-atrial natriuretic peptide, brain natriuretic peptide and its N-terminal moiety N-terminal pro-brain natriuretic peptide have also been found in critically ill patients. All of these peptides have been reported to reflect left ventricular dysfunction in these patients. The increased wall stress of the cardiac atria and ventricles is followed by the release of these natriuretic peptides. Furthermore, the release of atrial natriuretic peptide and brain natriuretic peptide might be triggered by members of the IL-6-related family and endotoxin in the critically ill. Apart from the vasoactive actions of circulating natriuretic peptides and their broad effects on the renal system, anti-ischemic properties and immunological functions have been reported for atrial natriuretic peptide. The early onset and rapid reversibility of left ventricular impairment in patients with good prognosis associated with a remarkably augmented plasma concentration of circulating natriuretic peptides suggest a possible role of these hormones in the monitoring of therapy success and the estimation of prognosis in the critically ill.

Metalloendopeptidase Inhibition Regulates Phosphorylation of p38???Mitogen-Activated Protein Kinase and Nitric Oxide Synthase in Heart After Endotoxemia

We tested the hypothesis that metalloendopeptidase inhibition using phosphoramidon during induction of endotoxemia 24 h later would down-regulate the protein expression of myocardial inducible nitric oxide synthase (iNOS) and phosphorylation of p38-mitogen-activated protein kinase (p38-MAPK). Male Sprague-Dawley rats (350-400 g) were randomly divided into sham-treated and LPS-treated groups (Escherichia. coli lipopolysaccharide [LPS] 2 mg/kg bolus + 2 mg/kg infusion for 30 min). The animals in each group were further subdivided into vehicle- and phosphoramidon (1 mg/kg bolus)-treated subgroups. Blood and heart samples were collected at 2- and 24-h postendotoxemia/phosphoramidon treatment. LPS at 2 h after its administration produced a significant decrease in mean arterial pressure that was blocked by phosphoramidon treatment. LPS at 2 and 24 h produced a significant elevation in the concentration of left ventricular endothelin-1 (ET-1) both in heart and plasma as compared with control group. This LPS-induced left ventricular ET-1 elevation at 24 h was significantly reduced by phosphoramidon. No significant alterations were observed in the myocardial protein expression of preproET-1, iNOS, and eNOS at 2 h post LPS. In 24-h post treatment groups phosphoramidon upregulated the expression of myocardial preproET-1 protein both in control and endotoxemic rat groups. Also, LPS-induced upregulated protein expression of myocardial-inducible nitric oxide synthase and increased levels of nitric oxide byproducts at 24 h were blocked by phosphoramidon. Phosphoramidon inhibited LPS-induced down-regulated expression of myocardial endothelial nitric oxide synthase and upregulated p38-MAPK phosphorylation. These results indicated that inhibition of metalloendopeptidase during induction of endotoxemia could regulate the phosphorylation of myocardial p38-MAPK and iNOS protein expression at 24-h post endotoxemia. We concluded that inhibition of metalloendopeptidases during early endotoxemia not only decreased the biosynthesis of ET-1 in heart locally but also simultaneously down-regulated myocardial protein expression of iNOS and p38-MAPK phosphorylation in the later stage of endotoxemia.

Plasma nitrite/nitrate and endothelin-1 concentrations in neonatal sepsis

AIM

To determine the changes in plasma nitrite/nitrate (NOx) and endothelin-1 (ET-1) concentrations during neonatal sepsis.

METHODS

In a prospective study, 60 consecutive newborns meeting the criteria for sepsis and without receiving exogenous nitric oxide (25 haemoculture-positive [HC+] and 35 haemoculture-negative [HC-]) were compared with 68 healthy newborns (46 full-term and 22 preterm). NOx and ET-1 concentrations were measured in each newborn within 48 h of diagnosis of sepsis and then every third day up to three determinations. SNAP-II and SNAPPE-II severity scores were performed at the moment of highest clinical severity.

RESULTS

At the beginning of the sepsis period, controls and septicaemic newborns had similar NOx and ET-1 levels, with the exception of infants with severe HC+ sepsis. Throughout the sepsis period, NOx increased in moderate HC+ sepsis and decreased in HC--sepsis, reaching a significant difference at the end of the study period (59.9 +/- 72.7 vs 33.9 15.3 micromol/L; p = 0.036). Meanwhile, ET-1 in newborns with severe HC+ sepsis remained higher than that in the moderate HC+ sepsis group and HC--group, reaching significant differences in all the periods. The highest ET-1 value was positively correlated with SNAP-II and SNAPPE-II scores.

CONCLUSION

NOx concentrations increased throughout the neonatal HC+ sepsis period, reaching significant differences after 7-9 d. The highest ET-1 levels in neonatal HC+ sepsis emerged before the NOx peak, at 3-5 d, and later decreased. Only newborns with severe HC+ sepsis presented a significant increase in ET-1 concentrations from the beginning of the septicaemic process.

Therapeutic potential for transient inhibition of adenosine deaminase in systemic inflammatory response syndrome

OBJECTIVE

We sought to determine the potential usefulness of 2'-deoxycoformycin (pentostatin), an inhibitor of adenosine deaminase, as a postinsult, or prophylactic treatment for systemic inflammatory response syndrome resulting from fecal peritonitis.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

Small animal basic science laboratory.

SUBJECTS

Male Spague-Dawley rats, weighing 300 to 350 g.

INTERVENTIONS

Rats with fecal peritonitis (intraperitoneal cecal slurry) were treated with 1 mg/kg pentostatin intraperitoneally 24 hrs before, or intravenously when signs of illness presented (2 hrs after induction of peritonitis). Signs of illness included tachycardia, tachypnea, and leukopenia. All rats received 50 mL/kg 0.9% saline resuscitative fluid at 2 hrs.

MEASUREMENTS AND MAIN RESULTS

Survival to day 6 was 100% in nonseptic sham rats, but 33% in untreated septic rats. In rats given pentostatin either 2 hrs after the insult, or 24 hrs before the insult, 6-day survival improved to 81% and 78%, respectively. Histology revealed diffuse peritonitis, and evidence of systemic inflammatory response syndrome, including local and distant site vascular damage and leukocyte activation. These responses to the septic challenge were abrogated by pentostatin treatment. Return of significant amount of tissue adenosine deaminase activity by 24 hrs and later recovery of white blood cell counts argue against any potential for inappropriate immunosuppression by pentostatin.

CONCLUSIONS

These data indicate that the novel use of pentostatin to prevent systemic inflammatory response syndrome secondary to fecal peritonitis shows uncommon promise as a therapeutic tool. All indices of systemic inflammatory response syndrome were abrogated and survival improved when pentostatin was not given until after signs of the illness became manifest. Because protection was afforded with treatment 24 hrs in advance of the inciting insult, pentostatin also has the unique potential for use as a true prophylactic agent.

Testicular macrophage modulation of Leydig cell steroidogenesis

This review will highlight recent advances in the study of the immuno-endocrinology of the testis, in particular how macrophage-derived inflammatory mediators affect Leydig cell functions. Both the beneficial and deleterious outcomes resulting from macrophage-Leydig cell interactions are discussed. A brief overview of testicular physiology is provided that discusses the functional and anatomical compartmentalization of the testis into the gamete and endocrine compartments where spermatogenesis and testosterone biosynthesis take place, respectively. The process of steroidogenesis including the activities of the steroidogenic enzymes and the role of steroidogenic acute regulatory protein (StAR) are described. The close physical association between Leydig cells and interstitial testicular macrophages suggests that these cells are functionally related. Under normal physiological and non-inflammatory conditions macrophages play an important role in Leydig cell development. If macrophages are absent from the testicular interstitium, Leydig cells fail to develop normally, which suggest that macrophages provide essential growth and differentiation factors for Leydig cells. In contrast, when macrophages are activated and elaborate inflammatory mediators, Leydig cell steroidogenesis is inhibited. Activated macrophages produce pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor (TNF) that are profoundly inhibitory to Leydig cells and appear to act as transcriptional repressors of steroidogenic enzyme gene expression. Macrophages also produce reactive oxygen species (ROS) such as hydrogen peroxide, which also inhibits Leydig cell functions. ROS appear to act acutely by perturbing Leydig cell mitochondria resulting in the inhibition of StAR protein expression. One important consequence of this immune modulation of Leydig cell function may be manifest behaviorally by switching the affected animal from 'testosterone' behavior, to 'sickness' behavior. Increased interest in immune-endocrine control of reproductive function over the past decade has stimulated research into the molecular and biochemical immunopathophysiology of the reproductive system. As investigations unravel mechanisms underlying reproductive dysfunction caused by inflammation and infection, an understanding of the role that immune-endocrine interactions play in the normal physiology of the reproductive system has emerged.

Decompensation characterized by decreased perfusion of the heart and brain during hemorrhagic shock: role of endothelin-1

BACKGROUND

Endothelin-1 (ET-1), a 21-amino-acid peptide produced by vascular endothelium, is a potent vasoconstrictor and a component of local regulation of vascular tone through its effect on underlying vascular smooth muscle. Hemorrhagic shock (HS) is characterized by compensatory regional vasoconstriction to decrease peripheral tissue perfusion and to maintain core organ perfusion. Decompensation occurs with prolonged duration of HS. In the present study, we hypothesized that systemic and vital organ tissue ET-1 concentrations would correlate with changes in systemic and vital organ perfusion associated with compensatory and decompensatory states of HS.

METHODS

After surgical instrumentation, HS was induced in male Sprague-Dawley rats by withdrawing blood via femoral artery to a mean arterial pressure of 35 to 40 mm Hg that was maintained for either 30 minutes or 90 minutes in separate groups of male Sprague-Dawley rats. Systemic hemodynamics and regional blood flow were measured using a radioactive microsphere technique. In separate groups of animals, sham, 30 minutes of HS, or 90 minutes of HS, plasma and tissue concentrations of ET-1 were determined using a radioimmunoassay technique.

RESULTS

HS maintained for 90 minutes was associated with increased arterial base deficit from 3.6 +/- 0.53 mEq/L to 13 +/- 0.37 mEq/L, decreased cardiac output from 79 +/- 18 mL/min to 18 +/- 5 mL/min, and increased systemic vascular resistance from 1,004 +/- 102 mm Hg/L. min to 2,392 +/- 447 mm. Hg/L min as compared with baseline values. With 90 minutes of HS as compared with 30 minutes of HS, perfusion was significantly decreased in brain (72 +/- 11 vs. 29 +/- 6 mL/min. 100 g tissue) and heart (483 +/- 30 vs. 173 +/- 38 mL/min. 100 g tissue) and kidney perfusion was decreased (from 114 +/- 28 mL/min/100 g tissue to 29 +/- 2 mL/min. 100 g tissue), and ET-1 concentration was increased significantly in brain (cerebral cortex, 89 +/- 14 pg/100 g tissue to 144 +/- 19 pg/100 g tissue; midbrain, 172 +/- 15 pg/100 g tissue to 211 +/- 10 pg/100 g tissue), heart (left ventricle, 312 +/- 11 pg/100 g tissue to 360 +/- 14 pg/100 g tissue), kidney (medulla, 857 +/- 61 pg/100 g tissue to 1,277 +/- 41 pg/100 g tissue), and plasma (5.31 +/- 0.6 pg/100 g tissue to 21.26 +/- 2.9 pg/mL).

CONCLUSION

Decreased vital organ and peripheral tissue perfusion, a primary decompensation effect of HS, was apparent with 90 minutes of HS but not with 30 minutes, and was associated with increased vital organ tissue and plasma ET-1 concentrations. These data suggest a role for ET-1 in control mechanisms of progressive vasoconstriction that occurs with prolonged duration of HS.

Sepsis-induced depressed contractile function of isolated ventricular myocytes is due to altered calcium transient properties

Chronic peritoneal sepsis in a rodent model produces myocardial dysfunction characterized by decreased rates of ventricular contraction and relaxation in the isolated heart preparation. However, it remains controversial whether the ventricular contractility is altered during sepsis. In the present study, we determined the effect of chronic peritoneal sepsis on the mechanical properties and intracellular Ca2+ handling of cardiac myocytes isolated from septic rats at 24 or 48 h. Mechanical properties were evaluated by use of an IonOptix MyoCam system. Myocytes were electrically stimulated at 0.5 Hz. The contractile properties analyzed included peak shortening (PS), time-to-peak shortening (TPS), time-to-90% relengthening (TR90), and maximal velocities of shortening and relengthening (+/-dL/dt). Intracellular Ca2+ handling was evaluated with fura-2 fluorescent dye. Myocytes obtained from 24-h postseptic animals exhibited a depressed PS (85% of control), normal TPS, prolonged TR90 (147% of control), and reduced +/-dL/dt (both 79% of control). Myocytes from 48-h postseptic animals also exhibited a reduced peak of intracellular Ca2+ sequestration (55% of control), but resting intracellular Ca2+ and Ca2+-transient decay were comparable with the values seen in myocytes from untreated rats. Myocytes from septic and control animals were equally responsive over a range of stimulation frequencies (0.1-5 Hz). Myocytes from septic animals were unresponsive (5% of control) to increase of extracellular Ca2+ (0.5-3 mM). These results demonstrate that sepsis produces substantial deficits in cardiac myocytes function that can be attributed to altered calcium transient properties.

Cardiac response to nitric oxide synthase inhibition using aminoguanidine in a rat model of endotoxemia

This study evaluates the effect of aminoguanidine, a preferential inhibitor of inducible nitric oxide synthase (iNOS), on the prevention of cardiac depression in acute endotoxemia. Cardiac performance was evaluated after 4 h of exposure to endotoxin. Rats (n = 5) were selected randomly to receive, by intraperitoneal injection, one of four treatments: saline, LPS (lipopolysaccharide, E. coli, 4 mg/kg, AG (aminoguanidine 100 mg/kg), and LPS + AG at various times. AG and saline treatments were administered 30 min before LPS and at 1 and 3 h after LPS injection. Hearts were perfused using the Langendorff isolated perfusion system and a balloon-tipped catheter was placed into the left ventricle to measure left ventricular developed pressure (LVDP). Myocyte contractile function was assessed with electrical field stimulation and video microscopy. Tissue was immunostained for the expression of iNOS and for nitrotyrosine, a byproduct of protein nitration by peroxynitrite. Perfused hearts from LPS-treated rats exhibited a 57% decrease (P < 0.05) in LVDP compared to saline-treated animals. No improvement in ventricular function was observed with the administration of AG. Similarly, cardiac myocytes prepared from LPS-treated animals demonstrated a significant (P < 0.05) reduction in percent and velocity of shortening and this effect was unaltered with the same dose of AG. AG administration significantly reduced serum nitrite/nitrate levels (P < 0.05) in endotoxemic rats to control levels. Localized expression of iNOS in the myocardium was lessened with AG treatment and was not associated with peroxynitrite formation in this model of endotoxemia. The results indicate that AG given in vivo before and after endotoxin (at a concentration sufficient to decrease NO production) did not reduce cardiac depression. We conclude that selective inhibition of iNOS and the reduction of NO production do not prevent cardiac dysfunction at an early stage in an acute model of endotoxemia.

Induction of peritoneal sepsis increases the susceptibility of isolated hearts to a calcium paradox-mediated injury

The present study was designed to test the hypothesis that induction of chronic peritoneal sepsis in rats would produce a more severe calcium paradox-mediated myocardial injury in isolated heart preparation than is seen in normal hearts, and that this would be inhibited by sucrose as in normal hearts. Male Sprague-Dawley rats were made septic using 200 mg of cecal material (obtained from a donor rat) suspended in 5 mL of 5% dextrose in sterile water D5 W/kg. In septic animals, the cecal material was injected in the peritoneum, while sham-septic animals received only D5 W/kg (5 mL/kg). A third group consisting of normal rats (no surgery) group was also included. Hearts were harvested from all three groups and were subjected to a calcium paradox-mediated injury in an isolated heart preparation. Hearts were perfused with Krebs-Henseleit (KH) medium and were allowed to stabilize, followed by a perfusion with Ca2+-free KH for 10 min. After this 10-min Ca2+-free KH perfusion, rats were reperfused with KH medium for 60 min. Ca2+-free KH medium was used in control experiments, while sucrose experiments were conducted with the same medium except that 150 mM sucrose replaced 75 mM NaCl. A marked decrease in ATP and phosphocreatine occurred during Ca2+ reperfusion in all hearts in absence of sucrose. In the presence of the disaccharide, no change in high-energy phosphate (HEP) levels was observed in normal hearts, while lower ATP concentrations were seen in sham and septic hearts. Thus, sucrose did not inhibit cellular injury in sham and septic hearts as it did in normal hearts, and this might be due to a smaller HEP availability. Control studies with normal, sham, and septic hearts exhibited cessation of contractions in the absence of Ca2+, and appearance of large amounts of cytosolic protein in the effluent perfusate during Ca2+ reperfusion. With normal hearts, perfusion with sucrose caused a 96% inhibition of the total creatine kinase (CK) release observed in control experiments. With sham hearts, 32% of CK release was inhibited by sucrose, while 68% of the CK release was attributed to stress associated with surgery performed in the sham-septic group. In septic hearts, only 8% of the CK release was inhibited by sucrose, suggesting that more severe myocardial injury occurs when septic hearts are subjected to a calcium paradox as compared to other groups. It is evident that sucrose can inhibit a small fraction of the CK release from septic hearts during the calcium paradox as compared to the large CK loss associated with sham sepsis. We have concluded that induction of sepsis made the heart more susceptible to a calcium paradox-mediated myocardial injury.

Nitric oxide-derived nitrate anion contributes to endotoxic shock and multiple organ injury/dysfunction

OBJECTIVE

Because nitrate represents the major end-product of nitric oxide in vivo and can affect enzyme activity, cell electrophysiological functions, and cell membrane integrity, we hypothesized that overaccumulated nitric oxide-derived nitrate anion in tissues or organs in vivo may contribute to endotoxic shock and multiple organ injury/dysfunction during endotoxemia.

DESIGN

Prospective, experimental animal study.

SETTING

Laboratory at a university hospital.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Rats were injected intraperitoneally with 5, 10, or 20 mg/kg lipopolysaccharide or saline and were studied in groups at 0, 6, 12, and 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Significant differences were seen between nitrate concentrations in the heart, lung, kidney, liver, brain, aorta, diaphragm, spleen, thymus, testis or ovary, hind limb muscle, intestine, adipose tissue, bone, bladder, urine and plasma, which imply a nitrate gradient between intracellular and extracellular compartments. Lipopolysaccharide significantly increased nitrate concentration at 12 hrs in most tissues and organs, except in the brain, adipose tissue, and muscle. It increased more in plasma than in tissues. The lipopolysaccharide dose-dependent nitrate concentration was observed only in the aorta and lungs. The nitrate concentration change was paralleled by the systemic inflammatory response syndrome, as indicated by alterations of myeloperoxidase activity and by impaired histologic and cellular membrane integrity in tissues and organs. Mean arterial pressure was negatively correlated with nitrate concentration modifications in the aorta during 24 hrs of endotoxemia.

CONCLUSIONS

These results collectively indicate that overaccumulated nitric oxide-derived nitrate anion in tissues or organs in vivo contributes to endotoxic shock and multiple organ injury/dysfunction during endotoxemia.

Preproendothelin-1 gene polymorphism is related to a change in vascular reactivity in the human mammary artery in vitro

A gene polymorphism of preproendothelin-1 (a G-to-T transversion that predicts a Lys/Asn change at codon 198) associated with an increased risk of hypertension has been recently described in patients carrying the T allele. No study has yet determined the impact of this polymorphism on vascular reactivity, although a functional role for endothelin-1 in the pathophysiology of hypertension has been clarified. At subthreshold concentrations, endothelin-1 and angiotensin II induce a potentiation of alpha-adrenergic-dependent vascular tone caused by an increased sensitivity of the contractile apparatus to calcium. We investigated phenylephrine-induced tone and its amplification by endothelin-1 and angiotensin II in human mammary artery rings in vitro. Contractions to phenylephrine (0.1 to 100 micromol) and endothelin-1 (0.1 to 300 nmol) were not significantly different in rings from GT/TT (n=27) and GG (n=21) patients. A subthreshold concentration of endothelin-1 (10 pmol) potentiated a phenylephrine-induced contraction (eg, 44 +/- 12% increase in tone with phenylephrine 1 micromol/L, P<0.001) that was significantly higher in the GT/TT group than in the GG group (eg, 44 +/- 12% versus 82 +/- 11%, P<0.01). A similar effect on response to phenylephrine was observed with a subthreshold concentration of angiotensin II. We also found a higher response to calcium in arteries from GT/TT patients. Endothelium-dependent or -independent relaxations were unaffected by the genotype. These data suggest that the preproendothelin-1 gene polymorphism is associated with a higher potentiating effect of endothelin-1 and angiotensin II, probably in relation with higher calcium sensitivity. These changes in vascular reactivity might help to understand the relations between this polymorphism and cardiovascular disorders.

Activation of cardiac endothelium as a compensatory component in endotoxin-induced cardiomyopathy: role of endothelin, prostaglandins, and nitric oxide

BACKGROUND

In view of growing evidence of an important endothelial paracrine regulation of cardiac function, the present study investigated the role of cardiac endothelium-derived endothelin-1 (ET-1), prostaglandins, and nitric oxide (NO) during endotoxin-induced cardiomyopathy in rabbits.

METHODS AND RESULTS

Immunohistochemical studies showed a marked transient coinduction of the inducible isoforms of NO synthase (NOS-2) and cyclooxygenase (COX-2) in endocardial endothelium and coronary arteriolar endothelium of hearts 12 hours after intravenous administration of lipopolysaccharide (LPS+12h); staining for both isoforms was much weaker 24 hours later (LPS+36h). Nitrotyrosine localization was similar to that of NOS-2, suggesting a NOS-2-related endothelial formation of peroxynitrite in septic hearts. Contractile performance of papillary muscles was depressed in both LPS-treated groups. In the LPS+12h group, however, isometric twitches were significantly prolonged (482+/-14 versus 420+/-14 ms in the saline-treated group, P<0.005). This twitch prolongation was completely reversed by simultaneous administration of BQ-123 and indomethacin to block endogenous ET-1 and prostaglandins, respectively. In addition, in the LPS+12h group, myocardial inotropic responsiveness to exogenous ET-1 was enhanced (P<0.01).

CONCLUSIONS

Cardiac endothelial activation and myocardial sensitization to endothelium-derived mediators may be part of an adaptive response in the early (12 hours) stages of septic cardiomyopathy.

The role of endothelin in the pathogenesis of Chagas' disease

Infection with Trypanosoma cruzi causes a generalised vasculitis of several vascular beds. This vasculopathy is manifested by vasospasm, reduced blood flow, focal ischaemia, platelet thrombi, increased platelet aggregation and elevated plasma levels of thromboxane A(2) and endothelin-1. In the myocardium of infected mice, myonecrosis and a vasculitis of the aorta, coronary artery, smaller myocardial vessels and the endocardial endothelium are observed. Immunohistochemistry studies employing anti-endothelin-1 antibody revealed increased expression of endothelin-1, most intense in the endocardial and vascular endothelium. Elevated levels of mRNA for prepro endothelin-1, endothelin converting enzyme and endothelin-1 were observed in the infected myocardium. When T. cruzi-infected mice were treated with phosphoramidon, an inhibitor of endothelin converting enzyme, there was a decrease in heart size and severity of pathology. Mitogen-activated protein kinases and the transcription factor activator-protein-1 regulate the expression of endothelin-1. Therefore, we examined the activation of mitogen-activated protein kinases in the myocardium by T. cruzi. Western blot demonstrated an extracellular signal regulated kinase. In addition, the activator-protein-1 DNA binding activity, as determined by electrophoretic mobility shift assay, was increased. Increased expression of cyclins A and cyclin D1 was observed in the myocardium, and immunohistochemistry studies revealed that interstitial cells and vascular and endocardial endothelial cells stained intensely with antibodies to these cyclins. These data demonstrate that T. cruzi infection of the myocardium activates extracellular signal regulated kinase, activator-protein-1, endothelin-1, and cyclins. The activation of these pathways is likely to contribute to the pathogenesis of chagasic heart disease. These experimental observations suggest that the vasculature plays a role in the pathogenesis of chagasic cardiomyopathy. Additionally, the identification of these pathways provides possible targets for therapeutic interventions to ameliorate or prevent the development of cardiomyopathy during T. cruzi infection.

alpha-atrial natriuretic peptide, cyclic guanosine monophosphate, and endothelin in plasma as markers of myocardial depression in human septic shock

OBJECTIVE

To assess the value of alpha-atrial natriuretic peptide (alpha-ANP), second messenger cyclic guanosine monophosphate (cGMP,) and endothelin as markers of myocardial depression in septic shock.

DESIGN

Prospective observational study.

SETTING

Medical intensive care unit (ICU) of a university hospital.

PATIENTS

Fourteen consecutive patients with septic shock and arterial and pulmonary artery catheters in place.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic variables and plasma levels of alpha-ANP, cGMP, and endothelin were measured every 6 hrs for 3 days after admission. Eight patients died from shock in the ICU. The nadir left ventricular stroke work index (LVSWI) was below 35 g/m2 in all patients, and the median peak circulating alpha-ANP (n < 68 pg/mL) was 276 pg/mL (range, 79-1056), the median peak cGMP (n < 2.1 ng/mL) was 8.1 ng/mL (range, 3.2-29.7), and the median peak endothelin (n < 5.3 pg/mL) was 15.5 pg/mL (range, 8.5-33.9), supranormal in all patients. Outcome groups differed in the course of cardiac index and LVSWI, which were lower in nonsurvivors despite similar filling pressures and more intensive inotropic treatment (p < .01). The course of alpha-ANP, cGMP, and endothelin plasma levels also differed between groups, with higher levels in nonsurvivors (p < .05). As for pooled data, the mean daily or nadir LVSWI inversely related to mean daily or peak alpha-ANP, cGMP, and endothelin levels, respectively (p < .05). The area under the receiver operating characteristic curve for myocardial depression (LVSWI < 35 g/m2) was for alpha-ANP and endothelin 0.77, and for cGMP 0.85 (p < .01). The optimum cutoff values for alpha-ANP, cGMP, and endothelin were 172 pg/mL, 4.5 ng/mL, and 10.0 pg/mL, respectively. The sensitivity for myocardial depression of alpha-ANP, cGMP, and endothelin was 68%, 77%, and 72%, and the specificity was 82%, 93%, and 69%, respectively.

CONCLUSIONS

Circulating alpha-ANP, endothelin, and, particularly, cGMP may be markers of the myocardial depression of human septic shock, which is associated with mortality.

The dissociation between upregulated endothelins and hemodynamic responses during polymicrobial sepsis

Polymicrobial sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase. Although studies have suggested that endothelins (ETs) contribute to the development of shock after a bolus injection of endotoxin, little is known about the role of ETs in the transition from the hyperdynamic phase to the hypodynamic phase of sepsis. To study this, male adult rats were subjected to sepsis by cecal ligation and puncture (CLP) followed by fluid resuscitation. Plasma levels of ET-1 and ET-2 were measured by radioimmunoassay at 2, 5, 10 h (i.e. the early stage of sepsis), and 20 h (late stage) following CLP or sham operation. Tissue levels of ET-1 and ET-2 were determined in the heart, lungs, small intestine, and spleen at 5 h after CLP or sham operation. In addition, preproendothelin-1 (precursor of ET-1) gene expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) at 5 h in the heart, lungs, small intestine, spleen, and liver. The results indicate that plasma levels of ET-1 and ET-2 were not different from values of sham groups at 2 and 20 h, but were significantly higher than the sham values at 5 and 10 h after CLP. While there were no significant increases in tissue levels of ET-1 and ET-2 at 5 h post-CLP, RT-PCR analysis indicates a significant upregulation of preproendothelin-1 gene expression in the heart, spleen, and liver (but not in the lungs or small intestine) at 5 h after the onset of sepsis. These results indicate that the heart, spleen, and liver appear to be important ET-producing organs during the early stage of sepsis. The lack of significant increases in tissue ET levels could be due to the possibility that the newly converted peptide is quickly transferred to the bloodstream. Since the hyperdynamic phase of sepsis occurs at 2-10 h and the hypodynamic phase occurs at 20 h after CLP, the increased plasma levels of ET at 5 and 10 h suggest that mediators other than ETs (such as adrenomedullin) are responsible for producing the biphasic hemodynamic responses during the progression of polymicrobial sepsis.