Antimicrobial peptides and other potential biomarkers of critical illness in SARS-CoV-2 patients with acute kidney injury. AMPAKI-CoV study

Antimicrobial peptides (AMPs) constitute a complex network of 10-100 amino acid sequence molecules widely distributed in nature. While over 300 AMPs have been described in mammals, cathelicidins and defensins remain the most extensively studied. Some publications have explored the role of AMPs in COVID-19, but these findings are preliminary, and in vivo studies are still lacking. In this study, we report the plasma levels of five AMPs (LL-37, α-defensin 1, α-defensin 3, β-defensin 1, and β-defensin 3), using the ELISA technique (MyBioSource, San Diego, CA, United States, kits MBS2601339 (beta-defensin 1), MBS2602513 (beta-defensin 3), MBS703879 (alpha-defensin 1), MBS706289 (alpha-defensin 3), MBS7234921 (LL37)), and the measurement of six cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1), through the magnetic bead immunoassay Milliplex® and the MAGPIX® System (MilliporeSigma, Darmstadt, Germany, kit HCYTOMAG-60 K (cytokines)), in 15 healthy volunteers, 36 COVID-19 patients without Acute Kidney Injury (AKI) and 17 COVID-19 patients with AKI. We found increased levels of α-defensin 1, α-defensin 3 and β-defensin 3, in our COVID-19 population, when compared to healthy controls, along with higher levels of interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1. These findings suggest that these AMPs and cytokines may play a crucial role in the systemic inflammatory response and tissue damage characterizing severe COVID-19. The levels of α-defensin 1 and α-defensin 3 were significantly higher in COVID-19 AKI group in comparison to the non-AKI group. Furthermore, IL-10 and the product IL-10 × IL-1B showed excellent performance in discriminating AKI, with AUCs of 0.86 and 0.88, respectively. Among patients with COVID-19, AMPs may play a key role in the inflammation process and disease progression. Additionally, α-defensin 1 and α-defensin 3 may mediate the AKI process in these patients, representing an opportunity for further research and potential therapeutic alternatives in the future.

Transcriptome analysis of six tissues obtained post-mortem from sepsis patients

Septic shock is a life-threatening clinical condition characterized by a robust immune inflammatory response to disseminated infection. Little is known about its impact on the transcriptome of distinct human tissues. To address this, we performed RNA sequencing of samples from the prefrontal cortex, hippocampus, heart, lung, kidney and colon of seven individuals who succumbed to sepsis and seven uninfected controls. We identified that the lungs and colon were the most affected organs. While gene activation dominated, strong inhibitory signals were also detected, particularly in the lungs. We found that septic shock is an extremely heterogeneous disease, not only when different individuals are investigated, but also when comparing different tissues of the same patient. However, several pathways, such as respiratory electron transport and other metabolic functions, revealed distinctive alterations, providing evidence that tissue specificity is a hallmark of sepsis. Strikingly, we found evident signals of accelerated ageing in our sepsis population.

Exercise Induced-Cytokines Response in Marathon Runners: Role of ACE I/D and BDKRB2 +9/-9 Polymorphisms

Renin-angiotensin system (RAS) and kallikrein-kinin system (KKS) have a different site of interaction and modulate vascular tone and inflammatory response as well on exercise adaptation, which is modulated by exercise-induced cytokines. The aim of the study was to evaluate the role of ACE I/D and BDKRB2 +9/−9 polymorphism on exercise-induced cytokine response. Seventy-four male marathon finishers, aged 30 to 55 years, participated in this study. Plasma levels of exercise-induced cytokines were determined 24 h before, immediately after, and 24 h and 72 h after the São Paulo International Marathon. Plasma concentrations of MCP-1, IL-6 and FGF-21 increased after marathon in all genotypes of BDKRB2. IL-10, FSTL and BDNF increased significantly after marathon in the genotypes with the presence of the −9 allele. FSTL and BDNF concentrations were higher in the −9/−9 genotype compared to the +9/+9 genotype before (p = 0.006) and after the race (p = 0.023), respectively. Apelin, IL-15, musclin and myostatin concentrations were significantly reduced after the race only in the presence of −9 allele. Marathon increased plasma concentrations of MCP1, IL-6, BDNF and FGF-21 in all genotypes of ACE I/D polymorphism. Plasma concentrations of IL-8 and MIP-1alpha before the race (p = 0.015 and p = 0.031, respectively), of MIP-1alpha and IL-10 after the race (p = 0.033 and p = 0.047, respectively) and VEGF 72 h after the race (p = 0.018) were lower in II homozygotes compared to runners with the presence of D allele. One day after the race we also observed lower levels of MIP-1alpha in runners with II homozygotes compared to DD homozygotes (p = 0.026). Before the marathon race myostatin concentrations were higher in DD compared to II genotypes (p = 0.009). Myostatin, musclin, IL-15, IL-6 and apelin levels decreased after race in genotypes with the presence of D allele. After the race ACE activity was negatively correlated with MCP1 (r = −56, p < 0.016) and positively correlated with IL-8, IL-10 and MIP1-alpha (r = 0.72, p < 0.0007, r = 0.72, p < 0.0007, r = 0.47, p < 0.048, respectively). The runners with the −9/−9 genotype have greater response in exercise-induced cytokines related to muscle repair and cardioprotection indicating that BDKRB2 participate on exercise adaptations and runners with DD genotype have greater inflammatory response as well as ACE activity was positively correlated with inflammatory mediators. DD homozygotes also had higher myostatin levels which modulates protein homeostasis.

Short-term Obesity Worsens Heart Inflammation and Disrupts Mitochondrial Biogenesis and Function in an Experimental Model of Endotoxemia

Cardiomyopathy is a well-known complication of sepsis that may deteriorate when accompanied by obesity. To test this hypothesis we fed C57black/6 male mice for 6 week with a high fat diet (60% energy) and submitted them to endotoxemic shock using E. coli LPS (10 mg/kg). Inflammatory markers (cytokines and adhesion molecules) were determined in plasma and heart tissue, as well as heart mitochondrial biogenesis and function. Obesity markedly shortened the survival rate of mouse after LPS injection and induced a persistent systemic inflammation since TNFα, IL-1β, IL-6 and resistin plasma levels were higher 24 h after LPS injection. Heart tissue inflammation was significantly higher in obese mice, as detected by elevated mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα). Obese animals presented reduced maximum respiratory rate after LPS injection, however fatty acid oxidation increased in both groups. LPS decreased mitochondrial DNA content and mitochondria biogenesis factors, such as PGC1α and PGC1β, in both groups, while NRF1 expression was significantly stimulated in obese mice hearts. Mitochondrial fusion/fission balance was only altered by obesity, with no influence of endotoxemia. Obesity accelerated endotoxemia death rate due to higher systemic inflammation and decreased heart mitochondrial respiratory capacity.

Banana green peels extract protects against nonalcoholic fatty liver disease in high-fat-fed mice through modulation of lipid metabolism and inflammation

We investigate the effect of the banana green peels extract (BPE) as a preventive treatment against NAFLD in high-fat diet fed mice. Mice received daily doses of 100 or 250 mg/kg of BPE for 12 weeks along with the high-fat diet. BPE reduced weight gain (p < .0001), adipose tissue hypertrophy (p < .0001), and improved glucose homeostasis (p < .0001). Plasma levels of glucose-dependent insulinotropic polypeptide, triglycerides, total cholesterol, LDL-cholesterol, non-esterified fatty acids, aspartate and alanine transaminase, leptin, and resistin were decreased in BPE treated mice (p < .05). BPE effects on lipid metabolism were associated with decreased gene expression of lipogenic enzymes and increased expression of enzymes related to fatty acid and cholesterol degradation (p < .05). Plasma and liver bile acid (BA) profiles were modulated by BPE, with positive correlations between specific BA and UCP-1, CPT-1 and PGC-1β expression in brown adipose tissue (p < .05). BPE reduced hepatic steatosis and inflammation, possibly due to reduced p65 NF-κB nuclear translocation (p < .05) and modulation of oxidative stress (p < .05). These data indicate that BPE is a source of phytochemical compounds with promising effects toward the prevention of metabolic disorders associated with obesity.

Endothelial injury in COVID-19 and septic patients

Systemic inflammatory response, as observed in sepsis and severe COVID-19, may lead to endothelial damage. Therefore, we aim to compare the extent of endothelial injury and its relationship to inflammation in both diseases.

We included patients diagnosed with sepsis (SEPSIS group, n = 21), mild COVID-19 (MILD group, n = 31), and severe COVID-19 (SEVERE group, n = 24). Clinical and routine laboratory data were obtained, circulating cytokines (INF-γ, TNF-α, and IL-10) and endothelial injury markers (E-Selectin, Tissue Factor (TF) and von Willebrand factor (vWF)) were measured.

Compared to the SEPSIS group, patients with severe COVID-19 present similar clinical and laboratory data, except for lower circulating IL-10 and E-Selectin levels. Compared to the MILD group, patients in the SEVERE group showed higher levels of TNF-α, IL-10, and TF. There was no clear relationship between cytokines and endothelial injury markers among the three studied groups; however, in SEVERE COVID-19 patients, there is a positive relationship between INF-γ with TF and a negative relationship between IL-10 and vWF.

In conclusion, COVID-19 and septic patients have a similar pattern of cytokines and endothelial dysfunction markers. These findings highlight the importance of endothelium dysfunction in COVID-19 and suggest that endothelium should be better evaluated as a therapeutic target for the disease.

Time Course and Role of Exercise-Induced Cytokines in Muscle Damage and Repair After a Marathon Race

Endurance exercise induces an increase in the expression of exercise-induced peptides that participate in the repair and regeneration of skeletal muscles. The present study aimed to evaluate the time course and role of exercise-induced cytokines in muscle damage and repair after a marathon race. Fifty-seven Brazilian male amateur marathon finishers, aged 30–55 years, participated in this study. The blood samples were collected 24 h before, immediately after, and 24 and 72 h after the São Paulo International Marathon. The leukogram and muscle damage markers were analyzed using routine automated methodology in the clinical laboratory. The plasma levels of the exercise-induced cytokines were determined using the Human Magnetic Bead Panel or enzyme-linked immunosorbent assays [decorin and growth differentiation factor 15 (GDF-15)]. A muscle damage was characterized by an increase in plasma myocellular proteins and immune changes (leukocytosis and neutrophilia). Running the marathon increased interleukin (IL)-6 (4-fold), IL-8 (1.5-fold), monocyte chemoattractant protein-1 (2.4-fold), tumor necrosis factor alpha (TNF-α) (1.5-fold), IL-10 (11-fold), decorin (1.9-fold), GDF-15 (1.8-fold), brain-derived neurotrophic factor (BDNF) (2.7-fold), follistatin (2-fold), and fibroblast growth factor (FGF-21) (3.4-fold) plasma levels. We also observed a reduction in musclin, myostatin, IL-15, and apelin levels immediately after the race (by 22–36%), 24 h (by 26–52%), and 72 h after the race (by 25–53%). The changes in BDNF levels were negatively correlated with the variations in troponin levels (r = −0.36). The variations in IL-6 concentrations were correlated with the changes in follistatin (r = 0.33) and FGF-21 (r = 0.31) levels after the race and with myostatin and irisin levels 72 h after the race. The changes in IL-8 and IL-10 levels had positive correlation with variation in musclin (p < 0.05). Regeneration of exercise-induced muscle damage involves the participation of classical inflammatory mediators, as well as GDF-15, BDNF, follistatin, decorin, and FGF-21, whose functions include myogenesis, mytophagia, satellite cell activation, and downregulation of protein degradation. The skeletal muscle damage markers were not associated to myokines response. However, BDNF had a negative correlation with a myocardial damage marker. The classical anti-inflammatory mediators (IL-10, IL-8, and IL-6) induced by exercise are associated to myokines response immediately after the race and in the recovery period and may affect the dynamics of muscle tissue repair.

Lower peripheral blood Toll-like receptor 3 expression is associated with an unfavorable outcome in severe COVID-19 patients

The role of innate immunity in COVID-19 is not completely understood. Therefore, this study explored the impact of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection on the expression of Pattern Recognition Receptors (PRRs) in peripheral blood cells and their correlated cytokines. Seventy-nine patients with severe COVID-19 on admission, according to World Health Organization (WHO) classification, were divided into two groups: patients who needed mechanical ventilation and/or deceased (SEVERE, n = 50) and patients who used supplementary oxygen but not mechanical ventilation and survived (MILD, n = 29); a control group (CONTROL, n = 17) was also enrolled. In the peripheral blood, gene expression (mRNA) of Toll-like receptors (TLRs) 3, 4, 7, 8, and 9, retinoic-acid inducible gene I (RIGI), NOD-like receptor family pyrin domain containing 3 (NLRP3), interferon alpha (IFN-α), interferon beta (IFN-β), interferon gamma (IFN-γ), interferon lambda (IFN-λ), pro-interleukin(IL)-1β (pro-IL-1β), and IL-18 was determined on admission, between 5–9 days, and between 10–15 days. Circulating cytokines in plasma were also measured. When compared to the COVID-19 MILD group, the COVID-19 SEVERE group had lower expression of TLR3 and overexpression of TLR4.

Cathelicidin protects mice from Rhabdomyolysis-induced Acute Kidney Injury

Background: Cathelicidins are ancient and well-conserved antimicrobial peptides (AMPs) with intriguing immunomodulatory properties in both infectious and non-infectious inflammatory diseases. In addition to direct antimicrobial activity, cathelicidins also participate in several signaling pathways inducing both pro-inflammatory and anti-inflammatory effects. Acute kidney injury (AKI) is common in critically ill patients and is associated with high mortality and morbidity. Rhabdomyolysis is a major trigger of AKI. Objectives: Here, we investigated the role of cathelicidins in non-infectious Acute kidney Injury (AKI). Method: Using an experimental model of rhabdomyolysis, we induced AKI in wild-type and cathelicidin-related AMP knockout (CRAMP^-/-) mice. Results: We previously demonstrated that CRAMP^-/- mice, as opposed wild-type mice, are protected from AKI during sepsis induced by cecal ligation and puncture. Conversely, in the current study, we show that CRAMP^-/- mice are more susceptible to the rhabdomyolysis model of AKI. A more in-depth investigation of wild-type and CRAMP^-/- mice revealed important differences in the levels of several inflammatory mediators. Conclusion: Cathelicidins can induce a varied and even opposing repertoire of immune-inflammatory responses depending on the subjacent disease and the cellular context.

Muscle degradation, vitamin D and systemic inflammation in hospitalized septic patients

PURPOSE

To date, the relationship between systemic inflammation and muscle changes observed by ultrasonography in septic patients in clinical studies is not known. Furthermore, the role of vitamin D on muscle changes in these patients needs to be investigated.

MATERIALS AND METHODS

Forty-five patients admitted to the ICU due to severe sepsis or septic shock. Blood samples were collected to evaluate systemic inflammation (interleukin (IL)-10, IL-1β, IL-1α, IL-6, IL-8 and tumor necrosis factor-α(TNF-α)) and vitamin D. Muscle mass was evaluated by ultrasound during hospitalization. Clinical tests of muscle strength (Medical Research Council (MRC) scale and handgrip) were performed after the awakening of patients.

RESULTS

There was a reduction in day 2 values to hospital discharge on TNF-alpha, IL-8, IL-6 and IL-10 (p < .05). The muscle mass showed a significant decline from day 6 of the ICU. After awakening, the patients had a significant increase in muscle strength (p < .05). There was a positive association between muscle mass variation (day 2 - ICU) with absolute values of IL-8 (r = 0.38 p = .05). For muscle strength, there was a negative association between handgrip strength with IL-8 (r = -0.36 p < .05) on ICU discharge. The vitamin D showed a positive association with the handgrip strength of the day 1 of the awakening (r = 0.51 p < .05).

CONCLUSIONS

In septic patients, there is an association between inflammation and changes in muscle mass and strength during ICU stay, which is similar to those observed in experimental studies. In addition, there was an association of vitamin D with recovery of muscle strength during hospitalization.

Hypertonic solution-induced preconditioning reduces inflammation and mortality rate

Background

Dysregulated inflammatory response is common cause of organ damage in critical care patients. Preconditioning/tolerance is a strategy to prevent exacerbated inflammation. The aim of this study is to analyze hypertonic saline 7.5% as a potential inducer of preconditioning that protect from a lethal dose of LPS and modulates systemic inflammatory profile in mice.

Methods

Male Balb/C mice received intravenous (i.v.) injections of Hypertonic solution (NaCl 7.5%) (0.8 ml) for 3 days, on day 8th was challenged with LPS 15 mg/kg. Controls with Saline 0.9%, urea and sorbitol were performed. Microarray of mRNA expression was analyzed from HS versus saline from macrophages to identified the pathways activated by HS.

Results

HS preconditioning reduced mortality after LPS injection as well reduced the cytokines release in plasma of the animals challenged by LPS. In order to check how HS induces a preconditioning state we measured plasma cytokines after each HS infusion. Repeated HS injections induced a state of preconditioning that reprograms the inflammatory response, resulting in reduced inflammatory cytokine production. A microarray of mRNA demonstrated that Hypertonic solution increased the expression of several genes in special Mapkbp1 and Atf3.

Conclusion

hypertonic solution induces preconditioning/tolerance reducing mortality and inflammatory response after LPS challenge.

Analysis of inflammatory and metabolic biomarkers in patients submitted to abdominoplasty after bariatric surgery

Purpose:

To evaluate the serum variations of Interleukins (Il) and CPR of abdominoplasties in post-bariatric patients and, to equate the homeostasis (HOMA) from the variations of glycemia and insulin to evolute the metabolic modifications.

Methods:

Fourteen women were submitted to abdominoplasties with weight loss after a gastroplasty. Levels of IL₄, IL₆, IL₁₀, CRP, glycemia and insulin were obtained during the pre-operative, trans-operative, 24 hours post, 7^th and 14^th postoperative days.

Results:

The IL₄ was higher at 24 hours post-surgery, and after a moderate decrease, it remained high until the 14^th day. The IL₆ and CRP had an expressive increase during the trans-operative period. The CRP remained high, and the IL₆ decreased on the 7^th and 14^th days. The IL₁₀ increased during the transoperative period, and it posteriorly decreased to lower levels in comparison to the pre-operative period. The already increased glycemia during the pre-operative period was even higher during the trans-operative and then, returned to preliminary values on the 7^th and 14^th days after surgery. The HOMA accompanied the insulin.

Conclusion:

The inflammatory and glycemic serum levels decrease after abdominiplasty in obese post-bariatric patients.

The PARP inhibitor olaparib exerts beneficial effects in mice subjected to cecal ligature and puncture and in cells subjected to oxidative stress without impairing DNA integrity: A potential opportunity for repurposing a clinically used oncological drug for the experimental therapy of sepsis

Poly(ADP-ribose) polymerase (PARP) is involved in the pathogenesis of cell dysfunction, inflammation and organ failure during septic shock. The goal of the current study was to investigate the efficacy and safety of the clinically approved PARP inhibitor olaparib in experimental models of oxidative stress in vitro and in sepsis in vivo. In mice subjected to cecal ligation and puncture (CLP) organ injury markers, circulating and splenic immune cell distributions, circulating mediators, DNA integrity and survival was measured. In U937 cells subjected to oxidative stress, cellular bioenergetics, viability and DNA integrity were measured. Olaparib was used to inhibit PARP. The results show that in adult male mice subjected to CLP, olaparib (1-10 mg/kg i.p.) improved multiorgan dysfunction. Olaparib treatment reduced the degree of bacterial CFUs. Olaparib attenuated the increases in the levels of several circulating mediators in the plasma. In the spleen, the number of CD4+ and CD8+ lymphocytes were reduced in response to CLP; this reduction was inhibited by olaparib treatment. Treg but not Th17 lymphocytes increased in response to CLP; these cell populations were reduced in sepsis when the animals received olaparib. The Th17/Treg ratio was lower in CLP-olaparib group than in the CLP control group. Analysis of miRNA expression identified a multitude of changes in spleen and circulating white blood cell miRNA levels after CLP; olaparib treatment selectively modulated these responses. Olaparib extended the survival rate of mice subjected to CLP. In contrast to males, in female mice olaparib did not have significant protective effects in CLP. In aged mice olaparib exerted beneficial effects that were less pronounced than the effects obtained in young adult males. In in vitro experiments in U937 cells subjected to oxidative stress, olaparib (1-100 μM) inhibited PARP activity, protected against the loss of cell viability, preserved NAD⁺ levels and improved cellular bioenergetics. In none of the in vivo or in vitro experiments did we observe any adverse effects of olaparib on nuclear or mitochondrial DNA integrity. In conclusion, olaparib improves organ function and extends survival in septic shock. Repurposing and eventual clinical introduction of this clinically approved PARP inhibitor may be warranted for the experimental therapy of septic shock.

Evolution of Biomarkers of Atherogenic Risk in Liver Transplantation Recipients

BACKGROUND

Cardiovascular disease is a major contributing factor to long-term mortality after liver transplantation (LT).

METHODS

This study evaluated the evolution of atherogenic risk in liver transplant recipients (LTRs). Thirty-six subjects were prospectively enrolled at 12 months and followed for 48 months after liver transplantation. Serum biomarkers of endothelial dysfunction (sICAM-1 and sVCAM-1), chronic inflammation (serum amyloid A), and oxidative stress (myeloperoxidase) were measured at 12 and 48 months after LT. Additionally, at 12 months all patients underwent a cardiac computed tomography (CT) scan and a coronary artery calcium score (CACS).

RESULTS

The prevalence of risk factors of metabolic syndrome (MS) increased over the course of the study. The patients' sVCAM-1 and sICAM-1 increased from 1.82 ± 0.44 ng/mL to 9.10 ± 5.82 ng/mL (P < .001) and 0.23 ± 0.09 ng/mL to 2.7 ± 3.3 ng/mL, respectively from month 12 to 48. Serum myeloperoxidase increased from 0.09 ± 0.07 ng/mL to 3.46 ± 3.92 ng/mL (P < .001) over the course of the study. Serum amyloid A also increased from 21.4 ± 40.7 ng/mL at entry to 91.5 ± 143.6 ng/mL at end of study (P < .001).

CONCLUSION

No association between these biomarkers and MS was noted. The cardiac CT revealed mild and moderate disease in 19% and 25% of the cohort, respectively. No association between serum biomarkers and CACS was noted. Serum biomarkers of atherogenic risk increase rapidly in LTRs and precede coronary plaques.

Reduction of venous pressure during the resection of liver metastases compromises enteric blood flow: IGFBP-1 as a novel biomarker of intestinal barrier injury

OBJECTIVES

Disruption of the intestinal barrier and bacterial translocation commonly occur when intestinal blood flow is compromised. The aim of this study was to determine whether liver resection induces intestinal damage.

METHODS

We investigated intestinal fatty-acid binding protein and insulin-like growth factor binding protein levels in the plasma of patients who underwent liver resection.

RESULTS

We show that liver resection is associated with significant intestinal barrier injury, even if the Pringle maneuver is not performed.

CONCLUSION

We propose the use of insulin-like growth factor binding protein-1 as a novel biomarker of intestinal damage in such situations.

Proteomic profiling identifies N-acetylmuramoyl-l-alanine amidase as a novel biomarker of sepsis

AIM

Sepsis is a critical condition that leads to high mortality and is the most common cause of death in intensive care units. Despite exhaustive efforts by the scientific community, a reliable biomarker for diagnosis, evolution and prognosis of sepsis is still lacking. Results & methodology: Here, using high-throughput proteomics, we describe N-acetylmuramoyl-l-alanine amidase as a novel candidate for differentiating infectious and noninfectious inflammatory syndromes.

DISCUSSION & CONCLUSION

This is the first description of N-acetylmuramoyl-l-alanine amidase as a biomarker that can be used alone or in conjunction with other biomarkers to facilitate the diagnosis of sepsis in the critically ill.

Hypertonic Saline (NaCl 7.5%) Reduces LPS-Induced Acute Lung Injury in Rats

Acute respiratory distress syndrome (ARDS) is the most severe lung inflammatory manifestation and has no effective therapy nowadays. Sepsis is one of the main illnesses among ARDS causes. The use of fluid resuscitation is an important treatment for sepsis, but positive fluid balance may induce pulmonary injury. As an alternative, fluid resuscitation with hypertonic saline ((HS) NaCl 7.5%) has been described as a promising therapeutical agent in sepsis-induced ARDS by the diminished amount of fluid necessary. Thus, we evaluated the effect of hypertonic saline in the treatment of LPS-induced ARDS. We found that hypertonic saline (NaCl 7.5%) treatment in rat model of LPS-induced ARDS avoided pulmonary function worsening and inhibited type I collagen deposition. In addition, hypertonic saline prevented pulmonary injury by decreasing metalloproteinase 9 (MMP-9) activity in tissue. Focal adhesion kinase (FAK) activation was reduced in HS group as well as neutrophil infiltration, NOS2 expression and NO content. Our study shows that fluid resuscitation with hypertonic saline decreases the progression of LPS-induced ARDS due to inhibition of pulmonary remodeling that is observed when regular saline is used.

The contributions of dipeptidyl peptidase IV to inflammation in heart failure

Circulating dipeptidyl peptidase IV (DPPIV) activity correlates with cardiac dysfunction in humans and experimental heart failure (HF) models. Similarly, inflammatory markers are associated with poorer outcomes in HF patients. However, the contributions of DPPIV to inflammation in HF remain elusive. Therefore, this study aimed to investigate whether the cardioprotective effects of DPPIV inhibition after myocardial injury are accompanied by reduced cardiac inflammation, whether circulating DPPIV activity correlates with the levels of systemic inflammatory markers in HF patients, and whether leukocytes and/or splenocytes may be one of the sources of circulating DPPIV in HF. Experimental HF was induced in male Wistar rats by left ventricular myocardial injury after radiofrequency catheter ablation. The rats were divided into three groups: sham, HF, and HF + DPPIV inhibitor (sitagliptin). Six weeks after surgery, cardiac function, perfusion and inflammatory status were evaluated. Sitagliptin treatment improved cardiac function and perfusion, reduced macrophage infiltration, and diminished the levels of inflammatory biomarkers including TNF-α, IL-1β, and CCL2. In HF patients, serum DPPIV activity correlated with CCL2, suggesting that leukocytes may be the source of circulating DPPIV in HF. Unexpectedly, DPPIV release was higher in splenocytes from HF rats and similar in HF circulating mononuclear cells compared with those from sham, suggesting an organ-specific modulation of DPPIV in HF. Collectively, our data provide new evidence that the cardioprotective effects of DPPIV inhibition in HF may be due to suppression of inflammatory cytokines. Moreover, they suggest that a vicious circle between DPPIV and inflammation may contribute to HF development and progression.

sRAGE in septic shock: a potential biomarker of mortality

Objective

To evaluate and understand the clinical implications of the plasma levels of a soluble isoform of a receptor for advanced glycation end products (sRAGE) in different stages of sepsis.

Methods

Serum sRAGE values in patients who were divided into intensive care unit control, severe sepsis, septic shock and recovery from septic shock groups were statistically analyzed to assess quantity (Kruskal-Wallis), variability (Levine test) and correlation (Spearman rank test) with certain inflammatory mediators (IL-1 α, IL-6, IL-8, IL-10, IP-10, G-CSF, MCP-1, IFN-γ and TNF-α).

Results

No changes in sRAGE levels were observed among the groups; however, the septic shock group showed differences in the variability of sRAGE compared to the other groups. A positive correlation with all the inflammatory mediators was reported in the septic shock group.

Conclusion

sRAGE levels are associated with worse outcomes in patients with septic shock. However, a statistical correlation analysis with other proinflammatory cytokines indicated that the pathways leading to those outcomes are different depending on the sRAGE levels. Future studies to elucidate the pathophysiological mechanisms involving sRAGE in models of sepsis are of great clinical importance for the safe handling of this biomarker.

"Neuropeptides in the brain defense against distant organ damage"

Delirium, or acute confusional state, is a common manifestation in diseases that originate outside the central nervous system, affecting 30-40% of elderly hospitalized patients and up to 80% of the critically ill, even though it remains unclear if severe systemic inflammation is able or not to induce cellular disturbances and immune activation in the brain. Neuropeptides are pleotropic molecules heterogeneously distributed throughout the brain and possess a wide spectrum of functions, including regulation of the inflammatory response, so we hypothesized that they would be the major alarm system in the brain before overt microglia activation. In order to investigate this hypothesis, we induced acute pancreatitis in 8-10week old rats and collected brain tissue, 12 and 24h following pancreatic injury, to measure neuropeptide and cytokine tissue levels. We found significantly higher levels of β-endorphin, orexin and oxytocin in the brain of rats submitted to pancreatic injury, when compared to healthy controls. Interestingly, these differences were not associated with increased local cytokine levels, putting in evidence that neuropeptide release occurred independently of microglia activation and may be a pivotal alarm system to initiate neurologic reactions to distant inflammatory non-infectious aggression.

HLA-A*31 as a marker of genetic susceptibility to sepsis

Objective

The HLA haplotype has been associated with many autoimmune diseases, but no associations have been described in sepsis. This study aims to investigate the HLA system as a possible marker of genetic sepsis susceptibility.

Methods

This is a prospective cohort study including patients admitted to an intensive care unit and healthy controls from a list of renal transplant donors. Patients with less 18 years of age; pregnant or HIV positive patients; those with metastatic malignancies or receiving chemotherapy; or with advanced liver disease; or with end-of-life conditions were excluded. The DNA was extracted from the whole blood and HLA haplotypes determined using MiliPlex^® technology.

Results

From October 2010 to October 2012, 1,121 patients were included (1,078 kidney donors, 20 patients admitted with severe sepsis and 23 with septic shock). HLA-A*31 positive subjects had increased risk of developing sepsis (OR 2.36, 95%CI 1.26-5.35). Considering a p value <0.01, no other significant association was identified.

Conclusion

HLA-A*31 expression is associated to risk of developing sepsis.

Neuropeptide downregulation in sepsis

Neuropeptides are an extremely conserved arm of neurobiology. Despite their effects as neurohormones and neurotransmitters, a multitude of other effects have been described, putting in evidence their importance as regulators of immune responses, such as chemotaxis, oxidative burst, pro-inflammatory signaling, and many others. The effects of neuropeptides in the pathophysiology of sepsis, however, remain poorly investigated. A prospective cohort study to investigate the effects of neuropeptides in sepsis was carried out. Here, we describe that neuropeptides are downregulated during septic shock. We propose that it may be a protective mechanism of the host to avoid further inflammatory injury.

Decreased parathyroid hormone levels despite persistent hypocalcemia in patients with kidney failure recovering from septic shock

INTRODUCTION

Hypocalcemia is a common and poorly understood finding in critically ill patients. The current study was designed to assess the association of ionized calcium, vitamin D, phosphorus and Parathyroid hormone levels in a cohort of patients with and without kidney dysfunction admitted for sepsis or non-infectious causes.

METHODS

Prospective cohort clinical and biochemical study.

RESULTS

We confirmed that hypocalcemia and hypovitaminosis D are a common finding in critically ill patients. Parathyroid hormone levels significantly rise in septic shock. In the recovery phase, however, despite persistent hypocalcemia, Parathyroid hormone levels abruptly decrease in patients with kidney dysfunction, but not in patients with normal renal function.

CONCLUSIONS

The systemic inflammatory response syndrome probably leads to inappropriately high Parathyroid hormone levels during septic shock. In the recovery phase, Parathyroid hormone levels decrease, but calcium levels remain low, displaying evidence that the parathyroid is not responding as expected. Since Parathyroid hormone receptors and calcium-sensing receptors have been described in immune cells and other cell types, we propose that these effects may have a plethora of other deleterious effects, with important implications to the pathogenesis of septic shock.

Superoxide dismutase activity in portal vein endothelium after partial liver resection

PURPOSE

To investigate superoxide dismutase (SOD) activity in the portal vein endothelium and malondialdehyde acid (MDA) production in liver tissue of rats submitted to 70% hepatectomy.

METHODS

Twelve rats were distributed in two groups (hepatectomy and sham). Animals were sacrificed on post operative day 1 and portal vein, liver tissue and blood samples were collected. Portal vein SOD production was measured using lucigenin-amplified chemiluminescence assays. MDA measurement was used as an index of oxidative stress through the formation of TBARS (Thiobarbituric Acid Reactive Species).

RESULTS

There was no difference in post operative bilirubin, AST, ALT levels between groups. DHL level was higher in the hepatectomy group (p=0.01). MDA production in the remnant liver tissue and endothelial portal vein SOD activity were also significantly (p<0.05) elevated in the hepatectomy group when compared to control group. There was no correlation between MDA and SOD activity. SOD activity, on the other hand, showed a positive correlation with LDH level (p=0.038) and MDA levels showed a positive correlation with AST and ALT levels (p<0.001).

CONCLUSION

There is an increased production of malondialdehyde acid in liver tissue after partial hepatectomy and increased activity of superoxide dismutase in portal vein endothelium as well.

Septic shock in older people: a prospective cohort study

Background

Septic shock is the first cause of death in Intensive Care Units. Despite experimental data showing increased inflammatory response of aged animals following infection, the current accepted hypothesis claims that aged patients are immunocompromised, when compared to young individuals.

Results

Here, we describe a prospective cohort study designed to analyze the immune profile of this population.

Conclusion

Older people are as immunocompetent as the young individual, regarding the cytokines, chemokines and growth factors response to devastating infection.

Hypertonic saline solution reduces the inflammatory response in endotoxemic rats

OBJECTIVE

Volume replacement in septic patients improves hemodynamic stability. This effect can reduce the inflammatory response. The objective of this study was to evaluate the effect of 7.5% hypertonic saline solution versus 0.9% normal saline solution for volume replacement during an inflammatory response in endotoxemic rats.

METHODS

We measured cytokines (serum and gut), nitrite, and lipid peroxidation (TBARS) as indicators of oxidative stress in the gut. Rats were divided into four groups: control group (C) that did not receive lipopolysaccharide; lipopolysaccharide injection without treatment (LPS); lipopolysaccharide injection with saline treatment (LPS +S); and lipopolysaccharide injection with hypertonic saline treatment (LPS +H). Serum and intestine were collected. Measurements were taken at 1.5, 8, and 24 h after lipopolysaccharide administration.

RESULTS

Of the four groups, the LPS +H group had the highest survival rate. Hypertonic saline solution treatment led to lower levels of IL-6, IL-10, nitric oxide, and thiobarbituric acid reactive substances compared to 0.9% normal saline. In addition, hypertonic saline treatment resulted in a lower mortality compared to 0.9% normal saline treatment in endotoxemic rats. Volume replacement reduced levels of inflammatory mediators in the plasma and gut.

CONCLUSION

Hypertonic saline treatment reduced mortality and lowered levels of inflammatory mediators in endotoxemic rats. Hypertonic saline also has the advantage of requiring less volume replacement.

A TRbeta-selective agonist confers resistance to diet-induced obesity

Thyroid hormone receptor beta (TRbeta also listed as THRB on the MGI Database)-selective agonists activate brown adipose tissue (BAT) thermogenesis, while only minimally affecting cardiac activity or lean body mass. Here, we tested the hypothesis that daily administration of the TRbeta agonist GC-24 prevents the metabolic alterations associated with a hypercaloric diet. Rats were placed on a high-fat diet and after a month exhibited increased body weight (BW) and adiposity, fasting hyperglycemia and glucose intolerance, increased plasma levels of triglycerides, cholesterol, nonesterified fatty acids and interleukin-6. While GC-24 administration to these animals did not affect food ingestion or modified the progression of BW gain, it did increase energy expenditure, eliminating the increase in adiposity without causing cardiac hypertrophy. Fasting hyperglycemia remained unchanged, but treatment with GC-24 improved glucose tolerance by increasing insulin sensitivity, and also normalized plasma triglyceride levels. Plasma cholesterol levels were only partially normalized and liver cholesterol content remained high in the GC-24-treated animals. Gene expression in liver, skeletal muscle, and white adipose tissue was only minimally affected by treatment with GC-24, with the main target being BAT. In conclusion, during high-fat feeding treatment with the TRbeta-selective agonist, GC-24 only partially improves metabolic control probably as a result of accelerating the resting metabolic rate.

Purine nucleotides reduce superoxide production by nitric oxide synthase in a murine sepsis model

Sepsis involves a systemic inflammatory response of multiple endogenous mediators, resulting in many of the injurious and sometimes fatal physiological symptoms of the disease. This systemic activation leads to a compromised vascular response and endothelial dysfunction. Purine nucleotides interact with purinoceptors and initiate a variety of physiological processes that play an important role in maintaining cardiovascular function. The purpose of the present study was to investigate the effects of ATP on vascular function in a lipopolysaccharide (LPS) model of sepsis. LPS induced a significant increase in aortic superoxide production 16 h after injection. Addition of ATP to the organ bath incubation solution reduced superoxide production by the aortas of endotoxemic animals. Reactive Blue, an antagonist of the P2Y receptor, blocked the effect of ATP on superoxide production, and the nonselective P2Y agonist MeSATP inhibited superoxide production. Nitric oxide synthase (NOS) inhibition by L-NAME blocked vascular relaxation and reduced superoxide production in LPS-treated animals. In the presence of L-NAME there was no ATP effect on superoxide production. A vascular reactivity study showed that ATP increased maximal relaxation in LPS-treated animals compared to controls. The presence of ATP induced increases in Akt and endothelial NOS phosphorylated proteins in the aorta of septic animals. ATP reduces superoxide release resulting in an improved vasorelaxant response. Sepsis may uncouple NOS to produce superoxide. We showed that ATP through Akt pathway phosphorylated endothelial NOS and "re-couples" NOS function.

Yo jyo hen shi ko, a novel Chinese herbal, prevents nonalcoholic steatohepatitis in ob/ob mice fed a high fat or methionine-choline-deficient diet

BACKGROUND

Oxidative stress plays a role in the pathogenesis of nonalcoholic steatohepatitis (NASH). Yo jyo hen shi ko (YHK) is a complex compound purported to reduce reactive oxygen species (ROS) by blocking the propagation of radical-induced reactions. The aim of this study was to evaluate the role of the effect of YHK in experimental NASH.

METHODS

NASH was induced in male ob/ob mice by a high-fat (HF) diet or methionine/choline-deficient (MCD) diet for 4 weeks. YHK-treated animals received YHK solution orally (20 mg/kg/day) in both experimental diets (n=6; each group) while control animals received only vehicle.

RESULTS

The MCD and HF groups developed moderate diffuse macrosteatosis, hepatocellular ballooning, and a diffuse inflammatory infiltrate. With the addition of YHK, there was a marked reduction in macrosteatosis in both groups. This was associated with decreased lipoperoxide and reduced glutathione-GSH concentrations as well as reduced serum aminotransferases and improved histological markers of inflammation. These changes were also associated with weight loss in the MCD+YHK group and diminished weight gain in the HF+YHK group.

CONCLUSION

YHK therapy blunts the development of macrosteatosis in these models of NASH and significantly reduces markers of oxidative stress. YHK also diminishes weight gain in this obesity prone model. Our findings warrant further study on the mechanisms involved with these effects.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 +/- 3.35; RCR: 2.55 +/- 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 +/- 1.53, 17.04 +/- 2.03, RCR: 3.15 +/- 0.15, 3.68 +/- 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

The effect of chronic nitric oxide inhibition on vascular reactivity and blood pressure in pregnant rats

CONTEXT

The exact mechanism involved in changes in blood pressure and peripheral vascular resistance during pregnancy is unknown.

OBJECTIVE

To evaluate the importance of endothelium-derived relaxing factor (EDRF) and its main component, nitric oxide, in blood pressure and vascular reactivity in pregnant rats.

DESIGN

Clinical trial in experimentation animals.

SETTING

University laboratory of Pharmacology.

SAMPLE

Female Wistar rats with normal blood pressure, weight (152 to 227 grams) and age (90 to 116 days).

INTERVENTION

The rats were divided in to four groups: pregnant rats treated with L-NAME (13 rats); pregnant control rats (8 rats); virgin rats treated with L-NAME (10 rats); virgin control rats (12 rats). The vascular preparations and caudal blood pressure were obtained at the end of pregnancy, or after the administration of L-NAME in virgin rats.

MAIN MEASUREMENTS

The caudal blood pressure and the vascular response to acetylcholine in pre-contracted aortic rings, both with and without endothelium, and the effect of nitric oxide inhibition, Nw-L-nitro-arginine methyl-ester (L-NAME), in pregnant and virgin rats. The L-NAME was administered in the drinking water over a 10-day period.

RESULTS

The blood pressure decreased in pregnancy. Aortic rings of pregnant rats were more sensitive to acetylcholine than those of virgin rats. After L-NAME treatment, the blood pressure increased and relaxation was blocked in both groups. The fetal-placental unit weight of the L-NAME group was lower than that of the control group.

CONCLUSION

Acetylcholine-induced vasorelaxation sensitivity was greater in pregnant rats and that blood pressure increased after L-NAME administration while the acetylcholine-induced vasorelaxation response was blocked.

Nonspecific blockade of vascular free radical signals by methylated arginine analogues

Methylated arginine analogues are often used as probes of the effect of nitric oxide; however, their specificity is unclear and seems to be frequently overestimated. This study analyzed the effects of NG-methyl-L-arginine (L-NMMA) on the endothelium-dependent release of vascular superoxide radicals triggered by increased flow. Plasma ascorbyl radical signals measured by direct electron paramagnetic resonance spectroscopy in 25 rabbits increased by 3.8 +/- 0.7 nmol/l vs baseline (28.7 +/- 1.4 nmol/l, P < 0.001) in response to papaverine-induced flow increases of 121 +/- 12%. In contrast, after similar papaverine-induced flow increases simultaneously with L-NMMA infusions, ascorbyl levels were not significantly changed compared to baseline. Similar results were obtained in isolated rabbit aortas perfused ex vivo with the spin trap alpha-phenyl-N-tert-butylnitrone (N = 22). However, in both preparations, this complete blockade was not reversed by co-infusion of excess L-arginine and was also obtained by N-methyl-D-arginine, thus indicating that it is not related to nitric oxide synthase. L-arginine alone was ineffective, as previously demonstrated for NG-methyl-L-arginine ester (L-NAME). In vitro, neither L-arginine nor its analogues scavenged superoxide radicals. This nonspecific activity of methylated arginine analogues underscores the need for careful controls in order to assess nitric oxide effects, particularly those related to interactions with active oxygen species.

Sex-related differences in the response of spontaneously hypertensive rats to angiotensin-converting enzyme inhibitor

We have compared the endothelium-dependent responses of thoracic aortic rings obtained from age-matched male and female SHR in order to explore gender differences in the effectiveness of antihypertensive drug therapy in correcting the endothelial dysfunction found in these animals. For this, concentration-effect curves to acetylcholine and sodium nitroprusside were obtained using aortic rings with and without endothelium isolated from male and female rats which had or had not been pre-treated with enalapril for 72 h (acute) or 15 d (chronic). The maximal responses achieved and the EC50s were determined. The blood pressure of male and female spontaneously hypertensive rats (SHR) decreased to normal levels within 72 h of initiating treatment with enalapril and remained normal during the remainder of the treatment period (15 d). However, enalapril was not effective in restoring a normal blood pressure in all of the male and female SHR. Female SHR were more responsive to enalapril after both acute and chronic treatment (70% of the females and 45% of the males became normotensive). Enalapril corrected the decreased response to acetylcholine in male but not in female SHR. An increased sensitivity to sodium nitroprusside, an endothelium-independent vasodilator, was observed after acute or chronic treatment with enalapril in aortic rings with endothelium from male SHR. Indomethacin restored the decreased response to acetylcholine in aortic rings from enalapril-treated females and potentiated the response to acetylcholine in aortic rings from treated male SHR. We conclude that: a) there are significant differences in the responses of male and female SHR to enalapril, b) the imbalance in endothelium-dependent relaxing and contracting factors in SHR is corrected by enalapril in male but not in female SHR, c) correction of the endothelial dysfunction probably occurs independently of the normalization of blood pressure levels and appears to be gender-dependent.

Vascular free radical release. Ex vivo and in vivo evidence for a flow-dependent endothelial mechanism

Mechanisms underlying production of vascular free radicals are unclear. We hypothesized that changes in blood flow might serve as a physiological stimulus for endothelial free radical release. Intact isolated aortas from 45 rabbits were perfused with the spin trap alpha-phenyl-N-tert-butylnitrone (PBN, 20 mmol/L) and formed radical adducts detected by electron paramagnetic resonance spectroscopy (EPR). Sequential perfusion at 2, 7.5, and 12 mL/min changed cumulative vascular PBN radical adduct yields, respectively, from 3.2 +/- 0.9 to 4.1 +/- 0.7 (P < .05) and 7.0 +/- 1.5 (P < .005) pmol/mg with endothelium and from 3.6 +/- 1.6 to 3.8 +/- 1.4 and 2.2 +/- 0.8 pmol/mg without endothelium (P = NS). In endothelialized aortas, superoxide dismutase (SOD) completely blocked flow-induced free radical production, whereas inactivated SOD, indomethacin, and the nitric oxide synthetase antagonist nitro-L-arginine methyl ester (L-NAME) had no effect; relaxations to acetylcholine remained unchanged with higher flows. To assess the role of flow on in vivo radical production, femoral arterial plasma levels of the ascorbyl radical, a stable ascorbate oxidation product, were measured by direct EPR in 56 other rabbits. Ascorbyl levels were assessed at baseline (30.2 +/- 0.7 nmol/L) and at peak-induced iliac flow changes. Flow increases from 25% to 100% due to saline injections through an extracorporeal aortic loop induced significant dose-dependent increases in ascorbyl levels (n = 5). In addition, after papaverine bolus injections, flow increased by 114 +/- 8% versus baseline, and ascorbyl levels increased by 5.4 +/- 0.7 nmol/L (n = 31, P < .001); similar results occurred with adenosine, isoproterenol, or hyperemia after 30-second occlusions (P < .05, n = 4 or 5 in each group). Active SOD completely blocked papaverine-induced ascorbyl radical increase, despite preserved flow response (delta ascorbyl = 0.02 +/- 1.6 nmol/L, P = NS); inactivated SOD, catalase, indomethacin, and L-NAME had no effect. Blood flow decreases of 65% to 100% due to phenylephrine or 60-second balloon occlusions were accompanied by an average decrease of 4.4 nmol/L (P < .05) in ascorbyl levels. No change in ascorbyl signal was observed when rabbit blood alone was submitted to in vitro flow increases through a tubing circuit. Thus, increases in blood flow trigger vascular free radical generation; such a response seems to involve endothelium-derived superoxide radicals unrelated to cyclooxygenase or nitric oxide synthetase activities. This mechanism may contribute to explain vascular free radical generation in physiological or pathological circumstances.

Comparison of the effect of endothelin on microvessels and macrovessels in Goldblatt II and deoxycorticosterone acetate-salt hypertensive rats

The response to endothelin, a novel 21-amino acid peptide, is investigated in isolated aortas with and without endothelium and in mesenteric microvessels in vivo-in situ, in Goldblatt II (GII) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Median effective concentrations and maximal responses to endothelin did not differ in aortas with endothelium isolated from GII, DOCA-salt hypertensive, and control rats. After removal of the endothelium, the potentiation of the aorta responses to endothelin was of the same magnitude in hypertensive and control rats. A closed-circuit television system was used to observe the microvascular bed of the exteriorized mesentery of anesthetized GII, DOCA-salt hypertensive, and control rats. The time necessary to induce a vasoconstrictor response was determined after the topical application of endothelin. Vessel diameters at rest and after endothelin application were also estimated. At the microcirculatory level, a greater reactivity to endothelin was observed in both hypertensive rat groups, whereas higher sensitivity to endothelin was recorded in the GII hypertensive microvessel preparations alone. It is suggested that the increased response to endothelin observed in hypertensive rats might be due to abnormal sensitivity or reactivity of the microvessels of these rats reflecting an alteration of the contractile sequence possibly at the plasma membrane level, or due to both. Endothelial dysfunction at the microcirculatory level, however, cannot be dismissed.