Renin-angiotensin system and inflammation update

The most classical view of the renin-angiotensin system (RAS) emphasizes its role as an endocrine regulator of sodium balance and blood pressure. However, it has long become clear that the RAS has pleiotropic actions that contribute to organ damage, including modulation of inflammation. Angiotensin II (Ang II) activates angiotensin type 1 receptors (AT1R) to promote an inflammatory response and organ damage. This represents the pathophysiological basis for the successful use of RAS blockers to prevent and treat kidney and heart disease. However, other RAS components could have a built-in capacity to brake proinflammatory responses. Angiotensin type 2 receptor (AT2R) activation can oppose AT1R actions, such as vasodilatation, but its involvement in modulation of inflammation has not been conclusively proven. Angiotensin-converting enzyme 2 (ACE2) can process Ang II to generate angiotensin-(1-7) (Ang-(1-7)), that activates the Mas receptor to exert predominantly anti-inflammatory responses depending on the context. We now review recent advances in the understanding of the interaction of the RAS with inflammation. Specific topics in which novel information became available recently include intracellular angiotensin receptors; AT1R posttranslational modifications by tissue transglutaminase (TG2) and anti-AT1R autoimmunity; RAS modulation of lymphoid vessels and T lymphocyte responses, especially of Th17 and Treg responses; interactions with toll-like receptors (TLRs), programmed necrosis, and regulation of epigenetic modulators (e.g. microRNAs and bromodomain and extraterminal domain (BET) proteins). We additionally discuss an often overlooked effect of the RAS on inflammation which is the downregulation of anti-inflammatory factors such as klotho, peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), transient receptor potential ankyrin 1 (TRPA1), SNF-related serine/threonine-protein kinase (SNRK), serine/threonine-protein phosphatase 6 catalytic subunit (Ppp6C) and n-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). Both transcription factors, such as nuclear factor κB (NF-κB), and epigenetic regulators, such as miRNAs are involved in downmodulation of anti-inflammatory responses. A detailed analysis of pathways and targets for downmodulation of anti-inflammatory responses constitutes a novel frontier in RAS research.

Water balance of lung and nitrogen oxide in blood at experimental autoimmune encephalomyelitis after capsaicin blockade of vagus nerve

THE PURPOSE OF THE RESEARCH

To study the water balance of lung and NO level in blood in experimental autoimmune encephalomyelitis combined with capsaicin blockade of vagus nerve.

METHODS

Experiments were conducted on 47 adult (16-week-old) male rats weighing 220-280 g. To simulate the experimental autoimmune encephalomyelitis (EAE) rats were subcutaneously injected with encephalitogenic mixture in complete Freund's adjuvant (0.2 ml; the content of inactivated Mycobacterium tuberculosis was 5 mg/ml) at the rate of 100 mg of homologous spinal cord homogenate per animal. Сapsaicin blockade was performed by bilateral application of 50 uM capsaicin («Sigma») on the neck portions of vagus nerves. The animals were divided into 4 groups: intact rats - control group1; rats with EAE; rats with capsaicin application on vagus nerve + EAE; sham operated rats subjected to vagus nerves allocation without the subsequent capsaicin application + EAE - control group 2. The next parameters were detected: the content of nitric oxide in blood plasma; protein content in broncho-alveolar lavage fluid; lung water balance indices including the amount of total, extra- and intravascular fluid and blood supply of lungs, which were calculated based on wet and dry lung mass and the hemoglobin content in blood and lung tissue determined by hemiglobincyanide method.

RESULTS

It was found that EAE is accompanied by an increase of total fluid, extravascular fluid (EVF) and blood supply of lungs on the background of increasing content of nitric oxide in arterial (art) and venous (ven) blood. In EAE and its combination with bilateral capsaicin blockade of vagus nerve a strong negative correlation between the NOart / NOven coefficient and EVF amount was found out. The blockade of capsaicin-sensitive vagal afferents normalized lung water balance impaired in EAE and restored the levels of nitric oxide in blood plasma.

CONCLUSION

The obtained results suggest that capsaicin-sensitive vagal afferents with NO-ergic mechanisms involvment take part in the development of pulmonary hyperhydration during experimental autoimmune encephalomyelitis.

Antisperm antibodies modify plasma membrane functional integrity and inhibit osmosensitive calcium influx in human sperm

BACKGROUND

The hypo-osmotic swelling (HOS) test evaluates the ability of the functional sperm plasma membrane to stretch following cell swelling when exposed to hypo-osmotic solutions. Sperm samples with low HOS scores show low fertilization and pregnancy rates during assisted reproductive techniques, though data are controversial. The aim of this study was to compare the results of the HOS test in a group of normozoospermic men with those in a group of subjects affected by autoimmune infertility due to the presence of antisperm antibodies (ASA) bound to the sperm surface.

METHODS

Sperm from normozoospermic and from infertile subjects affected by autoimmune infertility were exposed to hypo-osmolar conditions to verify the effects on intracellular calcium concentrations and acrosome reaction.

RESULTS

Sperm samples from infertile men with ASA showed HOS test scores that were significantly lower than those of normozoospermic subjects despite similar sperm viability percentages. Sperm with ASA bound to their plasma membrane showed a reduced rise in intracellular calcium concentrations and acrosome reaction after hypo-osmotic challenge with respect to sperm from normozoospermic subjects without ASA.

CONCLUSIONS

Infertile subjects with ASA have a reduced sperm plasma membrane functional integrity that could explain, at least in part, the low fertilization and pregnancy rates observed in these subjects during assisted reproductive procedures. Evaluation for the presence of ASA in all sperm samples showing low HOS test scores in the presence of normal sperm viability percentages is suggested.

Total lymphocyte count in peripheral blood of peritoneal dialysis patients: relationship to clinical parameters and outcome

BACKGROUND

Total lymphocyte count (TLC) is used as a nutritional status measurement. The impact of TLC on mortality in peritoneal dialysis (PD) patients is controversial. This study aimed at evaluating the effect of TLC on mortality, and assessing the relationship between TLC and nutritional status, anemia and erythropoietin (EPO) response, acute-phase response, dialysis adequacy and volume status in PD patients.

METHODS

Seventy-three PD patients were monitored for 3 yrs from the beginning of the treatment. Data recorded for each patient included demographic features, comorbidity, TLC, blood biochemistry, systolic and diastolic blood pressures (BP), indices of dialysis adequacy and nutritional status, total fluid removal and mortality. Adjusted mortality risk for TLC was estimated using the Cox's regression models composed by TLC and one covariate having a value p<0.05 in univariate analysis.

RESULTS

The 3-yr patient survival rates were significantly different among the TLC quartiles. The adjusted TLC was found, generally, to be a significant predictor of death in reduced Cox's models, except in models composed of TLC and total fluid removal or serum albumin. The receiver operating characteristics (ROC) analysis demonstrated that TLC provided a significant prediction of mortality. TLC correlated positively to total fluid removal, serum albumin, triglyceride and hematocrit, and negatively correlated to BP, high peritoneal transport and EPO-need. It did not correlate to other measures of nutritional status, dialysis adequacy and acute-phase response. Fluid removal and serum triglyceride were independent predictors of TLC in multivariate analysis.

CONCLUSIONS

Our findings suggest that TLC can be used as a simple prognostic tool in PD patients; however, the association between TLC and mortality is confounded by other prognostic factors. Volume status could be a more important factor affecting the TLC than nutritional status.