Gut Microbiota Disruption in Septic Shock Patients: A Pilot Study.

BACKGROUND The composition of the intestinal microbiota and its effect on septic shock patients in the intensive care unit (ICU) is unknown. In the present study we explored the hypothesis that bacterial diversity is decreased in septic shock patients and that this diversity may be improved by use of probiotics or enteral nutrition. MATERIAL AND METHODS A total of 15 stool samples were collected prospectively from septic shock patients in the ICU, while 15 samples from healthy subjects served as controls. Bacterial DNA was submitted for 16S rDNA gene sequencing. The relationship between intestinal microbiota and prognosis was evaluated. RESULTS Significantly lower bacterial diversity was found in septic shock patients compared with healthy subjects (p<0.05). However, there was no difference in bacterial diversity in the presence or absence of probiotics (p=0.59), enteral nutrition (p=0.59), or in-hospital death (p=0.93) in septic shock patients. A high abundance of Proteobacteria and Fusobacteria was observed in most septic shock patients, whereas low abundance was observed in healthy subjects (mean relative proportion: 23.71% vs. 3.53%, p<0.05; 1.27% vs. 0.12%, p=0.59). CONCLUSIONS Bacterial diversity was decreased, and 1 or 2 rare bacterial species were overgrown in septic shock patients. Bacterial diversity was not improved by use of probiotics or enteral nutrition. The small sample size of our study limits the interpretation of results.

Inhibition of gap junction intercellular communication is involved in silica nanoparticles-induced H9c2 cardiomyocytes apoptosis via the mitochondrial pathway.

Gap junction intercellular communication (GJIC) between cardiomyocytes is essential for synchronous heart contraction and relies on connexin-containing channels. Connexin 43 (Cx43) is a major component involved in GJIC in heart tissue, and its abnormal expression is closely associated with various cardiac diseases. Silica nanoparticles (SNPs) are known to induce cardiovascular toxicity. However, the mechanisms through which GJIC plays a role in cardiomyocytes apoptosis induced by SNPs remain unknown. The aim of the present study is to determine whether SNPs-decreased GJIC promotes apoptosis in rat cardiomyocytes cell line (H9c2 cells) via the mitochondrial pathway using CCK-8 Kit, scrape-loading dye transfer technique, Annexin V/PI double-staining assays, and Western blot analysis. The results showed that SNPs elicited cytotoxicity in H9c2 cells in a time- and concentration-dependent manner. SNPs also reduced GJIC in H9c2 cells in a concentration-dependent manner through downregulation of Cx43 and upregulation of P-Cx43. Inhibition of gap junctions by gap junction blocker carbenoxolone disodium resulted in decreased survival and increased apoptosis, whereas enhancement of the gap junctions by retinoic acid led to enhanced survival but decreased apoptosis. Furthermore, SNPs-induced apoptosis through the disrupted functional gap junction was correlated with abnormal expressions of the proteins involved in the mitochondrial pathway-related apoptosis such as Bcl-2/Bax, cytochrome C, Caspase-9, and Caspase-3. Taken together, our results provide the first evidence that SNPs-decreased GJIC promotes apoptosis in cardiomyocytes via the mitochondrial pathway. In addition, downregulation of GJIC by SNPs in cardiomyocytes is mediated through downregulation of Cx43 and upregulation of P-Cx43. These results suggest that in rat cardiomyocytes cell line, GJIC plays a protective role in SNPs-induced apoptosis and that GJIC may be one of the targets for SNPs-induced biological effects.