Baicalin Improves Survival in a Murine Model of Polymicrobial Sepsis via Suppressing Inflammatory Response and Lymphocyte Apoptosis

BACKGROUND: An imbalance between overwhelming inflammation and lymphocyte apoptosis is the main cause of high mortality in patients with sepsis. Baicalin, the main active ingredient of the Scutellaria root, exerts anti-inflammatory, anti-apoptotic, and even antibacterial properties in inflammatory and infectious diseases. However, the therapeutic effect of baicalin on polymicrobial sepsis remains unknown. METHODOLOGY/PRINCIPAL FINDINGS: Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in C57BL/6 mice. Mice were infused with baicalin intraperitoneally at 1 h, 6 h and 12 h after CLP. Survival rates were assessed over the subsequent 8 days. Bacterial burdens in blood and peritoneal cavity were calculated to assess the bacterial clearance. Neutrophil count in peritoneal lavage fluid was also calculated. Injuries to the lung and liver were detected by hematoxylin and eosin staining. Levels of cytokines, including tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10 and IL-17, in blood and peritoneum were measured by enzyme-linked immunosorbent assay. Adaptive immune function was assessed by apoptosis of lymphocytes in the thymus and counts of different cell types in the spleen. Baicalin significantly enhanced bacterial clearance and improved survival of septic mice. The number of neutrophils in peritoneal lavage fluid was reduced by baicalin. Less neutrophil infiltration of the lung and liver in baicalin-treated mice was associated with attenuated injuries to these organs. Baicalin significantly reduced the levels of proinflammatory cytokines but increased the level of anti-inflammatory cytokine in blood and peritoneum. Apoptosis of CD3(+) T cell was inhibited in the thymus. The numbers of CD4(+), CD8(+) T lymphocytes and dendritic cells (DCs) were higher, while the number of CD4(+)CD25(+) regulatory T cells was lower in the baicalin group compared with the CLP group. CONCLUSIONS/SIGNIFICANCE: Baicalin improves survival of mice with polymicrobial sepsis, and this may be attributed to its antibacterial property as well as its anti-inflammatory and anti-apoptotic effects

Neutralisation of peritoneal IL-17A markedly improves the prognosis of severe septic mice by decreasing neutrophil infiltration and proinflammatory cytokines.

PURPOSE: The current study aimed to elucidate the role of peritoneal fluid IL-17A in septic mice, and the effects of intraperitoneal or intravenous blockade of the IL-17A pathway by anti-IL17A antibody on survival, plasma, and peritoneal cavity cytokine profile in a murine caecal ligation and puncture (CLP) sepsis model. The main source of peritoneal fluid IL-17A in septic mice was identified. METHODS: Male C57BL/6 mice that underwent severe CLP or sham surgery were intraperitoneally or intravenously administered anti-IL17A antibodies or isotype antibodies. The survival rates were observed. IL-17A, TNF-α, and IL-6 cytokine levels were measured by ELISA. Surface and intracellular IL-17A immunofluorescence stains were detected by flow cytometry to identify the IL-17A-producing cells. RESULTS: The IL-17A level was elevated much higher and earlier in peritoneal fluid than in the blood of the CLP mice. The intraperitoneal IL-17A blockade more significantly protects against CLP-induced mortality than intravenous blockade because of decreased TNF-α and IL-6 levels both in peritoneal fluid and blood, neutrophil infiltration in the peritoneal cavity, and lung injury. γδ T lymphocytes were identified to be the main source of IL-17A in the peritoneal fluid of septic mice. CONCLUSIONS: The earlier and higher elevated IL-17A derived from γδ T cells in peritoneal fluid plays a critical role during polymicrobial severe sepsis and effect of intraperitoneal IL-17A antibody administration superior to intravenous administration on survival of severe CLP-induced septic mice. The intraperitoneal blockade of IL-17A decreases proinflammatory cytokine production, neutrophil infiltration, and lung injury, thereby improving septic mice survival, which provides a new potential therapy target for sepsis

Bacterial clearance after intraperitoneal anti-IL-17A antibody administration.

<p>The mice underwent a sham procedure, CLP, CLP with intraperitoneal anti-IL-17A, or isotype administration (n = 10 for each group). Blood and peritoneal lavage fluid were harvested 24 h after surgery. Mice that received intraperitoneal anti-IL-17A antibodies exhibited a deceased bacterial burden in the blood (A) and peritoneal cavity (B) compared with mice that received isotype antibodies or PBS. **P<0.01.</p

Cytokine levels in plasma and peritoneal lavage fluid after intraperitoneal or intravenous anti-IL-17A antibody blockade.

<p>The mice underwent a sham procedure, CLP, or CLP with intraperitoneal or intravenous anti-IL-17A administration (<i>n</i> = 5 for each group). The levels of TNF-α and IL-6 in the blood (A, B) and peritoneal lavage fluid (C, D) were measured 12 h after surgery. **<i>P</i><0.01, *<i>P</i><0.05.</p