sphingosine-kinase and Endotoxemia

Sepsis is a cluster of heterogeneous syndromes associated with progressive endotoxemic developments, ultimately leading to damage of multiple organs, including the heart. This study is to investigate the effects of apigenin on heart injury in lipopolysaccharide-induced endotoxemic rat model. Normal Wistar rats were randomly divided into four groups: control group, LPS group (15 mg/kg), LPS plus apigenin groups with different apigenin doses (50 mg/kg, 100 mg/kg). Serum levels of creatine kinase (CK), lactate dehydrogenase (LDH), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) were measured after the rats were sacrificed. SphK1/S1P signaling pathway proteins, cleaved caspase-3, cleaved caspase-9, Bax and Bcl-2 in heart were measured by Western blot. In vitro, we evaluated the protective effect of apigenin on rat embryonic heart-derived myogenic cell line H9c2 induced by LPS. Apigenin decreased serum levels of CK-MB, LDH, TNF-α, IL-6, IL-1β. SphK1/S1P signaling pathway proteins, cleaved caspase-3, cleaved caspase-9, Bax in heart were found inhibited and Bcl-2 increased in the apigenin groups in vivo. In addition, apigenin inhibited intracellular calcium, the MAPK pathway and SphK1/S1P signaling pathway in vitro. Apigenin exerts pronounced cardioprotection in rats subjected to LPS likely through suppressing myocardial apoptosis and inflammation by inhibiting the SphK1/S1P signaling pathway.

Topics: Animals; Anti-Inflammatory Agents; Apigenin; Cell Line; Endotoxemia; Heart; Heart Injuries; Lipopolysaccharides; Lysophospholipids; Male; Myocardium; Phosphotransferases (Alcohol Group Acceptor); Rats; Rats, Wistar; Signal Transduction; Sphingosine

Sepsis is a serious issue in the geriatric population due to its association with high mortality rates in the elderly. The increase in mortality in the elderly correlates with inflammation. We have previously demonstrated that the inflammatory response is exacerbated in a rodent endotoxemia model of sepsis in aged rats compared with young rats. However, the molecular mediators associated with this hyperinflammatory response in aged rats have not been completely determined. Sphingosine kinase‑1 (Sphk‑1), an enzyme present in neutrophils and macrophages, regulates proinflammatory responses associated with endotoxemia and sepsis. To determine whether Sphk‑1 is a molecular mediator associated with the observed hyperinflammatory response in aging, Sphk‑1 mRNA expression was examined in hepatic tissues of young and aged rats subjected to endotoxemia. A significant increase in Sphk‑1 mRNA was observed in endotoxemic aged rats compared with young rats. This increase was correlated with a significant increase in TNF‑α mRNA levels in the liver. CD14 is a receptor component for lipopolysaccharide (LPS) and therefore, CD14 mRNA expression in hepatic tissues of endotoxemic young and aged rats was examined. Of note, CD14 mRNA was significantly upregulated in endotoxemic aged rats. Sphk‑1 mRNA expression was significantly elevated in LPS‑treated Kupffer cells and this increase correlated with an increase in CD14 mRNA expression. Results of the present study indicated that increased Sphk‑1 expression in the liver in response to endotoxemia mediates the hyperinflammatory state observed in aged animals.

Topics: Age Factors; Animals; Endotoxemia; Gene Expression; Inflammation; Kupffer Cells; Lipopolysaccharide Receptors; Lipopolysaccharides; Liver; Male; Phosphotransferases (Alcohol Group Acceptor); Rats; RNA, Messenger; Signal Transduction; Tumor Necrosis Factor-alpha

Activated protein C (APC), the only FDA-approved biotherapeutic drug for sepsis, possesses anticoagulant, antiinflammatory, and barrier-protective activities. However, the mechanisms underlying its anti-inflammatory functions are not well defined. Here, we report that the antiinflammatory activity of APC on macrophages is dependent on integrin CD11b/CD18, but not on endothelial protein C receptor (EPCR). We showed that CD11b/CD18 bound APC within specialized membrane microdomains/lipid rafts and facilitated APC cleavage and activation of protease-activated receptor-1 (PAR1), leading to enhanced production of sphingosine-1-phosphate (S1P) and suppression of the proinflammatory response of activated macrophages. Deletion of the gamma-carboxyglutamic acid domain of APC, a region critical for its anticoagulant activity and EPCR-dependent barrier protection, had no effect on its antiinflammatory function. Genetic inactivation of CD11b, PAR1, or sphingosine kinase-1, but not EPCR, abolished the ability of APC to suppress the macrophage inflammatory response in vitro. Using an LPS-induced mouse model of lethal endotoxemia, we showed that APC administration reduced the mortality of wild-type mice, but not CD11b-deficient mice. These data establish what we believe to be a novel mechanism underlying the antiinflammatory activity of APC in the setting of endotoxemia and provide clear evidence that the antiinflammatory function of APC is distinct from its barrier-protective function and anticoagulant activities.

Topics: 1-Carboxyglutamic Acid; Animals; Endotoxemia; Integrins; Lipopolysaccharides; Lysophospholipids; Membrane Microdomains; Mice; Mice, Inbred C57BL; Mice, Knockout; Phosphotransferases (Alcohol Group Acceptor); Protein C; Sepsis; Sphingosine