Activation of mTOR/IκB-α/NF-κB pathway contributes to LPS-induced hypotension and inflammation in rats.

Mammalian target of rapamycin (mTOR), a serine/threonine kinase plays an important role in various pathophysiological processes including cancer, metabolic diseases, and inflammation. Although mTOR participates in Toll-like receptor 4 signalling in different cell types, the role of this enzyme in sepsis pathogenesis and its effects on hypotension and inflammation in endotoxemic rats remains unclear. In this study we investigated the effects of mTOR inhibition on lipopolysaccharide (LPS)-induced changes on expressions and/or activities of ribosomal protein S6 (rpS6), an mTOR substrate, nuclear factor-κB (NF-κB) p65, inhibitor κB (IκB)-α, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 with production of nitric oxide, peroxynitrite, prostacyclin, and tumor necrosis factor (TNF)-α and activity of myeloperoxidase (MPO), which results in hypotension and inflammation. Injection of LPS (10mg/kg, i.p.) to male Wistar rats decreased blood pressure and increased heart rate that were associated with elevated nitrotyrosine, 6-keto-PGF1α, and TNF-α levels and MPO activity, and increased expressions and/or activities of rpS6, NF-κB p65, iNOS, and COX-2 and decreased expression of IκB-α in renal, cardiac, and vascular tissues. LPS also increased serum and tissue nitrite levels. Rapamycin (1mg/kg, i.p.) given one h after injection of LPS reversed these effects of LPS. These data suggest that the activation of mTOR/IκB-α/NF-κB pathway associated with vasodilator and proinflammatory mediator formation contributes to LPS-induced hypotension and inflammation.

Contribution of PPARα/ß/γ, AP-1, importin-α3, and RXRα to the protective effect of 5,14-HEDGE, a 20-HETE mimetic, against hypotension, tachycardia, and inflammation in a rat model of septic shock.

OBJECTIVES: We have previously demonstrated that downregulation of the MyD88/TAK1-dependent signaling pathway associated with increased CYP4A1 expression and 20-HETE formation participates in the protective effect of N-(20-hydroxyeicosa-5[Z],14[Z]-dienoyl)glycine (5,14-HEDGE), a 20-HETE mimetic, against vascular hyporeactivity, hypotension, tachycardia, inflammation, and mortality in a rodent model of septic shock. The aim of this study was to determine whether increased renal and cardiovascular expression of PPARα/ß/γ and RXRα associated with decreased expression and/or activity of AP-1 and importin-α3 participates in the protective effect of 5,14-HEDGE in response to systemic administration of lipopolysaccharide (LPS). METHODS: Conscious male Wistar rats received saline (4 ml/kg) or LPS (10 mg/kg) at time 0. Blood pressure and heart rate were measured using a tail-cuff device. Separate groups of LPS-treated rats were given 5,14-HEDGE (30 mg/kg) 1 h after injection of saline or LPS. The rats were killed 4 h after saline or LPS administration and the kidney, heart, thoracic aorta, and superior mesenteric artery were collected for measurement of protein expression. RESULTS: Blood pressure fell by 33 mmHg and heart rate rose by 72 beats/min at 4 h after LPS administration. In LPS-treated rats, tissue protein expressions of cytosolic/nuclear PPARα/ß/γ and nuclear RXRα, in addition to nuclear translocation of PPARα/ß/γ proteins, were decreased, while cytosolic/nuclear AP-1 subunit c-jun/phosphorylated c-jun and importin-α3 protein expression as well as their nuclear translocation were increased. The LPS-induced changes were prevented by 5,14-HEDGE. CONCLUSIONS: The results suggest that an increase in the expression of PPARα/ß/γ and RXRα as well as a decrease in AP-1 and importin-α3 expression/activity participates in the protective effect of 5,14-HEDGE against hypotension, tachycardia, and inflammation during endotoxemia and thus have a beneficial effect in septic shock treatment.