Abstract
The adipocyte-derived hormone leptin is associated with hypertension. The involvement of cyclooxygenase-2 (COX-2) and its downstream vasomotor products prostaglandin (PG) and thromboxane (TX)A2 in the mechanisms of action of leptin have remained elusive. The aim of the present study was to investigate the effects of leptin on the expression of COX-2 by rat aortic endothelial cells (RAECs) and the concentration of its products, represented by 6-keto PGF1α and TXB2, in the culture media. RAECs were isolated, cultured and identified by immunofluorescence staining. The RAECs were incubated with different concentrations of leptin (10-10, 10-9 and 10-8 M) for various durations (36 or 48 h). COX-2 mRNA and protein expression in the cells was detected by reverse-transcription quantitative PCR and western blot analysis, respectively. The vasodilator 6-keto PGF1α and the vasoconstrictor TXB2 were detected in the supernatant by ELISA. The cultured cells displayed specific factor VIII expression in the cytoplasm. Compared with the PBS-treated control group, leptin significantly increased the expression of COX-2 mRNA and protein in a time- and dose-dependent manner (P<0.01). Furthermore, the vasodilator 6-keto PGF1α was increased and the TXB2/6-keto PGF1α ratio decreased only with relatively high concentrations of leptin (10-9 or 10-8 M; P<0.01), but TXB2 levels were not affected (P>0.05). In conclusion, leptin significantly increased the expression of inflammatory marker COX-2 and its downstream product 6-keto PGF1α, while also decreasing the TXB2/6-keto PGF1α ratio in vitro. These observations suggested that COX-2 may have an important role in the effects of leptin on inflammation, such as the low-inflammatory disease hypertension. However, selective COX-2 inhibitors may increase the risk of hypertension due to inhibiting 6-keto PGF1α, the vasodilator product of COX-2.