Protein Prenylation Contributes to the Effects of LPS on EFS-Induced Responses in Human Isolated Bronchi

Rho/Ras signaling pathways may play an important role in the mechanism of LPS-induced inflammation and bronchoconstriction. In this study, we investigated the effect of LPS on the transmural contractile tension induced by electrical field stimulation (EFS) of human isolated bronchi. The possible contribution of Rho/Ras signaling pathways was examined by using geranylgeranyl-pyrophosphate (GGPP) and farnesyl-pyrophosphate (FPP), the selective geranylgeranyl- pyrophosphate-transferase inhibitor GGTI2133, and the selective farnesyl-pyrophosphate transferase inhibitor FTI276, the hydroxy-3- methylglutaryl coenzyme A reductase inhibitor simvastatin and the Rho-associated coiled-coil-forming protein serine/threonine kinase inhibitor Y27632. LPS (300 ng/ml) significantly enhanced the EFS-induced contractile force of human bronchi (P < 0.05). The plateau was reached at 105.0 (±4.1) minutes; the maximal effect (Emax) value was 267.47 (±8.88) %, with a time to evoke a half-maximal contraction (t 1/2) of 40.5 (±2.0) minutes. Pretreatment with GGPP (5 μM) enhanced the EFS-mediated contractile tension (Emax, 164.56 ± 9.80% and the t 1/2 23.0 ± 2.5 min). Pretreatment with FPP (5 μM) was effective, as was GGPP, in enhancing the EFS response (Emax, of 189.23 ± 12.98% and a t 1/2of 17.0 ± 4.5 min). Furthermore, GGTI2133 (500 nM) and FTI276 (10 nM) significantly inhibited the effects of GGPP and FPP on EFS-induced response. Pretreatment with GGPP (5 μM) significantly enhanced the EFS response compared with the control and LPS-treated tissues; GGTI2133 (500 nM) significantly inhibited the EFS-induced contractile tension in LPS (300 ng/ml)-treated tissues, and it was not possible to calculate the t 1/2. In addition, simvastatin and Y27632 (both 1 μM) were effective in abolishing the contracturant effect of LPS. Our results provide mechanistic evidence for the enhanced bronchoconstriction induced by LPS in human isolated airways, the contribution of Rho/Ras pathways in this LPS response, and the protective role of statins.