Increased responsiveness to JNK1/2 mediates the enhanced HO-induced stimulation of Cl/HCO exchanger activity in immortalized renal proximal tubular epithelial cells from the SHR

S. Simão (1) , P. Gomes (1) , P.A. Jose (2) , P. Soares-Da-Silva (1)

1 Faculty of Medicine
2 and Department of Pediatrics

We have previously demonstrated that exogenous HO stimulates Cl/HCO exchanger activity in immortalized renal proximal tubular epithelial (PTE) cells from both the Wistar-Kyoto (WKY) rat and the spontaneously hypertensive rat (SHR), this effect being more pronounced in SHR cells. The aim of the present study was to examine the mechanism of HO-induced stimulation of Cl/HCO exchanger activity in WKY and SHR cells. It is now reported that the SHR PTE cells were endowed with an enhanced capacity to produce HO, comparatively with WKY cells and this was accompanied by a decreased expression of SOD2, SOD3, and catalase in SHR PTE cells. The stimulatory effect of HO on the exchanger activity was blocked by SP600125 (JNK inhibitor), but not by U0126 (MEK1/2 inhibitor) or SB203580 (p38 inhibitor) in both cell lines. Basal JNK1 and JNK2 protein expression was higher in SHR PTE cells than in WKY PTE cells. HO had no effect on p-JNK1/2 in WKY PTE cells over time. By contrast, HO treatment resulted in a rapid and sustained increase in JNK1/2 phosphorylation in SHR PTE cells, which was completely abolished by apocynin. Treatment of SHR PTE cells with apocynin significantly decreased the HO-induced stimulation of Cl/HCO exchanger activity. It is concluded that HO-induced stimulation of Cl/HCO exchanger activity is regulated by JNK1/2, particularly by JNK2, in SHR PTE cells. The imbalance between oxidant and antioxidant mechanisms in SHR PTE cells enhances the response of JNK1/2 to HO, which contributes to their increased sensitivity to HO.

Mots clés: BCECF-AM; BSA; DTT; EDTA; ERK; HEPES; JNK; MAPK; NADPH; NHE; Nox; PBS; PKA; PKC; PT; PTE; ROS; SDS-PAGE; SOD; SHR; WKY; Cl/HCO exchanger; Hypertension; Oxidative stress; HO

S. Simão, P. Gomes, P.A. Jose, P. Soares-Da-Silva. Increased responsiveness to JNK1/2 mediates the enhanced HO-induced stimulation of Cl/HCO exchanger activity in immortalized renal proximal tubular epithelial cells from the SHR. Biochemical Pharmacology, 2010, 80 (6), pp.913. ⟨10.1016/j.bcp.2010.05.013⟩. ⟨hal-00608937⟩