PGE2 enhances cytokine-elicited nitric oxide production in mouse cortical collecting duct cells

It has been documented that arginine vasopressin (AVP) and prostaglandin E2 (PGE2) regulate water reabsorption in renal tubular cells. The present study was attempted to delineate the downstream signaling of AVP and PGE2 in a cortical collecting duct cell line (M-1 cell). Using RT-PCR, we detected mRNA for V2 and VACM-1 but not for V1a and AII/AVP receptors of AVP. Furthermore, neither AVP nor V2 receptor agonist and antagonist alter cellular cAMP. These together with unchanged cellular Ca2+ by AVP suggested that AVP pathway was not operating in M-1 cells. All four classical PGE2 receptors with EP3 and EP4 as the most prominent were detected in M-1 cells. PGE2, 11-deoxy-PGE1 (EP2 and EP4 agonist), and 17-phenyl-trinor-PGE2 (EP1 agonist) increased cellular concentration of cAMP. There was no effect of PGE2 or EP1 agonist on cellular Ca2+. These findings provide evidence of the involvement of PGE2 cascade in M-1 cells. M-1 cells were capable of synthesizing nitric oxide (NO). Although individual cytokines did not affect NO production, a mixture of tumor necrosis factor-α, interleukin-1β, and interferon-γ elevated NO concentration to 4.5-fold of the control. Addition of PGE2 and db-cAMP to the cytokine mixture further increased NO production to 7.0- and 9.8-fold, respectively, of that seen in non-treated cells. PGE2 or db-cAMP alone, however, had no effect on NO production. The results of the study led us to speculate that enhanced production of cAMP via PGE2 signaling pathway in M-1 cells could either stimulate or attenuate water reabsorption in renal tubule. While an increase in cAMP alone may enhance water reabsorption, a concomitant increase in cAMP and cytokines may inhibit water reabsorption in renal tubule.