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Expression of nitric oxide synthase in rat glomerular mesangial cells mediated by cyclic AMP
Author(s) -
Mühl Heiko,
Kunz Dieter,
Pfeilschifter Josef
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb13019.x
Subject(s) - forskolin , mesangial cell , medicine , endocrinology , nitric oxide synthase , phosphodiesterase inhibitor , biology , chemistry , nitric oxide , stimulation , kidney
1 Treatment of rat mesangial cells with interleukin 1β (IL‐1β) or tumour necrosis factor α (TNFα) has been shown to induce a macrophage‐type of nitric oxide (NO) synthase. Here we report that adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) is another mediator that triggers induction of NO synthase in mesangial cells. 2 Incubation of mesangial cells with the β‐adrenoceptor agonist, salbutamol, forskolin or cholera toxin, which all activate adenylate cyclase and increase intracellular cyclic AMP concentration, increased nitrite formation in a dose‐dependent manner. Likewise, the addition of the membrane‐permeable cyclic AMP analogue, N 6 , 0–2′‐dibutyryladenosine 3′,5′‐phosphate (Bt 2 cyclic AMP) or the phosphodiesterase inhibitor, 3‐isobutyl‐1‐methylxanthine enhanced NO synthase activity in a dose‐dependent manner. 3 There was a lag period of about 8 h before a significantly enhanced secretion of nitrite could be detected upon exposure of cells to forskolin and for maximal stimulation, forskolin had to be present during the whole incubation period. 4 Treatment of mesangial cells with actinomycin D, cycloheximide or dexamethasone completely suppressed forskolin‐stimulated NO‐synthase activity, thus demonstrating that transcription and protein synthesis are necessary for nitrite formation. 5 Bt 2 cyclic AMP, the most potent inducer of nitrite production, increased NO synthase mRNA levels in mesangial cells in a time− and dose‐dependent fashion. Dexamethasone completely inhibited the increase of NO synthase mRNA in response to Bt 2 cyclic AMP. 6 Combination of Bt 2 cyclic AMP and IL‐1β or TNFα revealed a strong synergy in terms of nitrite formation. Time‐course studies indicated that cyclic AMP needed to be increased during the whole period of IL‐1β stimulation for maximal nitrite production. 7 These observations suggest that cyclic AMP controls NO synthase expression in mesangial cells. Furthermore, the signalling cascades triggered by IL‐1β and TNFα synergize with the cyclic AMP pathway to stimulate NO synthase activity.