Non-steroidal anti-inflammatory drugs activate NADPH oxidase in adipocytes and raise the H(2)O(2) pool to prevent cAMP-stimulated protein kinase a activation and inhibit lipolysis

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) —aspirin, naproxen, nimesulide, and piroxicam— lowered activation of type II cAMP-dependent protein kinase A (PKA-II) in isolated rat adipocytes, decreasing adrenaline- and dibutyryl cAMP (Bt(2)cAMP)-stimulated lipolysis. The molecular bases of insulin-like actions of NSAID were studied. RESULTS: Based on the reported inhibition of lipolysis by H(2)O(2), catalase was successfully used to block NSAID inhibitory action on Bt(2)cAMP-stimulated lipolysis. NSAID, at (sub)micromolar range, induced an H(2)O(2) burst in rat adipocyte plasma membranes and in whole adipocytes. NSAID-mediated rise of H(2)O(2) was abrogated in adipocyte plasma membranes by: diphenyleneiodonium, an inhibitor of NADPH oxidase (NOX); the NOX4 antibody; and cytochrome c, trapping the NOX-formed superoxide. These three compounds prevented the inhibition of Bt(2)cAMP-stimulated lipolysis by NSAIDs. Inhibition of aquaporin-mediated H(2)O(2) transport with AgNO(3) in adipocytes allowed NOX activation but prevented the lipolysis inhibition promoted by NSAID: i.e., once synthesized, H(2)O(2) must reach the lipolytic machinery. Since insulin inhibits adrenaline-stimulated lipolysis, the effect of aspirin on isoproterenol-stimulated lipolysis in rat adipocytes was studied. As expected, isoproterenol-mediated lipolysis was blunted by both insulin and aspirin. CONCLUSIONS: NSAIDs activate NOX4 in adipocytes to produce H(2)O(2), which impairs cAMP-dependent PKA-II activation, thus preventing isoproterenol-activated lipolysis. H(2)O(2) signaling in adipocytes is a novel and important cyclooxygenase-independent effect of NSAID.