NOX2 is the primary source of angiotensin II-induced superoxide in the macula densa.
Macula densa (MD)-mediated regulation of renal hemodynamics via tubuloglomerular feedback is regulated by interactions between factors such as superoxide (O(2)(-)) and angiotensin II (ANG II). We have reported that NaCl-induced O(2)(-) in the MD is produced by the NOX2 isoform of NADPH oxidase (NOX); however, the source of ANG II-induced O(2)(-) in MD is unknown. Thus we determined the pathways by which ANG II increased O(2)(-) in the MD by measuring O(2)(-) in ANG II-treated MMDD1 cells, a MD-like cell line. ANG II caused MMDD1 O(2)(-) levels to increase by more than twofold (P < 0.01). This increase was blocked by losartan (AT(1) receptor blocker) but not PD-123319 (AT(2) receptor antagonist). Apocynin (a NOX inhibitor) decreased O(2)(-) by 86% (P < 0.01), whereas oxypurinol (a xanthine oxidase inhibitor) and NS-398 (a cyclooxygenase-2 inhibitor) had no significant effect. The NOX-dependent increase in O(2)(-) was due to the NOX2 isoform; a short interfering (si)RNA against NOX2 blunted ANG II-induced increases in O(2)(-), whereas the NOX4/siRNA did not. Finally, we found that inhibiting the Rac1 subunit of NOX blunted ANG II-induced O(2)(-) production in NOX4/siRNA-treated cells but did not further decrease it in NOX2/siRNA-treated cells. Our results indicate that ANG II stimulates O(2)(-) production in the MD primarily via AT(1)-dependent activation of NOX2. Rac1 is required for the full activation of NOX2. This pathway may be an important component of ANG II enhancement of tubuloglomerular feedback.
Fu
Yiling
Y
Department of Physiology & Biophysics, University of Mississippi Medical Center, Jackson, MS 39216, USA.
Zhang
Rui
R
Lu
Deyin
D
Liu
Haifeng
H
Chandrashekar
Kiran
K
Juncos
Luis A
LA
Liu
Ruisheng
R
D000098:Acetophenones / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology; D025461:Feedback, Physiological / Q000502:physiology; D007686:Kidney Tubules, Distal / Q000098:blood supply / Q000166:cytology / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D034741:RNA, Small Interfering; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020830:rac1 GTP-Binding Protein
D000098:Acetophenones; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D009479:Neuropeptides; D034741:RNA, Small Interfering; C484602:Rac1 protein, mouse; D044140:Receptor, Angiotensin, Type 1; D014662:Vasoconstrictor Agents; D013481:Superoxides; D000804:Angiotensin II; C056165:acetovanillone; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein