HR or TNF-α upregulates superoxide generation by ATII cells. Superoxide anion generation by ATII cells was measured by a chemiluminescence-based assay. A: treatment with TNF-α (TNF), but not IL-17, significantly increased superoxide anion generation by normoxic (Norm) ATII cells compared with normoxia alone, which was significantly attenuated by apocynin (Apo) pretreatment. Combined treatment with IL-17 and TNF-α offered no significant change in superoxide anion generation by normoxic ATII cells compared with TNF-α treatment alone. *P < 0.05 vs. Norm; #P < 0.05 vs. Norm+TNF; §P < 0.05 vs. Norm+IL-17+TNF; n = 8/group. B: HR exposure of ATII cells significantly increased superoxide anion production compared with normoxia, which is significantly attenuated by apocynin. Treatment of HR-exposed ATII cells with TNF-α but not IL-17, significantly enhanced superoxide anion production by ATII cells compared with HR alone. However, combined treatment of HR-exposed ATII cells with IL-17 and TNF-α did not change superoxide anion production compared with treatment with TNF-α alone. *P < 0.05 vs. Norm; #P < 0.05 vs. HR; ##P < 0.05 vs. HR+IL-17; §P < 0.05 vs. HR+TNF; §§P < 0.05 vs. HR+IL-17+TNF; n = 8/group.