XDH and cardiac hypertrophy: In another study, overexpression of the small heat shock protein Hsp22 in mice was correlated with elevated ROS production via enhanced activity of NADPH oxidase, xanthine oxidase and mitochondrial complex I, as well as further cardiac hypertrophy induction—action that could be reversed with the antioxidant tempol that, in turn, reduces cardiac hypertrophy [73].