Richardson, Arlan

This study identifies 3-mercaptopyruvate sulfurtransferase (MPST) as a previously unrecognized regulator of neonatal airway epithelial development. In our neonatal patient-derived three-dimensional organotypic model, hyperoxia reduces MPST, and MPST loss alters mitochondrial metabolism and epithelial differentiation programs. These findings indicate that MPST deficiency contributes to mitochondrial dysfunction under hyperoxic conditions and highlight MPST-linked pathways as potential therapeutic targets to mitigate early-life airway injury and remodeling relevant to infants with bronchopulmonary dysplasia (BPD).

Increased BMP signaling and markers of osteogenic differentiation are strongly associated with regions of valvular calcification in aortic valves from humans with end-stage calcific aortic valve stenosis. While oxidative stress is also markedly elevated in these regions, it is unknown whether increasing antioxidant capacity can reduce pro-osteogenic signaling and valvular calcification. Therefore, we hypothesized that overexpression of manganese superoxide dismutase (MnSOD) can reduce pro-osteogenic signaling in the aortic valves from hypercholesterolemic mice, ultimately resulting in reduced valvular calcification and improved valvular function. We used Ldlr -/- /ApoB 100/100 (LA) mice that were wild-type for MnSOD (LA-MnSOD 0/0 ) or overexpressing MnSOD (LA-MnSOD Tg/0 ) and fed a western diet (TD88137) for six months. We first measured mRNA levels of the BMP ligands BMP2 and BMP4 (qRT-PCR), both of which were unchanged between LA-MnSOD 0/0 and LA-MNSOD Tg/0 mice. While there was a small but significant increase in Runx2 mRNA levels in LA-MnSOD Tg/0 mice compared to wild-type littermates (1.22±0.09, 1.0±0.09, qRT-PCR, p < 0.05.) gene expression levels of late stage osteoblast marker Sp7 were reduced by approximately 50% in LA-MnSOD Tg/0 compared to wild-type littermates (0.53±0.15, 1.0±0.24, qRT-PCR, p < 0.05). Sp7 protein levels (immunohistochemistry) were also significantly reduced in LA-MnSOD Tg/0 compared to wild-type littermates (164.5±12.3 RFU vs 259.6±10.4 RFU, p < 0.05). Critically, aortic valve calcification (Alizarin Red) was also significantly reduced in LA-MnSOD Tg/0 mice compared to their LA-MnSOD 0/0 littermates. Functionally, aortic valve cusp separation distance (high resolution echocardiography) was slightly improved in LA-MnSOD Tg/0 mice compared to LA-MnSOD 0/0 mice (0.98±0.04 mm vs 0.91±0.03 mm, p = n.s.). Collectively, these data suggest that increasing mitochondrial antioxidant capacity can reduce pro-osteogenic signaling and attenuate aortic valve calcification, and may be a potential therapeutic target to slow the progression of valvular calcification and dysfunction in patients with calcific aortic valve stenosis.

We previously reported that MnSOD‐deficiency does not cause overt vasomotor dysfunction in aged or hypercholesterolemic mice. To determine whether increasing MnSOD protects against vasomotor dysfunction and deleterious molecular changes in atherosclerosis, we crossed hypercholesterolemic mice with mice overexpressing MnSOD to test the hypothesis that lifelong increases in MnSOD protect against vasomotor dysfunction. We used Ldlr ‐/‐ /ApoB 100/100 mice that were wild‐type (MnSOD 0/0 ) or transgenic (MnSOD Tg/0 ) and fed a western diet for 6 months. We used organ bath chambers to measure aortic endothelium‐dependent relaxation (relaxation to acetylcholine, Ach), and mRNA from aortic arch was used for qRT‐PCR. Surprisingly, relaxation to Ach was unchanged between MnSOD 0/0 and MnSOD Tg/0 mice, as was relaxation to sodium nitroprusside. As expected, gene expression of MnSOD was significantly increased in the MnSOD Tg/0 mice compared to MnSOD 0/0 mice. Unlike our findings in MnSOD +/‐ mice, however (where Nox2 was increased), Nox2 expression was unchanged between MnSOD 0/0 and MnSOD Tg/0 mice. Importantly, markers of osteogenesis such as Runx2 and BMP2 were unchanged between genotypes. Furthermore, MnSOD overexpression did not alter cellular senescence markers. Collectively, our data support the surprising conclusion that physiologically relevant increases in MnSOD do not significantly affect endothelial function or molecular regulators of histopathological changes in advanced atherosclerosis in hypercholesterolemic mice.