Parris Colby L, Liu Catherine, Rani Alka, Tran Minh H, Li MingHua, Esquivel Carlos, Oropeza Andrea M, Wang Lei
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, FL, United States.
Am J Physiol Renal Physiol. 2025 Jul 21. doi: 10.1152/ajprenal.00195.2025.
Ischemia-reperfusion injury (IRI) remains a critical challenge to the survival of kidney transplantation (KTX) graft, with no effective prevention or treatment strategies currently available. Neuronal nitric oxide synthase β (NOS1β), the predominant splice variant of NOS1 and the main source of NO in the macula densa (MD), mediates tubuloglomerular feedback and regulates glomerular filtration rates. NOS1β activity in the MD is influenced by renal pH; however, the role of pH-dependent regulation of NOS1β in mitigating IRI and protecting transplanted kidney graft function remains unclear. To explore this, C57BL/6J mice were given oral NaHCO₃ or NaCl for two weeks before KTX. Blood and urine pH, NOS1β expression, NO levels, and transplant outcomes were evaluated. MD-specific NOS1 knockout (MD-NOS1KO) mice were used to assess the direct role of NOS1β. NOS1β expression decreased by approximately 60% three days post-KTX. MD-NOS1β deletion exacerbated graft injury. NOS1β activities showed a strong tubular pH dependence, with maximal activity near pH 8.0. Bicarbonate treatment increased NOS1β expression in the MD by 65% and significantly improved graft outcomes, lowering plasma creatinine by ~30% relative to NaCl-treated group. These protective effects were absent in MD-NOS1βKO mice. Proteomic analysis revealed 718 differentially expressed proteins, with several showing enrichment in NO signaling, tissue repair, and inflammatory response pathways. In summary, MD-NOS1β downregulation after transplantation contributes to graft injury. Raising renal pH with bicarbonate enhances NOS1β activity and protects graft function, suggesting a potential therapeutic strategy to reduce IRI in kidney transplants.
缺血再灌注损伤（IRI）仍然是肾移植（KTX）移植物存活面临的一项严峻挑战，目前尚无有效的预防或治疗策略。神经元型一氧化氮合酶β（NOS1β）是NOS1的主要剪接变体，也是致密斑（MD）中NO的主要来源，它介导肾小管-肾小球反馈并调节肾小球滤过率。MD中的NOS1β活性受肾脏pH值影响；然而，pH依赖性调节NOS1β在减轻IRI和保护移植肾移植物功能中的作用仍不清楚。为了探究这一点，在KTX前两周给C57BL/6J小鼠口服NaHCO₃或NaCl。评估血液和尿液pH值、NOS1β表达、NO水平及移植结果。采用MD特异性NOS1基因敲除（MD-NOS1KO）小鼠来评估NOS1β的直接作用。KTX后三天，NOS1β表达下降约60%。MD-NOS1β缺失加剧了移植物损伤。NOS1β活性表现出强烈的肾小管pH依赖性，在pH 8.0附近活性最高。碳酸氢盐治疗使MD中NOS1β表达增加65%，并显著改善了移植结果，与NaCl治疗组相比，血浆肌酐降低了约30%。这些保护作用在MD-NOS1βKO小鼠中不存在。蛋白质组学分析揭示了718种差异表达蛋白，其中几种在NO信号传导、组织修复和炎症反应途径中表现出富集。总之，移植后MD-NOS1β下调导致移植物损伤。用碳酸氢盐提高肾脏pH值可增强NOS1β活性并保护移植物功能，提示这是一种减少肾移植中IRI的潜在治疗策略。
