Impact of Hematopoietic CD14 on Oxidative Stress during Salt-Sensitive Hypertension and Kidney Injury

Key Points Deletion of CD14 in Dahl salt-sensitive females increased NADPH oxidase 2 oxidative stress in macrophages, exacerbated hypertension, and worsened kidney injury. Double knockout of CD14 and functional NADPH oxidase 2 via Ncf2 deletion ameliorated the exacerbated salt-sensitive phenotype of female salt-sensitive CD14−/− . Immune-specific double knockout of CD14 and p67phox via bone marrow transfer markedly attenuated hypertension and kidney damage. Background In high-salt diet-fed Dahl salt-sensitive rats, increased Cd14 expression by infiltrating macrophages accompanies hypertension and kidney damage. Interestingly, genetic deletion of Cd14 in the Dahl salt-sensitive rat model (SS CD14−/− ) conferred a significant exacerbation of salt-induced hypertension and associated kidney disease in females. We speculated that CD14 may function to modulate the production of reactive oxygen species in macrophages, since previous findings implicated hematopoietic NADPH oxidase 2 (NOX2)–derived superoxide in the pathogenesis of salt-sensitive hypertension. This study tested the hypothesis that the amplification of salt-sensitive hypertension and kidney damage in salt-sensitive females lacking CD14 is dependent on NOX2. Methods A double knockout salt-sensitive rat was bred to lack both CD14 and the critical p67 phox subunit of NOX2 (SS CD14−/−p67phox−/− ). In vivo and ex vivo experiments explored the consequences of CD14 deletion in addition to nonfunctional NOX2 on salt-induced BP, kidney damage, and inflammation. Complementary experiments using diseased human kidneys correlated our findings to humans. Results We found that SS CD14−/− peritoneal macrophages demonstrated increased NOX2 subunit mRNA and a greater capacity to produce NOX2-superoxide versus genetically intact Dahl salt-sensitive rats, whereas SS CD14−/−p67phox−/− macrophages did not produce superoxide. We also showed that SS CD14−/−p67phox−/− females had significantly attenuated salt-induced hypertension, kidney damage, and renal inflammation compared with SS CD14−/− , indicating that NOX2 mediates the exacerbation of disease in CD14 absence. A subsequent total body irradiation/bone marrow transfer approach using Dahl salt-sensitive female recipients and transfer of SS CD14−/−p67phox−/− bone marrow recapitulated these findings, demonstrating a clear interplay of CD14 and NOX2 specifically in immune cells. Finally, consistent with observations in the Dahl salt-sensitive rats, immunohistochemical observations in human tissue demonstrated a positive correlation between kidney damage, CD68 + macrophages, and CD14 in the kidney. Conclusions We highlight a novel regulatory pathway whereby hematopoietic CD14 influences NOX2-derived oxidative stress and therefore modulates the progression of hypertension and kidney disease.