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

Abstract

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 (SSCD14-/-) 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. The present study tested the hypothesis that the amplification of salt-sensitive hypertension and kidney damage in salt-sensitive females lacking CD14 is dependent upon NOX2.

Methods: A double knockout salt-sensitive rat was bred to lack both CD14 and the critical p67phox subunit of NOX2 (SSCD14-/-p67phox-/-). In vivo and ex vivo experiments explored the consequences of CD14 deletion in addition to nonfunctional NOX2 on salt-induced blood pressure, kidney damage, and inflammation. Complementary experiments utilizing diseased human kidneys correlated our findings to humans.

Results: We found that SSCD14-/- peritoneal macrophages demonstrated increased NOX2 subunit mRNA and a greater capacity to produce NOX2-superoxide versus Dahl salt-sensitive rats, while SSCD14-/-p67phox-/- macrophages did not produce superoxide. We also showed that SSCD14-/-p67phox-/- females had significantly attenuated salt-induced hypertension, kidney damage, and renal inflammation compared to SSCD14-/-, indicating that NOX2 mediates the exacerbation of disease in CD14 absence. A subsequent total body irradiation/bone marrow transfer approach utilizing Dahl salt-sensitive female recipients and transfer of SSCD14-/-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.