The role of the (pro)renin receptor in the development of neurogenic hypertension
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Despite the number of therapeutic interventions currently available for treating hypertension, approximately one-third of adult patients in the United States currently being treated remain hypertensive (43). As the number of hypertensive patients continues to grow, it is becoming increasingly important to investigate the different types of hypertension in order to have a greater understanding of the pathogenesis and identify potential targets for treatment. Neurogenic hypertension refers to hypertension resulting from a centrally mediated mechanism, likely involving a sustained increase in sympathetic nervous system activity. The renin-angiotensin aldosterone system (RAAS) is a physiological cascade responsible for restoring blood pressure when it drops. The rate-limiting step involves the enzyme renin. Although there is evidence of local RAAS activity in the brain, expression of renin in the brain is very low (125). The (pro)renin receptor ((P)RR) is able to bind and activate both renin and (pro)renin. Because the (P)RR and (pro)renin expression is high in the brain, it is possible that local RAAS activity is orchestrated by the (P)RR. In this study, we investigated if neuroinflammatory conditions could foster an environment that would allow for a rise in sympathetic nervous system activity (SNA) resulting from brain RAAS activity and the (P)RR. By treating neuronal cell cultures with proinflammatory cytokines, an anti-inflammatory agent, and (pro)renin, we explored any changes or differences in mRNA expression levels. Additionally, the effects of antioxidants were investigated. The results of this study showed that cells lacking antioxidants were more vulnerable to cellular stress and inflammation in the presence of increased (pro)renin. Proinflammatory stress was correlated with increased mRNA expression of proinflammatory and immune system regulatory genes in addition to increased expression of angiotensin II type I receptor, a vital component of RAAS. This could indicate that neuroinflammatory stress can be exacerbated and contribute to increased RAAS activity in the brain mediated by the (P)RR.