NADPH oxidases derived reactive oxygen species (ROS) play an important role in vascular function and remodeling in hypertension through redox signaling processes. Previous studies demonstrated that protein disulfide isomerase (PDI) regulates Nox1 expression and ROS generation in cultured vascular smooth muscle cells. However, the role of PDI in conductance and resistance arteries during hypertension development remains unknown. The aim of the present study was to investigate PDI expression and NADPH oxidase dependent ROS generation during hypertension development. Mesenteric resistance arteries (MRA) and thoracic aorta were isolated from 6, 8, and 12 week-old spontaneously hypertensive (SHR) and Wistar rats. ROS production (dihydroethidium fluorescence), PDI (WB, imunofluorescence), Nox1 and NOX4 (RT-PCR) expression were evaluated. Results show a progressive increase in ROS generation in MRA and aorta from 8 to 12 week-old SHR. This effect was associated with a concomitant increase in PDI and Nox1 expression only in MRA. Therefore, suggesting a positive correlation between PDI and Nox1 expression during the development of hypertension in MRA. In order to investigate if this effect was due to an increase in arterial blood pressure, pre hypertensive SHR were treated with losartan (20 mg/kg/day for 30 days), an AT1 receptor antagonist. Losartan decreased blood pressure and ROS generation in both vascular beds. However, only in SHR MRA losartan treatment lowered PDI and Nox1 expression to control levels. In MRA PDI inhibition (bacitracin, 0.5 mM) decreased Ang II redox signaling (p-ERK 1/2). Altogether, our results suggest that PDI plays a role in triggering oxidative stress and vascular dysfunction in resistance but not in conductance arteries, increasing Nox1 expression and activity. Therefore, PDI could be a new player in oxidative stress and functional alterations in resistance arteries during the establishment of hypertension.

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Diseases like hypertension are associated with vascular changes mediated by reactive oxygen species (ROS) such as changes in vascular tone, remodeling and inflammation. The major source of ROS in vascular cells is the enzyme NADPH oxidase, that is responsible for the increased production of these reactive species in hypertension. Protein disulfide isomerase (PDI), a endoplasmic reticulum chaperone, was identified as a protein capable of associate and regulate the activation of vascular NADPH oxidase. Studies have shown that inhibition of PDI is capable of reduce ROS generation in response to Angiotensin II (Ang II) in vascular smooth muscle cells. However, the role of PDI in ROS generation during hypertension development is unclear. Thus, teha aim of this study was to investigate the role of PDI in ROS generation in vascular beds of spontaneously hypertensive rats (SHR) during hypertension development. We used tranversal sections and samples of mesenteric resistance arteries, aorta, coronary and pulmonary arteries of 6, 8 and 12 weeks old Wistar and SHR rats, as well as Wistar and SHR rats treated with Losartan or Nifedipine. We analyze the ROS generation, PDI, Nox1 and Nox4 expression. The results showed a progressive increase in ROS generation, mRNA expression of Nox1 and PDI in mesenteric arteries, coronary arteries and pulmonary arteries of 8 weeks old SHR. Interestingly, this effect was not observed in aorta, although we detected an increased generation of ROS and Nox4 mRNA in SHR at 12 weeks these arteries. In order to investigate the correlation between the blood pressure increase, ROS generation and PDI expression, the animals were treated with anti hypertensive agents to reduce blood pressure. Treatment with Losartan (an AT1 receptor antagonist) reduced blood pressure and ROS generation as well as the expression of PDI and Nox1 in mesenteric arteries, coronary and pulmonary arteries of SHR. Interestingly, the same effect was not observed in animals treated with Nifedipine (a calcium channel blocker for L-type). Although, as Losartan, Nifedipine reduce blood pressure, ROS generation and Nox4 expression, unlike Losartan, treatment with Nifedipine did not reduce the expression of PDI. In summary, the results obtained suggest that the PDI expression was possibly related to the oxidative stress and not to increased blood pressure. Thus the PDI could be contributing to oxidative stress and vascular dysfunction in specific vascular beds, including resistance arteries during the development of hypertension.