Interleukin‐18 Enhances Contractile Responses to Phenylephrine in Pudendal Artery from Wistar Rats

Abstract

BackgroundHypertension is a major risk factor for the development of cardiovascular diseases and is a leading cause of mortality. The etiology of essential hypertension remains unclear, and its mechanisms are complex. Inflammation is a complex phenomenon, comprises the first response of the immune system in the presence of harmful stimuli and is considered to be a major cause of increased blood pressure. Indeed, low‐grade inflammation and activation of the immune system have been implicated in hypertension. Cytokine levels are elevated in hypertension and have been reported to be implicated in the associated disturbances in vascular reactivity reported in this disease. Clinical and population studies have consistently found increased circulating levels of interleukin 18 (IL‐18) in patients with hypertension.HypothesisThis study tests the hypothesis that IL‐18 will enhance contractile responses to phenylephrine in isolated arterial rings from rats.MethodsVascular function was performed on isolated pudendal arteries from male Wistar rats using wire myographs, kept in Krebs solution at 37°C, constantly aerated with 95%O2/5%CO2. Concentration‐response curves to phenylephrine (PE; 10‐9‐3x10‐5M), Acetylcholine (ACH; 10‐9 – 3x10‐5M) were performed in the absence or in the presence of IL‐18 (20ng/ml) for 1 hour. 10 minutes prior to the incubation with IL‐18, some arterial rings were incubated separately with the following agents: NADPH oxidase 2 inhibitor, gp91 ds‐tat (10‐5M); NADPH oxidase 1 and 4 inhibitor, GKT137831(10‐6M); and mitogen‐activated protein kinase (MKK / MEK) inhibitor, PD98059 (10‐5M) Concentration‐response curves were analyzed using non‐linear regression analysis. Data are presented as mean ± S.E.M. Statistical significance set at p<0.05. Data was analyzed with GraphPad Prism 9.2.0.ResultsIn the Wistar pudendal arterial rings, the potency of PE was increased in the presence of IL‐18 (pEC506.510 ± 0.3987 vs 6.022 ± 0.2738 for control; p = 0.0268) A, IL‐18 plus gp91 ds‐tat (pEC506.643 ± 0.2215 vs 6.264 ± 0.2471 for control; p = 0.0058) B and IL‐18 plus GKT137831 (pEC506.700 ± 0.2937 vs 6.272 ± 0.2963 for control; p = 0.0003) C. Incubation with IL‐18 plus PD98059 restored the contraction to PE to control levels. (pEC506.105 ± 0.4007 vs 6.170 ± 0.2847 for control; p = 0.7120) D. The relaxation response to ACh was not changed by IL‐18 after incubation for 1 hr.ConclusionOur results show that IL‐18 enhances the contractile responses to PE in pudendal arteries from Wistar rats by activation of the Mitogen‐Activated Protein Kinase/Extracellular Signal‐Regulated Kinase Pathway.