6β-Hydroxytestosterone, a metabolite of testosterone generated by CYP1B1, contributes to vascular changes in angiotensin II-induced hypertension in male mice

Abstract

Background: Previously, we showed that 6β-hydroxytestosterone (6β-OHT), a cytochrome P450 1B1 (CYP1B1)derived metabolite of testosterone, contributes to angiotensin II (Ang II)-induced hypertension in male mice. This study was conducted to test the hypothesis that 6β-OHT contributes to increased vascular reactivity, endothelial dysfunction, vascular hypertrophy, and reactive oxygen species production associated with Ang II-induced hypertension. Methods: Eight-to 10-week-old intact or castrated C57BL/6 J (Cyp1b1 +/+ and Cyp1b1 −/−) mice were anesthetized for implantation of a micro-osmotic pump which delivered Ang II (700 ng/kg/day) or saline for 14 days. Mice were injected with 6β-OHT (15 μg/g b.w every third day), flutamide (8 mg/kg every day), or its vehicle. Blood pressure was measured via tail-cuff. Vascular reactivity, endothelial-dependent and endothelial-independent vasodilation, media to lumen ratio, fibrosis by collagen deposition, and reactive oxygen species production by dihydroethidium staining were determined in the isolated thoracic aorta. Results: The response of thoracic aorta to phenylephrine and endothelin-1 was increased in Ang II-infused Cyp1b1 +/+ mice compared to intact Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice; these effects of Ang II were restored by treatment with 6β-OHT. Ang II infusion caused endothelial dysfunction, as indicated by decreased relaxation of the aorta to acetylcholine in Cyp1b1 +/+ but not Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice. 6β-OHT did not alter Ang II-induced endothelial dysfunction in Cyp1b1 +/+ mice but restored it in Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice. Ang II infusion increased media to lumen ratio and caused fibrosis and reactive oxygen species production in the aorta of Cyp1b1 +/+ mice. These effects were minimized in the aorta of Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice and restored by treatment with 6β-OHT. Treatment with the androgen receptor antagonist flutamide reduced blood pressure and vascular hypertrophy in castrated Ang IIinfused mice injected with 6β-OHT.

CYP1B1 as a therapeutic target in cardio-oncology

“…Similarly, Malik and colleagues have demonstrated an important role of CYP1B1 in hypertension and hypertension-associated pathophysiology [92]. Intriguingly, they have shown a sexually dimorphic role of CYP1B1 where CYP1B1 played a detrimental role in male rodents [93][94][95], while it had a protective effect in females [96,97]. The detrimental effects of CYP1B1 in male rodents have been attributed to CYP1B1-mediated production of 6β-hydroxytestosterone which was shown to exacerbate angiotensin II-induced hypertension [93], renal dysfunction [94], and vascular changes [95].…”

“…Intriguingly, they have shown a sexually dimorphic role of CYP1B1 where CYP1B1 played a detrimental role in male rodents [ 93–95 ], while it had a protective effect in females [ 96 , 97 ]. The detrimental effects of CYP1B1 in male rodents have been attributed to CYP1B1-mediated production of 6β-hydroxytestosterone which was shown to exacerbate angiotensin II-induced hypertension [ 93 ], renal dysfunction [ 94 ], and vascular changes [ 95 ]. On the other hand, the protective effects of CYP1B1 in female rodents have been attributed to CYP1B1-mediated metabolism of estrogen to 2-methoxyestradiol [ 96 , 97 ].…”

New Perspectives of CYP1B1 Inhibitors in the Light of Molecular Studies

“…Increased CYP1B1 expression is associated with cardiac hypertrophy [35][36][37][38], hypertension [39][40][41][42][43], atherosclerosis [44], cardiotoxicity, and vascular dysfunction. 6β-Hydroxytestosterone, a metabolite of testosterone generated by CYP1B1, contributes to vascular changes in angiotensin II-induced hypertension in male mice [45].…”

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“…Differences between men and women in RAS regulation could be attributed to a higher stimulation of ACE activity by androgens, as has been demonstrated in male mice [ 42 ], in which testosterone increases ACE activity, and also in women with hyperandrogenism from polycystic ovary syndrome [ 43 ]. This is further supported by sex differences in the regulation of arterial pressure and renal function by the RAS [ 44 ], with the balance tipped toward depressor pathways in women [ 45 ].…”