Disruption of the cytochrome P-450 1B1 gene exacerbates renal dysfunction and damage associated with angiotensin II-induced hypertension in female mice

Central Interaction of 2-Methoxyestradiol and Lipoxygenase in AngII-Hypertension

BACKGROUND

Our previous findings that arachidonic acid-12/15-lipoxygenase (LOX)-generated metabolite 12(S)-HETE contributes to angiotensin II (AngII)-induced hypertension and 17β-estradiol protects from AngII-induced hypertension via its cytochrome P450 (CYP)1B1-generated metabolite 2-methoxyestradiol in the paraventricular nucleus (PVN) in female mice led us to test the hypothesis that 2-methoxyestradiol acts by inhibiting the LOX/12(S)-HETE in the PVN.

METHODS

AngII was infused subcutaneously by osmotic pumps for 2 weeks in wild-type, LOX-knockout (LOXKO), and CYP1B1KO female mice. The blood pressure was measured by tail-cuff/radiotelemetry. Adenovirus (Ad)-GFP (green fluorescence protein)-LOX-short hairpin RNA, Ad-GFP-LOX-DNA, 12(S)-HETE, and 2-methoxyestradiol were injected selectively in PVN or intracerebroventricularly. Histological, immunohistochemical, and biochemical techniques were used to determine pathophysiological changes caused by various interventions.

RESULTS

AngII-induced hypertension that was exaggerated in CYP1B1KO compared with wild-type mice was minimized by PVN-LOX knockdown with Ad-LOX-short hairpin RNA and restored by PVN-LOX reconstitution with Ad-LOX-DNA in intact-LOXKO mice and exacerbated in ovariectomized-LOXKO mice. Furthermore, intracerebroventricular-12(S)-HETE restored AngII-induced increases in blood pressure, autonomic impairment, neuroinflammation, and renal pathogenesis in intact-LOXKO mice, which were exacerbated in ovariectomized-LOXKO mice. Intracerebroventricular-2-methoxyestradiol that reduced the LOX expression and 12(S)-HETE content in PVN minimized AngII effects mentioned above in ovariectomized-LOXKO mice transduced with intracerebroventricular-Ad-LOX-DNA.

CONCLUSIONS

These data suggest that 2-methoxyestradiol protects against AngII-induced hypertension and associated pathogenesis, most likely by inhibiting LOX/12(S)-HETE actions in the PVN of female mice. Therefore, the selective LOX inhibitors or 12(S)-HETE receptor antagonists could be useful in treating hypertension and its pathogenesis in postmenopausal, hypoestrogenic women or females with ovarian failure.

Inhibition of heme-thiolate monooxygenase CYP1B1 prevents hepatic stellate cell activation and liver fibrosis by accumulating trehalose

Activation of extracellular matrix-producing hepatic stellate cells (HSCs) is a key event in liver fibrogenesis. We showed that the expression of the heme-thiolate monooxygenase cytochrome P450 1B1 (CYP1B1) was elevated in human and mouse fibrotic livers and activated HSCs. Systemic or HSC-specific ablation and pharmacological inhibition of CYP1B1 attenuated HSC activation and protected male but not female mice from thioacetamide (TAA)-, carbon tetrachloride (CCl4)-, or bile duct ligation (BDL)-induced liver fibrosis. Metabolomic analysis revealed an increase in the disaccharide trehalose in CYP1B1-deficient HSCs resulting from intestinal suppression of the trehalose-metabolizing enzyme trehalase, whose gene we found to be a target of RARα. Trehalose or its hydrolysis-resistant derivative lactotrehalose exhibited potent antifibrotic activity in vitro and in vivo by functioning as an HSC-specific autophagy inhibitor, which may account for the antifibrotic effect of CYP1B1 inhibition. Our study thus reveals an endobiotic function of CYP1B1 in liver fibrosis in males, mediated by liver-intestine cross-talk and trehalose. At the translational level, pharmacological inhibition of CYP1B1 or the use of trehalose/lactotrehalose may represent therapeutic strategies for liver fibrosis.

Changes in cardiovascular arachidonic acid metabolism in experimental models of menopause and implications on postmenopausal cardiac hypertrophy

Menopause is a normal stage in the human female aging process characterized by the cessation of menstruation and the ovarian production of estrogen and progesterone hormones. Menopause is associated with an increased risk of several different diseases. Cardiovascular diseases are generally less common in females than in age-matched males. However, this female advantage is lost after menopause. Cardiac hypertrophy is a disease characterized by increased cardiac size that develops as a response to chronic overload or stress. Similar to other cardiovascular diseases, the risk of cardiac hypertrophy significantly increases after menopause. However, the exact underlying mechanisms are not yet fully elucidated. Several studies have shown that surgical or chemical induction of menopause in experimental animals is associated with cardiac hypertrophy, or aggravates cardiac hypertrophy induced by other stressors. Arachidonic acid (AA) released from the myocardial phospholipids is metabolized by cardiac cytochrome P450 (CYP), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes to produce several eicosanoids. AA-metabolizing enzymes and their respective metabolites play an important role in the pathogenesis of cardiac hypertrophy. Menopause is associated with changes in the cardiovascular levels of CYP, COX, and LOX enzymes and the levels of their metabolites. It is possible that these changes might play a role in the increased risk of cardiac hypertrophy after menopause.

2-Methoxyestradiol Ameliorates Angiotensin II-Induced Hypertension by Inhibiting Cytosolic Phospholipase A2α Activity in Female Mice

Supplemental Digital Content is available in the text.

We tested the hypothesis that CYP1B1 (cytochrome P450 1B1)-17β-estradiol metabolite 2-methoxyestradiol protects against Ang II (angiotensin II)–induced hypertension by inhibiting group IV cPLA₂α (cytosolic phospholipase A₂α) activity and production of prohypertensive eicosanoids in female mice. Ang II (700 ng/kg per minute, SC) increased mean arterial blood pressure (BP), systolic and diastolic BP measured by radiotelemetry, renal fibrosis, and reactive oxygen species production in wild-type mice (cPLA₂α^+/+/Cyp1b1^+/+) that were enhanced by ovariectomy and abolished in intact and ovariectomized-cPLA₂α^−/−/Cyp1b1^+/+ mice. Ang II–induced increase in SBP measured by tail-cuff, renal fibrosis, reactive oxygen species production, and cPLA₂α activity measured by its phosphorylation in the kidney, and urinary excretion of prostaglandin E₂ and thromboxane A₂ metabolites were enhanced in ovariectomized-cPLA₂α^+/+/Cyp1b1^+/+ and intact cPLA₂α^+/+/Cyp1b1^−/− mice. 2-Methoxyestradiol and arachidonic acid metabolism inhibitor 5,8,11,14-eicosatetraynoic acid attenuated the Ang II–induced increase in SBP, renal fibrosis, reactive oxygen species production, and urinary excretion of prostaglandin E₂, and thromboxane A₂ metabolites in ovariectomized-cPLA₂α^+/+/Cyp1b1^+/+ and intact cPLA₂α^+/+/Cyp1b1^−/− mice. Antagonists of prostaglandin E₂ and thromboxane A₂ receptors EP1 and EP3 and TP, respectively, inhibited Ang II–induced increases in SBP and reactive oxygen species production and renal fibrosis in ovariectomized-cPLA₂α^+/+/Cyp1b1^+/+ and intact cPLA₂α^+/+/Cyp1b1^−/− mice. These data suggest that CYP1B1-generated metabolite 2-methoxyestradiol mitigates Ang II–induced hypertension and renal fibrosis by inhibiting cPLA₂α activity, reducing prostaglandin E₂, and thromboxane A₂ production and stimulating EP1 and EP3 and TP receptors, respectively. Thus, 2-methoxyestradiol and the drugs that selectively block EP1 and EP3 and TP receptors could be useful in treating hypertension and its pathogenesis in females.

CYP1B1 as a therapeutic target in cardio-oncology

Cardiovascular complications have been frequently reported in cancer patients and survivors, mainly because of various cardiotoxic cancer treatments. Despite the known cardiovascular toxic effects of these treatments, they are still clinically used because of their effectiveness as anti-cancer agents. In this review, we discuss the growing body of evidence suggesting that inhibition of the cytochrome P450 1B1 enzyme (CYP1B1) can be a promising therapeutic strategy that has the potential to prevent cancer treatment-induced cardiovascular complications without reducing their anti-cancer effects. CYP1B1 is an extrahepatic enzyme that is expressed in cardiovascular tissues and overexpressed in different types of cancers. A growing body of evidence is demonstrating a detrimental role of CYP1B1 in both cardiovascular diseases and cancer, via perturbed metabolism of endogenous compounds, production of carcinogenic metabolites, DNA adduct formation, and generation of reactive oxygen species (ROS). Several chemotherapeutic agents have been shown to induce CYP1B1 in cardiovascular and cancer cells, possibly via activating the Aryl hydrocarbon Receptor (AhR), ROS generation, and inflammatory cytokines. Induction of CYP1B1 is detrimental in many ways. First, it can induce or exacerbate cancer treatment-induced cardiovascular complications. Second, it may lead to significant chemo/radio-resistance, undermining both the safety and effectiveness of cancer treatments. Therefore, numerous preclinical studies demonstrate that inhibition of CYP1B1 protects against chemotherapy-induced cardiotoxicity and prevents chemo- and radio-resistance. Most of these studies have utilized phytochemicals to inhibit CYP1B1. Since phytochemicals have multiple targets, future studies are needed to discern the specific contribution of CYP1B1 to the cardioprotective and chemo/radio-sensitizing effects of these phytochemicals.

2-Methoxyestradiol Attenuates Angiotensin II-Induced Hypertension, Cardiovascular Remodeling, and Renal Injury

Estradiol may antagonize the adverse cardiovascular effects of angiotensin II (Ang II). We investigated the effects of 2-methoxyestradiol (2-ME), a nonestrogenic estradiol metabolite, on Ang II-induced cardiovascular and renal injury in male rats. First, we determined the effects of 2-ME on Ang II-induced acute changes in blood pressure, renal hemodynamics, and excretory function. Next, we investigated the effects of 2-ME and 2-hydroxyestardiol (2-HE) on hypertension and cardiovascular and renal injury induced by chronic infusion of Ang II. Furthermore, the effects of 2-ME on blood pressure and cardiovascular remodeling in the constricted aorta (CA) rat model and on isoproterenol-induced (ISO) cardiac hypertrophy and fibrosis were examined. 2-ME had no effects on Ang II-induced acute changes in blood pressure, renal hemodynamics, or glomerular filtration rate. Both 2-ME and 2-HE reduced hypertension, cardiac hypertrophy, proteinuria, and mesangial expansion induced by chronic Ang II infusions. In CA rats, 2-ME attenuated cardiac hypertrophy and fibrosis and reduced elevated blood pressure above the constriction. Notably, 2-ME reduced both pressure-dependent (above constriction) and pressure-independent (below constriction) vascular remodeling. 2-ME had no effects on ISO-induced renin release yet reduced ISO-induced cardiac hypertrophy and fibrosis. This study shows that 2-ME protects against cardiovascular and renal injury due to chronic activation of the renin-angiotensin system. This study reports for the first time that in vivo 2-ME reduces trophic (pressure-independent) effects of Ang II and related cardiac and vascular remodeling.

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

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 II-infused mice injected with 6β-OHT.

Conclusions

6β-OHT is required for the action of Ang II to increase vascular reactivity and cause endothelial dysfunction, hypertrophy, and increase in oxygen radical production. The effect of 6β-OHT in mediating Ang II-induced hypertension and associated hypertrophy is dependent on the androgen receptor. Therefore, CYP1B1 could serve as a novel target for the development of therapeutics to treat vascular changes in hypertensive males.

Genetic polymorphisms associated with reactive oxygen species and blood pressure regulation

Hypertension is the most prevalent cause of cardiovascular disease and kidney failure, but only about 50% of patients achieve adequate blood pressure control, in part, due to inter-individual genetic variations in the response to antihypertensive medication. Significant strides have been made toward the understanding of the role of reactive oxygen species (ROS) in the regulation of the cardiovascular system. However, the role of ROS in human hypertension is still unclear. Polymorphisms of some genes involved in the regulation of ROS production are associated with hypertension, suggesting their potential influence on blood pressure control and response to antihypertensive medication. This review provides an update on the genes associated with the regulation of ROS production in hypertension and discusses the controversies on the use of antioxidants in the treatment of hypertension, including the antioxidant effects of antihypertensive drugs.

Neuroprotective effects of estrogen in CNS injuries: insights from animal models

Among the estrogens that are biosynthesized in the human body, 17β-estradiol (estradiol or E2) is the most common and the best estrogen for neuroprotection in animal models of the central nervous system (CNS) injuries such as spinal cord injury (SCI), traumatic brain injury (TBI), and ischemic brain injury (IBI). These CNS injuries are not only serious health problems, but also enormous economic burden on the patients, their families, and the society at large. Studies from animal models of these CNS injuries provide insights into the multiple neuroprotective mechanisms of E2 and also suggest the possibility of translating the therapeutic efficacy of E2 in the treatment SCI, TBI, and IBI in humans in the near future. The pathophysiology of these injuries includes loss of motor function in the limbs, arms and their extremities, cognitive deficit, and many other serious consequences including life-threatening paralysis, infection, and even death. The potential application of E2 therapy to treat the CNS injuries may become a trend as the results are showing significant therapeutic benefits of E2 for neuroprotection when administered into the animal models of SCI, TBI, and IBI. This article describes the plausible mechanisms how E2 works with or without the involvement of estrogen receptors and provides an overview of the known neuroprotective effects of E2 in these three CNS injuries in different animal models. Because activation of estrogen receptors has profound implications in maintaining and also affecting normal physiology, there are notable impediments in translating E2 therapy to the clinics for neuroprotection in CNS injuries in humans. While E2 may not yet be the sole molecule for the treatment of CNS injuries due to the controversies surrounding it, the neuroprotective effects of its metabolite and derivative or combination of E2 with another therapeutic agent are showing significant impacts in animal models that can potentially shape the new treatment strategies for these CNS injuries in humans.

2-Methoxyestradiol Reduces Angiotensin II-Induced Hypertension and Renal Dysfunction in Ovariectomized Female and Intact Male Mice

Cytochrome P450 1B1 protects against angiotensin II (Ang II)-induced hypertension and associated cardiovascular changes in female mice, most likely via production of 2-methoxyestradiol. This study was conducted to determine whether 2-methoxyestradiol ameliorates Ang II-induced hypertension, renal dysfunction, and end-organ damage in intact Cyp1b1-/-, ovariectomized female, and Cyp1b1+/+ male mice. Ang II or vehicle was infused for 2 weeks and administered concurrently with 2-methoxyestradiol. Mice were placed in metabolic cages on day 12 of Ang II infusion for urine collection for 24 hours. 2-Methoxyestradiol reduced Ang II-induced increases in systolic blood pressure, water consumption, urine output, and proteinuria in intact female Cyp1b1-/- and ovariectomized mice. 2-Methoxyestradiol also reduced Ang II-induced increase in blood pressure, water intake, urine output, and proteinuria in Cyp1b1+/+ male mice. Treatment with 2-methoxyestradiol attenuated Ang II-induced end-organ damage in intact Cyp1b1-/- and ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice and Cyp1b1+/+ male mice. 2-Methoxyestradiol mitigated Ang II-induced increase in urinary excretion of angiotensinogen in intact Cyp1b1-/- and ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice but not in Cyp1b1+/+ male mice. The G protein-coupled estrogen receptor 1 antagonist G-15 failed to alter Ang II-induced increases in blood pressure and renal function in Cyp1b1+/+ female mice. These data suggest that 2-methoxyestradiol reduces Ang II-induced hypertension and associated end-organ damage in intact Cyp1b1-/-, ovariectomized Cyp1b1+/+ and Cyp1b1-/- female mice, and Cyp1b1+/+ male mice independent of G protein-coupled estrogen receptor 1. Therefore, 2-methoxyestradiol could serve as a therapeutic agent for treating hypertension and associated pathogenesis in postmenopausal females, and in males.

6β-Hydroxytestosterone, a Cytochrome P450 1B1-Testosterone-Metabolite, Mediates Angiotensin II-Induced Renal Dysfunction in Male Mice

6β-Hydroxytestosterone, a cytochrome P450 1B1-derived metabolite of testosterone, contributes to the development of angiotensin II-induced hypertension and associated cardiovascular pathophysiology. In view of the critical role of angiotensin II in the maintenance of renal homeostasis, development of hypertension, and end-organ damage, this study was conducted to determine the contribution of 6β-hydroxytestosterone to angiotensin II actions on water consumption and renal function in male Cyp1b1(+/+) and Cyp1b1(-/-) mice. Castration of Cyp1b1(+/+) mice or Cyp1b1(-/-) gene disruption minimized the angiotensin II-induced increase in water consumption, urine output, proteinuria, and sodium excretion and decreases in urine osmolality. 6β-Hydroxytestosterone did not alter angiotensin II-induced increases in water intake, urine output, proteinuria, and sodium excretion or decreases in osmolality in Cyp1b1(+/+) mice, but restored these effects of angiotensin II in Cyp1b1(-/-) or castrated Cyp1b1(+/+) mice. Cyp1b1 gene disruption or castration prevented angiotensin II-induced renal fibrosis, oxidative stress, inflammation, urinary excretion of angiotensinogen, expression of angiotensin II type 1 receptor, and angiotensin-converting enzyme. 6β-Hydroxytestosterone did not alter angiotensin II-induced renal fibrosis, inflammation, oxidative stress, urinary excretion of angiotensinogen, expression of angiotensin II type 1 receptor, or angiotensin-converting enzyme in Cyp1b1(+/+)mice. However, in Cyp1b1(-/-) or castrated Cyp1b1(+/+) mice, it restored these effects of angiotensin II. These data indicate that 6β-hydroxytestosterone contributes to increased thirst, impairment of renal function, and end-organ injury associated with angiotensin II-induced hypertension in male mice and that cytochrome P450 1B1 could serve as a novel target for treating renal disease and hypertension in male mice.

Metabolism of benzo(a)pyrene by aortic subcellular fractions in the setting of abdominal aortic aneurysms

As exposure to polycyclic aromatic hydrocarbons (PAHs; a family of environmental toxicants) have been implicated in cardiovascular diseases, the ability of the aortic tissue to process these toxicants is important from the standpoint of abdominal aortic aneurysms and atherosclerosis. Benzo(a)pyrene (B(a)P), a representative PAH compound is released into the environment from automobile exhausts, industrial emissions, and considerable intake of B(a)P is also expected in people who are smokers and barbecued red meat eaters. Therefore, knowledge of B(a)P metabolism in the cardiovascular system will be of importance in the management of vascular disorders. Toward this end, subcellular fractions (nuclear, cytosolic, mitochondrial, and microsomal) were isolated from the aortic tissues of Apo E mice that received a 5 mg/kg/week of B(a)P for 42 days and 0.71 mg/kg/day for 60 days. The fractions were incubated with 1 and 3 μM B(a)P. Post incubation, samples were extracted with ethyl acetate and analyzed by reverse-phase HPLC. Microsomal B(a)P metabolism was greater than the rest of the fractions. The B(a)P metabolite levels generated by all the subcellular fractions showed a B(a)P exposure concentration-dependent increase for both the weekly and daily B(a)P treatment categories. The preponderance of B(a)P metabolites such as 7,8-dihydrodiol, 3,6-, and 6,12-dione metabolites are interesting due to their reported involvement in B(a)P-induced toxicity through oxidative stress.