CYP2J2 and EETs protect against pulmonary arterial hypertension with lung ischemia-reperfusion injury in vivo and in vitro.

BACKGROUND: Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to epoxyeicosatrienoic acids (EETs), which exert anti-inflammatory, anti-apoptotic, pro-proliferative, and antioxidant effects on the cardiovascular system. However, the role of CYP2J2 and EETs in pulmonary arterial hypertension (PAH) with lung ischemia-reperfusion injury (LIRI) remains unclear. In the present study, we investigated the effects of CYP2J2 overexpression and exogenous EETs on PAH with LIRI in vitro and in vivo. METHODS: CYP2J2 gene was transfected into rat lung tissue by recombinant adeno-associated virus (rAAV) to increase the levels of EETs in serum and lung tissue. A rat model of PAH with LIRI was constructed by intraperitoneal injection of monocrotaline (50 mg/kg) for 4 weeks, followed by clamping of the left pulmonary hilum for 1 h and reperfusion for 2 h. In addition, we established a cellular model of human pulmonary artery endothelial cells (HPAECs) with TNF-α combined with anoxia/reoxygenation (anoxia for 8 h and reoxygenation for 16 h) to determine the effect and mechanism of exogenous EETs. RESULTS: CYP2J2 overexpression significantly reduced the inflammatory response, oxidative stress and apoptosis associated with lung injury in PAH with LIRI. In addition, exogenous EETs suppressed inflammatory response and reduced intracellular reactive oxygen species (ROS) production and inhibited apoptosis in a tumor necrosis factor alpha (TNF-α) combined hypoxia-reoxygenation model of HPAECs. Our further studies revealed that the anti-inflammatory effects of CYP2J2 overexpression and EETs might be mediated by the activation of PPARγ; the anti-apoptotic effects might be mediated by the PI3K/AKT pathway. CONCLUSIONS: CYP2J2 overexpression and EETs protect against PAH with LIRI via anti-inflammation, anti-oxidative stress and anti-apoptosis, suggesting that increased levels of EETs may be a promising strategy for the prevention and treatment of PAH with LIRI.

CYP epoxygenase 2J2 prevents cardiac fibrosis by suppression of transmission of pro-inflammation from cardiomyocytes to macrophages.

Cytochrome P450 epoxygenase (CYP450)-derived epoxyeicosatrienoic acids (EETs) are important regulators of cardiac remodeling; but the underlying mechanism remains unclear. The present study aimed to elucidate how EETs regulated cardiac fibrosis in response to isoprenaline (Iso) or angiotensin (Ang) II. Cardiac-specific human CYP2J2 transgenic mice (Tr) and wild-type (WT) C57BL/6 littermates were infused with Iso- or Ang II. Two weeks after infusion, Tr mice showed more alleviative cardiac fibrosis and inflammation compared with WT mice. In vitro, we found Iso or Ang II induced nuclear transfer of NF-κB p65 and inflammatory cytokines expression in cardiomyocytes. Furthermore, inflammation response emerged in macrophages cultured in cardiomyocytes-conditioned medium. When pretreatment with 14,15-EET in cardiomyocytes, the inflammatory response was markedly suppressed and the transmission of inflammation from cardiomyocytes to macrophages was reduced. In conclusion, CYP2J2 and EETs prevent cardiac fibrosis and cardiac dysfunction by suppressing transmission of pro-inflammation from cardiomyocytes to macrophages in heart, suggesting that elevation of EETs level could be a potential strategy to prevent cardiac fibrosis.

Genetic markers in the EET metabolic pathway are associated with outcomes in patients with aneurysmal subarachnoid hemorrhage.

Preclinical studies show that epoxyeicosatrienoic acids (EETs) regulate cerebrovascular tone and protect against cerebral ischemia. We investigated the relationship between polymorphic genes involved in EET biosynthesis/metabolism, cytochrome P450 (CYP) eicosanoid levels, and outcomes in 363 patients with aneurysmal subarachnoid hemorrhage (aSAH). Epoxyeicosatrienoic acids and dihydroxyeicosatetraenoic acid (DHET) cerebrospinal fluid (CSF) levels, as well as acute outcomes defined by delayed cerebral ischemia (DCI) or clinical neurologic deterioration (CND), were assessed over 14 days. Long-term outcomes were defined by Modified Rankin Scale (MRS) at 3 and 12 months. CYP2C8*4 allele carriers had 44% and 36% lower mean EET and DHET CSF levels (P=0.003 and P=0.007) and were 2.2- and 2.5-fold more likely to develop DCI and CND (P=0.039 and P=0.041), respectively. EPHX2 55Arg, CYP2J2*7, CYP2C8*1B, and CYP2C8 g.36785A allele carriers had lower EET and DHET CSF levels. CYP2C8 g.25369T and CYP2C8 g.36755A allele carriers had higher EET levels. Patients with CYP2C8*2C and EPHX2 404del variants had worse long-term outcomes while those with EPHX2 287Gln, CYP2J2*7, and CYP2C9 g.816G variants had favorable outcomes. Epoxyeicosatrienoic acid levels were associated with Fisher grade and unfavorable 3-month outcomes. Dihydroxyeicosatetraenoic acids were not associated with outcomes. No associations passed Bonferroni multiple testing correction. These are the first clinical data demonstrating the association between the EET biosynthesis/metabolic pathway and the pathophysiology of aSAH.

Identification of genes and pathways involved in the synthesis of Mead acid (20:3n-9), an indicator of essential fatty acid deficiency.

In mammals, 5,8,11-eicosatrienoic acid (Mead acid, 20:3n-9) is synthesized from oleic acid during a state of essential fatty acid deficiency (EFAD). Mead acid is thought to be produced by the same enzymes that synthesize arachidonic acid and eicosapentaenoic acid, but the genes and the pathways involved in the conversion of oleic acid to Mead acid have not been fully elucidated. The levels of polyunsaturated fatty acids in cultured cells are generally very low compared to those in mammalian tissues. In this study, we found that cultured cells, such as NIH3T3 and Hepa1-6 cells, have significant levels of Mead acid, indicating that cells in culture are in an EFAD state under normal culture conditions. We then examined the effect of siRNA-mediated knockdown of fatty acid desaturases and elongases on the level of Mead acid, and found that knockdown of Elovl5, Fads1, or Fads2 decreased the level of Mead acid. This and the measured levels of possible intermediate products for the synthesis of Mead acid such as 18:2n-9, 20:1n-9 and 20:2n-9 in the knocked down cells indicate two pathways for the synthesis of Mead acid: pathway 1) 18:1n-9→(Fads2)→18:2n-9→(Elovl5)→20:2n-9→(Fads1)→20:3n-9 and pathway 2) 18:1n-9→(Elovl5)→20:1n-9→(Fads2)→20:2n-9→(Fads1)→20:3n-9.

The importance of the lipoxygenase-hepoxilin pathway in the mammalian epidermal barrier.

This review covers the background to discovery of the two key lipoxygenases (LOX) involved in epidermal barrier function, 12R-LOX and eLOX3, and our current views on their functioning. In the outer epidermis, their consecutive actions oxidize linoleic acid esterified in ω-hydroxy-ceramide to a hepoxilin-related derivative. The relevant background to hepoxilin and trioxilin biochemistry is briefly reviewed. We outline the evidence that linoleate in the ceramide is the natural substrate of the two LOX enzymes and our proposal for its importance in construction of the epidermal water barrier. Our hypothesis is that the oxidation promotes hydrolysis of the oxidized linoleate moiety from the ceramide. The resulting free ω-hydroxyl of the ω-hydroxyceramide is covalently bound to proteins on the surface of the corneocytes to form the corneocyte lipid envelope, a key barrier component. Understanding the role of the LOX enzymes and their hepoxilin products should provide rational approaches to ameliorative therapy for a number of the congenital ichthyoses involving compromised barrier function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

CYP3A4 mediates growth of estrogen receptor-positive breast cancer cells in part by inducing nuclear translocation of phospho-Stat3 through biosynthesis of (±)-14,15-epoxyeicosatrienoic acid (EET).

CYP3A4 expression in breast cancer correlates with decreased overall survival, but the mechanisms are unknown. Cytochrome P450 gene profiling by RNAi silencing demonstrates that CYP3A or 2C8 gene expression is specifically required for growth of the breast cancer lines MCF7, T47D, and MDA-MB-231. CYP3A4 silencing blocks the cell cycle at the G(2)/M checkpoint and induces apoptosis in the MCF7 line, thereby inhibiting anchorage-dependent growth and survival. CYP3A4 was profiled for NADPH-dependent arachidonic acid (AA) metabolism and synthesized AA epoxygenase products (±)-8,9-, (±)-11,12-, and (±)-14,15-epoxyeicosatrienoic acid (EET) (total turnover of ∼2 pmol/pmol CYP3A4/min) but not hydroxylase products (±)-15-, (±)-19-, or 20-hydroxyeicosatetraenoic acid. Furthermore, eicosanoid profiling revealed that MCF7 cells synthesize EETs in a CYP3A4-dependent manner. The (±)-14,15-EET regioisomer selectively rescues breast cancer cells from CYP3A4 silencing in a concentration-dependent fashion and promotes mitogenesis and anchorage-dependent cloning. Stat3 (Tyr-705) phosphorylation was inhibited by CYP3A4 silencing, providing a potential mechanism for CYP3A4 involvement in breast cancer cell growth. Silencing Stat3 blocks breast cancer cell growth and abrogates (±)-14,15-EET-induced proliferation, indicating a Stat3 requirement for (±)-14,15-EET-mediated cell growth. Although silencing of CYP3A4 reduces nuclear Tyr(P)-705-Stat3, (±)-14,15-EET restores this signaling process and promotes Tyr(P)-705-Stat3 translocation to the nucleus, suggesting that (±)-14,15-EET may be involved in an autocrine/paracrine pathway driving cell growth. These studies indicate that CYP3A4 is a highly active AA epoxygenase that promotes Stat3-mediated breast cancer cell growth in part through (±)-14,15-EET biosynthesis. Furthermore, these studies indicate an essential role for Stat3 as a mediator of epoxygenase activity in breast cancer.

Mutational and X-ray crystallographic analysis of the interaction of dihomo-gamma -linolenic acid with prostaglandin endoperoxide H synthases.

Prostaglandin endoperoxide H synthases-1 and -2 (PGHSs) catalyze the committed step in prostaglandin biosynthesis. Both isozymes can oxygenate a variety of related polyunsaturated fatty acids. We report here the x-ray crystal structure of dihomo-gamma-linolenic acid (DHLA) in the cyclooxygenase site of PGHS-1 and the effects of active site substitutions on the oxygenation of DHLA, and we compare these results to those obtained previously with arachidonic acid (AA). DHLA is bound within the cyclooxygenase site in the same overall L-shaped conformation as AA. C-1 and C-11 through C-20 are in the same positions for both substrates, but the positions of C-2 through C-10 differ by up to 1.74 A. In general, substitutions of active site residues caused parallel changes in the oxygenation of both AA and DHLA. Two significant exceptions were Val-349 and Ser-530. A V349A substitution caused an 800-fold decrease in the V(max)/K(m) for DHLA but less than a 2-fold change with AA; kinetic evidence indicates that C-13 of DHLA is improperly positioned with respect to Tyr-385 in the V349A mutant thereby preventing efficient hydrogen abstraction. Val-349 contacts C-5 of DHLA and appears to serve as a structural bumper positioning the carboxyl half of DHLA, which, in turn, positions properly the omega-half of this substrate. A V349A substitution in PGHS-2 has similar, minor effects on the rates of oxygenation of AA and DHLA. Thus, Val-349 is a major determinant of substrate specificity for PGHS-1 but not for PGHS-2. Ser-530 also influences the substrate specificity of PGHS-1; an S530T substitution causes 40- and 750-fold decreases in oxygenation efficiencies for AA and DHLA, respectively.