Retinoic acid metabolism by a system reconstituted with cytochrome P-450

doi:10.1016/0003-9861(84)90353-9

Archives of Biochemistry and Biophysics

Volume 234, Issue 1, October 1984, Pages 305-312

https://doi.org/10.1016/0003-9861(84)90353-9 Get rights and content

Abstract

Feeding rats with a diet containing a hundred times the normal amount of vitamin A resulted, within 2 to 3 weeks, in an increase in total hepatic microsomal cytochrome P-450 content. This was associated, in isolated microsomes, with an enhanced conversion of all-trans-retinoic acid to polar metabolites, including a two- to threefold increased production of 4-hydroxy- and 4-oxo-retinoic acid, whether expressed per microsomal protein or per cytochrome P-450. Unlike effects of other inducers (e.g., phenobarbital or methylcholanthrene), activities of benzphetamine, aminopyrine, and ethylmorphine demethylases or benzopyrene hydroxylase were not increased. Furthermore, the CO-reduced difference spectral peak was shifted towards 449 nm. On sodium dodecyl sulfate-gel electrophoresis, one band was increased with electrophoretic mobility identical to that of cytochrome P-450f, a recently isolated new form which has a CO-reduced difference spectral peak at 448 nm. In a system reconstituted with NADPH-cytochrome P-450 reductase, NADPH, and phospholipid, purified cytochromes P-450f and b were discovered to promote conversion of retinoic acid to polar metabolites, including 4-hydroxy-retinoic acid.

References (25)

A.B. Roberts et al.
J. Biol. Chem
(1979)
A.B. Roberts et al.
Arch. Biochem. Biophys
(1980)
M. Sato et al.
Arch. Biochem. Biophys
(1982)
C.S. Lieber et al.
J. Biol. Chem
(1970)
T. Omura et al.
J. Biol. Chem
(1964)
D.W. Nebert et al.
J. Biol. Chem
(1968)
A.Y.H. Lu et al.
Biochem. Biophys. Res. Commun
(1972)
A.H. Phillips et al.
J. Biol. Chem
(1962)
M.A. Leo et al.
Gastroenterology
(1982)
D.E. Ryan et al.
J. Biol. Chem
(1980)

O.H. Lowry et al.

J. Biol. Chem

(1951)

D.E. Ryan et al.

J. Biol. Chem

(1984)

Cited by (150)

Ethanol induced hepatic mitochondrial dysfunction is attenuated by all trans retinoic acid supplementation
2015, Life Sciences
Citation Excerpt :
Alcoholism is characterized by a general deficiency in micronutrient status, including vitamin A. Alcoholics were reported to have impaired nutritional status of vitamin A with reduced serum vitamin A level [1]. This might be due to the increased metabolism and mobilization of vitamin A from the liver, [2,3] or the inhibition of retinoic acid biosynthesis [4]. But supplementation of vitamin A exacerbates the existing condition [5,6].
Alcoholics have reduced vitamin A levels in serum since vitamin A and ethanol share the same metabolic pathway. Vitamin A supplementation has an additive effect on ethanol induced toxicity. Hence in this study, we assessed the impact of supplementation of all trans retinoic acid (ATRA), an active metabolite of vitamin A on ethanol induced disruptive alterations in liver mitochondria.
Male Sprague Dawley rats were grouped as follows: I: Control; II: Ethanol (4 g/kg b.wt./day); III: ATRA (100 μg/kg b.wt./day); and IV: Ethanol (4 g/kg b.wt./day) + ATRA (100 μg/kg b.wt./day). Duration of the experiment was 90 days, after which the animals were sacrificed for the study. The key enzymes of energy metabolism, reactive oxygen species, mitochondrial membrane potential and hepatic mRNA expressions of Bax, Bcl-2, c-fos and c-jun were assessed.
Ethanol administration increased the reactive oxygen species generation in mitochondria. It also decreased the activities of the enzymes of citric acid cycle and oxidative phosphorylation. ATP content and mitochondrial membrane potential were decreased and cytosolic cytochrome c was increased consequently enhancing apoptosis. All these alterations were altered significantly on ATRA supplementation along with ethanol. These results were reinforced by our histopathological studies.
ATRA supplementation to ethanol fed rats, led to reduction in oxidative stress, decreased calcium overload in the matrix and increased mitochondrial membrane potential, which might have altered the mitochondrial energy metabolism and elevated ATP production thereby reducing the apoptotic alterations. Hence ATRA supplementation seemed to be an effective intervention against alcohol induced mitochondrial dysfunction.
Enzymology of retinoic acid biosynthesis and degradation
2013, Journal of Lipid Research
Citation Excerpt :
A frameshift mutation in human CYP26C1 has been recently linked to focal facial dermal dysplasia type IV, a rare syndrome characterized by facial lesions resembling aplasia cutis (135). In addition to the three CYP26 enzymes, several members of other CYP families, including human CYP3A4, CYP3A5, CYP3A7, CYP1A1, CYP4A11, CYP2C8, CYP2C9, CYP2C22, CYP2C39, CYP2S1, and CYP2E1 (136–150), have been shown to catabolize atRA. While CYP2C8 is catalytically more efficient than either CYP2C9 or CYP3A4, the overall contribution of CYP2C8 to atRA hydroxylation may not be much greater than that of CYP3A4 and CYP2C9, because the two latter enzymes are expressed at about 10-fold higher levels than CYP2C8 (139).
All-trans-retinoic acid is a biologically active derivative of vitamin A that regulates numerous physiological processes. The concentration of retinoic acid in the cells is tightly regulated, but the exact mechanisms responsible for this regulation are not completely understood, largely because the enzymes involved in the biosynthesis of retinoic acid have not been fully defined. Recent studies using in vitro and in vivo models suggest that several members of the short-chain dehydrogenase/reductase superfamily of proteins are essential for retinoic acid biosynthesis and the maintenance of retinoic acid homeostasis. However, the exact roles of some of these recently identified enzymes are yet to be characterized. The properties of the known contributors to retinoid metabolism have now been better defined and allow for more detailed understanding of their interactions with retinoid-binding proteins and other retinoid enzymes. At the same time, further studies are needed to clarify the interactions between the cytoplasmic and membrane-bound proteins involved in the processing of hydrophobic retinoid metabolites. This review summarizes current knowledge about the roles of various biosynthetic and catabolic enzymes in the regulation of retinoic acid homeostasis and outlines the remaining questions in the field.
The Intersection Between the Aryl Hydrocarbon Receptor (AhR)- and Retinoic Acid-Signaling Pathways
2007, Vitamins and Hormones
Citation Excerpt :
However, data implicate other CYP450 families in atRA metabolism. An early study suggested that CYP2C7 and 2B1 may have significant contributions in rat (Leo et al., 1984). However, these enzymes are not TCDD inducible (Chu et al., 2001), indicating that 2B1 does not contribute to changes following TCDD exposure.
Data from a variety of animal and cell culture model systems have demonstrated an interaction between the aryl hydrocarbon receptor (AhR)‐ and retinoic acid (RA)‐signaling pathways. The AhR¹ was originally identified as the receptor for the polycyclic aromatic hydrocarbon family of environmental contaminants; however, recent data indicate that the AhR binds to a variety of endogenous and exogenous compounds, including some synthetic retinoids. In addition, activation of the AhR pathway alters the function of nuclear hormone‐signaling pathways, including the estrogen, thyroid, and RA pathways. Activation of the AhR pathway through exposure to environmental compounds results in significant changes in RA synthesis, catabolism, transport, and excretion. Some effects on retinoid homeostasis mediated by the AhR pathway may result from the interactions of these two pathways at the level of activating or repressing the expression of specific genes. This chapter will review these two pathways, the evidence demonstrating a link between them, and the data indicating the molecular basis of the interactions between these two pathways.
PPARα activators down-regulate CYP2C7, a retinoic acid and testosterone hydroxylase
2004, Toxicology
Peroxisome proliferators (PP) are a large class of structurally diverse chemicals that mediate their effects in the liver mainly through the peroxisome proliferator-activated receptor α (PPARα). Exposure to PP results in down-regulation of CYP2C family members under control of growth hormone and sex steroids including CYP2C11 and CYP2C12. We hypothesized that PP exposure would also lead to similar changes in CYP2C7, a retinoic acid and testosterone hydroxylase. CYP2C7 gene expression was dramatically down-regulated in the livers of rats treated for 13 weeks by WY-14,643 (WY; 500 ppm) or gemfibrozil (GEM; 8000 ppm). In the same tissues, exposure to WY and GEM and to a lesser extent di-n-butyl phthalate (20 000 ppm) led to decreases in CYP2C7 protein levels in both male and female rats. An examination of the time and dose dependence of CYP2C7 protein changes after PP exposure revealed that CYP2C7 was more sensitive to compound exposure compared to other CYP2C family members. Protein expression was decreased after 1, 5 and 13 weeks of PP treatment. CYP2C7 protein expression was completely abolished at 5 ppm WY, the lowest dose tested. GEM and DBP exhibited dose-dependent decreases in CYP2C7 protein expression, becoming significant at 1000 ppm or 5000 ppm and above, respectively. These results show that PP exposure leads to changes in CYP2C7 mRNA and protein levels. Thus, in addition to known effects on steroid metabolism, exposure to PP may alter retinoic acid metabolism.
Characterization of a new endogenous vitamin A metabolite
2002, Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
Here, we describe the discovery of a new major endogenous vitamin A metabolite with particularly high hepatic concentrations. This metabolite was isolated from mouse livers and was characterized as 9-cis-4-oxo-13,14-dihydro-retinoic acid (RA) based on mass spectral, ultraviolet, and nuclear magnetic resonance analyses. It was also detected in one human liver. To gain further insight into endogenous retinoid metabolism, mice were fed over a period of 14 days ad libitum with diets enriched with different amounts of retinyl palmitate [15,000, 45,000 or 150,000 international units (IU)/kg diet]. Higher retinyl palmitate amounts in the diet resulted surprisingly in a dose-dependent decrease in all-trans-RA levels in serum, kidney, and brain, whereas levels of 9-cis-4-oxo-13,14-dihydro-RA, retinol, and retinyl esters were dose-dependently elevated in serum, kidney, and liver. 13-cis-RA levels could be detected in serum, liver, and kidney, but were unaffected by the dietary vitamin A status. 9-cis-RA levels were below the detection limit of 0.2 ng/ml serum or 0.4 ng/g tissue. This study indicates that the oxidation at C4 of the cyclohexenyl ring, isomerization of the C9/C10 double bond, and reduction of the C13/C14 double bond are major endogenous metabolic pathways of vitamin A.
Liarozole markedly increases all trans-retinoic acid toxicity in mouse limb bud cell cultures: A model to explain the potency of the aromatic retinoid (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthylenyl)-1-propenyl] benzoic acid
2002, Toxicology and Applied Pharmacology
The remarkable toxicity of (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthylenyl)-1-propenyl] benzoic acid (TTNPB) compared to all trans-retinoic acid (tRA) is due to multiple factors, including reduced affinities for cytosolic binding proteins (CRABPs), resistance to metabolism, and prolonged nuclear receptor activation. To further investigate the role of half-life in retinoid toxicity, experiments were performed to determine whether, and to what extent, inhibition of tRA metabolism by liarozole increased its toxicity comparable to that of TTNPB in the mouse limb bud system. Liarozole is a known inhibitor of tRA 4-hydroxylation (CYP26). In the absence of liarozole, the IC50 for inhibition of chondrogenesis by tRA was 140 nM compared to 0.3 nM for TTNPB, a 467-fold difference. Following the addition of liarozole (10⁻⁶ M) to limb bud cultures, the potency of tRA to inhibit chondrogenesis was increased approximately 14-fold (IC50 of 9.8 nM). Although liarozole markedly increased toxicity of tRA in mouse limb bud micromass cultures, tRA metabolism was inhibited only about 10%. These results indicate that a relatively minor decrease in the metabolism of tRA in the mouse limb bud system is associated with a marked enhancement of toxicity that is likely related to the prolongation of tRA half-life during a critical period of development. Thus, the prolonged half-life of TTNPB is the most significant factor contributing to the remarkable teratogenicity of this synthetic aromatic retinoid.

View all citing articles on Scopus

^☆: This study was supported by DHHS Grants AM 32810, AA 05934, and AA 03508; and the Veterans Administration.

View full text

CommunicationRetinoic acid metabolism by a system reconstituted with cytochrome P-450☆

Abstract

J. Biol. Chem

Arch. Biochem. Biophys

Arch. Biochem. Biophys

J. Biol. Chem

J. Biol. Chem

J. Biol. Chem

Biochem. Biophys. Res. Commun

J. Biol. Chem

Gastroenterology

J. Biol. Chem

J. Biol. Chem

J. Biol. Chem

Communication
Retinoic acid metabolism by a system reconstituted with cytochrome P-450☆