Immunocytochemical study of cytochrome P450 (1A1/1A2) induction in murine ocular tissues

doi:10.1016/S0014-4835(95)80004-2

Experimental Eye Research

Volume 60, Issue 2, February 1995, Pages 143-152

https://doi.org/10.1016/S0014-4835(95)80004-2 Get rights and content

C57BL/6 and DBA/2 mice were injected intraperitoneally with β-naphthoflavone in corn oil and killed 48 hr later. Control animals received an injection of corn oil. The immunoreactivity of cytochrome P450 1A1/1A2 expressed in different ocular tissues and liver was examined with goat anti-P450 antibody (primary antibody) and gold-conjugated anti-goat antibody (secondary antibody). DBA/2 mice, which are non-responsive to aryl hydrocarbon treatment, showed negligible levels of immunoreactivity toward anti-P450 1A1/1A2 antibody in all ocular tissues, whether or not the animals were treated with β-naphthoflavone. In responsive C57BL/6 mice, however, the immunoreactivity of the uveal tissues, especially ciliary non-pigmented epithelium, was markedly increased by β-naphthoflavone treatment. The time course of induction of P450 1A1/1A2 immunoreactivity was very similar for the liver and ciliary non-pigmented epithelium, although the maximum level of immunoreactivity of the ciliary epithelium reached in 48 hr after inducer treatment was about 25% of that of liver. The present results support our previous observations that the P4501A enzyme activities (e.g. aryl hydrocarbon hydroxylase) in the liver and eye of C57BL/6 mice are under the same genetic regulation. Further, this study is the first demonstration of P450 isoform induction in specific ocular tissues of the whole animal.

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With the world’s population continuing to age into the 70s, 80s, and even early 100s, ophthalmic diseases, including glaucoma, age-related macular degeneration (AMD), ocular surface diseases, loss of vision, and even blindness, are on the rise. At the other end of the spectrum, young patients with inherited retinal diseases, for example, retinitis pigmentosa, are finding new hope in the form of gene therapy. In the research and development of these new therapies and modalities, ocular pharmacokinetics (PK) will play an increasing role, from drug discovery and candidate selection through dose selection for human proof-of-concept and full development, assessing efficacy and safety, including systemic exposure. An understanding of the principles and technologies for studying ocular PK is particularly important. This chapter summarizes ocular PK associated primarily with topical ocular and intravitreal routes of administration, briefly touching on other routes, for example, subconjunctival or subretinal, in the case of gene therapy. Various excellent reviews are available elsewhere (Agrahari et al., 2016; Gaudana et al., 2010; Del Amo et al., 2017; Urtti, 2006; Ghate and Edelhauser, 2006; Shen et al., 2018; Schoenwald, 2003).
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In the past few years, several efflux transporters and metabolizing enzymes have been recognized to restrict ocular drug absorption. In this chapter, we have made an attempt to provide an overview of healthy and disease state impact on the expression of metabolizing enzymes. Moreover, we have also discussed the potential interplay between membrane transporters and metabolizing enzymes within ocular tissues and strategies to circumvent these processes.
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Citation Excerpt :
Several compounds bearing oxime functional group, including amidoximes, have been found to donate NO in the presence of rat liver microsomal cytochromes P450 [6–8]. Several CYP enzymes are known to be expressed also in ocular tissues [10–13]. They might thus provide a pathway for NO donation of amidoximes in the eye.
Novel 1-R-imidazole-5-amidoximes and 1-R-5-cyano-imidazole-4-amidoximes (R: H, Me, Bn) were prepared from their corresponding nitriles and were tested for their efficacy to lower intraocular pressure (IOP) in rabbits. The ability of these compounds to donate nitric oxide (NO) was studied by observing the stimulation of formation of cyclic guanosine-3′,5′-monophosphate (cGMP) in the incubation of porcine iris-ciliary body. In the incubation experiments, 1-methylimidazole-5-amidoxime and 1(H)-imidazole-4(5)-amidoxime stimulated formation of cGMP indicating NO donating ability of these compounds. 1-Methylimidazole-5-amidoxime lowered IOP significantly after intravitreal injection.
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Previously we have reported our analyses of cytochrome P450 (CYP) expression in rat ocular tissues and in our current study we have extended these analyses to the different stages of growth in both male and female rats. Additionally, we have examined the expression levels of the different conjugation enzymes, sulfotransferases (SULTs), UDP-glucuronosyl transferases (UGTs) and glutathione S-transferases (GSTs), in ocular tissues. In 5-week-old animals, the CYP genes, CYP2B2 and CYP3A1, were abundantly expressed in the lens, with higher CYP1A1 expression detectable in the extra-lenticular tissues, of both genders. However, the expression of CYP1A2 and CYP2E1 in female ocular tissues was more extensive than in male. Moreover, in females the expression of the phenol-sulfating SULTs, ST1A1, ST1B1 and ST1C1, was more abundant in the extra-lenticular tissues, whereas the levels of the hydroxysteroid-sulfating SULTs, ST2A1 and ST2A5, predominated in the lens. The expression levels of the UGTs, UGT1A1, UGT1A6 and UGT2B1, were also higher in the female extra-lenticular tissues but the expression of the GSTA subfamily (GSTA1 and GSTA2) was very weak in the ocular tissues of both genders. The overall gene expression profiles were found to change with the age of the animals (from 3 to 8 weeks) and, in general, the expression levels of the CYPs and SULTs declined with age, whereas the levels of the UGTs and GSTs increased. These results demonstrate that the expression profiles of drug metabolising enzymes show both region- and gender-specific patterns in rat ocular tissues.
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Introduction: Xenobiotic metabolism in extrahepatic tissues has been extensively studied in vitro, but it is difficult to estimate in vivo the share of xenobiotic transformation in extrahepatic tissues for lack of a suitable approach. In this paper an in vivo rat model for assessment of extrahepatic metabolism is described, and the model was investigated using the conversion of lidocaine to monoethylglycinexylidide (MEGX). Methods: The rats were anesthetized with ethyl ether inhalation. The liver was exposed, the liver artery ligated, and the portal vein was clamped at its distal end. The left hepatic lobe was partly excised along its inferior margin, and a heparinized silicone catheter, diameter 0.2 cm, was inserted into the portal and left hepatic veins to allow the recirculation of portal vein blood. A sham operation was performed in the control group. Results: Phenol red test showed that hepatic blood supply was absolutely blocked in model rats. At 30 min after establishing the portal-cavum bypass, the renal function and electrolytes did not change, but serum glucose decreased by 64.4 ± 30.4%; 30 min after intravenous administration of 1.0% lidocaine 2 mg · kg⁻¹, serum MEGX in model rats was 32.0 ± 7.14% of that in the control group, which mostly existed in a free form and was not induced by phenobarbital pretreatment. Discussion: The model is easy to establish and provides an in vivo method to study the extrahepatic metabolism of xenobiotics.

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Experimental Eye Research

References (29)

Localization, distribution, and induction of xenobiotic-metabolizing enzymes and aryl hydrocarbon hydroxylase activity within lung

Pharmacol. Ther.

Oxidative stress as a mediator of apoptosis

Immunol. Today

Apoptosis: final common pathway of photoreceptor death in rd, rds, and rhodopson mutant mice

Neuron

Enzymes of mercapturate synthesis and other drug-metabolizing reactions-specific localization in the eye

Exp. Eye Res.

Subcellular localization of cytochrome P450, and activities of several enzymes responsible for drug metabolism in the human brain

Biochem. Pharmacol.

Drug metabolizing enzymes in the brain and cerebral microvessels

Brain Res. Rev.

Induction of alkoxyresorufin O-dealkylases and UDP-glucuronosyl transferase by phenobarbital and 3-methylcholanthrene in primary cultures of porcine ciliary epithelial cells

Biochem. Pharmacol.

Genetically regulated aryl hydrocarbon hydroxylase induction in the eye: Possible significance of the drug-metabolizing enzyme system for the retinal pigmented epithelium-choroid

Exp. Eye Res.

Aryl hydrocarbon hydroxylase induction in retinal pigmented epithelium: possible association of genetic differences in a drug-metabolizing enzyme system with retinal degeneration

Exp. Eye Res.

The role of reactive oxygen species, cytokines and cytochrome P450 in pulmonary damage due to hyperoxia

Med. Hypoth.

Cyp1A1: friend or foe?

Drug Metab. Rev.

Aqueous humor and the intraocular pressure

Role of human cytochrome P-450s in risk assessment and susceptibility to environmentally based disease

J. Toxicol. Environ. Health

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