Bilirubin glucosyl- and glucuronyltransferases. A comparative study and the effects of drugs

Recent progress in adverse events of carboxylic acid non-steroidal anti-inflammatory drugs (CBA-NSAIDs) and their association with the metabolism: the consequences on mitochondrial dysfunction and oxidative stress, and prevention with natural plant extracts

INTRODUCTION

Carboxylic acid non-steroidal anti-inflammatory drugs (CBA-NSAIDs) are extensively used worldwide due to their antipyretic, analgesic, and anti-inflammatory effects. CBA-NSAIDs have reasonable margin of safety at therapeutic doses, and in the current climate, do not possess addiction potential like opioid drugs. Studies have revealed that various adverse events of CBA-NSAIDs are related mitochondrial dysfunction and oxidative stress.

AREAS COVERED

This review article summarizes adverse events induced by CBA-NSAIDs, mechanisms of mitochondrial damage, oxidative stress, and metabolic interactions. Meanwhile, this review discusses the treatment and prevention of CBA-NSAIDs damage by natural plant extracts based on antioxidant effects.

EXPERT OPINION

CBA-NSAIDs can induce reactive oxygen species (ROS) production, mediate DNA, protein and lipid damage, lead to imbalance of cell antioxidant status, change of mitochondrial membrane potential, activate oxidative stress signal pathway, thus leading to oxidative stress and cell damage. Adverse events caused by CBA-NSAIDs often exhibit dose and time dependence. In order to avoid adverse events caused by CBA-NSAIDs, it is necessary to provide detailed patient consultation and eliminate influencing factors. Moreover, constructive research studies on the organ-specific toxicity and mechanism of natural plant extracts in preventing and treating metabolic abnormalities of CBA-NSAIDs, will provide important value for warning and guidance for use of CBA-NSAIDs.

Ultraviolet filter compounds in human lenses: 3-hydroxykynurenine glucoside formation

Experiments have been conducted on various aspects of the biosynthetic pathway leading to the formation of 3-hydroxykynurenine glucoside (3OHKG), the major tryptophan-derived human lens UV filter compound. Measurable levels of the reactive metabolite, 3-hydroxykynurenine (3OHKyn) were found in normal human lenses, including lens nuclei. 3OHKyn was able to enter organ-cultured lenses and to serve as a substrate for production of 3OHKG. Thus lenticular 3OKHyn can potentially be derived either by metabolism of Trp in the lens or from transport into the lens. Lens incubation followed by dissection showed that the equatorial region was probably the major site of synthesis of 3OHKG. The concentration of 3OHKG was relatively constant along the visual axis but was significantly lower in the equatorial region: a pattern also found for Kyn and 3OHKyn. No evidence, however could be obtained for hydrolysis of 3OHKG by lens homogenates.

Effects of cimetidine on drug metabolism in rat pups

The effects of cimetidine on drug metabolism were studied in male and female rat pups and compared to similar effects in adult rats. As in adult rats, cimetidine 50 mg/kg/day i.p. for 7 days in the 2nd, 3rd, 4th or 5th weeks of life resulted in prolonged pentobarbitone sleeping times (diminished pentobarbitone hydroxylase activities), particularly when administered during the 3rd week. These effects of cimetidine were reversible since they continued only up to 2 weeks in males and 4 weeks in females, but by the 6th week were no longer observed. Pretreatment with cimetidine 15, 25 and 50 mg/kg/day i.p. for 7 days, resulted in a dose-dependent inhibition of aminopyrine N-demethylase and aniline hydroxylase as well as a prolongation of pentobarbitone sleeping time in both pups and adults, aniline hydroxylase being the least affected. In general, female pups were more adversely affected than male pups and adults. The therapeutic and toxicological relevance of these results in man are discussed.

Glucose and sulfate conjugation of phenolic compounds by the spiny lobster (Panulirus argus)

Previous work has shown that the hepatopancreas of the spiny lobster (Panulirus argus) contains a mixed-function oxidase system capable of catalyzing the monooxygenation of polycyclic aromatic hydrocarbons to highly toxic products similar to those formed by mammalian tissues. Studies were designed to determine the ability of the spiny lobster to conjugate the phenolic compounds 4-methylumbelliferone, p-nitrophenol, beta-naphthol, and 3-hydroxybenzo[a]pyrene with endogenous molecules. The hepatopancreas contained UDP-glucose (UDPG) dependent glucosyltransferase, while no activity was detected when UDP-glucuronic acid was used as the cosubstrate. Atypical Michaelis-Menten kinetics result with varying concentrations of UDPG, indicating that multiple forms of glucosyltransferase may exist in this organ. The activity was localized in the microsomal fraction, exhibited a pH optimum at 8.0-8.5, and a temperature optimum of 30 degrees C. Sulfate conjugation was found only in the cytosolic fraction of the antennal gland and used adenosine 3'-phosphate 5'-phosphosulfate (PAPS) as the sulfate donor (Km(apparent) = 9.0 +/- 4.9 microM). Hepatopancreas cytosol inhibited sulfotransferase activity. The pH optimum of antennal gland sulfotransferase was a function of the substrate and ranged from 5.5 to 7.4. Analysis of spiny lobster urine 24 hr following exposure to 3-hydroxybenzo[a]pyrene demonstrated the ability of the lobster to form both the sulfate and glucoside conjugate in vivo.