Changes in some hepatic enzyme activities related to phase II drug metabolism in male and female rats as a function of age

New insight on the mechanism of eating disorder in females based on metabolic differences of bisphenol S in female and male zebrafish

The different capacity of glucuronic acid metabolism might lead to the difference of bisphenol S (BPS) residual in tissues of male and female zebrafish. This may be the fundamental reason why BPS causes different effects in females and males. Here, adult zebrafish are exposed to 1, 10 and 100 μg/L BPS for 35 days to explore the main effect on females. After exposure, the liver of females showed stronger BPS metabolism ability than males, resulting in the accumulation of BPS in the gut of females. The results of neurotransmitters in gut of females revealed that the content of serotonin was decreased by BPS treatments. In addition, the mRNA expression levels of tryptophan 5-monooxygenase (Tph1) that regulated serotonin synthesis was reduced in gut of females in all BPS groups, and Tph1 protein has very high affinity with BPS molecule. Adult females treated with BPS exhibited symptoms including overeating, a decrease of serotonin in the gut, hypoglycemia and hyperlipidemia, a similar effect of Tph1 protein inhibitor LP533401 on adult females. This hypoglycemia stimulates brain agrp/pomc and orexin neurons to induce overfeeding behavior, causing intestinal homeostasis imbalance and hyperlipidemia. Our data elucidate a potential pathogenesis of eating disorder under pollutant stress.

Ontogeny of Hepatic Transporters and Drug-Metabolizing Enzymes in Humans and in Nonclinical Species

The liver represents a major eliminating and detoxifying organ, determining exposure to endogenous compounds, drugs, and other xenobiotics. Drug transporters (DTs) and drug-metabolizing enzymes (DMEs) are key determinants of disposition, efficacy, and toxicity of drugs. Changes in their mRNA and protein expression levels and associated functional activity between the perinatal period until adulthood impact drug disposition. However, high-resolution ontogeny profiles for hepatic DTs and DMEs in nonclinical species and humans are lacking. Meanwhile, increasing use of physiologically based pharmacokinetic (PBPK) models necessitates availability of underlying ontogeny profiles to reliably predict drug exposure in children. In addition, understanding of species similarities and differences in DT/DME ontogeny is crucial for selecting the most appropriate animal species when studying the impact of development on pharmacokinetics. Cross-species ontogeny mapping is also required for adequate translation of drug disposition data in developing nonclinical species to humans. This review presents a quantitative cross-species compilation of the ontogeny of DTs and DMEs relevant to hepatic drug disposition. A comprehensive literature search was conducted on PubMed Central: Tables and graphs (often after digitization) in original manuscripts were used to extract ontogeny data. Data from independent studies were standardized and normalized before being compiled in graphs and tables for further interpretation. New insights gained from these high-resolution ontogeny profiles will be indispensable to understand cross-species differences in maturation of hepatic DTs and DMEs. Integration of these ontogeny data into PBPK models will support improved predictions of pediatric hepatic drug disposition processes. SIGNIFICANCE STATEMENT: Hepatic drug transporters (DTs) and drug-metabolizing enzymes (DMEs) play pivotal roles in hepatic drug disposition. Developmental changes in expression levels and activities of these proteins drive age-dependent pharmacokinetics. This review compiles the currently available ontogeny profiles of DTs and DMEs expressed in livers of humans and nonclinical species, enabling robust interpretation of age-related changes in drug disposition and ultimately optimization of pediatric drug therapy.

Combination of micellar electrokinetic and high-performance liquid chromatographies to assess age-related changes in the in vitro metabolism of Fischer 344 rat liver

The metabolism of doxorubicin, a widely used anticancer drug, is different in young adult and old cancer patients. In this study, we demonstrate that micellar electrokinetic chromatography with laser-induced fluorescence detection is highly suited to monitor the metabolism of doxorubicin in subcellular fractions isolated from young adult (11 months, 100% survival rate) and old (26 months, ~25% survival rate) Fischer 344 rat livers. The relative amounts of doxorubicin metabolized in both mitochondria-enriched and postmitochondria fractions of young adult were larger than the respective fractions of old rat liver. 7-Deoxydoxorubicinolone and 7-deoxydoxorubicinone were identified using internal standard addition and structural elucidation by high-performance liquid chromatography with combined laser-induced fluorescence and mass spectrometry detection. Although high-performance liquid chromatography with combined laser-induced fluorescence and mass spectrometry detection is more useful in the identification of compounds, micellar electrokinetic chromatography with laser-induced fluorescence detection has low-sample requirements, simplified sample processing procedures, short analysis times and low limit of detection. Therefore, the combination of these two techniques provides a powerful approach to investigate metabolism of fluorescent drugs in aging studies.

UDP-glucuronosyltransferases (UGTs) in neuro-olfactory tissues: expression, regulation, and function

This work aims to review uridine diphosphate (UDP)-glucuronosyltransferase (UGT) expression and activities along different neuronal structures involved in the common physiological process of olfaction: olfactory epithelium, olfactory bulb, and olfactory cortex. For the first time, using high-throughput in situ hybridization data generated by the Allen Brain Atlas (ABA), we present quantitative analysis of spatial distribution of UGT genes in the mouse brain. The olfactory area is a central nervous system site with the highest expression of UGTs, including UGT isoforms not previously identified in the brain. Since there is evidence of the transfer of xenobiotics to the brain through the nasal pathway, circumventing the blood-brain barrier, olfactory UGTs doubtlessly share the common function of detoxification, but they are also involved in the metabolism and turnover of exogenous or endogenous compounds critical for physiological olfactory processing in these tissues. The function of olfactory UGTs will be discussed with a special focus on their participation in the perireceptor events involved in the modulation of olfactory perception.

Age decreased steady-state concentrations of genistein in plasma, liver, and skeletal muscle in Sprague-Dawley rats

Soy isoflavones are associated with low incidence of cardiovascular diseases (CVD) and hormone-dependent cancers, but no solid information is available on the relative deposition of isoflavones in the body as a function of age. One-year-old (adult) male Sprague-Dawley rats were fed control diet or one of three high-genistein isoflavone (HGI) diets at a dose of 62, 154, or 308 genistein mg/kg (ppm) diet for 5 weeks; 2-year-old (old) were fed a dose of 154 or 308 ppm. Steady-state genistein concentrations in plasma, liver, and gastrocnemius muscle of the adult rats after 12 h fast revealed a linear dose-dependent manner (P < or = 0.0001). However, there was no such relationship in the old rats. Nevertheless, old rats fed the 308 ppm genistein diet had significantly lower steady-state genistein concentrations in plasma and liver than the adult rats did (P < or = 0.05); but similar genistein concentration in muscle. The results of this study indicate that steady-state genistein concentrations in tissues of adult rats after 12 h fast exhibited a dose-dependent fashion and were diminished in specific tissues by age.

The effect of age and gender on glucuronidation and sulphation in rat liver: a study using paracetamol as a model substrate

The effect of age and sex on glucuronidation and sulphation was studied in vitro in rat liver fractions, using paracetamol (acetaminophen) as substrate. Glucuronidation was more rapid in females; sulphation in males. Age was not a determinant of either metabolic pathway in either sex.

Age-related changes in membrane lipid composition, fluidity and respiratory burst in rat peritoneal neutrophils

The O2*(-) production has been studied in rat peritoneal neutrophils of different age (3, 12 and 24 months), in order to analyse whether the neutrophil respiratory burst is modified with increasing age. To stimulate NADPH oxidase, the enzyme responsible for the respiratory burst, two stimuli that act in different way have been used: phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (N-FMLP). Production of O2*(-) decreased with age in neutrophils stimulated with N-FMLP (about 40%), but not in the stimulated with PMA. No difference in NADPH oxidase activity was found with age. The NADPH is supplied to the respiratory burst mainly by the pentose phosphate shunt. A progressive and significant decrease in the two most important enzymes of this route, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, was detected as a function of age; in spite of this reduction, the NADPH produced by cells from old animals seems not limiting for the O2*(-) production. The N-FMLP-induced decrease in the O2*(-) production may be related to the age-dependent increase in the membrane fluidity observed. A decline in the cholesterol/phospholipid ratio and a rise in the total polyunsaturated fatty acids content were found, that correlated well with the increase in the membrane fluidity. The decrease (50%) of phosphatidylinositols in the 24-month-old animals may be also related to the age-impairment in the respiratory burst found after stimulation with N-FMLP. These studies suggest that the age-related alterations in neutrophil may result in diminished neutrophil function and increased susceptibility to infection in the ageing.

The influence of age and some inducers on UDP-glucuronyltransferase activity

UDP-glucuronyltransferase (UDP-GT) activity was examined in male Wistar rats aged 0.5, 1, 2, 4, 8, 12, 20, and 28 months. The rats were treated with phenobarbital (75 mg/kg, 72 and 48 h before death), beta-naphthoflavone or dexamethasone (40 mg/kg and 20 mg/kg, respectively, for three days before death). Prior to decapitation the rats were fasted for 12 h. Hepatic microsomes were prepared according to the method of Dallner. UDP-GT activity was determined by the method of Burchell and Weatherill. p-Nitrophenol was used as an aglucone. UDP-GT activity decreased rapidly in the control rats aged from two weeks to four months. In the older control rats the activity tended to increase. Two-week-old rats treated with phenobarbital showed a slightly increased UDP-GT activity. In the older animals (up to one year) UDP-GT activity increased to 150% of the control value and stayed at this level in the remaining age groups. beta-Naphthoflavone was a more potent inducer of UDP-GT than phenobarbital. The activity of beta-naphthoflavone-induced UDP-GT was low in the youngest rats. It was about 180% in two-month-old rats and reached 260% of the control value in eight-month-old rats. Although the activity decreased in the older rats, it still exceeded 200%. Dexamethasone did not affect UDP-GT activity. Only in two-week-old and two-month-old rats did we observe a slight increase in the activity of UDP-GT.

Changes in superoxide dismutase activity in liver and lung of old rats

Superoxide dismutase activity was measured in liver and lung from 3 and 24 month-old rats. Both total SOD and Mn-SOD activity decreased significantly in the liver of old rats. Recent results from our laboratory have indicated that during aging, the activity of Cu/Zn-SOD decreases in rat liver and that there is an accumulation of altered protein. It was also shown that the old Cu/Zn-SOD had one histidine fewer than the young one. In the present study, the immunoprecipitation experiments showed that the amount of immunoprecipitable Mn-SOD from liver of old rats was greater than from young ones, but when amino acid residues were measured in purified young and old Mn-SOD from liver, no change was observed. In lung, no significant age-related differences in total SOD, Cu/Zn-SOD and Mn-SOD activity were found, nor was there accumulation of altered protein during aging.

Decrease in free-radical production with age in rat peritoneal macrophages

The respiratory-burst reaction has been studied in rat peritoneal macrophages of different ages (3, 12 and 24 months) using phorbol 12-myristate 13-acetate (PMA) to stimulate NADPH oxidase. Production of O2-. and H2O2 decreased with age (about 50 and 75% respectively); however, no difference in NADPH oxidase activity was found. NO. production was also reduced with age (40%). Furthermore, a progressive and significant decrease in the pentose phosphate flux was detected as a function of age in control and PMA-stimulated macrophages. The NADPH/NADP+ ratio decreased with age in control and PMA-stimulated macrophages. Glucose uptake was lower in middle-aged (12 months) and old (24 months) animals but no differences were found between these groups.

Changes in the histidine residues of Cu/Zn superoxide dismutase during aging

Cu/Zn-Superoxide dismutase activity (Cu/Zn-SOD) was studied in liver from 3- and 24-month-old rat. A significant decrease of enzyme activity in liver of the aged rat was found. Various amino acid residues and protein carbonyl groups (CO) were measured in purified young and old enzyme. It was found that the 'old' enzyme had one histidine fewer and higher CO content than the 'young' Cu/Zn-SOD. Inactivation 'in vitro' of purified commercial bovine erythrocyte Cu/Zn-SOD led to a decrease in the enzymatic activity, an increase in the CO and one histidine residue modified. A similar behavior between aging and oxidation was suggested.

Gender-related differences in the amount and functional state of rat liver UDP-glucuronosyltransferase

The basis for gender-dependent differences in rates of glucuronidation of xenobiotics is uncertain. To clarify this issue, the glucuronidation of p-nitrophenol was compared in liver microsomes from adult male and female rats. The activity of native UDP-glucuronosyltransferase was 47% higher in microsomes from male than from female rats. Immunoblotting of microsomal protein with anti-UDP-glucuronosyltransferase antiserum revealed 66% more immunoreactive protein in male microsomes. A kinetic method for measuring glucuronidating enzyme content confirmed the result of the immunoblot. Responses of UDP-glucuronosyltransferase to activation by palmitoyllysophosphatidylcholine or high pressure indicated that the activity of the enzyme was more latent in male than in female microsomes. Differences in enzyme latency could be due to differences in membrane structure. A comparison of microsomal fatty acid composition revealed significantly higher levels of oleic and linoleic acids and lower levels of stearic and docosahexaenoic acids in male than in female microsomes. The phospholipid composition, ratio of cholesterol:phospholipid, and membrane fluidity were similar in male and female microsomes. These results indicate that gender-dependent differences in UDP-glucuronosyltransferase activity are due to differences in both the amount and functional state of the enzyme.

Age-dependent intestinal hydrolysis of valproate glucuronide in rat

1. Age-dependent differences in the intestinal hydrolysis of the glucuronide conjugate of valproic acid were evaluated in the Fisher-344 rat at 14 and 40 days, and 24 months of age. 2. Hydrolysis occurred more quickly when incubations were conducted under anaerobic as compared with aerobic conditions. 3. The rate of hydrolysis of valproate glucuronide was most rapid in the contents of the large intestine (caecum and colon); no difference in rate was noted between age groups during incubations with large intestinal contents. 4. Hydrolysis in the tissues of the large and small intestines, and the contents of the small intestine, was more rapid in the 14-day-old rat than in the older age groups. Differences in the rates and sites of hydrolysis in the 14-day-old animal may be due to regional differences in the number and types of microorganisms or mammalian beta-glucuronidase present in the gastrointestinal tract. 5. Differences in intestinal hydrolysis of valproate glucuronide may account in part for age-related changes in enterohepatic recirculation of valproate in young animals; other mechanisms apparently are responsible for altered valproate disposition in senescent animals.

Respiratory burst reaction changes with age in rat peritoneal macrophages

The respiratory burst reaction, estimated as O2.- production, has been studied in rat peritoneal macrophages of different age (3, 12 and 24 months). To stimulate NADPH oxidase, the enzyme responsible for the respiratory burst, various stimuli that act in different ways have been used: PMA (phorbol myristate acetate), Con-A (concanavalin A) and N-FMLP (N-formyl-methionyl-leucyl-phenylalanine). All produced a decrease in response with age, with that from PMA being the greatest. The PMA-induced decrease in the O2.- production may be related to the inactivation of NADPH-producing enzymes such as glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase that we have found with age. Glutathione reductase, an enzyme that participates in the maintenance of the redox status in the cell, also showed an age-related decrease. Enzymes that participate in oxygen species scavenging, such as glutathione peroxidase and Cu/Zn superoxide dismutase, did not change with age, although an age-related decrease in catalase activity was found.