The effect of the acute-phase response on in vitro drug metabolism and plasma protein binding in the horse

Types of acute phase reactants and their importance in vaccination

Vaccines are considered to be one of the most cost-effective life-saving interventions in human history. The body's inflammatory response to vaccines has both desired effects (immune response), undesired effects [(acute phase reactions (APRs)] and trade-offs. Trade-offs are more potent immune responses which may be potentially difficult to separate from potent acute phase reactions. Thus, studying acute phase proteins (APPs) during vaccination may aid our understanding of APRs and homeostatic changes which can result from inflammatory responses. Depending on the severity of the response in humans, these reactions can be classified as major, moderate or minor. In this review, types of APPs and their importance in vaccination will be discussed.

Pharmacokinetics of cisplatin in the absence or presence of zengmian yiliu granules (a traditional Chinese medicine compound) in rats determined via ICP-MS: an investigation on drug-herb interactions

CONTEXT

Cisplatin is a highly effective chemotherapeutic agent against many tumors; however, it has potent adverse effects. Zengmian Yiliu granule (ZMYL), a traditional Chinese medicine (TCM) compound, has been clinically used against platinum (Pt)-induced toxicity and to enhance the efficacy of cisplatin.

OBJECTIVE

The study was conducted to investigate the likelihood of potential pharmacokinetics drug-herbs interaction (DHI) between cisplatin and ZMYL.

MATERIALS AND METHODS

An improved ICP-MS method combined with ultrafiltration and microwave-assisted digestion was performed to determine the total and free Pt concentrations in rat plasma after intraperitoneal administration of cisplatin (9 mg/kg) or a combined administration with ZMYL (1 g/kg) by gavage.

RESULTS

ZMYL produced a potential DHI on the pharmacokinetic parameters of cisplatin, calculated from the total Pt concentration. The clearance rate decreased from 110.52 to 66.12 mLh(-1 )kg(-1), the mean residence time extended from 63.1 to 164.54 h, the area under the plasma concentration-time curve increased from 86.58 to 152.93 µg h mL(-1), the elimination half-life extended from 48.38 to 126.4 h, and the elimination rate constant decreased from 0.017 to 0.006 h, in the ZMYL combination group (p < 0.05). In terms of free Pt concentration, the apparent volume of distribution and clearance rate was statistically different (p < 0.05). The Pt plasma protein binding ratios in the early dose stages were significantly boosted by the co-administration of ZMYL (p < 0.01).

DISCUSSION AND CONCLUSION

ZMYL is a potential complementary and alternative medicine for cisplatin chemotherapy. The therapeutic benefits of ZMYL-cisplatin chemotherapy derived from pharmacokinetic interaction needs further investigation.

Freund's adjuvant-induced inflammation: clinical findings and its effect on hepcidin mRNA expression in horses

Hypoferremia observed during systemic inflammatory disorders is regulated by hepcidin. Hepcidin up-regulation is particularly important during acute inflammation, as it restricts the availability of iron, which is necessary for pathogenic microorganism growth before adaptive immunity occurs. The aim of this study was to evaluate the clinical findings and hepatic hepcidin mRNA expression in horses using a Freund's complete adjuvant (FCA) model of inflammation. The expression of hepcidin mRNA in the liver was determined in healthy horses following two intramuscular injections of FCA at 0 h and 12 h. Plasma iron and fibrinogen concentrations were measured at multiple time points between 0 h and 240 h post-FCA injection (PI). Hepcidin mRNA expression was determined by RT-qPCR using liver biopsy samples performed at 0 h (control), 6 h and 18 h PI. The mean plasma fibrinogen level was significantly different from the control values only between 120 and 216 h PI. The mean plasma iron level was significantly lower than the control between 16 and 72 h PI, reaching the lowest levels at 30 h PI (33 % of the initial value), and returned to the reference value from 96 h PI to the end of the experiment. Hepcidin mRNA expression increased at 6 h PI and remained high at 18 h PI. The iron plasma concentration was an earlier indicator of inflammatory processes in horses when compared with fibrinogen and might be useful for the early detection of inflammation in the horse. FCA administration caused the rapid onset of hypoferremia, and this effect was likely the result of up-regulated hepatic hepcidin gene expression. This study emphasizes the importance of hepcidin and iron metabolism during inflammation in horses.

Comparative expression of liver cytochrome P450-dependent monooxygenases in the horse and in other agricultural and laboratory species

The apoprotein expression and the catalytic activities of cytochrome P450s involved in the biotransformation of xenobiotics were investigated in horse liver microsomes and compared with those of food producing (cattle, pigs, broiler chicks, and rabbits) and laboratory species (rats). Western blot analysis revealed the presence of proteins immunorelated to rat CYP 1A, CYP 2B, CYP 2E, and CYP 3A subfamilies in hepatic microsomes from horses and from any other examined species. With the exception of the N-demethylation of N-nitrosodimethylamine in broiler chicks, all the recorded interspecies differences were quantitative in nature. Equine preparations proved the most active in the biotransformation of the CYP 1A substrates ethoxy- and methoxyresorufin and the least active in the metabolism of aminopyrine and ethoxycoumarin. On a comparative basis, large differences were observed in the rate of the in vitro metabolism of model substrates between "minor" (rabbits, horses) and "major" food producing species. Taken in due consideration the limitations of the in vitro approach, results from this study reinforce the conclusion that studies on drug efficacy and residue depletion should be performed in each target species.

Adverse drug reactions and interactions in the horse

Drugs undergo extensive evaluation before they are marketed. The occurrence of adverse reactions, however, may be so rare that thousands of patients must receive the drug before reliable data are available. It is necessary that veterinarians be informed about the drugs they use, be able to recognize drug-associated complications, know how to evaluate the patient for evidence of drug-associated toxicity, report adverse effects of drugs to the respective manufacturers, and be prepared to provide medical support and antidotal treatment (if it exists) for a patient if toxicosis occurs.

Biotransformation Enzymes as Determinants of Xenobiotic Toxicity in Domestic Animals

After coming in contact with living organisms, the majority of foreign compounds undergo a number of chemical reactions known as biotransformations. These are performed by hepatic and extra-hepatic enzyme systems and usually yield more polar derivatives, referred to as 'metabolites', which may leave the body via the urinary and biliary routes or be excreted in animal products such as milk and eggs. Biotransformation does not always imply detoxification because in certain instances metabolites will be produced that are capable of reacting with tissue macromolecules or acquiring toxic properties different to or greater than those of the parent molecule. In this review, which is focused on domestic animals, the role played by oxidative, reductive, hydrolytic and conjugative biotransformation enzymes in the activation/detoxification of xenobiotics is examined. The relationship between extra-hepatic metabolism and target organ toxicity as well as the action of rumen microflora on feed additives, phytotoxins, and pesticides are then discussed. Some of the most important metabolic-based species-related susceptibilities to different poisons, and the influence of enzyme inducers or inhibitors on xenobiotic toxicity and drug safety are also reviewed.

The suppressive effects of lipopolysaccharide-induced acute phase response on hepatic cytochrome P450-dependent drug metabolism in rabbits

The acute phase response (APR) was induced by five separate intravenous (i.v.) injections of Escherichia coli lipopolysaccharide (LPS, 17 microg/kg each time) in rabbits, with intervals of 1 h. This model was used to study the effects of APR on the activities of hepatic microsomal cytochrome P450 (CYP)-dependent enzyme including drug metabolism. Five female rabbits were included in each of four groups, a control group and three LPS-treated groups (group I, II and III). The rabbits of the control, group I, II and III were killed at 1, 1, 3 and 7 days after saline (control only) or the LPS injection, respectively. The APR was confirmed by increases in rectal body temperature, plasma concentrations of interleukin-6 and C-reactive protein (CRP). Pharmacokinetics of antipyrine before death were examined in every group. Antipyrine was administered (5 mg/kg) at 24 h (control and group I), 3 days (group II) and 7 days (group III) after the first LPS injection. Total body clearance (Cl(tot)) of antipyrine tended to decrease in group I. All the livers were excised for measuring CYP-dependent activities. Total CYP content and several CYP-dependent activities (aminopyrine N-demethylation, aniline 4-hydroxylation and caffeine 3-demethylation) decreased in group I. The maximum velocity (Vmax) values of those enzymes, and the amount of CYP1A1/1A2 and CYP2E1 apoproteins appeared to decrease. Michaelis constant (Km) values of those enzymes were not affected by the APR. Rectal body temperature recovered to normal at 3 days after the first LPS injection in group II and III. The concentration of CRP, albumin, total CYP content and the plasma clearance of antipyrine returned to the control levels at 7 days after the first LPS injection. These results suggest that the metabolism of drugs, including CYP-dependent drug metabolizing activity, is suppressed markedly in incipient APR induction in rabbits, and the drug metabolizing capacity is returned to normal at 7 days after APR induction.