High density lipoproteins (HDL) and physical activity: the influence of physical exercise, age and smoking on HDL-cholesterol and the HDL-/total cholesterol ratio.

220 trained men, examined the day before participation in a cross country ski-race, had significantly higher HDL-cholesterol and HDL-/total cholesterol ratio than untrained men, but did not differ signficantly from untrained women. HDL-cholesterol was significantly higher in skiers above 60 years than in skiers of younger age. Tobacco smokers ahd lower HDL-cholesterol and HDL-/total cholesterol ratio than non-smokers, but the differences were only significant in skiers, not in controls. HDL-cholesterol was positively correlated to total cholesterol in skiers. The HDL-cholesterol level may possibly contribute to the lower morbidity of CHD in men who are physically active during leisure time.     

Effect of the leukotriene B4 receptor antagonist, SC-41930, on experimental allergic encephalomyelitis (EAE) in the guinea pig.

The accepted model for the human demyelinating disease, multiple sclerosis (MS), is experimental allergic encephalomyelitis (EAE). We assessed the ability of SC-41930(7-[3(4-acetyl-3-methoxy-2-propyl-phenoxy)-propoxy]- 3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxyl acid), to modulate the symptoms of acute EAE generated in guinea pigs. Animals were pretreated with SC-41930 (20 mg/kg, i.p.) for two days followed by thrice-weekly maintenance. At day 52, a significant number of the SC-41930-treated animals were alive as compared to EAE alone. Control animals had an increase in body weight while EAE animals lost over 20% (p less than 0.5) of their body weight by day 18. SC-41930-treatment significantly reduced, but did not completely inhibit the cachectic response. The results indirectly implicate LTB4 in the pathogenesis of EAE. Agents that modify this model be useful in the treatment of human MS.     

Inflammatory mediators in cotton-top tamarins (CTT) with acute and chronic colitis.

Spontaneous colitis in CTT's presents cytological characteristics similar to chronic ulcerative colitis in humans, e.g. inflammatory cell infiltrate and crypt abscesses. To better characterize CTT colitis as a potential model for human inflammatory bowel disease (IBD), inflammatory mediators identified in colonic tissue of human IBD patients and/or experimental colitis models were assayed. Inflammatory mediator changes in plasma and colon from tamarins with acute (n = 10) and chronic (n = 10) colitis (by mucosal biopsy) were assayed by RIAs. Similar inflammatory mediators were found in the CTT's with acute colitis. In the plasma, PAF and PGE2 levels were lower in acute colitis CTT's, no LTB4 was detected, and histamine levels were not different from chronic colitic animals. In the colon, myeloperoxidase and interleukin-1 beta were significantly higher in acute colitis, PGE2 and LTB4 were higher but not significantly, and PAF was not different from chronic CTT's. These data suggest that a combination of events are occurring in the pathogenesis of tamarin colitis that involves some of the same mediators that are found in the human disease and in other experimental models. The importance of these findings to human IBD remains for further investigation; however, the spontaneous primate model offers an exciting approximation of the disease development and merits further investigation for understanding the pathogenesis of human IBD as well as to aid in development of targeted therapeutics.     

Functional characterization of human N-acetyltransferase 2 (NAT2) single nucleotide polymorphisms

N-Acetyltransferase 2 (NAT2) catalyses the activation and/or deactivation of a variety of aromatic amine drugs and carcinogens. Polymorphisms in the N-acetyltransferase 2 (NAT2) gene have been associated with a variety of drug-induced toxicities, as well as cancer in various tissues. Eleven single nucleotide polymorphisms (SNPs) have been identified in the NAT2 coding region, but the specific effects of each of these SNPs on expression of NAT2 protein and N-acetyltransferase enzymatic activity are poorly understood. To investigate the functional consequences of SNPs in the NAT2 coding region, reference NAT2*4 and NAT2 variant alleles possessing one of the 11 SNPs in the NAT2 coding region were cloned and expressed in yeast (Schizosaccharomyces pombe). Reductions in catalytic activity for the N-acetylation of a sulfonamide drug (sulfamethazine) and an aromatic amine carcinogen (2-aminofluorene) were observed for NAT2 variants possessing G191A (R64Q), T341C (I114T), A434C (E145P), G590A (R197Q), A845C (K282T) or G857A (G286T). Reductions in expression of NAT2 immunoreactive protein were observed for NAT2 variants possessing T341C, A434C or G590A. Reductions in protein stability were noted for NAT2 variants possessing G191A, A845C, G857A or, to some extent, G590A. No significant differences in mRNA expression or transformation efficiency were observed among any of the NAT2 alleles. These results suggest two mechanisms for slow acetylator phenotype(s) and more clearly define the effects of individual SNPs on human NAT2 expression, stability and catalytic activity.     

Pharmacological activity of the second generation leukotriene B4 receptor antagonist,SC-53228:

Inflammatory bowel disease is a chronic inflammatory disorder of the gastrointestinal tract that includes ulcerative colitis and Crohn's disease. Leukotriene B₄ is thought to be a prominent proinflammatory mediator in these diseases, in that leukotriene B₄ levels are increased in the colonic mucosa of inflammatory bowel disease patients and there is increased polymorphonuclear leukocyte infiltration of these tissues. SC-53228(+)-(S)-7-[3-[2(-cyclopropylmethyl)-3-methoxy-4-[(methylamino)carbonyl]phenoxy]propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2-propanoic acid, a second generation LTB₄ receptor antagonist, was evaluated for therapeutic efficacy in a rodent model of acute colonic inflammation induced by short chain organic acids, as well as for effects on rodent liver. When given intracolonically to mice, SC-53228 inhibited neutrophil infiltration, assessed by myeloperoxidase (MPO) levels, with an ED₅₀ value of 9±1.2 mg/kg. When given by gavage, SC-53228 inhibited neutrophil influx in colitic mice with an ED₅₀ value of 30 mg/kg. These results were also confirmed histologically. Furthermore, high dose oral SC-53228 treatment had no effect on liver cytochrome P-450 content, fatty acyl CoA oxidase or liver weight in rats and mice. Together, these data suggest that SC-53228 may be efficacious orally and locally, as well as safe for use in trials for the medical management of IBD.     

DNA adduct levels and intestinal lesions in congenic rapid and slow acetylator syrian hamsters admi food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)

Epidemiological studies indicate that rapid acetylators with a high intake of well-done red meat have an increased risk of colorectal cancer. Arylamine N-acetyltransferase enzymes (E.C. 2.3.1.5) activate carcinogenic heterocyclic amines found in the crust of fried meat via O-acetylation of their N-hydroxylamines to reactive intermediates that bind covalently to DNA and produce mutations. Syrian hamsters as well as humans express two N-acetyltransferase isozymes (NAT1 and NAT2) which differ in substrate specificity and genetic control. Nucleic acid substitutions in the NAT2 gene segregate individuals into rapid, intermediate and slow acetylator phenotypes. In the present paper, we examined the role of the polymorphic NAT2 acetylator genotype in carcinogenesis induced by the food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) by comparing Syrian hamster lines congenic at the NAT2 locus. No differences were found between rapid and slow acetylator congenic hamsters in levels of intestinal PhIP-DNA adducts. In contrast to previous studies in rats, no carcinogen-related induction of the preneoplastic lesions aberrant crypt foci or tumors was found in the intestines of rapid and slow acetylator congenic Syrian hamsters administered PhIP or IQ.     

SCREENING METHOD FOR URINARY BLADDER TUMOR DETECTION IN THE SYRIAN HAMSTER

A screening method is described for the detection of urinary bladder tumors in Syrian hamsters. The urinary bladder is removed, stained with 0.2% methylene blue in sodium phosphate buffer, pinned out flat, and fixed for 1 h in 4% paraformaldehyde in sodium phosphate buffer. The urinary bladder is examined with a dissecting microscope for the presence of stained and/or irregular areas and nodules, which are subjected to histological analysis. The screening method may reduce the possibility of missing small lesions with regular gross examination or the need to examine over 100 slides per animal.     

Investigating the effect of autoinduction in cynomolgus monkeys of a novel anticancer MDM2 antagonist,idasanutlin, and relevance to humans

1.?Idasanutlin (RG7388) is a potent p53-MDM2 antagonist currently in clinical development for treatment of cancer. The purpose of the present studies was to investigate the cause of marked decrease in plasma exposure after repeated oral administration of RG7388 in monkeys and whether the autoinduction observed in monkeys is relevant to humans.

2.?In monkey liver and intestinal microsomes collected after repeated oral administration of RG7388 to monkeys, significantly increased activities of homologue CYP3A8 were observed (ex vivo). Investigation using a physiologically based pharmacokinetic (PBPK) model suggested that the loss of exposure was primarily due to induction of metabolism in the gut of monkeys.

3.?Studies in monkey and human primary hepatocytes showed that CYP3A induction by RG7388 only occurred in monkey hepatocytes but not in human hepatocytes, which suggests the observed CYP3A induction is monkey specific.

4.?The human PK data obtained from the first cohorts confirmed the lack of relevant induction as predicted by the human hepatocytes and the PBPK modelling based on no induction in humans.