Methylation and gene expression responses to ethanol feeding and betaine supplementation in the cystathionine beta synthase-deficient mouse.

BACKGROUND: Alcoholic steatohepatitis (ASH) is caused in part by the effects of ethanol (EtOH) on hepatic methionine metabolism. METHODS: To investigate the phenotypic and epigenetic consequences of altered methionine metabolism in this disease, we studied the effects of 4-week intragastric EtOH feeding with and without the methyl donor betaine in cystathionine beta synthase (CßS) heterozygous C57BL/6J mice. RESULTS: The histopathology of early ASH was induced by EtOH feeding and prevented by betaine supplementation, while EtOH feeding reduced and betaine supplementation maintained the hepatic methylation ratio of the universal methyl donor S-adenosylmethionine (SAM) to the methyltransferase inhibitor S-adenosylhomocysteine (SAH). MethylC-seq genomic sequencing of heterozygous liver samples from each diet group found 2 to 4% reduced methylation in gene bodies, but not promoter regions of all autosomes of EtOH-fed mice, each of which were normalized in samples from mice fed the betaine-supplemented diet. The transcript levels of nitric oxide synthase (Nos2) and DNA methyltransferase 1 (Dnmt1) were increased, while those of peroxisome proliferator receptor-α (Pparα) were reduced in EtOH-fed mice, and each was normalized in mice fed the betaine-supplemented diet. DNA pyrosequencing of CßS heterozygous samples found reduced methylation in a gene body of Nos2 by EtOH feeding that was restored by betaine supplementation and was correlated inversely with its expression and positively with SAM/SAH ratios. CONCLUSIONS: The present study has demonstrated relationships among EtOH induction of ASH with aberrant methionine metabolism that was associated with gene body DNA hypomethylation in all autosomes and was prevented by betaine supplementation. The data imply that EtOH-induced changes in selected gene transcript levels and hypomethylation in gene bodies during the induction of ASH are a result of altered methionine metabolism that can be reversed through dietary supplementation of methyl donors.

Ineffectiveness of tigecycline against persistent Borrelia burgdorferi.

The effectiveness of a new first-in-class antibiotic, tigecycline (glycylcycline), was evaluated during the early dissemination (1 week), early immune (3 weeks), or late persistent (4 months) phases of Borrelia burgdorferi infection in C3H mice. Mice were treated with high or low doses of tigecycline, saline (negative-effect controls), or a previously published regimen of ceftriaxone (positive-effect controls). Infection status was assessed at 3 months after treatment by culture, quantitative ospA real-time PCR, and subcutaneous transplantation of joint and heart tissue into SCID mice. Tissues from all saline-treated mice were culture and ospA PCR positive, tissues from all antibiotic-treated mice were culture negative, and some of the tissues from most of the mice treated with antibiotics were ospA PCR positive, although the DNA marker load was markedly decreased compared to that in saline-treated mice. Antibiotic treatment during the early stage of infection appeared to be more effective than treatment that began during later stages of infection. The viability of noncultivable spirochetes in antibiotic-treated mice (demonstrable by PCR) was confirmed by transplantation of tissue allografts from treated mice into SCID mice, with dissemination of spirochetal DNA to multiple recipient tissues, and by xenodiagnosis, including acquisition by ticks, transmission by ticks to SCID mice, and survival through molting into nymphs and then into adults. Furthermore, PCR-positive heart base tissue from antibiotic-treated mice revealed RNA transcription of several B. burgdorferi genes. These results extended previous studies with ceftriaxone, indicating that antibiotic treatment is unable to clear persisting spirochetes, which remain viable and infectious, but are nondividing or slowly dividing.

Persistence of Borrelia burgdorferi following antibiotic treatment in mice.

The effectiveness of antibiotic treatment was examined in a mouse model of Lyme borreliosis. Mice were treated with ceftriaxone or saline solution for 1 month, commencing during the early (3 weeks) or chronic (4 months) stages of infection with Borrelia burgdorferi. Tissues from mice were tested for infection by culture, PCR, xenodiagnosis, and transplantation of allografts at 1 and 3 months after completion of treatment. In addition, tissues were examined for the presence of spirochetes by immunohistochemistry. In contrast to saline solution-treated mice, mice treated with antibiotic were consistently culture negative, but tissues from some of the mice remained PCR positive, and spirochetes could be visualized in collagen-rich tissues. Furthermore, when some of the antibiotic-treated mice were fed on by Ixodes scapularis ticks (xenodiagnosis), spirochetes were acquired by the ticks, as determined based upon PCR results, and ticks from those cohorts transmitted spirochetes to naïve SCID mice, which became PCR positive but culture negative. Results indicated that following antibiotic treatment, mice remained infected with nondividing but infectious spirochetes, particularly when antibiotic treatment was commenced during the chronic stage of infection.

Immunogenicity of Borrelia burgdorferi arthritis-related protein.

Immunization against arthritis-related protein (Arp) elicits antibody in mice that resolves arthritis but is not protective against challenge with Borrelia burgdorferi. In mice immunized against Arp, an unrelated 37-kDa protein (P37-42), outer surface protein A (OspA), or glutathione S-transferase (GT) and then challenged by syringe or tick, only OspA conferred protection. Passive transfer of Arp antiserum into infected SCID mice induced arthritis resolution, but antisera to P37-42, OspA, GT, or six overlapping Arp peptide fragments did not. Results suggest that the arthritis-resolving immunogenicity is specific to Arp, but the relevant epitopes may be conformational.