Comparison of gene expression changes induced by biguanides in db/db mice liver.

Large-scale clinical studies have shown that the biguanide drug metformin, widely used for type 2 diabetes, to be very safe. By contrast, another biguanide, phenformin, has been withdrawn from major markets because of a high incidence of serious adverse effects. The difference in mode of action between the two biguanides remains unclear. To gain insight into the different modes of action of the two drugs, we performed global gene expression profiling using the livers of obese diabetic db/db mice after a single administration of phenformin or metformin at levels sufficient to cause a significant reduction in blood glucose level. Metformin induced modest expression changes, including G6pc in the liver as previously reported. By contrast, phenformin caused changes in expression level of many additional genes. We used a knowledge-based bioinformatic analysis to study the effects of phenformin. Differentially expressed genes identified in this study constitute a large gene network, which may be related to cell death, inflammation or wound response. Our results suggest that the two biguanides show a similar hypoglycemic effect in db/db mice, but phenformin induces a greater stress on the liver even a short time after a single administration. These findings provide a novel insight into the cause of the relatively high occurrence of serious adverse effect after phenformin treatment.

Tenascin-C is upregulated in the skin lesions of patients with atopic dermatitis.

BACKGROUND: Tenascin-C is a large, hexameric extracellular matrix glycoprotein that is expressed during embryogenesis, carcinogenesis and wound healing. In normal adult human skin the expression level of tenascin-C is low, but levels are elevated in skin tumors and rise significantly in the dermal compartment during wound healing. Although the expression of tenascin-C could be upregulated by inflammatory cytokines, the role of tenascin-C in atopic dermatitis (AD) is still unclear. OBJECTIVE: To identify genes that plays a role in AD. METHODS: We screened for differentially expressed genes in lesional and non-lesional skin of AD patients using DNA microarray. Then we monitored with quantitative PCR the expression of the novel disease related genes in human keratinocytes or pinnae from NC/Nga mice. RESULTS: We found that tenascin-C gene expression was expressed at higher levels in lesional skin compared to non-lesional skin of the patients, whereas it was not upregulated in the skin of psoriatic patients or healthy controls. In human cultured keratinocytes, tenascin-C was markedly upregulated by IL-4 and IL-13, and moderately upregulated by IFN-gamma. Tenascin-C expression was also upregulated in the AD-like skin lesions induced in NC/Nga mice ears by intradermal injection of mite antigen, and this upregulation was inhibited by prednisolone. CONCLUSION: These results suggest that upregulation of the tenascin-C expression is specific to AD lesions, and that tenascin-C may therefore play a critical role in regulating the underlining inflammatory processes, which are involved in the pathology of AD.

Gene expression of enzymes for tryptophan degradation pathway is upregulated in the skin lesions of patients with atopic dermatitis or psoriasis.

BACKGROUND: Atopic dermatitis (AD) and psoriasis are common inflammatory skin diseases. Although many reports implicate Th2 cytokines in the pathophysiology of AD and Th1 cytokines in psoriasis, the precise etiology of these diseases remains elusive. OBJECTIVE: We investigated novel AD- or psoriasis-related genes to further understand the pathogenesis of these diseases. METHODS: We performed a comprehensive analysis of mRNA expression in skin biopsies from AD or psoriasis patients using DNA microarrays. Quantitative PCR was then used to monitor the expression of novel disease-related genes in human keratinocytes or pinnae from NC/Nga mice. RESULTS: Levels of mRNA for IDO (indoleamine 2,3-dioxygenase) and kynureninase, enzymes constituting the tryptophan degradation pathway, were found to be upregulated in the skin lesions as compared to the uninvolved skin of patients with AD or psoriasis. Expression of these two genes was induced in human epidermal keratinocytes stimulated with IFN-gamma in vitro. Moreover, in NC/Nga mice, the expression of kynureninase mRNA in the ear skin was induced following development of AD-like skin lesions. CONCLUSION: The tryptophan degradation pathway may play an important role in the pathophysiology of AD and psoriasis.

Gene expression analysis of atopic dermatitis-like skin lesions induced in NC/Nga mice by mite antigen stimulation under specific pathogen-free conditions.

BACKGROUND: Atopic dermatitis (AD) is a chronic relapsing inflammation characterized by pruritic and eczematous skin lesions usually observed in patients with a familial history of atopic diseases, but its exact etiology is unclear. An animal model is indispensable for the analysis of the pathogenesis and the development of new drugs to treat this disease. Here, we compare changes in gene expression profiles in the AD-like skin lesions of NC/Nga or BALB/c mice stimulated intradermally by mite antigen under specific pathogen-free (SPF) conditions. METHODS: Mite Extract-Dp was injected intradermally into the right and left pinnae and into the skin of the back of NC/Nga or BALB/c mice in 2 places once per 3 days, and the clinical symptoms and the ear thickness were measured. On day 14 or day 28 after starting mite extract injection, we collected plasma and pinnae from NC/Nga or BALB/c mice. The amount of total immunoglobulin E (IgE) in plasma was assayed. We analyzed mRNA transcripts in pinnae using real-time quantitative PCR for the murine counterparts of several known allergy-related genes. Moreover, genome-wide gene expression in pinnae from NC/Nga mice was analyzed using high-density oligonucleotide arrays (GeneChip, Affymetrix). RESULTS: From 2 weeks after stimulation, marked skin inflammation was induced in the pinnae of NC/Nga but not BALB/c mice. However, IgE levels in sera rose equally in both strains. Quantitative PCR analysis and comprehensive GeneChip analysis of the AD-like pinna skin lesions revealed that their development was accompanied by changes in expression of more than 1,000 genes. These included cytokines, cytokine receptors, proteases, and adhesion molecules. Furthermore, genes thus far not reported in association with AD were also affected. CONCLUSION: From these results, the NC/Nga mouse model using mite sensitization under SPF conditions could be useful for elucidating the mechanisms of AD pathogenesis and developing more effective therapy for AD.

High-density oligonucleotide array analysis of mRNA transcripts in peripheral blood cells of severe atopic dermatitis patients.

BACKGROUND: There are few laboratory tests for evaluating atopic dermatitis (AD) with the exception of IgE levels or the eosinophil count. We attempted to identify new diagnostic markers by screening the genome-wide expression of transcripts in peripheral blood mononuclear cells (PBMC). METHODS: For this study, we enrolled 7 nonatopic healthy volunteers, 5 AD patients who responded well to treatment and 6 who responded poorly. We compared genome-wide transcript levels in PBMC derived from patients with severe AD and healthy volunteers using high-density oligonucleotide arrays (GeneChip, Affymetrix). After the first screening with GeneChip, we employed real-time quantitative PCR to confirm differential expression levels. RESULTS: Screening with GeneChip showed that the levels of a total of 92 transcripts increased at least 3-fold in one population compared to another. After further evaluation of these genes with real-time quantitative PCR, the levels of 4 transcripts were confirmed to be significantly different in PBMC from AD patients compared to controls, namely IFN-gamma, TRAIL (TNF-related apoptosis-inducing ligand), ISGF-3 (STAT1) and defensin-1. With the exception of IFN-gamma, none of these genes has previously been implicated in AD pathology. CONCLUSION: These 4 transcripts in PBMC are expected to be useful markers for evaluating AD.