Polymorphisms in the transforming growth factor‐β1 gene and the risk of asthma: A meta‐analysis

Background and objective: Polymorphisms in the transforming growth factor‐β1 (TGF‐β1) gene have been implicated in susceptibility to asthma, but a large number of studies have reported inconclusive results. A meta‐analysis was performed to investigate the association between polymorphisms in the TGF‐β1 gene and asthma susceptibility. Methods: Searches were performed of Medline (Ovid), PubMed, the Chinese Biological Medicine Database (CBM), the Chinese Journals Full‐text Database (CNKI), the Cochrane Library Database and the Web of Science, covering all papers published up to 30 April 2009. Statistical analysis was performed using Revman4.2.8 and STATA10.0 software. Results: Two polymorphisms (?509C/T and 915G/C(G25C)) were investigated in 14 studies, involving 2979 asthma patients and 4941 control subjects. The results showed that individuals carrying the ?509T allele (TT+TC) had a 36% increased risk of asthma, when compared with homozygotes (?509CC) (OR 1.36, 95% CI: 1.12–1.65). However, there was no significant association with risk of asthma in carriers of the 915C allele (GC+CC) compared with 915GG homozygotes (OR 1.05, 95% CI: 0.65–1.70). In a subgroup analysis by ethnicity, the risk of asthma associated with the ?509T allele was significantly elevated among Asians (OR 1.50, 95% CI: 1.04–2.17) but not Caucasians (OR 1.16, 95% CI: 1.00–1.36). In a subgroup analysis by age, the ?509T allele was associated with a significantly elevated risk of asthma among adults (OR 1.45, 95% CI: 1.09–1.92) but not children (OR 1.19, 95% CI: 0.96–1.46). Conclusions: This meta‐analysis suggested that the ?509C/T polymorphism in the TGF‐β1 gene may be a risk factor for asthma. To further evaluate gene–gene and gene–environment interactions between polymorphisms in the TGF‐β1 gene and asthma susceptibility, more studies involving thousands of patients are required.     

Hypoxia stimulates hepatocyte epithelial to mesenchymal transition by hypoxia‐inducible factor and transforming growth factor‐β‐dependent mechanisms

Background/Aims: During development of liver fibrosis, an important source of myofibroblasts is hepatocytes, which differentiate into myofibroblasts by epithelial to mesenchymal transition (EMT). In epithelial tumours and kidney fibrosis, hypoxia, through activation of hypoxia‐inducible factors (HIFs), is an important stimulus of EMT. Our recent studies demonstrated that HIF‐1α is important for the development of liver fibrosis. Accordingly, the hypothesis was tested that hypoxia stimulates hepatocyte EMT by a HIF‐dependent mechanism. Methods: Primary mouse hepatocytes were exposed to room air or 1% oxygen and EMT evaluated. In addition, bile duct ligations (BDLs) were performed in control and HIF‐1α‐deficient mice and EMT quantified. Results: Exposure of hepatocytes to 1% oxygen increased expression of α‐smooth muscle actin, vimentin, Snail and fibroblast‐specific protein‐1 (FSP‐1). Levels of E‐cadherin and zona occludens‐1 were decreased. Upregulation of FSP‐1 and Snail by hypoxia was completely prevented in HIF‐1β‐deficient hepatocytes and by pretreatment with SB431542, a transforming growth factor‐β (TGF‐β) receptor inhibitor. HIFs promoted TGF‐β‐dependent EMT by stimulating activation of latent TGF‐β1. To determine whether HIF‐1α contributes to EMT in the liver during the development of fibrosis, control and HIF‐1α‐deficient mice were subjected to BDL. FSP‐1 was increased to a greater extent in the livers of control mice when compared with HIF‐1α‐deficient mice. Conclusions: Results from these studies demonstrate that hypoxia stimulates hepatocyte EMT by a HIF and TGF‐β‐dependent mechanism. Furthermore, these studies suggest that HIF‐1α is important for EMT in the liver during the development of fibrosis.     

Agrocybe aegerita polysaccharide combined with chemotherapy improves tumor necrosis factor‐α and interferon‐γ levels in rat esophageal carcinoma

Natural compounds have generated great interest as alternative treatments of diseases like cancer. Here, we investigated the anti‐tumor mechanism of one such compound, Agrocybe aegerita polysaccharide, by assessing expression of tumor necrosis factor‐α (TNF‐α) and interferon‐γ (IFN‐γ) in rat esophageal carcinoma (EC). EC was induced in healthy Wistar rats by methyl‐n‐amyl nitrosamine. Subsequently, rats were administered cancer treatment daily for 4 weeks, as follows: the normal control group (the only group not treated with methyl‐n‐amyl nitrosamine) and model group received only distilled water; the chemotherapy group received tegafur treatment; and the combination group received tegafur combined with A. aegerita polysaccharide. In normal and combination groups, body weight increased gradually after each week of treatment (P < 0.05), while body weights did not change in model and chemotherapy groups. Using enzyme linked immunosorbent assay, we found serum TNF‐α was lower in the combination group (31.56 ± 7.20 pg/L) than either the model (46.24 ± 8.52 pg/L) or chemotherapy (52.39 ± 9.16 pg/L) group, and, while higher, was more similar to the normal controls (25.08 ± 2.93 pg/L; P < 0.05), a finding that was confirmed by the immunohistochemistry of esophageal samples. In contrast, serum IFN‐γ was higher in the combination group (97.20 ± 10.92 pg/L) than in either the model (76.11 ± 11.92 pg/L) or chemotherapy (76.04 ± 9.85 pg/L) group, but lower than in the normal group (117.56 ± 10.88; P < 0.05), also confirmed by immunohistochemistry. Therefore, Agrocybe aegerita polysaccharide, when combined with chemotherapy, can regulate immune function in EC, potentially by modulating cytokine activity, specifically downregulation of TNF‐α and upregulation of IFN‐γ.     

Expression of transforming growth factor alpha and epidermal growth factor receptor in human hepatocellular carcinoma

Abstract: Transforming growth factor alpha (TGF-alpha) is thought to be involved in liver regeneration, cellular proliferation, and hepatocarcinog-enesis. We have looked at the relationship between TGF-alpha and it's receptor, and have attempted to relate the expression of TGF-alpha and it's receptor to the differentiation of hepatocellular carcinoma (HCC) on serial sections of HCC. We examined immunohistochemically the expression of the TGF-alpha and of epidermal growth factor receptor (EGFR) proteins in the same area of 53 nodules (<5 cm in diameter) of HCC obtained from patients. Immnnoreactive proteins were visualized by using a biotin-streptoavidin system (LSAB Kit, Dako). TGF-alpha was strongly expressed in 29 of 53 (54.7%) nodules. Specimens strongly positive for TGF-alpha were found mainly in well-differentiated HCC, while specimens positive for EGFR were found mainly in poorly differentiated HCC (p<0.05). In the tissues that stained weakly positive for TGF-alpha, the expression of EGFR differed significantly, according to the degree of HCC histologic differentiation (p<0.05). These results led us to speculate that the expression of TGF-alpha and EGFR might be related to the pattern of histologic differentiation of HCC.     

The −509C/T polymorphism of transforming growth factor‐β1 is associated with increased risk for development of chronic idiopathic neutropenia

Objective: Impaired granulopoiesis in chronic idiopathic neutropenia (CIN) has been associated with an inflammatory bone marrow (BM) microenvironment consisting of pro‐inflammatory and pro‐apoptotic mediators, such as tumor necrosis factor (TNF)‐α, transforming growth factor (TGF)‐β1, and Fas‐Ligand (Fas‐L). In this study, we evaluated the frequency of TNF‐α, TGF‐β1 and Fas‐L gene polymorphisms in CIN patients and explored their role in excessive cytokine production and their association with CIN development. Methods: The TNF‐α?308G/A, TGF‐β1 ?509C/T, +869T/C, +915G/C, and Fas‐L ?844T/C polymorphisms were studied in 57 CIN patients, and 100 healthy controls from Crete, a well‐defined area with genetically homogeneous population, using a polymerase chain reaction‐based restriction fragment length polymorphism assay. Results: The mutant genotype C/T or T/T of TGF‐β1 ?509C/T polymorphism was more common in CIN patients than in controls (P = 0.033). Compared to wild‐type genotype, the TT genotype was associated with increased risk for CIN development (OR: 5.7; 95% CI: 1.18–27.26; P = 0.033). Compared to controls, patients with CT and TT genotypes displayed increased TGF‐β1 levels in serum (P < 0.0001 and P = 0.0002, respectively) and BM (P < 0.0001 and P = 0.0002, respectively). No significant difference was found between patients and controls in the frequency of TNF‐α?308G/A, TGF‐β1 +869T/C and +915G/C and Fas‐L ‐844T/C polymorphisms. Conclusions: The TGF‐β1 ?509C/T polymorphism is associated with increased risk for CIN and contributes to the pathophysiology of the disorder by inducing TGF‐β1 overproduction. This is the first study providing evidence that genetic factors may predispose to CIN and may have a role in the pathophysiology of the disorder.     

Splenocyte apoptosis in Plasmodium berghei ANKA infection: possible role of TNF‐α and TGF‐β

Cerebral malaria is associated with the circulating levels of tumour necrosis factor alpha (TNF‐α) and transforming growth factor β (TGF‐β), but association between these two cytokines and implications in splenocyte apoptosis remain largely obscured. We have evaluated the outcome of TGF‐β and TNF‐α production in the context of splenocyte apoptosis during Plasmodium berghei ANKA (PbA) infection. Blood‐stage PbA infection confirmed blood–brain barrier disruption, disarray of white pulp, increase in percentage of sub‐G0/G1 and splenocyte apoptosis. Flow cytometric analysis reveals up‐regulation of Fas‐L followed by caspase‐8 and caspase‐3 activation and signifies possible involvement of Fas‐L‐mediated splenocyte apoptosis. We have observed down‐regulation of TGF‐β and up‐regulation of TNF‐α in tissue and serum level, respectively, during PbA infection. Association between the production of TGF‐β and the severity of malaria infection in splenocytes was verified with TGF‐β inhibitor that exacerbated the apoptotic process. In contrary, TNF‐α inhibitor causes significant delay in apoptotic process, but could not alter the lethality of parasite. Thus, results from this study suggest that the critical balance between TGF‐β and TNF‐α might have a key role on Fas‐L‐mediated splenocyte apoptosis during experimental cerebral malaria.     

Effect of recombinant human transforming growth factor β1 on immune responses in patients with chronic hepatitis B

ABSTRACT— Studies were undertaken to examine the effect of recombinant human transforming growth factor beta 1 (rTGF-β1) on cellular and humoral immune responses of peripheral blood mononuclear cells (PBMC) from patients with chronic hepatitis B. The addition of TGF-β1 caused a significant dose-dependent inhibition of hepatitis B (HB) core Ag-stimulated interferon-γ and antibody to HB core Ag production and proliferation of PBMC from chronic hepatitis patients and HB-immune donors. TGF-β1 also induced a significant reduction in pokeweed mitogen-stimulated IgG and IgM production, as well as phytohemagglutinin p-stimulated proliferative response of PBMC. The degree of inhibition of TGF-β1 did not differ between antigen-specific and -nonspecific cellular and humoral immune responses, and between control individuals and patients. Pretreatment study with TGF-β1 showed that the activities of T cells, B cells and monocytes were similarly inhibited. Further, TGF-β1 inhibited activities of HLA class I antigen-matched cytotoxic T cells from patients with chronic hepatitis B for HBV DNA-transfected HepG2 cells in a ⁵¹Cr release assay. The results suggest that TGF-β1 may play a role in the regulation of antigen-dependent and -independent immune responses in patients with chronic hepatitis B.