The microbiome and rheumatic heart disease: current knowledge and future perspectives.

Rheumatic heart disease (RHD) is a cardiovascular disease caused by an autoimmune response to group A Streptococcus (GAS) infection resulting in the damage of heart valves. RHD is the most commonly acquired heart disease among children and young adults with a global burden of over 40 million cases accounting for 306,000 deaths annually. Inflammation in the heart valves caused due to molecular mimicry between the GAS antigens and host cardiac proteins is facilitated by cytokines, cross-reactive antibodies and CD4+ T cells. The complex interaction between genetic and environmental factors linked with erratic events leads to the loss of immunological tolerance and autoimmunity in RHD. Despite extensive research on the etiopathogenesis of RHD, the precise mechanism underpinning the initiation of acute rheumatic fever (ARF) to the progression of RHD still remains elusive. Mounting evidences support the contribution of the human microbiome in the development of several immune-mediated diseases including rheumatoid arthritis, juvenile idiopathic arthritis, Kawasaki disease, inflammatory bowel disease and type 1 diabetes. The microbiome and their metabolites could play a crucial role in the integrity of the epithelial barrier, development of the immune system, inflammation and differentiation of T cell subsets. Consequently, microbiome dysbiosis might result in autoimmunity by molecular mimicry, epitope spreading and bystander activation. This review discusses various aspects of the interaction between the microbiome and the immune system in order to reveal causative links relating dysbiosis and autoimmune diseases with special emphasis on RHD.

Thyroid-Stimulating Hormone Favors Runx2-Mediated Matrix Mineralization in HOS and SaOS2 Cells: An In Vitro and In Silico Approach.

Osteoporosis is a skeletal disease that is both systemic and silent characterized by an unbalanced activity of bone remodeling leading to bone loss. Rising evidences demonstrate that thyroid stimulating hormone (TSH) has an important role in the regulation on the metabolism of bone. However, TSH regulation on human osteoblast essential transcriptional factors has not been identified. Current study examined the role of TSH on human osteoblastic Runx2 expression and their functional genes by in vitro and in slico analysis. Human osteoblast like (HOS and SaoS-2) cells were cultured with DMEM and treated with hTSH at the concentration of 0.01 ng/mL and 10 ng/mL. After treatment, osteoblastic Runx2 and IGF-1R beta expression were studied using RT-PCR and western blot analysis. TSH treatment induced osteoblastic essential transcriptional factor, Runx2 in HOS and SaOS2 cells on 48 h duration and elevated the expression of IGF-IR ß gene and Protein in SaoS-2 cells. TSH also promotes Runx2 responsive genes such as ALP, Collagen and osteocalcin in SaOS2 cells on day 2 to day 14 of 10 ng/mL of treatment and favors' matrix mineralization matrix in these cells. In addition, TSH facilitated human osteoblastic cells to mineralize their matrix confirmed by day 21 of alizarin red calcium staining. In silico study was performed to check CREB and ELK1 interaction with Runx2. Results of in silico analysis showed that TSH mediated signalling molecules such as CREB and ELK1 showed interaction with Runx2 which involve in osteobalstic gene expression and differentiation. Present findings confirm that TSH promotes Runx2 expression, osteoblastic responsive genes and bone matrix formation.

Association of HLA-DRB1 Alleles with Rheumatic Fever and Rheumatic Heart Disease: A Meta-analysis.

BACKGROUND: Rheumatic fever (RF) and its sequel rheumatic heart disease (RHD) is an autoimmune disease caused by an abnormal host immune response to group A streptococcus (GAS) infection. The HLA class II molecules are entailed in immune-mediated infectious, inflammatory, and autoimmune diseases including RHD. However, HLA class II genes are reported to be associated with RF/RHD across different populations with a very little consistency. OBJECTIVE: The aim of the study is to investigate the association between HLA class II genes and RF/RHD by meta-analysis. METHODS: A comprehensive literature search was conducted to identify all relevant case-control studies published before December 31, 2019. The data were extracted using standardized form and pooled odds ratio (OR) with 95% confidence interval (CI) are calculated to assess the strength of the association between HLA class II genes and RF/RHD. RESULTS: Thirteen studies for HLA-DRB1 alleles (1065 patients and 1691 controls) and eight studies for HLA-DQB1 alleles (644 patients and 1088 controls) were finally included. The meta-analysis showed a significantly higher frequency of HLA-DRB1*07 allele (OR = 1.68, P < .0001) in RF/RHD patients when compared to controls, while the frequency of HLA-DRB1*15 allele (OR = 0.60, P = .03) was significantly lower in RF/RHD patients than in controls. However, there were no significant differences in the frequency of HLA-DQB1 alleles between RF/RHD patients and controls. CONCLUSIONS: The results of the meta-analysis suggest that the differential presentation of autoimmune peptides by HLA-DRB1*07 (susceptible) and HLA-DRB1*15 (protective) alleles with different affinities may play a crucial role in the pathogenesis of RF/RHD.

The Spectrum of CYP21A2 Gene Mutations from 16 Families of Congenital Adrenal Hyperplasia: Genotype-Phenotype Correlation.

Aim: Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder of the adrenal steroidogenic pathway. The most common form of CAH is due to 21-hydroxylase deficiency resulting from mutations in CYP21A2 gene. The present study aimed to identify CYP21A2 common gene mutations, phenotype correlation, and to analyze the segregation pattern in CAH patients, parents, and siblings. Materials and Methods: Sixteen families having at least one classic CAH child in each family, a total of 58 subjects were recruited. The presence of six most common gene mutations, namely, Intron 2 (c.293-13A/C>G), c.844G>T (p.Val282Leu), c.1019G>A (p.Arg340His), c.92C>T (p.Pro31Leu), c.955C>T (p.Gln319*), and c.518T>A (p.Ile173Asn) in CYP21A2 gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using specific primers. Results: Out of 16 classic CAH females analyzed, salt-wasting (SW) form was present in 12 (75%) and simple virilizing form in four (25%) children. Isolated clitoromegaly was the most common clinical presentation followed by ambiguous genitalia. The most common mutation observed in CAH patient population was Intron 2 (c.293-13A/C>G) (100%) followed by p.Pro31Leu (98%), p.Gln319* (93%), p.Val282Leu (91.4%), and p.Ile173Asn (19%). Although p.Arg340His mutation was not observed in this study. Interestingly, Intron 2 (c.293-13A/C>G) homozygous was observed in 31.3% of the entire study cohort and p.Ile173Asn mutation was found to be associated with SW form. Conclusions: Our results suggested a high prevalence of CYP21A2 gene mutations among CAH patients and heterogeneous mutation spectrum in their families of south Indian cohort. The outcomes afford valuable evidence for premarital and prenatal screening as well as planning suitable programs to prevent the development of CAH in Indian population.

Lack of Association Between TNF-α, IFN-γ, IL-10 Gene Polymorphisms and Rheumatic Heart Disease in South Indian Population.

BACKGROUND: Proinflammatory and anti-inflammatory cytokines play a crucial role in the development and maintenance of immune mediated inflammatory diseases including rheumatic heart disease (RHD). Polymorphisms in tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL)-10 genes influence the differential cytokine expression as well as the pathogenesis of various inflammatory and autoimmune diseases. OBJECTIVE: The aim of the study is to investigate the association between TNF-α, IFN-γ, and IL-10 gene polymorphisms and RHD in South Indian population. MATERIALS AND METHODS: TNF-α (-308, -238), IFN-γ (+874), and IL-10 (-1082, -819, -592) gene polymorphisms were determined in 100 patients with RHD and 127 healthy siblings by PCR. RESULTS: There was no significant difference in the genotype, allele, and haplotype frequencies of TNF-α, IFN-γ, and IL-10 polymorphisms between RHD patients and healthy siblings. CONCLUSION: The present study suggests that TNF-α, IFN-γ, and IL-10 gene variants may not be associated with the development of RHD in South Indian population.

Association of IL17 and IL23R gene polymorphisms with rheumatic heart disease in South Indian population.

BACKGROUND: IL-23/Th17 signaling pathway plays a crucial role in the cell-mediated immune response against bacterial infections and also in the pathogenesis of inflammatory and autoimmune diseases. Recent studies indicate that Th17 cell-associated cytokines are involved in the progression and maintenance of valvular lesions in rheumatic heart disease (RHD). Variants in the genes of cytokines that are potentially involved in Th17 response may influence interindividual differences in their expression levels, thereby contributing to the pathogenesis of immune-mediated diseases such as RHD. OBJECTIVE: The aim of the study is to investigate the association of IL17A, IL17F, and IL23R gene variants with the risk perception of RHD. METHODS: A total of 225 individuals (99 RHD patients and 126 healthy siblings) were recruited for the study. The IL17A (rs2275913), IL17F (rs763780), and IL23R (rs10889677) polymorphisms were determined by polymerase chain reaction restriction fragment length polymorphisms and amplification-refractory mutation system-polymerase chain reaction methods, respectively. RESULTS: The frequency of IL17A (rs2275913) A/A genotype was significantly high in pooled RHD patients (odds ratio [OR] = 2.76; pc = 0.021), rheumatic fever (RF) patients (OR = 14.5; pc = 0.0001), and mitral valvular lesions patients (OR = 2.74; pc = 0.039) when compared to healthy siblings. However, the IL17F (rs763780) and IL23R (rs10889677) polymorphisms did not show any association with RHD. CONCLUSIONS: The results suggest that IL17A (rs2275913) polymorphism is associated with the development of RF/RHD in South Indian population. Further studies are required to substantiate the association of these genes with the disease risk.

"HLA-G 3'UTR gene polymorphisms and rheumatic heart disease: a familial study among South Indian population".

BACKGROUND: Rheumatic heart disease (RHD) is an autoimmune disease where cross reactive CD4+ T cells are involved in the pathogenesis of valvular damage. Human Leukocyte Antigen-G (HLA-G), an immunosuppressive molecule playing a crucial role in the inhibition of T cell response is associated with the pathogenesis of various autoimmune and inflammatory diseases. Genetic polymorphisms within the 3'untranslated region (UTR) of HLA-G influences its expression and thus disease pathogenesis. Hence, the present study aims to unravel the association of 14 bp Ins/Del (rs66554220) and +3142 C/G (rs1063320) polymorphisms in 3' UTR of HLA-G with RHD. METHODS: This familial study consists of 99 RHD families (99 RHD patients, 140 parents and 126 healthy siblings). The 14 bp Ins/Del and +3142 C/G polymorphisms were evaluated by PCR using sequence specific primers and its transmission disequilibrium (TD) was tested by TD test in 70 trio families. RESULTS: The frequency of +3142 C/C genotype was high in patients with combined valvular lesions (CVL) (OR = 5.88; pc = 0.012) and pooled RHD patients (P: OR = 2.76; p = 0.043; pc = 0.076) when compared to healthy siblings. Under the additive (OR = 5.50; pc = 0.026) and recessive genetic model (OR = 5.88; pc = 0.012), the +3142 C/C genotype was significantly associated with CVL in patients. CONCLUSION: The results suggest that the +3142 C/C genotype may be associated with minor risk for the development of RHD and is more likely to influence the severity of the disease.