Lucila Sandoval-Ramírez

Association of β-Defensin 1 Single Nucleotide Polymorphisms with Atopic Dermatitis

Background: Atopic dermatitis (AD) is a chronic multifactorial allergic disease with unclear etiology. The antimicrobial human β-defensin 1 is chemotactic for dendritic cells, which are important regulators of allergic immune responses. In an attempt to identify useful markers that could predict susceptibility to AD, we investigated single nucleotide polymorphisms (SNPs) of the β-defensin 1 gene (DEFB1) with potential functional consequences. Methods: Four SNPs of the DEFB1 gene were genotyped either by real-time polymerase chain reaction or polymerase chain reaction-restriction fragment length polymorphisms in 59 patients with AD and 151 controls from the Mexican population. Correlation analyses were carried out between genetic, environmental and clinical variables in AD patients. Results: The genotypes associated with susceptibility to AD and no other allergy were 692 GG (OR = 3.21, 95% CI 1.37–7.34) and 1654 AA (OR = 17.37, 95% CI 1.62–860.83). The allele 668 C is a risk factor for AD (OR = 2.23, 95% CI 1.22–4.01) and the allele A in site 1836 correlates with earlier age at onset (Spearman’s ρ = 0.232; p = 0.03). The prolonged duration of breastfeeding correlates with earlier age at onset as well as with the severity of AD. Conclusions: The DEFB1 gene is probably involved in the incidence and development of AD, but additional functional studies will be necessary to understand the biological role of these SNPs.

Polymorphisms C677T and A1298C in the MTHFR gene in Mexican patients with rheumatoid arthritis treated with methotrexate: implication with elevation of transaminases

Rheumatoid arthritis (RA) is the prototype of the rheumatic diseases worldwide. Methotrexate (MTX) is the drug of first choice in the treatment of this disease due to its immunosuppressant effect. However, side events are present in 30% of the patients. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are involved in the metabolism of MTX. Earlier studies reported an association between these polymorphisms and elevation of hepatic enzymes. We analyzed the frequencies of both polymorphisms and the presence of transaminasemia in 70 Mexican patients with rheumatic arthritis treated with MTX. The 19% (13/70) of patients had an increase in the serum level of transaminases. The A1298C polymorphism was associated with elevation of transaminases (P=0.024). The identification of MTHFR genotypes for C677T and A1298C polymorphisms could lead clinicians to identify patients in risk of elevation of transaminases, and give them an individualized treatment, as is a goal of pharmacogenetics.

Allele frequency distribution of CYP2C9*2 and CYP2C9*3 polymorphisms in six Mexican populations

Allele frequency differences of functional CYP2C9 polymorphisms are responsible for some of the variation in drug response observed in human populations. The most relevant CYP2C9 functional variants are CYP2C9*2 (rs1799853) and CYP2C9 3 (rs1057910). These polymorphisms show variation in allele frequencies among different population groups. The present study aimed to analyze these polymorphisms in 947 Mexican-Mestizo from Mexico City and 483 individuals from five indigenous Mexican populations: Nahua, Teenek, Tarahumara, Purepecha and Huichol. The CYP2C9*2 allele frequencies in the Mestizo, Nahua and Teenek populations were 0.051, 0.007 and 0.005, respectively. As for CYP2C9 3, the allelic frequencies in the Mestizo, Nahua and Teenek populations were 0.04, 0.005 and 0.005, respectively. The CYP2C9 2 and CYP2C9 3 alleles were not observed in the Tarahumara, Purepecha and Huichol populations. These findings are in agreement with previous studies reporting very low allele frequencies for these polymorphisms in American Indigenous populations.

Cytotoxic and antitumour activity from Bursera fagaroides ethanol extract in mice with L5178Y lymphoma

Chloroform extracts of Bursera fagaroides (Burseracea) have previously shown antitumour activity against the Walker carcinoma 256 tumour system (WA16). In the present work we have determined the cytotoxic and antitumour activity of the ethanol extract (70%) of the bark of B. fagaroides using the L5178Y lymphoma. The cytotoxic activity is expressed as the ED50 of the L5178Y lymphoma cells in culture, (20 µg/mL) whilst the antitumour activity was shown via a tumour growing inhibition test, measuring survival of BALB/c mice (2 × 104 cells L5178Y i.p.). 24 h after inoculation mice were treated with 50 or 100 mg/kg of extract daily, over 15 days in independent groups of 10, using two administration routes. We observed the tumour evolution with and without treatment. Oral administration resulted in 8% of mice being tumour free after 60 day whilst intraperitoneal administration showed 26% survived at a dose of 100 mg/kg/day for 15 days. A significant increase in the survival of the treated animals (at 50 mg/kg/day over 15 days) was found compared with those treated with placebo or without treatment. Copyright

MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis

MTHFR polymorphisms C677T and A1298C are associated with reduced MTHFR enzyme activity and hyperhomocysteinemia, which has been associated with osteoporosis. The A163G polymorphism in osteoprotegerin (OPG) has been studied in osteoporosis with controversial results. The objective of the present study was to investigate the association(s) among MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis. The femoral neck and lumbar spine bone mineral densities (BMDs) were measured in 71 RA patients, and genotyping for the three polymorphisms was performed via restriction fragment length polymorphism analysis. Patients with osteoporosis/osteopenia exhibited statistically significant differences in the genotype frequencies of MTHFR C677T as well as an association with femoral neck BMD; TT homozygotes had lower BMDs than patients with the CT genotype, and both of these groups had lower BMDs than patients with the CC genotype. The associations of the MTHFR C677T polymorphism with osteoporosis/osteopenia and femoral neck BMD suggest that these polymorphisms confer a risk of developing osteoporosis in patients with rheumatoid arthritis, a risk that may be reduced with folate and B complex supplementation.

Y-Chromosome Haplotypes for Six Short Tandem Repeats (STRs) in a Mexican Population

BACKGROUND Short tandem repeats (STRs) on the non-pseudoautosomal region of the Y-chromosome are DNA polymorphic markers able to solve special cases in legal medicine, for instance in paternity testing where the alleged father is not available, and in forensic situations, such as rape cases, where mixtures of male/female DNA are present. METHODS Six STR polymorphisms from the Y-chromosome (DYS19, DYS385, DYS389/I, DYS390, DYS391, and DYS393) were PCR-typed in 120 males from the northwest region of Mexico by means of native polyacrylamide gel electrophoresis and silver staining. RESULTS Allele frequencies were estimated for each STR. Their gene diversity ranged from 51.4% for DYS393 to 92.5% for DYS385. Mexican Y-STR allele distributions displayed similarity (p >0.05) with previously reported U.S. Hispanics for DYS19, DYS389/I, DYS390, DYS391, and DYS393. Although Mexicans showed the same modal allele for DYS385 (11/14; 24.4%) with regard to most European populations, differences in allele distributions were observed (p <0.01). The haplotype diversity and the male discriminatory capacity of this six-locus system were 99.3 and 84.1%, respectively. CONCLUSIONS This knowledge permits the effective use of these six Y-chromosome markers in legal medicine casework in the studied population. This STR-system offers a great potential to identify males and male-lineages, and can be used confidentially in paternity testing and forensic analysis in the Mexican population.

Phenytoin and electric shock-induced apoptosis in rat peripheral blood lymphocytes

The apoptotic index (AI) of peripheral blood lymphocytes (PBL) and plasma corticosterone (CS) levels were determined in Wistar rats treated with phenytoin (PHT) at therapeutic and toxic doses (100 or 200 mg/kg/day, respectively, over a period of 7 days) and stressed by bifrontal electric shock (60 Hz/40 mA/0.2 seg). The values of CS and AI were found to be significantly higher in rats submitted to electric shock (ES) and in rats treated with therapeutic and toxic doses of PHT plus ES, than in rats treated only with PHT (P<0.001). The plasma concentrations of PHT were found to be significantly higher in rats treated with toxic doses than in those treated with therapeutic doses (P<0.001), while the control group (without treatment) and vehicle group (propilenglycol-ethanol-water, 40:10:50), showed low levels of CS, and less than 1% of AI. The DNA analysis by electrophoresis in agarose in all the groups was positive, displaying the ladder pattern characteristic of apoptotic process (200 bp), except in the control groups (no treatment and vehicle treated). Our results demonstrate that chronic stress, caused by ES, produces an elevation of CS. The values of apoptosis were correlated with the CS levels, suggesting that the apoptotic inductor process is a consequence of an increase in the concentration of corticosterone in plasma, in response to the hypothalamic-pituitary-adrenals (HPA) axis activation, while phenytoin at therapeutic doses is only a moderate apoptosis inductor.

Renin gene haplotype diversity and linkage disequilibrium in two Mexican and one German population samples

Introduction. Renin is the main rate-limiting enzyme in the renin—angiotensin—aldosterone system. Its gene, REN, is a candidate crucial factor in essential hypertension and cardiovascular disease. The aim of this study was to evaluate allele and haplotype distributions of REN polymorphisms, and to estimate normalised linkage disequilibrium (D’) in Mexican and German populations. Materials and methods. Four groups were studied for the REN single nucleotide polymorphisms (SNPs) 1205C>T, 1303G>A, and 10607G>A, in population samples of Mexican Mestizo (n = 86), Mexican Huichol (n = 49), German (n = 39), and individuals with hypertension diagnosis (n = 66). Polymorphisms were detected by PCR—RFLP. Genotype, allele and haplotype frequencies were estimated. Results. SNP 1205C>T and 10607G>A allele and genotype distribution showed inter-group differences. The 1205T and 10607A allele showed a significance difference in hypertensive population. Haplotype analysis also showed some inter-group differences, especially in 1205C-1303G-10607G, 1205C-1303G-10607A and 1205T-1303G-10607G haplotypes. The segregation analysis disclosed complete linkage disequilibrium between 1205 and 1303 loci. Conclusion. These results provide an example of genetic diversity in related populations and illustrate the convenience of increasing the number of loci in associative studies between diseases and candidate genes.

Linkage Disequilibrium Between IDUA kpnI-VNTR Haplotype in Mexican Patients with MPS-I

BACKGROUND The MPS-I is an autosomal recessive disorder caused by mutations in the IDUA gene that induce to a deficiency of glycosidase alpha-L-iduronidase that is required for degradation of heparan and dermatan sulfate. This disorder expresses a wide range of clinical symptoms. METHODS Kpnl (K) and VNTR (V) intragenic polymorphisms at the IDUA gene were studied in mestizo and Huichol Indian Mexican populations as well in 13 MPS-I patients. Data from Australian normal and MPS-I (2-4) individuals were also studied. RESULTS Genotypes for IDUA K and V sites in Mexicans were in agreement with Hardy-Weinberg expectations, except for site K in Huichols. Individually, allele frequency distributions were different (p < 0.05) in the two normal groups for the V site. K-V haplotype frequency distributions (HFDs) in these two normal groups were also different as compared with normal Australians. In Mexican MPS-I patients, HFD was different (p < 0.05) with respect to both Mexican normal groups, and non-different when compared with normal or MPS-I Australians. This can be taken as evidence of linkage disequilibrium between K-V polymorphism and MPS-I gene mutation(s) at the IDUA region. A similar finding was reported. However, disequilibrium in Mexicans was determined by haplotypes different from those in Australia. In Mexican MPS-I patients, haplotype K2-V1 is increased and K1-V3 decreased with respect to the Mexican mestizo (p < 0.05), while in Australians, MPS-I patients had an increase of haplotypes K2-V2 and K1-V2 with respect to expected frequency. CONCLUSIONS The similar HFD between Mexican and Australian MPS-I patients suggests a common genetic origin, that MPS-I mutations were introduced to Mexico by Spaniards, and that such mutations predate the dispersion between Mexican and Australian Caucasian ancestors. The differences in disequilibrium are explained rather by genetic drift.