Characterization of the dengue outbreak in Nuevo Leon state, Mexico, 2010

We studied serotypes circulating dengue virus (DENV) cases, entomological Breteau index, rain-fall index and epidemiology of groups affected during the 2010 outbreak in Nuevo Leon, Mexico. From 2,271 positive cases, 94% were dengue classic and 6% dengue hemorrhagic fever; DENV1 was mainly isolated (99%) (Central-American lineage of American-African-genotype). We found correlation between two environmental phenomena (Increment of rainfall and vector-indexes) (p ≤ 0.05) with epidemiological, clinical and risk of DENV-1 ongoing transmission.

Prevalence of the -308 and -238 tumor necrosis factor alpha (TNF-α) promoter polymorphisms in Mexican chronic hepatitis C patients

BACKGROUND

Tumor necrosis factor alpha (TNF-α) has been involved in the pathogenesis of chronic hepatitis C virus (HCV) infection. Two polymorphisms at positions -308 and -238 in the TNF-α promoter region influence TNF-α expression and these have been linked to a number of infectious diseases.

AIM

To analyze the prevalence of the -308 and -238 TNF-α polymorphisms in a group of Mexican HCV-infected patients and in healthy control subjects not related to the patients.

MATERIAL AND METHODS

Both polymorphisms were determined in peripheral blood samples from 48 patients with positive anti-HCV antibodies and discernible HCV-RNA levels. Twenty five patients were women and 23 were men. The control group included 100 healthy subjects. Forty-four were women and 56 were men. The polymorphisms were evaluated by polymerase chain reaction amplification (PCR), followed by the Restriction Fragment Length Polymorphism (RFLP) method.

RESULTS

The prevalence of the -308 TNF-α polymorphism was found to be 12% in patients with chronic hepatitis C and 20% in control subjects, (P=0.2616); whereas that of the -238 TNF-α polymorphism was found to be 2% and 12% in patients and control subjects, respectively (P=0.061). The TNF-α genotypes were found to be in Hardy-Weinberg equilibrium.

CONCLUSIONS

No association was found between -308 and -238 TNF-α polymorphisms and chronic hepatitis C in the Mexican group studied. Our data suggest that additional studies increasing the sample size and a control group which has been exposed to an equal risk of infection are required to investigate whether these polymorphisms represent genetic susceptibility for chronic HCV infection.

Dengue virus antibodies in blood donors from an endemic area

We evaluated the incidence of anti-Dengue virus (DENV) antibodies and dengue viremia in a region of Mexico with a high prevalence of dengue. DENV is the most important arthropod-borne virus in terms of human morbidity and mortality in America We tested 800 blood donors from a tertiary care teaching hospital that provides care in Northeast Mexico, to identify anti-DENV IgM and IgG antibodies by enzyme-linked immunosorbent assay (ELISA) and DENV genome by reverse transcription polymerase chain reaction (RT-PCR). In addition, routine tests for donors including Brucella, Hepatitis C virus (HCV), Venereal Disease Research Laboratory (VDRL), HIV-1 and HBsAg identification were performed. We found that 59% of donors were reactive for anti-DENV IgG and none of them had reported recent DENV infection; however, 16 (2%) were reactive for anti-DENV IgM antibodies. None of them were viremic at the time of donation. Routine tests showed that the prevalence of anti-Brucella was 0.71%, anti-HCV 0.71%, anti-HIV-1-2 0.14%, HBsAg 0.14% and VDRL test 0.57%. Although DENV transmission by blood transfusion had not been confirmed in Mexico, the finding of a high prevalence of anti-DENV IgM-positive donors with asymptomatic manifestations and the recent viremia reported in blood donors suggests that this route of transmission might be possible.

Additive effect of ethanol and HCV subgenomic replicon expression on COX-2 protein levels and activity

The mechanisms by which alcohol exacerbates liver injury in patients with hepatitis C are unknown. We used the hepatitis C virus (HCV) subgenomic replicon cell system to evaluate the effect of ethanol on HCV replication and viral protein synthesis. Our results demonstrate that alcohol stimulates HCV replicon expression at both HCV-RNA and protein levels. Furthermore, we observed that ethanol treatment showed an additive effect in cyclooxygenase-2 (COX-2) protein expression and activity already induced by HCV viral proteins, and in turn increased HCV viral expression. Our results suggest that COX-2 activity is involved in ethanol-induced HCV-RNA and NS5A protein expression, because acetylsalicylic acid (ASA), a COX-1/2 inhibitor, blocked this induction and downregulated COX-2 protein expression and activity. Therefore, we suggest that ethanol increases HCV replication expression, at least in part, by upregulating a key cellular regulator of oxidative stress pathway known as COX-2 or its products.

Tumor necrosis factor alpha down-regulates expression of the alpha1(I) collagen gene in rat hepatic stellate cells through a p20C/EBPbeta- and C/EBPdelta-dependent mechanism

Tumor necrosis factor alpha (TNF-alpha) is one of the key cytokines of the acute phase response and of many inflammatory processes. This cytokine has several antifibrogenic actions and down-regulates the expression of the type I collagen genes and induces the expression of metalloproteinases. Because TNF-alpha directly antagonizes some fibrogenic actions of transforming growth factor beta(1) (TGF-beta(1)), we considered it important to map the cis-acting regulatory element of the alpha1(I) collagen (col1a1) promoter involved in TNF-alpha responsiveness in hepatic stellate cells (HSC), to investigate the transcription factors that bind to it, and to establish possible mechanisms by which TNF-alpha down-regulates its expression. In this article, we show the presence of a functional TNF-alpha-responsive element (TaRE) in the -378 to -345 region of the col1a1 promoter. This element colocalizes with a previously reported TGF-beta(1)-responsive element. We further demonstrate that TNF-alpha induces nuclear translocation and binding of transcriptional complexes containing p20C/EBPbeta, p35C/EBPbeta, and C/EBPdelta to this sequence of the promoter. Transient overexpression of C/EBPdelta or p20C/EBPbeta, the natural dominant negative form of C/EBPbeta in HSC, down-regulated activity of a CAT reporter vector driven by -412 to +110 of the col1a1 promoter. Taken together, these data suggest that the -378 to -340 region of the col1a1 promoter is the site of convergence of different stimuli that ultimately modulate col1a1 gene transcription.

Hydrogen peroxide: a link between acetaldehyde-elicited alpha1(I) collagen gene up-regulation and oxidative stress in mouse hepatic stellate cells

Ethanol induces liver fibrosis by several means that include, among others, the direct fibrogenic actions of acetaldehyde and the induction of an oxidative stress response. However, the mechanisms responsible for these activities, and the possible connections between oxidative stress and acetaldehyde-induced fibrosis are not well understood. In this communication we investigated the molecular mechanisms whereby acetaldehyde induces mouse alpha1(I) procollagen (col1a1) gene expression in cultured hepatic stellate cells. Transfection assays using reporter plasmids driven by different segments of the col1a1 promoter localized an acetaldehyde-responsive element (AcRE) between nucleotides -370 and -345. We also show that acetaldehyde enhances binding of a CCAAT/enhancer binding protein-beta (C/EBPbeta)-containing complex to this element, and that this effect is due, at least in part, to an increase in the concentration of nuclear p35C/EBPbeta protein. Although this element overlaps to a previously described transforming growth factor beta1 (TGF-beta1)-responsive element, the stimulatory effect of acetaldehyde is not mediated through this cytokine, because addition of neutralizing anti-TGF-beta1 antibodies does not prevent acetaldehyde-elicited col1a1 up-regulation. On the other hand, this effect is blocked by the addition of catalase, an H(2)O(2) scavenger. Moreover, this ethanol metabolite stimulates production of H(2)O(2) in stellate cells. Thus, these results suggest that acetaldehyde-induced col1a1 up-regulation is mediated, at least in part, through H(2)O(2). Altogether, these data suggest that the -370 to -344 region of the col1a1 gene is a point of convergence of the action of numerous extracellular stimuli that ultimately leads to col1a1 up-regulation. In addition, we have established a direct connection between oxidative stress and enhanced col1a1 expression induced by acetaldehyde.