Jemni Ben Chibani

Update in chronic obstructive pulmonary disease: role of antioxidant and metabolizing gene polymorphisms

ABSTRACT Chronic obstructive pulmonary disease (COPD) is characterized by systemic and local chronic inflammation and oxidative stress. The sources of the increased oxidative stress in COPD patients derive from the increased burden of inhaled oxidants such as cigarette smoke and other forms of particulate or gaseous air pollution and from the increase in reactive oxygen species (ROS) generated by several inflammatory, immune, and structural airways cells. There is increasing evidence that genetic factors may also contribute to the pathogenesis if COPD, particularly antioxidant genes, which may confer a susceptibility to environmental insults such as cigarette smoke and thereafter development of COPD. Consequently, heme oxygenase-1 (HO-1), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), microsomal epoxide hydrolase (EPHX1), and cytochrome P450 (CYP) genetic polymorphisms may have an important role in COPD pathogenesis. In this review the authors summarized the most recent findings dealing with these antioxidant genes contributing to the free radical neutralization and xenobiotic enzymes playing a role in different phases of cell detoxification reactions related to the redox status imbalance in COPD, with an emphasis on their possible roles in disease progression.

HEMOGLOBINOPATHIES IN NORTH AFRICA: A REVIEW

Hemolytic anemias are very common diseases. Among these diseases, hemoglobinopathies are widely spread throughout the Mediterranean Basin, including North Africa (Tunisia, Algeria and Morocco). Their severity and disabling nature make them a major public health problem. This study includes our data on the Tunisian hemoglobinopathies together with all the reports concerning epidemiological, clinical and molecular aspects in Algerian and Moroccan populations. Investigation methods begin with the application of several techniques for hemoglobin (Hb) analyses [electrophoresis and isoelectric focusing (IEF), micro-chromatography assay] of anemic patients in various hospital departments. Molecular investigation by DNA analyses completes the hematological and biochemical studies using polymerase chain reaction (PCR) followed by enzymatic digestion and/or denaturing gradient gel electrophoresis (DGGE), single strand conformation polymorphism (SSCP) and sequencing. These methods offer screening for a large number of families affected by sickle cell disease and thalassemia. In Tunisia, Algeria, and Morocco, more than 45 mutations have been identified on the β-globin gene. The most common in Tunisia and in Algeria are codon 39 (C>T) and IVS-I-110 (G>A), which together account for more than 50% of all mutations. In Morocco, the predominant mutations are codon 39 and frameshift codon (FSC) 8 (–AA). The identification of molecular defects in the βgene contributes to the development of diagnostic tests (prenatal diagnosis), and gives us the opportunity to help many couples. Our studies of the haplotypes of the βS, codon 39 and IVS-I-110 origins allowed the hypothesis of a Benin origin for βS, a local North African origin for codon 39 and an Eastern Mediterranean origin for IVS-I-110. The analysis of polymorphisms associated with a moderate phenotype of β-thalassemia (β-thal) and sickle cell disease in North Africa has shown, in several cases, a strong association with some mutations and restriction fragment length polymorphisms (RFLP) haplotype IX on the β-globin locus and the −158 (C>T) polymorphism in 5′ on the Gγ-globin gene. Finally, more knowledge on the regulation of the β-globin locus may contribute to the improvement of investigation, monitoring and treatment of hemoglobinopathies.

Correlation of EPHX1, GSTP1, GSTM1, and GSTT1 genetic polymorphisms with antioxidative stress markers in chronic obstructive pulmonary disease

ABSTRACT This study was undertaken to ascertain if a relationship existed between oxidative status and polymorphisms of microsomal epoxide hydrolase X1 (EPHX1), glutathione S-transferase P1 (GSTP1), GSTM1, and GSTT1 in chronic obstructive pulmonary disease (COPD). Erythrocyte glutathione peroxidase (GSH-px), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), and plasma GST activities and total antioxidant status (TAS) as antioxidative stress markers were determined and compared either with individual and combined genotypes of EPHX1 exon 3, GSTP1 exon 5, GSTM1, and GSTT1 polymorphisms in COPD patients and healthy controls from the central area of Tunisia. Statistical data processing revealed significantly lower GSH-px, GR, SOD, CAT, GST, and TAS values in COPD patients in comparison to the control group (P < .001). As for genotypes, there was a no significant association in each of the 6 parameters and individual genotypes (P > .05). A significant correlation between the studied parameters and combined null GSTM1/null GSTT1 (GSH-px: P < .001, GR: P = .026, CAT: P = .018, GST: P = .022, TAS: P = .046), His113His EPHX1/null GSTM1 (GSH-px: P = .001, GST: P = .0012, TAS: P = .013), His113His EPHX1/Val105Val GSTP1 (GSH-px: P = .048, CAT: P = .026, GST: P = .031), and null GSTM1/Val105Val GSTP1 (GSH-px: P = .011, GR: P = .0028, GST: P = .0054, TAS: P = .032) was found in patients. In conclusion, combined genetic polymorphisms of GSTM1, GSTT1, GSTP1, and EPHX1 may have favorable effects on redox balance in COPD patients.

The Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape

Over the past few years, studies of DNA isolated from human fossils and archaeological remains have generated considerable novel insight into the history of our species. Several landmark papers have described the genomes of ancient humans across West Eurasia, demonstrating the presence of large-scale, dynamic population movements over the last 10,000 years, such that ancestry across present-day populations is likely to be a mixture of several ancient groups [1-7]. While these efforts are bringing the details of West Eurasian prehistory into increasing focus, studies aimed at understanding the processes behind the generation of the current West Eurasian genetic landscape have been limited by the number of populations sampled or have been either too regional or global in their outlook [8-11]. Here, using recently described haplotype-based techniques [11], we present the results of a systematic survey of recent admixture history across Western Eurasia and show that admixture is a universal property across almost all groups. Admixture in all regions except North Western Europe involved the influx of genetic material from outside of West Eurasia, which we date to specific time periods. Within Northern, Western, and Central Europe, admixture tended to occur between local groups during the period 300 to 1200 CE. Comparisons of the genetic profiles of West Eurasians before and after admixture show that population movements within the last 1,500 years are likely to have maintained differentiation among groups. Our analysis provides a timeline of the gene flow events that have generated the contemporary genetic landscape of West Eurasia.Summary Over the past few years, studies of DNA isolated from human fossils and archaeological remains have generated considerable novel insight into the history of our species. Several landmark papers have described the genomes of ancient humans across West Eurasia, demonstrating the presence of large-scale, dynamic population movements over the last 10,000 years, such that ancestry across present-day populations is likely to be a mixture of several ancient groups [1, 2, 3, 4, 5, 6, 7]. While these efforts are bringing the details of West Eurasian prehistory into increasing focus, studies aimed at understanding the processes behind the generation of the current West Eurasian genetic landscape have been limited by the number of populations sampled or have been either too regional or global in their outlook [8, 9, 10, 11]. Here, using recently described haplotype-based techniques [11], we present the results of a systematic survey of recent admixture history across Western Eurasia and show that admixture is a universal property across almost all groups. Admixture in all regions except North Western Europe involved the influx of genetic material from outside of West Eurasia, which we date to specific time periods. Within Northern, Western, and Central Europe, admixture tended to occur between local groups during the period 300 to 1200 CE. Comparisons of the genetic profiles of West Eurasians before and after admixture show that population movements within the last 1,500 years are likely to have maintained differentiation among groups. Our analysis provides a timeline of the gene flow events that have generated the contemporary genetic landscape of West Eurasia.

Screening for Alpha 1 antitrypsin deficiency in Tunisian subjects with obstructive lung disease: a feasibility report.

BackgroundAATD is one of the most common inherited disorders in the World. However, it is generally accepted that AATD in North African populations is not a risk factor for lung and/or liver disease, based on a number of small studies. We therefore planned a screening study for detection of AATD in patients with OLD in a cohort of patients from Kairouan in central Tunisia. Methods: One hundred twenty patients with OLD (asthma, emphysema, COPD) were enrolled in the screening programme. Laboratory diagnosis for AATD was performed according to current diagnostic standards.ResultsWe found that 6/120 OLD patients carried an AAT deficient allele, 1 PI*MZ, 1 PI*MPlowel, 3 PI*MMmalton, 1 PI*MMwurzburg.Conclusionthis pilot study demonstrated that alleles related to deficiency of AAT are not absent in the Tunisian population, and that rare AATD variants prevailed over commonest PI*Z variant. These results would support a larger scale screening for AATD in Tunisia.

Regulation of SCN5A by microRNAs: miR-219 modulates SCN5A transcript expression and the effects of flecainide intoxication in mice

BACKGROUND The human cardiac action potential in atrial and ventricular cells is initiated by a fast-activating, fast-inactivating sodium current generated by the SCN5A/Nav1.5 channel in association with its β1/SCN1B subunit. The role of Nav1.5 in the etiology of many cardiac diseases strongly suggests that proper regulation of cell biology and function of the channel is critical for normal cardiac function. Hence, numerous recent studies have focused on the regulatory mechanisms of Nav1.5 biosynthetic and degradation processes as well as its subcellular localization. OBJECTIVE The purpose of this study was to investigate the role of microRNAs in the Scn5a/Nav1.5 posttranscriptional regulation. METHODS Quantitative polymerase chain reaction, immunohistochemical and electrophysiological measurements of distinct microRNA gain-of-function experiments in cardiomyocytes for the assessment of Scn5a expression. RESULTS Functional studies of HL-1 cardiomyocytes and luciferase assays in fibroblasts demonstrate that Scn5a is directly (miR-98, miR-106, miR-200, and miR-219) and indirectly (miR-125 and miR-153) regulated by multiple microRNAs displaying distinct time-dependent profiles. Cotransfection experiments demonstrated that miR-219 and miR-200 have independent opposite effects on Scn5a expression modulation. Of all the microRNAs studied, only miR-219 increases Scn5a expression levels, leading to altered contraction rhythm of HL-1 cardiomyocytes. Electrophysiological analyses in HL-1 cells revealed that miR-219 increases the sodium current. In vivo administration of miR-219 does not alter normal cardiac rhythm, but abolishes some of the effects of flecainide intoxication in mice, particularly QRS prolongation. CONCLUSION This study demonstrates the involvement of multiple microRNAs in the regulation of Scn5a. Particularly, miR-219 increases Scn5a/Nav1.5 transcript and protein expression. Our data suggest that microRNAs, such as miR-219, constitute a promising therapeutical tool to treat sodium cardiac arrhythmias.

Xmn I polymorphism associated with concomitant activation of Gγ and Aγ globin gene transcription on a β0-thalassemia chromosome

The -158 (C→T) nucleotide change, known as Xmn I polymorphism, occurs in (G)γ-globin gene promoter, and results in elevated fetal hemoglobin (HbF). We found this mutation in cis of a β(0)-thalassemia splicing mutation. Despite the complete absence of adult HbA, the phenotype was only moderately severe with no detectable alteration of α-globin gene expression. Interestingly, the β-globin locus haplotype has not been described to bear the (G)γ promoter mutation. Using a gene-specific real-time RT-PCR approach, we found a dramatic increase of both (G)γ and (A)γ mRNA accumulated in the reticulocytes, suggesting that the (G)γ-promoter mutation, alone or in association with another genetic modification, alters in concert the transcription of both (G)γ and (A)γ. This observation is discussed in light of recent regulatory model for β-globin locus.

Cryptic splicing sites are differentially utilized in vivo.

It has long been considered that cryptic splice sites are ignored by the splicing machinery in the context of intact genuine splice sites. In the present study, it is shown that cryptic splice sites are utilized in all circumstances, when the authentic site is intact, partially functional or completely abolished. Their use would therefore contribute to a background lack of fidelity in the context of the wild‐type sequence. We also found that a mutation at the 5′ splice site of β‐globin intron 1 accomodates multiple cryptic splicing pathways, including three previously reported pathways. Focusing on the two major cryptic 5′ splice sites within β‐globin exon 1, we show that cryptic splice site selection ex vivo varies depending upon: (a) the cell stage of development during terminal erythroid differentiation; (b) the nature of the mutation at the authentic 5′ splice site; and (c) the nature of the promoter. Finally, we found that the two major cryptic 5′ splice sites are utilized with differential efficiencies in two siblings sharing the same β‐globin chromosome haplotype in the homozygous state. Collectively, these data suggest that intrinsic, sequence specific factors and cell genetic background factors both contribute to promote a subtle differential use of cryptic splice sites in vivo.

Combined Analysis of EPHX1, GSTP1, GSTM1 and GSTT1 Gene Polymorphisms in Relation to Chronic Obstructive Pulmonary Disease Risk and Lung Function Impairment

Smoking is considered as the major causal factor of chronic obstructive pulmonary disease (COPD). Nevertheless, a minority of chronic heavy cigarette smokers develops COPD. This suggests important contribution of other factors such as genetic predisposing. Our objective was to investigate combined role of EPHX1, GSTP1, M1 and T1 gene polymorphisms in COPD risk, its phenotypes and lung function impairment. Prevalence of EPHX1, GSTP1, M1 and T1 gene polymorphisms were assessed in 234 COPD patients and 182 healthy controls from Tunisia. Genotypes of EPHX1 (Tyr113His; His139Arg) and GSTP1 (Ile105Val; Ala114Val) polymorphisms were performed by PCR-RFLP, while the deletion in GSTM1 and GSTT1 genes was determined using multiplex PCR. Analysis of combinations showed a significant association of 113His/His EPHX1/null-GSTM1 (OR = 4.07) and null-GSTM1/105Val/Val GSTP1 (OR = 3.56) genotypes with increased risk of COPD (respectively P=0.0094 and P=0.0153). The null-GSTM1/ null-GSTT1, 105Val/Val GSTP1/null GSTT1, 113His/His EPHX1/null-GSTM1 and null-GSTM1/105Val/Val GSTP1 genotypes were related to emphysema (respectively P = 0.01; P = 0.009; P = 0.008 and P = 0.001). Combination of 113His/His EPHX1/null-GSTM1 genotypes showed a significant association with the decrease of ΔFEV1 in patients (P = 0.028). In conclusion, our results suggest combined EPHX1, GSTP1, GSTM1 and GSTT1 genetic polymorphisms may play a significant role in the development of COPD, emphysema and decline of the lung function.

Alpha-1 antitrypsin gene polymorphism in Chronic Obstructive Pulmonary Disease (COPD)

Alpha-1-antitrypsin (AAT) plays an important role in the pathogenesis of emphysema, the pathological lesion underlying the majority of the manifestations of Chronic Obstructive Pulmonary Disease (COPD). In this study we tested the hypothesis that common AAT polymorphisms influence the risk of developing COPDs. We investigated PiM1 (Ala213Val), PiM2 (Arg101His), PiM3 (Glu376Asp), PiS (Glu264Val) and PiZ (Glu342Lys) SERPINA1 alleles in 100 COPD patients and 200 healthy controls. No significant differences were observed in allele frequencies between COPD patients and controls, neither did haplotype analysis show significant differences between the two groups. A cross-sectional study revealed no significant relationship between common SERPINA1 polymorphisms (PiM1, PiM2, PiM3) and the emphysematous type of COPD. In addition, FEV1 annual decline, determined during a two-year follow up period, revealed no difference among carriers of the tested polymorphisms.