A polymorphism in the CCL2 chemokine gene is associated with asthma risk: a case-control and a family study in Tunisia

Effect of Dermatophagoides pteronyssinus extract on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells of allergic asthma patients

PURPOSE

House dust mite allergy constitutes a risk factor for asthma development and is associated with a faster decline of lung function in allergic asthmatics (AAs). To evaluate the effect of Dermatophagoides pteronyssinus (Dp) allergens on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells (PBMCs) isolated from the blood of AAs.

MATERIALS AND METHODS

The cells from AAs, allergic rhinitis without asthma patients (ARs), and healthy controls (HCs) were cultured in the presence of Dp, lipopolysaccharide (LPS), or without any stimulation. The expression of 84 genes was evaluated using a low-density microarray whereas, the quantitative expression analysis of selected genes was performed using a real-time polymerase chain reaction. The concentration of selected proteins in the cell culture supernatants was assessed using ELISA.

RESULTS

Stimulation of PBMCs with Dp and LPS resulted in a significant upregulation of 8 and 15 among 84 studied genes, respectively. The greatest upregulation was observed for CCL2 and CCL3 using Dp and LPS, respectively. In comparison with HCs, in AAs, significantly increased upregulation of CCL2 in response to Dp was found. The secretion of CCL2 and CCL3 by PBMCs reflected the pattern of gene expression at the mRNA level. The mean Dp-stimulated secretion of CCL2 by PBMCs of ARs was less than in AAs (p ​< ​0.01), both being notably greater than in the HCs (p ​< ​0.01).

CONCLUSION

Rapid and potent upregulation of CCL2 expression by PBMCs in response to Dp may constitute an important contribution to the development of allergic asthma.

Causal relationship between humidifier disinfectant exposure and Th17-mediated airway inflammation and hyperresponsiveness

In this study, we investigated whether humidifier disinfectants (HDs) induce asthmatic airway inflammation in an animal model and compared the features of HD-induced inflammatory symptoms with ovalbumin (OVA)-induced allergic asthma. Mice were intratracheally instilled three times with either the control or 0.1, 0.3, or 0.5 mg/kg of polyhexamethylene guanidine phosphate (PHMG-P). To characterize asthmatic features, the following parameters were analyzed: (i) differential cell counts and cytokine expression in the bronchoalveolar lavage fluid (BALF); (ii) presence of mucus-producing goblet cells and pulmonary eosinophilic infiltration in the lungs; (iii) serum immunoglobulin levels; and (iv) airway hyperresponsiveness (AHR). RNA-Seq and bioinformatics tools were used to investigate whether PHMG-P altered asthma-related gene expression in lung tissues. The PHMG-P exposure groups showed higher peribronchial/perivascular inflammation, elevated goblet cell hyperplasia, and inhaled methacholine-induced airway resistance. Additionally, IL-13 and IL-17 in BALF were significantly increased in the PHMG-P exposure groups. However, there were no significant differences in total serum IgE and BALF IL-4 and IL-5 levels in the PHMG-P exposure groups compared to the control group. PHMG-P exposure modulated the expression of genes related to Th17 signaling pathways including the IL-17A, IL-23, and STAT3 signaling pathways, but not the Th2 signaling pathway. Altogether, our results suggest that repeated exposure to low does PHMG-P induces asthma-like symptoms and is thus a possible risk factor for developing asthma. The PHMG-P-induced asthmatic airway inflammation showed a different pattern from that found in typical allergic asthma and may be related to irritant-induced airway inflammation and hyperresponsiveness characterized by Th2-low, Th17-related, IgE-independent, and mixed granulocytic features.

Protective Effect of the MCP-1 Gene Haplotype against Schizophrenia

While cytokines and their genetic variants have been intensively studied in schizophrenia, little attention has been focused on chemokines in the last years. The monocyte chemoattractant protein 1 (MCP-1) is known to attract peripheral monocytes to the brain during an inflammatory reaction and to affect the T helper (Th) cell development by stimulating Th2 polarization. Owing to the neuroinflammation in schizophrenia and the variable level of MCP-1 in these patients' sera, we proposed to analyze the impact of functional genetic variants of the MCP-1 gene (MCP-1-2518A/G (rs1024611), MCP-1-362G/C (rs2857656), and MCP-1 int1del554-567 (rs3917887)) in schizophrenic patients. We conducted a case-control study on a Tunisian population composed of 200 patients and 200 controls using RFLP-PCR. Our results indicated that the minor alleles (-2518G and Del554-567) were significantly more prevalent in controls than in patients (P=0.001/adjusted OR = 0.42, P=0.04/adjusted OR = 0.64), whereas, for -362C minor allele, increased risk of schizophrenia was revealed (P=0.001, adjusted OR = 2.38). In conclusion, we have identified the haplotype combination -2581G/-362G/int1del554-567 that could mediate protection against schizophrenia (P=0.0038, OR = 0.19) and the effect could result more strongly from the MCP-1 -2582G with -362G variants, whereas the effect of int1del554-567 may in part be explained by its LD with -362.

Association between MCP-1 -2518A>G polymorphism and asthma susceptibility: a meta-analysis

The published data on the association between MCP-1 -2518A>G polymorphism and asthma susceptibility are inconclusive. Therefore, we performed a meta-analysis to estimate the impact of MCP-1 -2518A>G polymorphism on asthma susceptibility. PubMed, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) databases were used to identify eligible studies. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to calculate the strength of association. Sensitivity analysis was performed to evaluate the influence of individual studies on the estimates of overall effect, and funnel plots and Egger's test were used to assess publication bias. Eight publications with 1562 asthma patients and 1574 controls were finally identified. Overall, we found no significant association between MCP-1 -2518A>G polymorphism and asthma susceptibility in any of the genetic model comparisons. After stratified analysis by ethnicity, the results showed that a significant association with asthma risk was found in Caucasians in all the genetic models. However, a protective association was found in Africans under the dominant model. The present meta-analysis suggested that the MCP-1 -2518 A>G polymorphism is a risk factor for asthma in the Caucasian population, nevertheless it has a protective effect in the African population.

miR-511-3p protects against cockroach allergen-induced lung inflammation by antagonizing CCL2

miR-511-3p, encoded by CD206/Mrc1, was demonstrated to reduce allergic inflammation and promote alternative (M2) macrophage polarization. Here, we sought to elucidate the fundamental mechanism by which miR-511-3p attenuates allergic inflammation and promotes macrophage polarization. Compared with WT mice, the allergen-challenged Mrc1-/- mice showed increased airway hyperresponsiveness (AHR) and inflammation. However, this increased AHR and inflammation were significantly attenuated when these mice were pretransduced with adeno-associated virus-miR-511-3p (AAV-miR-511-3p). Gene expression profiling of macrophages identified Ccl2 as one of the major genes that was highly expressed in M2 macrophages but antagonized by miR-511-3p. The interaction between miR-511-3p and Ccl2 was confirmed by in silico analysis and mRNA-miR pulldown assay. Further evidence for the inhibition of Ccl2 by miR-511-3p was given by reduced levels of Ccl2 in supernatants of miR-511-3p-transduced macrophages and in bronchoalveolar lavage fluids of AAV-miR-511-3p-infected Mrc1-/- mice. Mechanistically, we demonstrated that Ccl2 promotes M1 macrophage polarization by activating RhoA signaling through Ccr2. The interaction between Ccr2 and RhoA was also supported by coimmunoprecipitation assay. Importantly, inhibition of RhoA signaling suppressed cockroach allergen-induced AHR and lung inflammation. These findings suggest a potentially novel mechanism by which miR-511-3p regulates allergic inflammation and macrophage polarization by targeting Ccl2 and its downstream Ccr2/RhoA axis.

Association of ICAM-1 (K469E) and MCP-1 -2518 A>G gene polymorphism with brain abscess

Brain abscess develops in response to a parenchymal infection. Intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) play vital role in central nervous system (CNS) diseases. We studied ICAM-1 (K469E) and MCP-1 (-2518 A>G) polymorphisms among brain abscess patients. The genotypic distributions of ICAM-1 (K469E) and MCP-1 (-2518 A>G) were significantly different between patients and controls. Further, patient with predisposing factors, and also with culture result, we found significant association. The study revealed that the polymorphisms of these molecules lead to increased production, which appears to be a risk for the development of brain abscess.

CCL2/CCR2-dependent recruitment of Th17 cells but not Tc17 cells to the lung in a murine asthma model

BACKGROUND

Interleukin (IL)-17 has been implicated in the pathogenesis of asthma and the progression of airway inflammation. Here, we used a model of allergic asthma and found that the frequencies of IL-17-secreting T helper (Th)17 and CD8 (Tc)17 cells were both significantly increased, as was the expression of the CC chemokine receptor (CCR2) on the surface of these cells. CC chemokine ligand 2 (CCL2) has been shown to mediate the activation and recruitment of inflammatory cells in asthma, which are also skewed after ovalbumin (OVA) challenge. However, the role of CCL2 on Th17 cells and Tc17 cells in asthma has not been illuminated.

METHODS

Mice that were sensitized and challenged with OVA received anti-CCL2 antibody (Ab; 5 μg/day intratracheally) or CCR2 antagonist (RS504393, 2 mg/kg/day intraperitoneally) prior to the challenge. Some mice received an isotype control Ab or vehicle alone. We then assessed the effects of allergic asthma and anti-CCL2 Ab or CCR2 antagonist treatment on the levels of IL-17 and CCL2, the Th17 and Tc17 cell frequencies and lung tissue inflammation.

RESULTS

We demonstrated that CCL2 and IL-17 levels and the frequency of Th17 and Tc17 cells in lung tissues and bronchoalveolar lavage fluid increased in the asthma group compared with the normal control mice. Blocking the CCL2/CCR2 axis greatly reduced the Th17 but not the Tc17 cell frequency, and revealed a suppressive effect on airway inflammation.

CONCLUSION

These findings indicate a role for the CCL2/CCR2 axis in mediating Th17 but not Tc17 cell migration during acute allergic airway inflammation.

IL-17A and IL-17F genes variants and susceptibility to childhood asthma in Tunisia

OBJECTIVES

IL-17A and IL-17F are new pro-inflammatory cytokines implicated in neutrophilic inflammation and thus, involved in the pathogenesis of asthma. We investigated the possible association among asthma and IL-17A -197G/A (rs2275913), IL-17F 7488A/G (rs763780) and IL-17F 7383A/G (rs2397084).

METHODS

The study was performed in 171 patients with asthma (mean age 9.5 years, 105 boys, and 66 girls) and 171 healthy individuals matched with patients in age and sex. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to detect genes' polymorphisms.

RESULTS

IL-17A -197G/A and IL-17F 7383A/G were associated with asthma in children (p = 0.008, p = 0.001, respectively). No association was found with IL-17F 7488A/G polymorphism. Haplotype analysis revealed a significant association between GA and AG haplotypes and asthma (p = 0.004, p = 0.02). When patients were stratified according to the atopic status, no significant association was detected with any of the three studied variants.

CONCLUSION

Our results suggested that SNPs in IL-17A and IL-17F confer susceptibility to childhood asthma in Tunisia.

The rs1024611 regulatory region polymorphism is associated with CCL2 allelic expression imbalance

CC chemokine ligand 2 (CCL2) is the most potent monocyte chemoattractant and inter-individual differences in its expression level have been associated with genetic variants mapping to the cis-regulatory regions of the gene. An A to G polymorphism in the CCL2 enhancer region at position -2578 (rs1024611; A>G), was found in most studies to be associated with higher serum CCL2 levels and increased susceptibility to a variety of diseases such as HIV-1 associated neurological disorders, tuberculosis, and atherosclerosis. However, the precise mechanism by which rs1024611influences CCL2 expression is not known. To address this knowledge gap, we tested the hypothesis that rs1024611G polymorphism is associated with allelic expression imbalance (AEI) of CCL2. We used haplotype analysis and identified a transcribed SNP in the 3'UTR (rs13900; C>T) can serve as a proxy for the rs1024611 and demonstrated that the rs1024611G allele displayed a perfect linkage disequilibrium with rs13900T allele. Allele-specific transcript quantification in lipopolysaccharide treated PBMCs obtained from heterozygous donors showed that rs13900T allele were expressed at higher levels when compared to rs13900C allele in all the donors examined suggesting that CCL2 is subjected to AEI and that that the allele containing rs1024611G is preferentially transcribed. We also found that AEI of CCL2 is a stable trait and could be detected in newly synthesized RNA. In contrast to these in vivo findings, in vitro assays with haplotype-specific reporter constructs indicated that the haplotype bearing rs1024611G had a lower or similar transcriptional activity when compared to the haplotype containing rs1024611A. This discordance between the in vivo and in vitro expression studies suggests that the CCL2 regulatory region polymorphisms may be functioning in a complex and context-dependent manner. In summary, our studies provide strong functional evidence and a rational explanation for the phenotypic effects of the CCL2 rs1024611G allele.

Expression analysis of asthma candidate genes during human and murine lung development

BACKGROUND

Little is known about the role of most asthma susceptibility genes during human lung development. Genetic determinants for normal lung development are not only important early in life, but also for later lung function.

OBJECTIVE

To investigate the role of expression patterns of well-defined asthma susceptibility genes during human and murine lung development. We hypothesized that genes influencing normal airways development would be over-represented by genes associated with asthma.

METHODS

Asthma genes were first identified via comprehensive search of the current literature. Next, we analyzed their expression patterns in the developing human lung during the pseudoglandular (gestational age, 7-16 weeks) and canalicular (17-26 weeks) stages of development, and in the complete developing lung time series of 3 mouse strains: A/J, SW, C57BL6.

RESULTS

In total, 96 genes with association to asthma in at least two human populations were identified in the literature. Overall, there was no significant over-representation of the asthma genes among genes differentially expressed during lung development, although trends were seen in the human (Odds ratio, OR 1.22, confidence interval, CI 0.90-1.62) and C57BL6 mouse (OR 1.41, CI 0.92-2.11) data. However, differential expression of some asthma genes was consistent in both developing human and murine lung, e.g. NOD1, EDN1, CCL5, RORA and HLA-G. Among the asthma genes identified in genome wide association studies, ROBO1, RORA, HLA-DQB1, IL2RB and PDE10A were differentially expressed during human lung development.

CONCLUSIONS

Our data provide insight about the role of asthma susceptibility genes during lung development and suggest common mechanisms underlying lung morphogenesis and pathogenesis of respiratory diseases.

The source matters: no impact of the CCL2/MCP-1-1-2518G polymorphism of the donor on renal allograft outcome during the first year after transplantation

Chemokines are involved in the recruitment of inflammatory cells to vascularized allografts. The chemokine CCL2/MCP-1 is expressed during allograft dysfunction, which is associated with the recruitment of inflammatory cells. Both intrinsic renal cells (donor origin) as well as infiltrating inflammatory cells (recipient origin) can be a source of CCL2/MCP-1. We previously demonstrated that the recipient MCP-1-2518G polymorphism is associated with increased CCL2/MCP-1 production by inflammatory cells and decreased renal allograft survival. We evaluated the impact of the MCP-1-2518G polymorphism in donor cells on renal allograft outcomes. We enrolled 252 recipients of kidney allografts in this retrospective study who had received grafts from 152 cadaveric donors. The CCL2/MCP-1 genotype was assessed using genomic DNA isolated from cryopreserved donor splenocytes. Outcome parameters studied were acute biopsy proven rejection (Banff criteria), serum creatinine, and glomerular filtration rate (GFR) at 1 year after transplantation, allograft loss, and death. MCP-1-2518 genotypes were in HW equilibrium. A/A was present in 125 (49.6%), A/G in 107 (42.5%), and G/G in 20 (7.9%) donor kidneys. There were no significant differences in the number of rejection episodes, the number of allograft losses, serum creatinine, GFR, or overall survival 1 year after transplantation. In contrast with the detrimental effect of the CCL2/MCP-1 polymorphism of the recipient, the CCL2/MCP-1 polymorphism of the donor has no impact on the allograft outcome during the first year after transplantation. The impact on the long-term outcomes needs further evaluation.