Unraveling a new player in multiple sclerosis pathogenesis: The RNA-binding protein HuR.

BACKGROUND: ELAV-like proteins are a small family of RNA-binding proteins that are fundamental players in post-transcriptional mechanisms and are involved in the pathogenesis of neurologic and psychiatric disorders. HuR, the ubiquitously expressed member of the family, is also implicated in sustaining inflammation and inflammatory diseases, supporting the production of pro-inflammatory cytokines. Inflammation plays a central role in Multiple Sclerosis (MS), which represents the most common cause of permanent physical disability in young adults. MS is a chronic autoimmune disease affecting the Central Nervous System, with a complex aetiology involving genetic, environmental and epigenetic factors. No data are available on the potential entanglement of HuR in MS pathogenesis in patients. In the present work, we aimed at exploring HuR protein levels in peripheral blood mononuclear cells (PBMCs) from MS patients, compared to healthy controls. To further elucidate the possible involvement of HuR in MS, we also investigated the relationship between this specific RNA-binding protein and HSP70-2 protein, also considering the HSP70-2 rs1061581 polymorphism, given that HSP70-2 mRNA has been reported as a HuR target and this specific polymorphism to be associated with MS risk. METHODS: Alleles and genotypes for HSP70-2 rs1061581 polymorphism were assessed, by using a Polymerase Chain Reaction-Restriction Fragment Length Polymorphism, followed by digestion with restriction enzyme, in MS patients and healthy controls. PBMCs from a subgroup of patients and controls were used to evaluate HuR and HSP70-2 protein content by Western blot. RESULTS: PBMCs from 52 MS patients had a lower HuR and higher HSP70-2 protein content compared to 43 healthy controls. An increase of 100 units of HuR significantly decreased the risk of developing MS by 9.8% (OR: 0.902, 95% CI: 0.83-0.98), controlling for HSP70-2 protein expression, HSP70-2 rs1061581 genotype, age and sex. Moreover, holding HuR levels, an increase of 100 units of HSP70-2 protein significantly increased the MS risk by 18.1% (OR: 1.181, 95% CI: 1.03-1.36) and the genetic susceptibility of developing MS for HSP70-2 rs1061581 GG carriers is confirmed. Of interest, MS patients with a moderate to severe form of MS (MSSS ≥ 3) showed a trend towards a reduction of HuR protein levels compared to patients with mild disease severity (MSSS < 3). CONCLUSIONS: HuR protein levels are reduced in MS patients compared to healthy subjects, and the protein amount may continue to decline with disease progression, suggesting a putative role of this RNA-binding protein. Moreover, our results suggest that MS pathology may have disrupted the link between HuR and its target transcript HSP70-2. It will be important to further explore the exact role of HuR in MS, considering the complex interplay with other RNA-binding factors and target mRNAs.

The Possible Involvement of HLA Class III Haplotype (RAGE, HSP70 and TNF Genes) in Alzheimer's Disease.

In the central nervous system Hsp70s seems to have a protective role in repair and removal of cellular proteins damaged by stress conditions. A protective role of Hsp70 was also shown in Alzheimer Disease. The HSP70-1 +190 G/C polymorphism is located in the gene 5'UTR region and it is implicated in alteration of the transcription binding factor; HSP70-2 +1267 A/G causes a silent mutation in the coding region and it seems to influence the mechanism of mRNA translation; HSP70-hom +2437 A/G causes a substitution Met → The (M493T) in the coding region and it seems to influence the bond with the substrate and therefore on the chaperone activity of hsp70. The aim of our study will be to investigate Alzheimer susceptibility to Hsp70 polymorphisms, taking into account our previous findings on HLA class III region, and to hypothesize a role of HLA class III haplotype configuration based on the variants of three genes: RAGE, HSP70 and TNF. We studied these polymorphisms with PCR-RFLP and PCR-TSP. We investigated 173 AD patients and 211 control subjects. Our results have shown a statistically significant decrease of the C allele frequency of the HSP70-1 +190 G/C polymorphism in AD patients vs controls (P value = 0,018), as well as the G allele of HSP70-2 +1267 G/A (p value = 0,02). We focalized our attention on haplotype reconstruction. We have observed a significant statistically decrease of GGT haplotype frequency (empirical p-value=0.0133 ); GAT haplotype was statistically significant increase in AD patients compared with control (empirical p-value=0.007). The total HLA class III haplotype are reconstructed. The causative haplotypes are the following ones: TTGATGGG ( p value =0,005; empirical p =0,0042); TTGATAGG (p value =0,45; empirical p =0,034). Patients with these haplotypes may show an earlier onset of the disease than patients with TTGGTGGG (p value=0,0138; empirical p =0,0102); TTCGTGGG (p value=0,021; empirical p =0,017); TTCGTGGA (p value =0,058; empirical p =0,043) haplotypes. The overall variation of the haplotypes formed by the RAGE and TNF and HSP70 variants influenced the presence of the AD phenotype (omnibus association LR test p-value 0.00185), HSP701 and HSP702 showed independent effect on AD risk after adjusting for the effect of the entire haplotype (conditional LR test p-value=0.0114 and p-value=0.0044 respectively). These data confirm the involvement of HLA class III in AD.

HLA class III genes involvement in Kawasaki disease: a case-control study in Caucasian population.

Kawasaki disease (KD) is an acute, multisystemic, febrile vasculitis of unknown aetiology, which affects young children mainly under 5 years of age. The clinical variability has until now prevented to decrypt KD aetiological factors. Recently, the importance of genetics and the pivotal role of the immune system have emerged. To investigate in this direction, genomic DNA from 74 Caucasian KD cases and 440 healthy controls has been analysed to characterize functional polymorphisms of relevant HLA class III genes: AGER -429 and -374, TNF -857, -308 and -238, HSPA1A +190, HSPA1B +1267 and HSPA1L +2437. Allele, genotype and haplotype frequencies were therefore compared with the chi-squared test and Fisher's exact test. Our data showed significant deviations between patients with Kawasaki disease and controls concerning the TNF -308 polymorphism genotype (GG: P = 0.0449) and allele (G,A: P = 0.0433) and -238 polymorphism genotype frequencies (AA: P = 0.0351). Moreover, we found differences concerning the HSPA1A +190 polymorphism (GC: P = 0.0317) and the HSPA1L +2437 polymorphism (TT: P = 0.0072; TC: P = 0.0250; T: P = 0.0037; C: P = 0.0037). The calculation of TNF -238 and HSPA1L haplotype frequencies also pointed out a statistically significant decrease in patients of CG haplotype (P = 0.0001), which could have a role in protecting from the inflammatory processes that characterize the disease progression. The results obtained point to a possible involvement of the entire HLA class III region in KD susceptibility.

The human leukocyte antigen class III haplotype approach: new insight in Alzheimer's disease inflammation hypothesis.

The Alzheimer's disease "inflammation hypothesis" has emerged only recently, suggesting the risk of developing AD might be influenced by variants of genes encoding for inflammatory mediators. In order to investigate in this direction, genomic DNA from 194 Italian AD cases and 454 healthy controls matched by gender and ethnicity was analyzed for the Receptor for Advanced Glycation End products (RAGE, HLA class III-centromere portion) -374 and - 429 SNPs and for the Tumor Necrosis Factor-alpha (TNF-α, HLA class III-telomere portion) -857, -308 and -238 SNPs by RFLP and Real Time PCR. Our data show statistically significant deviations between AD patients and healthy controls concerning RAGE -374 SNP genotype (TT: p=0.0084) and allele (T, A: p=0.0081) frequencies; TNF-α -308 SNP AA genotype (p=0.0433) and TNF-α -238 SNP genotype (GG: p=0.0138) and allele (G, A: p=0.0151) frequencies. Furthermore, significant differences between the study groups and regarding RAGE TC (p=0.05) and AC (p=0.009) haplotypes are present, while TNF-α haplotype reconstruction point out a statistically significant difference between patients and controls regarding AGG haplotype (p=0.002). Finally, from the combination of the individually significant SNPs of the two genes (RAGE -374, TNF-α -238 and -308) we performed an HLA class III haplotype reconstruction finding significant differences between AD subjects and controls regarding the TAG (p=0.019) and TGA (p=0.008) haplotypes. The implication of these haplotypes with the disease points to a possible involvement of entire HLA class III region in AD susceptibility.

APJ polymorphisms in coronary artery disease patients with and without hypertension.

Apelin is an endogenous peptide that increases cardiac inotropism through its APJ receptor. Certain findings indicate that the apelinergic system may have a pathophysiological role in cardiovascular disease and there is evidence showing the role of the apelinergic system in blood pressure regulation in vitro and in animal models. The role of the apelin-APJ system in cardiovascular physiology and its interaction with other neuroendocrine pathways has not been fully elucidated. However, the small number of reported studies indicates that apelin signaling may be involved in the regulation of blood pressure, cardiac contractile function, fluid balance, angiogenesis and inhibition of apoptosis. We evaluated the possible relationship between the G212A and A445C APJ polymorphisms and coronary artery disease (CAD) in Italian patients and in healthy controls by RFLP-PCR. We analyzed the allelic and genotypic frequencies of APJ polymorphisms in 664 patients (378 with hypertension) and 143 controls. There were no differences between allelic and genotypic frequencies in patients in respect to the controls for both polymorphisms analyzed. In the CAD population, there was an increased frequency of the G212 allele in patients with hypertension in respect to patients without hypertension. No differences were present in the two subgroups for the A445C polymorphism. Although the functional role of the G212A polymorphism has not yet been identified, it is possible to hypothesize that the presence of the A allele may cause a gain in function of the apelin/APJ system associated with a lower risk of hypertension.