Current advances in the human lupus genetics

The interplay between p66Shc, reactive oxygen species and cancer cell metabolism

The adaptor protein p66Shc links membrane receptors to intracellular signalling pathways and has the potential to respond to energy status changes and regulate mitogenic signalling. Initially reported to mediate growth signals in normal and cancer cells, p66Shc has also been recognized as a pro-apoptotic protein involved in the cellular response to oxidative stress. Moreover, it is a key element in processes such as cancer cell proliferation, tumor progression, metastasis and metabolic reprogramming. Recent findings on the role of p66Shc in the above-mentioned processes have been obtained through the use of various tumor cell types, including prostate, breast, ovarian, lung, colon, skin and thyroid cancer cells. Interestingly, the impact of p66Shc on the proliferation rate was mainly observed in prostate tumors, while its impact on metastasis was mainly found in breast cancers. In this review, we summarize the current knowledge about the possible roles of p66Shc in different cancers.

Investigating the role of angiogenesis in systemic lupus erythematosus

OBJECTIVE

We aimed to elucidate the roles of six pro-angiogenic factors, namely, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), placental growth factor (PlGF), hepatocyte growth factor (HGF), transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha), in the pathogenesis of systemic lupus erythematosus (SLE).

METHODS

A group of 75 patients with SLE and a control group of 40 healthy volunteers were recruited. Angiogenic factors were tested through enzyme-linked immunosorbent assay (ELISA) measurement. The angiogenic activities of the patients with SLE and the healthy controls were assessed and a correlation analysis of these angiogenic factors was conducted.

RESULTS

A much higher level of angiogenic activity was shown in the serum of patients with SLE than that of the healthy controls, yet no statistically significant difference was found in the angiogenic activities of active SLE and inactive SLE. Serum VEGF level in the active SLE group was significantly higher than that in the control group and the inactive SLE group, and serum HGF level was strongly positively correlated with VEGF in all SLE groups; meanwhile, there was also a statistically significant positive correlation between TNF-alpha and VEGF in all SLE groups. There was a statistically significant positive correlation between serum VEGF level and bFGF level in the active SLE group. There was a slightly negative correlation between serum HGF level and TGF-beta level in the SLE group, but this negativity did not reach the significance level. Likewise, positive correlation was also shown in the serum VEGF level and PlGF level, yet not in bFGF with PlGF.

CONCLUSION

Circulating serum angiogenic cytokines may be disease markers of SLE activity. Anti-angiogenic agents such as thalidomide and endogenous angiogenesis inhibitors such as endostatin are potentially effective and promising therapies in the treatment of SLE.

CCR5-Delta32: implications in SLE development

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease with strong genetic and environmental components. Previous studies have shown increased levels of several chemokines in active SLE. C-C chemokine receptor type 5 (CCR5) is involved in the recruitment of inflammatory cells into tissues, and mechanisms modulating CCR5 expression and function may interfere in SLE development, influencing the clinical course of the disease. The aim of this study was to evaluate the possible association between the CCR5∆32 base-pair deletion polymorphism and SLE disease in a group of Portuguese patients. A total of 219 patients with SLE and 205 healthy individuals were studied. The frequency of CCR5/∆32 heterozygotes was lower in patients with SLE than in controls (8% vs. 15% OR = 0.5162; P = 0.0319), suggesting a protective association between CCR5∆32 allele and SLE. These results highlight the protective role of Th1 cells that express CCR5 in SLE pathogenesis.

The association of single nucleotide polymorphism within vascular endothelial growth factor gene with systemic lupus erythematosus and lupus nephritis

There were no statistically significant difference in allele and genotype frequency of the polymorphisms within the vascular endothelial growth factor (VEGF) gene (-460 and +405) between 193 systemic lupus erythematosus patients and 234 healthy controls. However, the +405 GG was significantly associated with lupus nephritis (LN) patients with low VEGF mRNA expression and LN with end-stage renal disease.

Single-nucleotide polymorphisms and haplotype of CYP2E1 gene associated with systemic lupus erythematosus in Chinese population

Introduction

Cytochrome P-450 2E1 (CYP2E1) is an important member of the CYP superfamily, which is involved in the metabolism and activation of many low molecular weight toxic compounds. We tried to investigate the possible association of CYP2E1 tag single nucleotide polymorphisms (SNPs) with susceptibility to systemic lupus erythematosus (SLE) in a Chinese Han population.

Methods

The coding and flanking regions of the CYP2E1 gene were scanned for polymorphisms and tag SNPs were selected. A two-stage case-control study was performed to genotype a total of 876 SLE patients and 680 geographically matched healthy controls (265 cases and 288 controls in stage I and 611 cases and 392 controls in stage II). SLE associations of alleles, genotypes and haplotypes were tested by age and sex adjusted logistic regression. The gene transcription quantitation was carried out for peripheral blood mononuclear cell (PBMC) samples from 120 healthy controls.

Results

Tag SNP rs2480256 was found significantly associated with SLE in both stages of the study. The "A" allele was associated with slightly higher risk (odds ratio (OR) = 1.165, 95% confidence interval (CI) 1.073 to 1.265, P = 2.75E-4) and "A/A" genotype carriers were with even higher SLE risk (OR = 1.464 95% CI 1.259 to 1.702, P = 7.48E-7). When combined with another tag SNP rs8192772, we identified haplotype "rs8192772-rs2480256/TA" over presented in SLE patients (OR 1.407, 95% CI 1.182 to 1.675, P = 0.0001) and haplotype "TG" over presented in the controls (OR 0.771, 95% CI 0.667 to 0.890, P = 0.0004). The gene transcription quantitation analysis further proved the dominant effect of rs2480256 as the "A/A" genotype showed highest transcription.

Conclusions

Our results suggest the involvement of CYP2E1 as a susceptibility gene for SLE in the Chinese population.

Expression and function of the P2X(7) purinergic receptor in patients with systemic lupus erythematosus and rheumatoid arthritis

Because the synthesis of pro-inflammatory cytokines and apoptosis of lymphoid cells can be induced through P2X(7), we decided to study its expression, function (apoptosis, shedding of CD62L and synthesis of IL-1beta induced by ATP) and genetic polymorphisms (1513 AC and -762 T/C) in peripheral blood mononuclear cells from 101 patients with systemic lupus erythematosus (SLE), 122 with rheumatoid arthritis (RA) and 90 healthy controls. We found no significant differences in the distribution of 1513 and -762 genotypes of P2X(7) gene in SLE or RA patients compared with healthy controls. However, a diminished induction of apoptosis of CD4(+) T lymphocytes and monocytes was observed in SLE patients with the 1513 AC genotype, and the release of IL-1beta upon stimulation with ATP was significantly decreased in SLE patients. In contrast, in RA patients we detected that the release of IL-1beta was increased. In addition, in patients with SLE and RA the SNPs 1513 AC was associated with a low expression of P2X(7). These results suggest a possible involvement of P2X(7) in the pathogenesis of inflammatory autoimmune diseases.

FcRL3 gene promoter variant is associated with peripheral arthritis in Crohn's disease

BACKGROUND

The mechanisms responsible for the pathogenesis of peripheral arthropathies (PA) in Crohn's disease (CD) are largely unknown, although many studies indicate that genetic and environmental factors are likely to contribute to risk.

METHODS

Because variants in the Fc receptor-like 3 (FcRL3) gene have recently been associated with rheumatoid arthritis and several other autoimmune diseases, we tested 2 FcRL3 promoter variants (-169 C>T and -110 G>A) for association with PA in Spanish CD patients that were recruited from a single center and followed for at least 4 years (mean follow-up time, 11 years).

RESULTS

Among the 342 CD patients evaluated, there were 88 cases of peripheral arthropathy; 31 were classified as arthritis and 57 were classified as arthralgia. We used contingency tables and logistic regression to test for association between PA or either subtype and FcRL3 and other factors that have previously been associated with extraintestinal manifestations in CD.

CONCLUSIONS

We found that female sex, colonic involvement, and the AA genotype at -110 G>A were associated with increased risk of both subtypes of PA, although the association appears to be stronger for arthritis than for arthralgia.

DcR3 as a diagnostic parameter and risk factor for systemic lupus erythematosus

In this study, we investigated the diagnostic value of serum death decoy receptor 3 (DcR3) for systemic lupus erythematosus (SLE). The possible pathogenic role of DcR3 in SLE was also assessed. Serum DcR3 levels of 90 SLE patients, 11 patients with rheumatic conditions and 123 healthy controls were determined by ELISA. In all, 43% of the SLE patients, 9% of patients with rheumatic conditions and 2.4% of the normal healthy individuals presented elevated serum DcR3 levels. A higher percentage of DcR3-positive SLE patients, compared with DcR3-negative SLE patients, showed abnormally high serum IgE levels, a surrogate marker of T(h)2-type immune responses. To determine the cause and effect relationship of DcR3 expression and a T(h)2-prone status, we studied young DcR3 transgenic (Tg) mice, whose transgene was driven by an actin promoter. These mice had IL-4 overproduction and augmented serum IgE levels, signs of dominant T(h)2 immune responses. To determine possible SLE pathogenic roles of DcR3, the T-cell-depleted bone marrow of DcR3 Tg mice was transplanted into lethally irradiated syngeneic C57BL/6 female mice. The recipients developed an SLE-like syndrome. They presented anti-dsDNA and anti-nuclear antibodies, along with renal and liver pathology compatible with that of SLE. In total, 90% of Tg bone marrow-transplanted mice, compared with 20% of wild-type bone marrow-transplanted mice, perished within 12 months after the transplantation. Our results showed that serum DcR3 could serve as an additional parameter for SLE diagnosis and that DcR3 secreted from cells of hematopoietic origin was SLE pathogenic in mice.

The proapoptotic and antimitogenic protein p66SHC acts as a negative regulator of lymphocyte activation and autoimmunity

The ShcA locus encodes 3 protein isoforms that differ in tissue specificity, subcellular localization, and function. Among these, p66Shc inhibits TCR coupling to the Ras/MAPK pathway and primes T cells to undergo apoptotic death. We have investigated the outcome of p66Shc deficiency on lymphocyte development and homeostasis. We show that p66Shc−/− mice develop an age-related lupus-like autoimmune disease characterized by spontaneous peripheral T- and B-cell activation and proliferation, autoantibody production, and immune complex deposition in kidney and skin, resulting in autoimmune glomerulonephritis and alopecia. p66Shc−/− lymphocytes display enhanced proliferation in response to antigen receptor engagement in vitro and more robust immune responses both to vaccination and to allergen sensitization in vivo. The data identify p66Shc as a negative regulator of lymphocyte activation and show that loss of this protein results in breaking of immunologic tolerance and development of systemic autoimmunity.

The synergistic effect of FC gamma receptor IIa and interleukin-10 genes on the risk to develop systemic lupus erythematosus in Thai population

Several linkage analyses have consistently shown that systemic lupus erythematosus (SLE) susceptible genes are located on chromosome 1q21-44. In this study, two major candidate genes, interleukin-10 (IL-10) and Fc gamma receptor IIa (FcgammaRIIa), within these regions were investigated in Thai SLE patients. The genotyping of three single-nucleotide polymorphisms (promoter area: -1082, -819 and -592) within IL-10 gene and one polymorphism (change amino acid at position 131) within FcgammaRIIa gene was determined in 195 SLE patients and 159 ethnically matched controls. The RR/RH genotypes of FcgammaRIIa were found to be significantly increased in SLE patients compared with healthy controls [OR = 2.01, 95% confidence interval (CI) = 1.28-3.14, P= 0.001]. Interestingly, the synergistic effect between RR/RH genotypes of FcgammaRIIa and ACC/ACC haplotype of IL-10 in susceptibility to SLE was observed (OR = 7.84, 95% CI = 1.60-52.04, P= 0.002). In addition, the FcgammaRIIa, RR homozygotes was also strongly associated with anticardiolipin antibody production (OR = 6.09, 95% CI = 1.38-30.54, P= 0.006). The result demonstrated that ACC haplotype of IL-10 gene and FcgammaRIIa R131 polymorphism can be used as marker for genetic susceptibility and severity to SLE in Thai population, particularly individuals carrying both specific genotypes.

Physiopathologie du lupus érythémateux systémique

Innate immunity is directly implicated in the pathophysiology of lupus through the dendritic cell system and the activation by immune complexes of some toll-like receptors (TLR). Interferon-alpha plays a key role in the pathophysiology of lupus and represents a promising target for immune therapy. Dendritic cells are activated and able to capture large quantities of nuclear antigen-containing bodies to stimulate specific adaptive immune response.

Association of a common complement receptor 2 haplotype with increased risk of systemic lupus erythematosus

A genomic region on distal mouse chromosome 1 and its syntenic human counterpart 1q23-42 show strong evidence of harboring lupus susceptibility genes. We found evidence of linkage at 1q32.2 in a targeted genome scan of 1q21-43 in 126 lupus multiplex families containing 151 affected sibpairs (nonparametric linkage score 2.52, P = 0.006). A positional candidate gene at 1q32.2, complement receptor 2 (CR2), is also a candidate in the murine Sle1c lupus susceptibility locus. To explore its role in human disease, we analyzed 1,416 individuals from 258 Caucasian and 142 Chinese lupus simplex families and demonstrated that a common three-single-nucleotide polymorphism CR2 haplotype (rs3813946, rs1048971, rs17615) was associated with lupus susceptibility (P = 0.00001) with a 1.54-fold increased risk for the development of disease. Single-nucleotide polymorphism 1 (rs3813946), located in the 5' untranslated region of the CR2 gene, altered transcriptional activity, suggesting a potential mechanism by which CR2 could contribute to the development of lupus. Our findings reveal that CR2 is a likely susceptibility gene for human lupus at 1q32.2, extending previous studies suggesting that CR2 participates in the pathogenesis of systemic lupus erythematosus.

Is FCRL3 a new general autoimmunity gene?

Autoimmunity is a multistep pathogenic process, which arises in genetically predisposing individuals as a result of the harmful influence of environmental factors causing the breakdown of immune tolerance and induction of self-reactive immune response. Recent findings resolved common pathogenic mechanisms shared between different autoimmune diseases and suggested for the existence of genetic loci that could be involved in general autoimmunity and hence contribute to susceptibility of several autoimmune diseases. To date, several loci responsible for general autoimmunity have been identified. The Fc receptor-like 3 (FCRL3) gene is one of those loci for which a significant association with a number of autoimmune diseases such as rheumatoid arthritis (RA), autoimmune thyroid disease, and systemic lupus erythematosus (SLE) has been recently shown in Japanese. However, studies in Caucasians failed to confirm a strong association of this gene with RA and SLE and therefore made questionable the putative role of FCRL3 in general autoimmunity. In this review, we discuss whether the FCRL3 gene is a newly discovered gene contributing to shared susceptibility between autoimmune diseases.

Systemic lupus erythematosus: multiple immunological phenotypes in a complex genetic disease

Systemic lupus erythematosus (SLE) is a complex polygenic autoimmune disease characterized by the presence of anti-nuclear autoantibodies (ANAs) that are often detectable years prior to the onset of clinical disease. The disease is associated with a chronic activation of the immune system, with the most severe forms progressing to inflammatory damage that can impact multiple organ systems in afflicted individuals. Current therapeutic strategies poorly control disease manifestations and are generally immunosuppressive. Recent studies in human patient populations and animal models have associated elements of the innate immune system and abnormalities in the immature B lymphocyte receptor repertoires with disease initiation. A variety of cytokines, most notably type I interferons, play important roles in disease pathogenesis and effector mechanisms. The genetic basis for disease susceptibility is complex, and analyses in humans and mice have identified multiple susceptibility loci, several of which are located in genomic regions that are syntenic between humans and mice. The complexities of the genetic interactions that mediate lupus have been investigated in murine model systems by characterizing the progressive development of disease in strains expressing various combinations of susceptibility alleles. These analyses indicate that genetic epistasis dramatically impact disease development and support the feasibility of identifying molecular pathways that can suppress disease progression without completely impairing normal immune function.

Current topics in human SLE genetics

Susceptibility to systemic lupus erythematosus (SLE) depends on genetic and environmental factors. Genome scan studies have identified eight chromosomal regions with significant linkage to SLE that are confirmed by individual cohorts, suggesting that susceptibility genes may be identified within each of these loci. Linkage studies and single nucleotide polymorphisms (SNPs) have led to the identification of positional candidate genes, and their functional allelic variants have demonstrated molecular pathogenesis of the disease. The discovery of positional candidate genes that are associated with various autoimmune diseases signifies a common pathway in the mechanism of these diseases. Copy polymorphisms in susceptibility genes provide evidence in how genetic plasticity affects complex phenotypes as seen in SLE.

Biomarkers for systemic lupus erythematosus: a review and perspective

PURPOSE OF REVIEW

Despite decades of extensive work in the understanding of the etiopathogenesis of systemic lupus erythematosus, few biomarkers have been validated and widely accepted for this disease. The lack of reliable, specific biomarkers not only hampers clinical management of systemic lupus erythematosus but also impedes development of new therapeutic agents. This paper reviews briefly the historical aspects of systemic lupus erythematosus biomarkers and summarizes recent studies on candidate biomarkers.

RECENT FINDINGS

Recognizing the urgent need for lupus biomarkers, a Lupus Biomarker Working Group has recently been initiated to facilitate collaborative efforts aimed at identifying and validating biomarkers for systemic lupus erythematosus. Based on available data, several laboratory markers have shown promise as biomarkers for susceptibility, diagnosis, and disease activity. These include Fc receptor genes (disease susceptibility), complement C4d-bound erythrocytes (diagnosis or disease activity), CD27 plasma cells (disease activity), 'interferon signature' (disease activity), and anti-C1q antibodies (disease activity and organ involvement).

SUMMARY

There is a longstanding and recently rejuvenated enthusiasm for biomarkers that precisely and specifically reflect the pathophysiologic and clinical changes in systemic lupus erythematosus. Promising candidate biomarkers have been identified but must still be validated through rigorous, large-scale multicenter studies.