Targeting Phospholipase D4 Attenuates Kidney Fibrosis

Multi-omics analysis reveals the protective effects of Chinese yam polysaccharide against cisplatin-induced renal interstitial fibrosis

BACKGROUND

Chinese yam polysaccharide (SYDT) has been reported to protect renal function and mitigate renal fibrosis in mice with diabetic nephropathy. Based on a multi-omics analysis, the objectives of this study were to determine the effect of SYDT on cisplatin (CDDP)-induced chronic renal interstitial fibrosis (RIF) and the underlying molecular mechanisms using an in vivo model.

METHODS

Rats were intraperitoneally injected with a single dose of CDDP and then treated with SYDT or amifostine (AMF). The levels of urinary N-acetyl-β-d-glucosaminidase (NAG), blood urea nitrogen (BUN) and serum creatinine (Scr) were detected to assess renal function. Renal tissue damage and fibrosis were evaluated using hematoxylin and eosin (H&E) and Masson's trichrome staining, respectively. In addition, this study applied transcriptomics and metabolomics to predict the possible mechanism of SYDT action, which was verified by several relevant examinations.

RESULTS

SYDT significantly protected the renal function, alleviated renal tissue damage and fibrosis, as well as decreased the protein levels of vimentin, α-SMA and CTGF, whereas SYDT significantly increased MMP-1 protein level in renal tissues from rats treated with CDDP. There were 1130 differently expressed genes (DEGs) between the CDDP model and SYDT-M groups proved by transcriptome analysis, indicating that metabolic pathways were likely the primary targets of relevance. Consistent with the transcriptome analysis, metabolome analysis identified 276 differentially expressed metabolites (DEMs) between the SYDT-M and CDDP model groups, with predominant clustering within glycerophospholipid metabolism. Integrative analysis of the transcriptome and metabolome indicated that SYDT inhibited the glycerophospholipid metabolism pathway by regulating the target genes Gpd2, Gpam, Agpat3, Lcat, and Pla2g4b. Notably, integrative analysis showed that the Phospholipase D (PLD) signaling pathway may be the most relevant target. Moreover, related signaling pathway analysis confirmed that SYDT inhibited CDDP-induced RIF in rats by down-regulating the PLD pathway.

CONCLUSION

Our study showed that the alleviation of CDDP-induced RIF in vivo can be achieved through the inhibition of glycerophospholipid metabolism and PLD signaling pathways by SYDT.

Phospholipase D Family Member 4 Regulates Microglial Phagocytosis and Remyelination via the AKT Pathway in a Cuprizone-Induced Multiple Sclerosis Mouse Model

AIMS

Remyelination is an endogenous repair process that is often deficient in multiple sclerosis (MS). Stimulation of remyelination is thought to help limit the progression of MS. This study aimed to investigate the expression pattern and function of a microglial phagocytosis-related gene, phospholipase D family member 4 (PLD4), in a cuprizone (CPZ)-induced MS mouse model.

METHODS

The extent of remyelination was assessed using LFB staining. Myelin phagocytosis assay was used to investigate the effect of Pld4 on microglial phagocytic activity.

RESULTS

Pld4 was upregulated in the corpus callosum during demyelination and remyelination. AAV9-mediated Pld4 deficiency impaired remyelination and reduced the number of Olig2-positive cells. In the corpus callosum of Pld4-deficient mice, the microglial phagocytosis marker MAC2 was reduced, accompanied by inhibition of TrkA/AKT signaling. Similarly, the phagocytosis assay showed that Pld4 knockdown significantly inhibited myelin debris phagocytosis by BV2 cells. The AKT activator SC79 reversed the Pld4 deficiency-induced inhibition of microglial phagocytic activity and rescued the impaired remyelination in Pld4-deficient mice.

CONCLUSION

PLD4 is upregulated in CPZ-induced MS and modulates microglial phagocytosis and remyelination via the AKT pathway. Our findings provide experimental evidence for a better understanding of the molecular mechanism of MS.

Abdominal obesity and CKD: A potential mediating role of serum metabolites in the UK Biobank population

BACKGROUND

It is generally known that although a connection between abdominal obesity and chronic kidney disease (CKD) is well-established, there is a lack of systematic research investigating the specific roles of serum metabolites, including lipid metabolites, amino acid metabolites, carbohydrate metabolites and inflammatory substances in explaining this associations.

METHODS

We included 118,020 general patients with data of serum metabolites from UK Biobank. We defined abdominal obesity and CKD based on waist circumference and ICD-10 criteria. The serum metabolites were assessed by a high-throughput nuclear magnetic resonance (NMR) based metabolic biomarker profiling platform. We conducted mediation analysis by R software and used the proportion of mediation to quantify the mediation effect.

RESULTS

This study demonstrated that lipid metabolites played a more important role in mediating the relationship between abdominal obesity and CKD than amino acid metabolites and carbohydrate metabolites. And Glycoprotein Acetyls (GlycA) was the strongest mediator for the correlation between abdominal obesity and CKD, accounting for 26.4 %. And In the mediation analysis stratified by sex, we found that the mediating effects of lipid metabolites were mostly higher in men than in women, while GlycA accounted for the largest proportion of the mediation association in both two groups (31.0 % for women and 19.8 % for men).

CONCLUSION

Among lipid metabolites, amino acid metabolites, carbohydrate metabolites and inflammatory substances, our study showed that infammation marker GlycA was the novel and key mediator for the correlation between abdominal obesity and CKD.

Mechanism of Chaihuang-Yishen formula to attenuate renal fibrosis in the treatment of chronic kidney disease: Insights from network pharmacology and experimental validation

Renal fibrosis represents a pivotal characteristic of chronic kidney disease (CKD), for which effective interventions are currently lacking. The Src kinase activates the phosphatidylinositol-3 kinases (PI3K)/Akt1 pathway to promote renal fibrosis, casting a promising target for anti-fibrosis treatment. Chaihuang-Yishen formula (CHYS), a traditional Chinese medicinal prescription, has a validated efficacy in the treatment of CKD, however, with the underlying mechanism unresolved. This study aimed to uncover the pharmacological mechanisms mediating the effect of CHYS in treating renal fibrosis using network pharmacology followed by experimental validation. The chemical compounds of CHYS were retrieved from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database or published literature, followed by the prediction of their targets using SwissTargetPrediction software. Disease (CKD/renal fibrosis)-related targets were retrieved from the Genecards database. Protein-protein interaction (PPI) network was generated using the drug-disease common targets and visualized in Cytoscape software. The drug-disease targets were further subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses by Metascape software. Additionally, the compound-target-pathway network was established in Cytosape to identify key compounds, targets, and pathways. Network pharmacology analysis screened out 96 active compounds and 837 potential targets within the 7 herbal/animal medicines of CHYS, among which 237 drug-disease common targets were identified. GO and KEGG analysis revealed the enrichment of fibrosis-related biological processes and pathways among the 237 common targets. Compound-target-pathway network analysis highlighted protein kinases Src and Akt1 as the top two targets associated with the anti-renal fibrosis effects of CHYS. In UUO mice, treatment with CHYS attenuates renal fibrosis, accompanied by suppressed expression and phosphorylation activation of Src. Unlike Src, CHYS reduced Akt1 phosphorylation without affecting its expression. In summary, network pharmacology and in vivo evidence suggest that CHYS exerts its anti-renal fibrosis effects, at least in part, by inhibiting the Src/Akt1 signaling axis.

Discovery of PLD4 modulators by high-throughput screening and kinetic analysis

Phospholipase D3 (PLD3) and D4 (PLD4) are endolysosomal exonucleases of ssDNA and ssRNA that regulate innate immunity. Polymorphisms of these enzymes are correlated with numerous human diseases, including Alzheimer's, rheumatoid arthritis, and systemic sclerosis. Pharmacological modulation of these immunoregulatory proteins may yield novel immunotherapies and adjuvants. A previous study reported a high-throughput screen (N = 17,952) that discovered a PLD3-selective activator and inhibitor, as well as a nonselective inhibitor, but failed to identify selective modulators of PLD4. However, modulators selective for PLD4 are therapeutically pertinent, since recent reports have shown that regulating this protein has direct implications in cancer and autoimmune diseases. Furthermore, the high expression of PLD4 in dendritic and myeloid cells, in comparison to the broader expression of PLD3, presents the opportunity for a cell-targeted immunotherapy. Here, we describe screening of an expended diversity library (N = 45,760) with an improved platform and report the discovery of one inhibitor and three activators selective for PLD4. Furthermore, kinetic modeling and structural analysis suggest mechanistic differences in the modulation of these hits. These findings further establish the utility of this screening platform and provide a set of chemical scaffolds to guide future small-molecule development for this novel immunoregulator target.

Improved predictability of pancreatic ductal adenocarcinoma diagnosis using a blood immune cell biomarker panel developed from bulk mRNA sequencing and single-cell RNA-sequencing

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) remains a devastating cancer due to its poor survival rate, early detection, and resectability. This study aimed to determine the peripheral blood mononuclear cell (PBMC) immune biomarkers in patients with PDAC and investigate the PDAC-specific peripheral blood biomarker panel and validate its clinical performance.

METHODS

In this prospective, blinded, case-control study, a biomarker panel formula was generated using a development cohort-including healthy controls, patients at high risk of PDAC, and patients with benign pancreatic disease, PDAC, or other gastrointestinal malignancies-and its diagnostic performance was verified using a validation cohort, including patients with ≥ 1 lesion suspected as PDAC on computed tomography (CT).

RESULTS

RNA-sequencing of PBMCs from patients with PDAC identified three novel immune cell markers, IL-7R, PLD4, and ID3, as specific markers for PDAC. Regarding the diagnostic performance of the regression formula for the three biomarker panels, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 84.0%, 78.8%, 47.2%, 95.6%, and 79.8%, respectively. Based on the formula scores for the biomarker panel, the false-negative rate (FNR) of the biomarkers was 8% (95% confidence interval [CI] 3.0-13.0), which was significantly lower than that based on CT in the validation cohort (29.2%, 95% CI 20.8-37.6).

CONCLUSIONS

The regression formula constructed using three PBMC biomarkers is an inexpensive, rapid, and convenient method that shows clinically useful performance for the diagnosis of PDAC. It aids diagnoses and differential diagnoses of PDAC from pancreatic disease by lowering the FNR compared to CT. Clinical trial registration Clinical Research Information Service, KCT0004614 (08 January 2020).

A novel lipid metabolism gene signature for clear cell renal cell carcinoma using integrated bioinformatics analysis

Background: Clear cell renal cell carcinoma (ccRCC), which is the most prevalent type of renal cell carcinoma, has a high mortality rate. Lipid metabolism reprogramming is a hallmark of ccRCC progression, but its specific mechanism remains unclear. Here, the relationship between dysregulated lipid metabolism genes (LMGs) and ccRCC progression was investigated. Methods: The ccRCC transcriptome data and patients' clinical traits were obtained from several databases. A list of LMGs was selected, differentially expressed gene screening performed to detect differential LMGs, survival analysis performed, a prognostic model established, and immune landscape evaluated using the CIBERSORT algorithm. Gene Set Variation Analysis and Gene set enrichment analysis were conducted to explore the mechanism by which LMGs affect ccRCC progression. Single-cell RNA-sequencing data were obtained from relevant datasets. Immunohistochemistry and RT-PCR were used to validate the expression of prognostic LMGs. Results: Seventy-one differential LMGs were identified between ccRCC and control samples, and a novel risk score model established comprising 11 LMGs (ABCB4, DPEP1, IL4I1, ENO2, PLD4, CEL, HSD11B2, ACADSB, ELOVL2, LPA, and PIK3R6); this risk model could predict ccRCC survival. The high-risk group had worse prognoses and higher immune pathway activation and cancer development. Conclusion: Our results showed that this prognostic model can affect ccRCC progression.

Role of miRNA-145, 148, and 185 and Stem Cells in Prostate Cancer

MicroRNAs (miRNAs) are small non-coding RNA molecules that play a role in cancer linked to the regulation of important cellular processes and pathways involving tumorigenesis, cell proliferation, differentiation, and apoptosis. A lot of human miRNA sequences have been identified which are linked to cancer pathogenesis. MicroRNAs, in prostate cancer (PC), play a relevant role as biomarkers, show a specific profile, and have been used as therapeutic targets. Prostate cancer (PC) is the most frequently diagnosed cancer in men. Clinical diagnoses among the gold standards for PC diagnosis and monitoring are prostate-specific antigen (PSA) testing, digital rectal examination, and prostate needle biopsies. PSA screening still has a large grey area of patients, which leads to overdiagnosis. Therefore, new biomarkers are needed to improve existing diagnostic tools. The miRNA expression profiles from tumour versus normal tissues are helpful and exhibit significant differences not only between cancerous and non-cancerous tissues, but also between different cancer types and subtypes. In this review, we focus on the role of miRNAs-145, 148, and 185 and their correlation with stem cells in prostate cancer pathogenesis. MiR-145, by modulating multiple oncogenes, regulates different cellular processes in PC, which are involved in the transition from localised to metastatic disease. MiR-148 is downregulated in high-grade tumours, suggesting that the miR-148-3 family might act as tumour suppressors in PC as a potential biomarker for detecting this disease. MiR-185 regulation is still unclear in being able to regulate tumour processes in PC. Nevertheless, other authors confirm the role of this miRNA as a tumour suppressor, suggesting its potential use as a suitable biomarker in disease prognosis. These three miRNAs are all involved in the regulation of prostate cancer stem cell behaviour (PCSCs). Within this contest, PCSCs are often involved in the onset of chemo-resistance in PC, therefore strategies for targeting this subset of cells are strongly required to control the disease. Hence, the relationship between these two players is interesting and important in prostate cancer pathogenesis and in PCSC stemness regulation, in the attempt to pave the way for novel therapeutic targets in prostate cancer.

Delineating toxicity mechanisms associated with MRI contrast enhancement through a multidimensional toxicogenomic profiling of gadolinium

Gadolinium is a metal used in contrast agents for magnetic resonance imaging. Although gadolinium is widely used in clinical settings, many concerns regarding its toxicity and bioaccumulation after gadolinium-based contrast agent administration have been raised and published over the last decade. To date, most toxicological studies have focused on identifying acute effects following gadolinium exposure, rather than investigating associated toxicity mechanisms. In this study, we employ functional toxicogenomics to assess mechanistic interactions of gadolinium with Saccharomyces cerevisiae. Furthermore, we determine which mechanisms are conserved in humans, and their implications for diseases related to the use of gadolinium-based contrast agents in medicine. A homozygous deletion pool of 4291 strains were screened to identify biological functions and pathways disturbed by the metal. Gene ontology and pathway enrichment analyses showed endocytosis and vesicle-mediated transport as the main yeast response to gadolinium, while certain metabolic processes, such as glycosylation, were the primary disrupted functions after the metal treatments. Cluster and protein-protein interaction network analyses identified proteins mediating vesicle-mediated transport through the Golgi apparatus and the vacuole, and vesicle cargo exocytosis as key components to reduce the metal toxicity. Moreover, the metal seemed to induce cytotoxicity by disrupting the function of enzymes (e.g. transferases and proteases) and chaperones involved in metabolic processes. Several of the genes and proteins associated with gadolinium toxicity are conserved in humans, suggesting that they may participate in pathologies linked to gadolinium-based contrast agent exposures. We thereby discuss the potential role of these conserved genes and gene products in gadolinium-induced nephrogenic systemic fibrosis, and propose potential prophylactic strategies to prevent its adverse health effects.

Comprehensive proteomic quantification of bladder stone progression in a cystinuric mouse model using data-independent acquisitions

Cystinuria is one of various disorders that cause biomineralization in the urinary system, including bladder stone formation in humans. It is most prevalent in children and adolescents and more aggressive in males. There is no cure, and only limited disease management techniques help to solubilize the stones. Recurrence, even after treatment, occurs frequently. Other than a buildup of cystine, little is known about factors involved in the formation, expansion, and recurrence of these stones. This study sought to define the growth of bladder stones, guided by micro-computed tomography imaging, and to profile dynamic stone proteome changes in a cystinuria mouse model. After bladder stones developed in vivo, they were harvested and separated into four developmental stages (sand, small, medium and large stone), based on their size. Data-dependent and data-independent acquisitions allowed deep profiling of stone proteomics. The proteomic signatures and pathways illustrated major changes as the stones grew. Stones initiate from a small nidus, grow outward, and show major enrichment in ribosomal proteins and factors related to coagulation and platelet degranulation, suggesting a major dysregulation in specific pathways that can be targeted for new therapeutic options.

Modulators of immunoregulatory exonucleases PLD3 and PLD4 identified by high-throughput screen

PLD3 and PLD4 have recently been revealed to be endosomal exonucleases that regulate the innate immune response by digesting the ligands of nucleic acid sensors. These enzymes can suppress RNA and DNA innate immune sensors like toll-like receptor 9, and PLD4-deficent mice exhibit inflammatory disease. Targeting these immunoregulatory enzymes presents an opportunity to indirectly regulate innate immune nucleic acid sensors that could yield immunotherapies, adjuvants, and nucleic acid drug stabilizers. To aid in delineating the therapeutic potential of these targets, we have developed a high-throughput fluorescence enzymatic assay to identify modulators of PLD3 and PLD4. Screening of a diversity library (N = 17952) yielded preferential inhibitors of PLD3 and PLD4 in addition to a PLD3 selective activator. The modulation models of these compounds were delineated by kinetic analysis. This work presents an inexpensive and simple method to identify modulators of these immunoregulatory exonucleases.

MicroRNA miR-145-5p inhibits Phospholipase D 5 (PLD5) to downregulate cell proliferation and metastasis to mitigate prostate cancer

Prostate cancer (PCa), a frequently detected malignant tumor, is the fifth leading global cancer mortality cause in men. Although research has improved the PCa survival rate, significantly reduced survival occurs among patients at the metastatic stage. MiRNAs, which are short non-coding proteins, are crucial for several biological roles, essential for PCa proliferation, differentiation, multiplication, and migration. The investigation aimed to explore miR-145-5p and PLD5 association and clarify their function in regulating proliferation in PCa cell lines.The study used PC-3, LNCaP, DU-145 PCa, and RWPE-1 non-cancerous cell line, PCa, and BPH tissue specimens, and nude mice to validate results. MiR-145-5p and PLD5 manifestation were assessed through RT-qPCR. PLD5 and miR-145 binding was determined through dual-luciferase reporter gene assays. Validation of cell proliferation, migration, and invasion was assessed through MTT, scratch wound, and transwell assays, respectively.The results indicated a downregulation of miR-145-5p level in PCa cell lines and tissues in comparison to the non-cancerous controls. PLD5 overexpression exerted a cancerous effect while mimicking of miR-145-5p reversed the PLD5-oncogenic effects and significantly inhibited PCa cells proliferation, migration, invasion, and metastasis.In conclusion, the study revealed that miR-145-5p upregulated apoptosis and repressed migration, invasion, and metastasis of PCa via direct PLD5 modulation.

Genetic and pharmacological inhibition of fatty acid-binding protein 4 alleviated inflammation and early fibrosis after toxin induced kidney injury

Considerable data have suggested that acute kidney injury (AKI) is often incompletely repaired and could lead to chronic kidney disease (CKD). As we known, toxin-induced nephropathy triggers the rapid production of proinflammatory mediators and the prolonged inflammation allows the injured kidneys to develop interstitial fibrosis. In our previous study, fatty acid-binding protein 4 (Fabp4) has been reported to be involved in the process of AKI. However, whether Fabp4 plays crucial roles in toxin-induced kidney injury remained unclear. To explore the effect and mechanism of Fabp4 on toxin induced kidney injury, folic acid (FA) and aristolochic acid (AA) animal models were used. Both FA and AA injected mice developed severe renal dysfunction and dramatically inflammatory response (IL-6, MCP1 and TNF-a), which further lead to early fibrosis confirmed by the accumulation of extracellular matrix proteins (α-Sma, Fn, Col1 and Col4). Importantly, we found that FA and AA induced-kidney injury triggered the high expression of Fabp4 mRNA/protein in tubular epithelial cells. Furthermore, pharmacological and genetic inhibition of Fabp4 significantly attenuated FA and AA induced renal dysfunction, pathological damage, and early fibrosis via the regulation of inflammation, which is mediated by suppressing p-p65/p-stat3 expression via enhancing Pparγ activity. In summary, Fabp4 in tubular epithelial cells exerted the deleterious effects during the recovery of FA and AA induced kidney injury and the inhibition of Fabp4 might be an effective therapeutic strategy against the progressive AKI.

Lipid Mediators Regulate Pulmonary Fibrosis: Potential Mechanisms and Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease of unknown etiology characterized by distorted distal lung architecture, inflammation, and fibrosis. The molecular mechanisms involved in the pathophysiology of IPF are incompletely defined. Several lung cell types including alveolar epithelial cells, fibroblasts, monocyte-derived macrophages, and endothelial cells have been implicated in the development and progression of fibrosis. Regardless of the cell types involved, changes in gene expression, disrupted glycolysis, and mitochondrial oxidation, dysregulated protein folding, and altered phospholipid and sphingolipid metabolism result in activation of myofibroblast, deposition of extracellular matrix proteins, remodeling of lung architecture and fibrosis. Lipid mediators derived from phospholipids, sphingolipids, and polyunsaturated fatty acids play an important role in the pathogenesis of pulmonary fibrosis and have been described to exhibit pro- and anti-fibrotic effects in IPF and in preclinical animal models of lung fibrosis. This review describes the current understanding of the role and signaling pathways of prostanoids, lysophospholipids, and sphingolipids and their metabolizing enzymes in the development of lung fibrosis. Further, several of the lipid mediators and enzymes involved in their metabolism are therapeutic targets for drug development to treat IPF.

DGKα in Neutrophil Biology and Its Implications for Respiratory Diseases

Diacylglycerol kinases (DGKs) play a key role in phosphoinositide signaling by removing diacylglycerol and generating phosphatidic acid. Besides the well-documented role of DGKα and DGKζ as negative regulators of lymphocyte responses, a robust body of literature points to those enzymes, and specifically DGKα, as crucial regulators of leukocyte function. Upon neutrophil stimulation, DGKα activation is necessary for migration and a productive response. The role of DGKα in neutrophils is evidenced by its aberrant behavior in juvenile periodontitis patients, which express an inactive DGKα transcript. Together with in vitro experiments, this suggests that DGKs may represent potential therapeutic targets for disorders where inflammation, and neutrophils in particular, plays a major role. In this paper we focus on obstructive respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD), but also rare genetic diseases such as alpha-1-antitrypsin deficiency. Indeed, the biological role of DGKα is understudied outside the T lymphocyte field. The recent wave of research aiming to develop novel and specific inhibitors as well as KO mice will allow a better understanding of DGK's role in neutrophilic inflammation. Better knowledge and pharmacologic tools may also allow DGK to move from the laboratory bench to clinical trials.

Role of phospholipase D in bleomycin-induced mitochondrial reactive oxygen species generation, mitochondrial DNA damage, and pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a pernicious lung disease characterized by alveolar epithelial apoptosis, dysregulated repair of epithelial injury, scar formation, and respiratory failure. In this study, we identified phospholipase D (PLD)-generated phosphatidic acid (PA) signaling in the development of pulmonary fibrosis (PF). Of the PLD isoenzymes, the protein expression of PLD2, but not PLD1, was upregulated in lung tissues from IPF patients and bleomycin challenged mice. Both PLD1 (Pld1^-/-)- and PLD2 (Pld2^-/-)-deficient mice were protected against bleomycin-induced lung inflammation and fibrosis, thereby establishing the role of PLD in fibrogenesis. The role of PLD1 and PLD2 in bleomycin-induced lung epithelial injury was investigated by infecting bronchial airway epithelial cells (Beas2B) with catalytically inactive mutants of PLD (hPLD1-K898R or mPld2-K758R) or downregulation of expression of PLD1 or PLD2 with siRNA. Bleomycin stimulated mitochondrial (mt) superoxide production, mtDNA damage, and apoptosis in Beas2B cells, which was attenuated by the catalytically inactive mutants of PLD or PLD2 siRNA. These results show a role for PLD1 and PLD2 in bleomycin-induced generation of mt reactive oxygen species, mt DNA damage, and apoptosis of lung epithelial cells in mice. Thus, PLD may be a novel therapeutic target in ameliorating experimental PF in mice.

PLD4 is a genetic determinant to systemic lupus erythematosus and involved in murine autoimmune phenotypes

Objectives

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterised by autoantibody production and widespread inflammation damaging many organs. Previous genome-wide association studies (GWASs) have revealed over 80 genetic determinants of SLE, but they collectively explain a fraction of the heritability, and only a few were proven in vivo for the involvement in SLE. We conducted a meta-analysis of SLE GWAS in the Japanese population, followed by functional analyses of a susceptibility gene with use of mutant mice.

Methods

We conducted a meta-analysis of two GWASs comprising a total of 1363 cases and 5536 controls using the 1000 Genome Project data as an imputation reference. Enrichment analyses for functional annotations were conducted. We examined Phospholipase D4 (Pld4) mutant mice to assess functional involvement of a genetic determinant.

Results

We found a total of 14 significant loci, which included rs2582511 in AHNAK2/PLD4 recently reported in a Chinese study and a novel locus of rs143181706 in MAMLD1 (p=7.9×10−11 and 3.7×10–8, respectively). PLD4 risk allele was associated with anti-dsDNA antibody production. Enrichment analysis of genetic signals revealed involvement of a wide range of immune-related cells and pathways. Pld4 mutant mice revealed remarkably low body weight. The mice demonstrated autoimmune phenotypes compatible with SLE, including splenomegaly and lymphadenopathy, expansion of B cells and hypersecretion of BAFF and production of autoantibodies especially anti-nuclear antibody and anti-dsDNA antibody.

Conclusions

 We found a novel susceptibility gene to SLE. Pld4 mutant mice revealed autoimmune phenotypes suggesting functional involvement of PLD4 with the basics of SLE.