Lupus Prone Research Articles

Sex Differences of the Endothelin System in the Cardio-Renal Axis of a Lupus Prone Mouse Model

Systemic Lupus Erythematosus (SLE) is the most common form of lupus autoimmunity. It is characterized by overactivation of toll-like receptor 7 (TLR7) and immune complex deposition in target organs including the kidney and vasculature. A lupus diagnosis disproportionately affects women at a rate of 9:1 compared to men. Clinically, patients present with heterogenous symptoms including chronic hypertension, heart failure, renal failure, vascular disease, and neuropathies. Despite a variety of clinical presentations of lupus, elevated endothelin-1 (ET-1) has been detected in both male and female lupus patients' plasma compared to healthy controls. However, the exact sex differences in ET-1 in the development of lupus and its associated cardiovascular complications remain unknown. Therefore, we hypothesized that acceleration of SLE through TLR7 activation promotes sex-dependent regulation of the ET system within the cardiorenal axis. To investigate this, female and male lupus-prone B6.Nba2 mice were treated with a TLR7/8 agonist (R848; 100ug/30ul) or acetone as a control topically twice a week for 4 weeks. After the R848 treatment, mice were followed for 12 more weeks until the 16-week terminal timepoint where the kidney and heart tissues were collected and tissue ET-1, endothelin receptor A (ETA) and endothelin receptor B (ETB) were analyzed by ELISA, RTqPCR, and immunoblotting. At the RNA level, cardiac Ednra expression trended towards upregulation in females, whereas males remained unchanged compared to their respective controls. At the protein level, both sexes tended to decrease ETA receptor levels. Renal Ednra expression trended towards downregulation in females but was unchanged in treated males, which was opposite of renal protein ETA where females were unchanged, and males trended towards reduction. Interestingly, Ednrb and Edn1 trended towards an increase in both the cardiac and renal system in both sexes. However, at the protein level only female cardiac ET-1 was significantly elevated (p<0.0001) while renal ET-1 levels were unchanged. Males demonstrated a significant increase in both cardiac (p=0.0004) and renal ET-1 (p=0.0127). Analysis of female cardiac ETB receptor levels yielded a significant reduction (p=0.0025) and an increasing trend in renal levels. Both cardiac and renal ETB was unchanged in males. The sex differences in the cardiorenal ET system regulation warrants further exploration and possible therapeutic treatments into cardiorenal lupus associated pathologies. Veterans Affairs Biomedical Laboratory Research & Development Career Development Award (CDA-2) 1IK2BX005605-01 to J.P.V.B, Medical University of South Carolina College of Medicine Program Project Grant to and J.P.V.B., and Medical University of South Carolina Core Centers for Clinical Research Project Award P30AR072582 to M.A.C and J.P.V.B. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

OC 19.1 Vascular Injury Derived Exosomes Accelerate Renal Damage in Lupus Prone Mice

OC 19.1 Vascular Injury Derived Exosomes Accelerate Renal Damage in Lupus Prone Mice

Characterization of Ly108-H1 Signaling Reveals Ly108-3 Expression and Additional Strain-Specific Differences in Lupus Prone Mice.

Ly108 (SLAMF6) is a homophilic cell surface molecule that binds SLAM-associated protein (SAP), an intracellular adapter protein that modulates humoral immune responses. Furthermore, Ly108 is crucial for the development of natural killer T (NKT) cells and CTL cytotoxicity. Significant attention has been paid towards expression and function of Ly108 since multiple isoforms were identified, i.e., Ly108-1, Ly108-2, Ly108-3, and Ly108-H1, some of which are differentially expressed in several mouse strains. Surprisingly, Ly108-H1 appeared to protect against disease in a congenic mouse model of Lupus. Here, we use cell lines to further define Ly108-H1 function in comparison with other isoforms. We show that Ly108-H1 inhibits IL-2 production while having little effect upon cell death. With a refined method, we could detect phosphorylation of Ly108-H1 and show that SAP binding is retained. We propose that Ly108-H1 may regulate signaling at two levels by retaining the capability to bind its extracellular as well as intracellular ligands, possibly inhibiting downstream pathways. In addition, we detected Ly108-3 in primary cells and show that this isoform is also differentially expressed between mouse strains. The presence of additional binding motifs and a non-synonymous SNP in Ly108-3 further extends the diversity between murine strains. This work highlights the importance of isoform awareness, as inherent homology can present a challenge when interpreting mRNA and protein expression data, especially as alternatively splicing potentially affects function.

A Selective Neutraligand for CXCL12/SDF-1α With Beneficial Regulatory Functions in MRL/Lpr Lupus Prone Mice.

Dysregulation of CXCL12/SDF-1-CXCR4/CD184 signaling is associated with inflammatory diseases and notably with systemic lupus erythematosus. Issued from the lead molecule chalcone-4, the first neutraligand of the CXCL12 chemokine, LIT-927 was recently described as a potent analogue with improved solubility and stability. We aimed to investigate the capacity of LIT-927 to correct immune alterations in lupus-prone MRL/lpr mice and to explore the mechanism of action implemented by this small molecule in this model. We found that in contrast to AMD3100, an antagonist of CXCR4 and agonist of CXCR7, LIT-927 reduces the excessive number of several B/T lymphocyte subsets occurring in the blood of sick MRL/lpr mice (including CD3+/CD4-/CD8-/B220+ double negative T cells). In vitro, LIT-927 downregulated the overexpression of several activation markers on splenic MRL/lpr lymphocytes. It exerted effects on the CXCR4 pathway in MRL/lpr CD4+ T spleen cells. The results underline the importance of the CXCL12/CXCR4 axis in lupus pathophysiology. They indicate that neutralizing CXCL12 by the neutraligand LIT-927 can attenuate hyperactive lymphocytes in lupus. This mode of intervention might represent a novel strategy to control a common pathophysiological mechanism occurring in inflammatory diseases.

Decreased Protein Kinase C-β Type II Associated with the Prominent Endotoxin Exhaustion in the Macrophage of FcGRIIb−/− Lupus Prone Mice is Revealed by Phosphoproteomic Analysis

Dysfunction of FcGRIIb, the only inhibitory receptor of the FcGR family, is commonly found in the Asian population and is possibly responsible for the extreme endotoxin exhaustion in lupus. Here, the mechanisms of prominent endotoxin (LPS) tolerance in FcGRIIb−/− mice were explored on bone marrow-derived macrophages using phosphoproteomic analysis. As such, LPS tolerance decreased several phosphoproteins in the FcGRIIb−/− macrophage, including protein kinase C-β type II (PRKCB), which was associated with phagocytosis function. Overexpression of PRKCB attenuated LPS tolerance in RAW264.7 cells, supporting the role of this gene in LPS tolerance. In parallel, LPS tolerance in macrophages and in mice was attenuated by phorbol 12-myristate 13-acetate (PMA) administration. This treatment induced several protein kinase C families, including PRKCB. However, PMA attenuated the severity of mice with cecal ligation and puncture on LPS tolerance preconditioning in FcGRIIb−/− but not in wild-type cells. The significant reduction of PRKCB in the FcGRIIb−/− macrophage over wild-type cell possibly induced the more severe LPS-exhaustion and increased the infection susceptibility in FcGRIIb−/− mice. PMA induced PRKCB, improved LPS-tolerance, and attenuated sepsis severity, predominantly in FcGRIIb−/− mice. PRKCB enhancement might be a promising strategy to improve macrophage functions in lupus patients with LPS-tolerance from chronic infection.

Effect of Gluten Containing Diet on Pristane Induced Lupus Prone Mice

Effect of Gluten Containing Diet on Pristane Induced Lupus Prone Mice

Frequency of CD4+Foxp3+ Treg Cells Increase But is Unable to Control Nephritis in Lupus Prone Mice

Frequency of CD4+Foxp3+ Treg Cells Increase But is Unable to Control Nephritis in Lupus Prone Mice

Lupus nephritis reoccurs following transplantation in the lupus prone mouse

The incidence and pathomechanism of recurrent lupus nephritis (RLN) after transplantation is not clearly understood. Burning out of the autoimmune process or local immunoregulatory mechanisms in the kidney may be responsible for the low incidence of recurrence. These mechanisms cannot be investigated in human subjects, due to post-transplant immunosuppression. To investigate the pathomechanisms of RLN, male and female kidneys were transplanted from FAS deficient lupus prone (LPR) or control (FAS intact) MRL mice into either LPR or MRL recipients. Urinary protein and blood urea were assessed. Double negative (DN) lymphocyte proliferation was determined by flow cytometry. Two months after transplantation inflammatory infiltration of the glomerular, vascular and interstitial compartments were determined. Renal function as demonstrated by blood urea levels was normal in MRL recipients, but elevated in LPR recipients, independent of the donor strain. Paralleling functional results, inflammatory infiltration was mild or absent in MRL recipients of MRL grafts, and mild to moderate in MRL recipients of LPR grafts, suggesting that kidney removal from the autoimmune (LPR) environment significantly reduced inflammation. Graft infiltration was most severe in LPR recipients: grafts were similarly inflamed independent of the donor. All LPR recipients had significantly less CD4+ Th cells versus MRL mice. Transplantation of LPR grafts into MRL recipients reduced CD4+ Th cell percentage, accompanied by a slight induction of lupus autoantibody production. Our results demonstrate that lupus nephritis is not kidney specific in the LPR model with recurrence after transplantation in the absence of immunosuppression.

Suppression of Glomerulonephritis in NZB/NZW Lupus Prone Mice by Adoptive Transfer of Ex Vivo Expanded Regulatory T Cells

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown cause characterized by expansion of autoreactive lymphocytes. Regulatory T cells (Tregs) are a component of the normal immune system and contribute to the maintenance of peripheral tolerance. Treg abnormalities have been associated with several autoimmune diseases and there is interest in the role of Tregs in SLE. We previously demonstrated that transfer of expanded CD4+CD25+CD62LHI Tregs slows the development of lupus in (NZBxNZW)F1 (B/W) mice. However in the absence of Treg specific surface antigens, cell purification remains a compromise between the breadth and purity of the population isolated. Importantly, purified populations always contain Foxp3− effector T cells (Teffs) that theoretically could exacerbate autoimmunity in the recipient. Here we explore the impact of transferring the more comprehensive, but less pure Treg subset defined by CD4+CD25+ expression on development of murine lupus. All cells were FACS sorted and expanded prior to adoptive transfer. Development of proteinuria and survival were measured. We found that exogenous expansion of CD4+CD25+ cells produced a population containing 70–85% CD4+Foxp3+Tregs. Expanded Tregs had higher CTLA-4 and Foxp3 expression, increased in vitro suppression capacity, and prolonged in vivo survival as compared to freshly isolated cells. Adoptive transfer of expanded CD4+CD25+ Tregs inhibited the onset of glomerulonephritis and prolonged survival in mice. Importantly the population of Teff contained within the adoptively transferred cells had reduced survival and proliferation capacity as compared to either co-transferred Tregs or transferred Teffs expanded in the absence of Tregs. These studies demonstrate that adoptive transfer of expanded CD4+CD25+Foxp3+Tregs has the capacity to inhibit the onset of murine lupus and that this capacity is significant despite transfer of co-cultured Teff cells. These data indicate that when co-expanded with regulatory T cells, exogenously activated Teffs from autoimmune patients may not pose a significant risk of promoting disease.

T.4. Depression is an Early Disease Manifestation in Lupus Prone MRL/lpr Mice

T.4. Depression is an Early Disease Manifestation in Lupus Prone MRL/lpr Mice

Sa.34. Interleukin-21 Receptor-deficient MRL-Faslpr Lupus Prone Mice Have Significantly Reduced B Cell-mediated Pathogenesis and Delayed Disease Progression

Sa.34. Interleukin-21 Receptor-deficient MRL-Faslpr Lupus Prone Mice Have Significantly Reduced B Cell-mediated Pathogenesis and Delayed Disease Progression

Paucity of V-D-D-J Rearrangements and VH Replacement Events in Lupus Prone and Nonautoimmune TdT−/− and TdT+/+ Mice

CDR3 regions containing two D segments, or containing the footprints of V(H) replacement events, have been reported in both mice and humans. However, the 12-23 bp rule for V(D)J recombination predicts that D-D rearrangements, which would occur between 2 recombination signal sequences (RSSs) with 12-bp spacers, should be extremely disfavored, and the cryptic RSS used for V(H) replacement is very inefficient. We have previously shown that newborn mice, which lack TdT due to the late onset of its expression, do not contain any CDR3 with D-D rearrangements. In the present study, we test our hypothesis that most D-D rearrangements are due to fortuitous matching of the second apparent D segment by TdT-introduced N nucleotides. We analyzed 518 sequences from adult MRL/lpr- and C57BL/6 TdT-deficient B cell precursors and found only two examples of CDR3 with D-D rearrangements and one example of a potential V(H) replacement event. We examined rearrangements from pre-B cells, marginal zone B cells, and follicular B cells from mice congenic for the Lbw5 (Sle3/5) lupus susceptibility loci and from other strains of mice and found very few examples of CDR3 with D-D rearrangements. We assayed B progenitor cells, and cells enriched for receptor editing, for DNA breaks at the "cryptic heptamer" but such breaks were rare. We conclude that many examples of apparent D-D rearrangements in the mouse are likely due to N additions that fortuitously match short stretches of D genes and that D-D rearrangements and V(H) replacement are rare occurrences in the mouse.