The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis.

In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's α subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.

Kidney-targeted inhibition of protein kinase C-α ameliorates nephrotoxic nephritis with restoration of mitochondrial dysfunction.

To investigate the role of protein kinase C-α (PKC-α) in glomerulonephritis, the capacity of PKC-α inhibition to reverse the course of established nephrotoxic nephritis (NTN) was evaluated. Nephritis was induced by a single injection of nephrotoxic serum and after its onset, a PKC-α inhibitor was administered either systemically or by targeted glomerular delivery. By day seven, all mice with NTN had severe nephritis, whereas mice that received PKC-α inhibitors in either form had minimal evidence of disease. To further understand the underlying mechanism, label-free shotgun proteomic analysis of the kidney cortexes were performed, using quantitative mass spectrometry. Ingenuity pathway analysis revealed 157 differentially expressed proteins and mitochondrial dysfunction as the most modulated pathway. Functional protein groups most affected by NTN were mitochondrial proteins associated with respiratory processes. These proteins were down-regulated in the mice with NTN, while their expression was restored with PKC-α inhibition. This suggests a role for proteins that regulate oxidative phosphorylation in recovery. In cultured glomerular endothelial cells, nephrotoxic serum caused a decrease in mitochondrial respiration and membrane potential, mitochondrial morphologic changes and an increase in glycolytic lactic acid production; all normalized by PKC-α inhibition. Thus, PKC-α has a critical role in NTN progression, and the results implicate mitochondrial processes through restoring oxidative phosphorylation, as an essential mechanism underlying recovery. Importantly, our study provides additional support for targeted therapy to glomeruli to reverse the course of progressive disease.

The amino acid sensor GCN2 inhibits inflammatory responses to apoptotic cells promoting tolerance and suppressing systemic autoimmunity.

Efficient apoptotic cell clearance and induction of immunologic tolerance is a critical mechanism preventing autoimmunity and associated pathology. Our laboratory has reported that apoptotic cells induce tolerance by a mechanism dependent on the tryptophan catabolizing enzyme indoleamine 2,3 dioxygenase 1 (IDO1) in splenic macrophages (MΦ). The metabolic-stress sensing protein kinase GCN2 is a primary downstream effector of IDO1; thus, we tested its role in apoptotic cell-driven immune suppression. In vitro, expression of IDO1 in MΦs significantly enhanced apoptotic cell-driven IL-10 and suppressed IL-12 production in a GCN2-dependent mechanism. Suppression of IL-12 protein production was due to attenuation of IL-12 mRNA association with polyribosomes inhibiting translation while IL-10 mRNA association with polyribosomes was not affected. In vivo, apoptotic cell challenge drove a rapid, GCN2-dependent stress response in splenic MΦs with increased IL-10 and TGF-ß production, whereas myeloid-specific deletion of GCN2 abrogated regulatory cytokine production with provocation of inflammatory T-cell responses to apoptotic cell antigens and failure of long-tolerance induction. Consistent with a role in prevention of apoptotic cell driven autoreactivity, myeloid deletion of GCN2 in lupus-prone mice resulted in increased immune cell activation, humoral autoimmunity, renal pathology, and mortality. In contrast, activation of GCN2 with an agonist significantly reduced anti-DNA autoantibodies and protected mice from disease. Thus, this study implicates a key role for GCN2 signals in regulating the tolerogenic response to apoptotic cells and limiting autoimmunity.

Leptin deficiency down-regulates IL-23 production in glomerular podocytes resulting in an attenuated immune response in nephrotoxic serum nephritis.

Leptin, one of the typical adipokines, is reported to promote Th17 cell responses and to enhance production of proinflammatory cytokines. To clarify the role of leptin in the regulation of the IL-23/IL-17 axis and the development of kidney disease, we used a murine model of nephrotoxic serum (NTS) nephritis (NTN). Sheep NTS was administered in wild-type C57BL/6J mice and food-restricted, leptin-deficient C57BL/6J-ob/ob(FR-ob/ob) mice after preimmunization with sheep IgG. The profile of mRNA expression relevant to T helper lymphocytes in the kidneys was analyzed by quantitative real-time PCR (qRT-PCR). Cultured murine glomerular podocytes and peritoneal exudate macrophages (PEMs) were used to investigate the direct effect of leptin on IL-23 or MCP-1 production by qRT-PCR. Kidney injury and macrophage infiltration were significantly attenuated in FR-ob/obmice 7 days after NTS injection. The Th17-dependent secondary immune response against deposited NTS in the glomeruli was totally impaired in FR-ob/obmice because of deteriorated IL-17 and proinflammatory cytokine production including IL-23 and MCP-1 in the kidney. IL-23 was produced in glomerular podocytes in NTN mice and cultured murine glomerular podocytes produced IL-23 under leptin stimulation. MCP-1 production in PEMs was also promoted by leptin. Induction of MCP-1 expression was observed in PEMs regardless of Ob-Rb, and the leptin signal was transduced without STAT3 phosphorylation in PEMs. Leptin deficiency impairs the secondary immune response against NTS and down-regulates IL-23 production and Th17 responses in the NTN kidney, which is accompanied by decreased MCP-1 production and macrophage infiltration in the NTN kidney.

Amino acid metabolism inhibits antibody-driven kidney injury by inducing autophagy.

Inflammatory kidney disease is a major clinical problem that can result in end-stage renal failure. In this article, we show that Ab-mediated inflammatory kidney injury and renal disease in a mouse nephrotoxic serum nephritis model was inhibited by amino acid metabolism and a protective autophagic response. The metabolic signal was driven by IFN-γ-mediated induction of indoleamine 2,3-dioxygenase 1 (IDO1) enzyme activity with subsequent activation of a stress response dependent on the eIF2α kinase general control nonderepressible 2 (GCN2). Activation of GCN2 suppressed proinflammatory cytokine production in glomeruli and reduced macrophage recruitment to the kidney during the incipient stage of Ab-induced glomerular inflammation. Further, inhibition of autophagy or genetic ablation of Ido1 or Gcn2 converted Ab-induced, self-limiting nephritis to fatal end-stage renal disease. Conversely, increasing kidney IDO1 activity or treating mice with a GCN2 agonist induced autophagy and protected mice from nephritic kidney damage. Finally, kidney tissue from patients with Ab-driven nephropathy showed increased IDO1 abundance and stress gene expression. Thus, these findings support the hypothesis that the IDO-GCN2 pathway in glomerular stromal cells is a critical negative feedback mechanism that limits inflammatory renal pathologic changes by inducing autophagy.

Human anti-α3(IV)NC1 antibody drug conjugates target glomeruli to resolve nephritis.

Current therapies to limit kidney disease progression lack specificity and often have systemic toxicity. To approach this problem, we postulated that a human monoclonal antibody (F1.1), directed against the noncollagenous-1 domain (NC1) of α3(IV) collagen that localizes in glomeruli, could serve as a vehicle for targeted drug delivery. Given enhanced exposure of the NC1 domain of α3(IV) during glomerular diseases, with limited epitope expression in other organs, α3(IV)NC1 provides an ideal target for delivery of disease-modifying agents. As a potential disease-modifying agent, we initially took advantage of recent observations that PGE2 promoted recovery after established injury during the course of nephrotoxic nephritis. To address the general applicability of the approach, the efficacy of glomerular delivery of dexamethasone was also examined. To achieve glomerular targeted therapy, PGE2 and dexamethasone were coupled to F1.1. After confirmation of the composition and activity of the conjugates, both glomerular localization and the capacity of the conjugates to modify disease were evaluated. After injection into mice with established nephritis, resolution of disease was enhanced with both agents, with normalization of histology and improved blood urea nitrogen levels in conjugate-treated mice compared with untreated mice. The results provide a novel means of targeting glomeruli during nephritis, irrespective of cause, by providing efficient drug delivery, with the potential of limiting systemic effects.

HRES-1/Rab4-mediated depletion of Drp1 impairs mitochondrial homeostasis and represents a target for treatment in SLE.

OBJECTIVE: Accumulation of mitochondria underlies T-cell dysfunction in systemic lupus erythematosus (SLE). Mitochondrial turnover involves endosomal traffic regulated by HRES-1/Rab4, a small GTPase that is overexpressed in lupus T cells. Therefore, we investigated whether (1) HRES-1/Rab4 impacts mitochondrial homeostasis and (2) Rab geranylgeranyl transferase inhibitor 3-PEHPC blocks mitochondrial accumulation in T cells, autoimmunity and disease development in lupus-prone mice. METHODS: Mitochondria were evaluated in peripheral blood lymphocytes (PBL) of 38 SLE patients and 21 healthy controls and mouse models by flow cytometry, microscopy and western blot. MRL/lpr mice were treated with 125 µg/kg 3-PEHPC or 1 mg/kg rapamycin for 10 weeks, from 4 weeks of age. Disease was monitored by antinuclear antibody (ANA) production, proteinuria, and renal histology. RESULTS: Overexpression of HRES-1/Rab4 increased the mitochondrial mass of PBL (1.4-fold; p=0.019) and Jurkat cells (2-fold; p=0.000016) and depleted the mitophagy initiator protein Drp1 both in human (-49%; p=0.01) and mouse lymphocytes (-41%; p=0.03). Drp1 protein levels were profoundly diminished in PBL of SLE patients (-86±3%; p=0.012). T cells of 4-week-old MRL/lpr mice exhibited 4.7-fold over-expression of Rab4A (p=0.0002), the murine homologue of HRES-1/Rab4, and depletion of Drp1 that preceded the accumulation of mitochondria, ANA production and nephritis. 3-PEHPC increased Drp1 (p=0.03) and reduced mitochondrial mass in T cells (p=0.02) and diminished ANA production (p=0.021), proteinuria (p=0.00004), and nephritis scores of lupus-prone mice (p<0.001). CONCLUSIONS: These data reveal a pathogenic role for HRES-1/Rab4-mediated Drp1 depletion and identify endocytic control of mitophagy as a treatment target in SLE.

Absence of CD59 exacerbates systemic autoimmunity in MRL/lpr mice.

CD59 is a GPI-anchored membrane regulator of complement expressed on blood cells as well as peripheral tissues. It protects host cells from complement injury by inhibiting formation of the membrane attack complex. Recent studies in mice have suggested also a role of CD59 in T cell immune response that was mechanistically independent of complement. In the present study, we investigated the function of CD59 in the MRL/lpr model of murine lupus. We backcrossed the Cd59a knockout (Cd59a(-/-)) mouse onto the MRL/lpr background and compared Cd59a(+/+)-MRL/lpr and Cd59a(-/-)-MRL/lpr littermates for the development of systemic autoimmunity. We found that CD59a deficiency significantly exacerbated the skin disease and lymphoproliferation characteristic of MRL/lpr mice. It also increased autoantibody titers and caused a higher level of proteinuria in male MRL/lpr mice. Bone marrow transfer experiments indicated that CD59a expression on both bone marrow-derived cells and peripheral tissues played a role in lymphoproliferation, whereas the skin disease phenotype is determined mainly by local CD59a expression. Importantly, C3 gene deletion or C5 neutralization with a blocking mAb in Cd59a(-/-)-MRL/lpr mice did not rescue the proautoimmune phenotype associated with CD59a deficiency. These results together suggest that CD59a inhibits systemic autoimmunity in MRL/lpr mice through a complement-independent mechanism.

Lupus Nephritis: Animal Modeling of a Complex Disease Syndrome Pathology.

Nephritis as a result of autoimmunity is a common morbidity associated with Systemic Lupus Erythematosus (SLE). There is substantial clinical and industry interest in medicinal intervention in the SLE nephritic process; however, clinical trials to specifically treat lupus nephritis have not resulted in complete and sustained remission in all patients. Multiple mouse models have been used to investigate the pathologic interactions between autoimmune reactivity and SLE pathology. While several models bear a remarkable similarity to SLE-driven nephritis, there are limitations for each that can make the task of choosing the appropriate model for a particular aspect of SLE pathology challenging. This is not surprising given the variable and diverse nature of human disease. In many respects, features among murine strains mimic some (but never all) of the autoimmune and pathologic features of lupus patients. Although the diversity often limits universal conclusions relevant to pathogenesis, they provide insights into the complex process that result in phenotypic manifestations of nephritis. Thus nephritis represents a microcosm of systemic disease, with variable lesions and clinical features. In this review, we discuss some of the most commonly used models of lupus nephritis (LN) and immune-mediated glomerular damage examining their relative strengths and weaknesses, which may provide insight in the human condition.

Case report: Successful treatment of OXA-23 Acinetobacter baumannii neurosurgical infection and meningitis with sulbactam-durlobactam combination therapy.

Meningitis caused by Acinetobacter species is a rare complication of neurosurgical procedures, although it is associated with high morbidity and mortality. Carbapenem-resistant Acinetobacter is particularly difficult to treat, considering the limited selection and tolerability of effective antimicrobials. Sulbactam-durlobactam was approved by the FDA in 2023 for treatment of hospital-acquired and ventilator-associated pneumonia due to susceptible strains of Acinetobacter, including carbapenem-resistant Acinetobacter baumannii. Here, we present a case of carbapenem-resistant Acinetobacter baumannii neurosurgical infection and meningitis successfully treated with sulbactam-durlobactam combination therapy.

Prostaglandin E2 promotes cellular recovery from established nephrotoxic serum nephritis in mice, prosurvival, and regenerative effects on glomerular cells.

We postulated that prostaglandin E2 (PGE2), which exhibits regulatory functions to control immune-mediated inflammation, fibrosis, oxidative stress, and tissue/cellular regeneration, has the potential to improve the course of nephritis. Therefore, the therapeutic potential of prostanoid on established nephritis in mice was evaluated focusing on its role on renal cellular recovery, with emphasis on its cytoprotecting and growth-promoting effects. Acute nephritis was induced in mice by single injection of nephrotoxic serum (NTS), followed by PGE2 administration with severity of nephritis evaluated over time. Mice injected with PGE2 recovered promptly with normalization of blood urea nitrogen and urine protein levels and histology. Recovery was observed with dosing of prostanoid at day 1, as well as day 4. With the use of selective EP1-4 receptor agonists, EP3 receptor has been identified as important in mediating beneficial effects of PGE2 in our system. PGE2 normalized glomerular cell losses during nephrotoxic serum-induced nephritis, restored synaptopodin distribution and F-actin filaments arrangement in glomeruli. In cell culture, PGE2 reduced nephrotoxim serum (NTS)-induced apoptosis of glomerular cells and promoted cell reproliferation after NTS-mediated injury. In conclusion, PGE2 treatment promotes resolution of glomerular inflammation. Consistent with this observation, the regenerative and cytoprotective effects of prostanoid on glomerular cells in culture were observed, suggesting that PGE2 may be beneficial in the treatment of glomerulonephritis.

A human monoclonal antibody against the collagen type IV α3NC1 domain is a non-invasive optical biomarker for glomerular diseases.

Progressive kidney disease is a significant clinical problem. However, despite research aimed toward developing improved predictors of disease, the major tool to assess kidney ultrastructure damage is the kidney biopsy. Here we tested the capability of a labeled human monoclonal antibody (F1.1), directed against the NC1 domain of α3(IV) collagen, to detect pathologic kidney alterations in vivo using mouse models of nephrotoxic serum-induced nephritis and puromycin aminoglycoside nephrosis. The F1.1 antibody-fluorophore conjugate signal rapidly localized specifically to injured glomeruli in both the severe and mild kidney disease models while minimally labeling healthy kidney. This differential labeling is likely due to cryptic NC1-domain exposure as enzymatic or chemical treatment of healthy human or mouse kidney sections significantly increased F1.1 binding to the glomeruli. Finally, kidney tissue from patients with renal disease show significant glomerular staining by F1.1 indicating that exposure of the NC1 domain occurs in clinically relevant circumstances. Thus, NC1 domain exposure may represent an in situ biomarker for assessment of kidney injury. Our study suggests that F1.1 and similar antibodies may represent a new class of non-invasive renal imaging reagents.

Anti-tumor necrosis factor α treatment of interferon-α-induced murine lupus nephritis reduces the renal macrophage response but does not alter glomerular immune complex formation.

OBJECTIVE: To analyze the mechanism for the therapeutic effects of tumor necrosis factor α (TNFα) inhibition in a murine model of systemic lupus erythematosus. METHODS: We used the (NZB × NZW)F(1) (NZB/NZW) mouse model of interferon-α-induced lupus nephritis and treated mice with TNF receptor type II (TNFRII) Ig after TNFα expression was detected in the kidneys. Autoantibodies were measured by enzyme-linked immunosorbent assay (ELISA), and autoantibody- forming cells were determined using an enzyme-linked immunospot assay. Activation of splenocytes was analyzed by flow cytometry. Kidneys were harvested and analyzed using flow cytometry, immunohistochemistry, ELISA, Western blotting, and real-time polymerase chain reaction. RESULTS: TNFRII Ig treatment stabilized nephritis and markedly prolonged survival. Autoantibody production and systemic immune activation were not inhibited, but the renal response to glomerular immune complex deposition was attenuated. This was associated with decreases in renal production of chemokines, renal endothelial cell activation, interstitial F4/80(high) macrophage accumulation, tubular damage, and oxidative stress. In contrast, perivascular lymphoid aggregates containing B cells, T cells, and dendritic cells accumulated unabated. CONCLUSION: Our data suggest that TNFα is a critical cytokine that amplifies the response of the nephron to immune complex deposition, but that it has less influence on the response of the systemic vasculature to inflammation.

IFN-α confers resistance of systemic lupus erythematosus nephritis to therapy in NZB/W F1 mice.

The critical role of IFN-α in the pathogenesis of human systemic lupus erythematosus has been highlighted in recent years. Exposure of young lupus-prone NZB/W F1 mice to IFN-α in vivo leads to an accelerated lupus phenotype that is dependent on T cells and is associated with elevated serum levels of BAFF, IL-6, and TNF-α, increased splenic expression of IL-6 and IL-21, formation of large germinal centers, and the generation of large numbers of short-lived plasma cells that produce IgG2a and IgG3 autoantibodies. In this study, we show that both IgG2a and IgG3 autoantibodies are pathogenic in IFN-α-accelerated lupus, and their production can be dissociated by using low-dose CTLA4-Ig. Only high-dose CTLA4-Ig attenuates both IgG2a and IgG3 autoantibody production and significantly delays death from lupus nephritis. In contrast, BAFF/APRIL blockade has no effect on germinal centers or the production of IgG anti-dsDNA Abs but, if given at the time of IFN-α challenge, delays the progression of lupus by attenuating systemic and renal inflammation. Temporary remission of nephritis induced by combination therapy with cyclophosphamide, anti-CD40L Ab, and CTLA4-Ig is associated with the abrogation of germinal centers and depletion of short-lived plasma cells, but relapse occurs more rapidly than in conventional NZB/W F1 mice. This study demonstrates that IFN-α renders NZB/W F1 relatively resistant to therapeutic intervention and suggests that the IFN signature should be considered when randomizing patients into groups and analyzing the results of human clinical trials in systemic lupus erythematosus.

Pathology and protection in nephrotoxic nephritis is determined by selective engagement of specific Fc receptors.

Introduction of heterologous anti-glomerular basement membrane antiserum (nephrotoxic serum, NTS) into presensitized mice triggers the production of IgG anti-NTS antibodies that are predominantly IgG2b and the glomerular deposition of pathogenic immune complexes, leading to accelerated renal disease. The pathology observed in this model is determined by the effector cell activation threshold that is established by the coexpression on infiltrating macrophages of the IgG2a/2b restricted activation receptor FcgammaRIV and its inhibitory receptor counterpart, FcgammaRIIB. Blocking FcgammaRIV with a specific monoclonal antibody thereby preventing IgG2b engagement or treatment with high dose intravenous gamma-globulin (IVIG) to down-regulate FcgammaRIV while up-regulating FcgammaRIIB, protects mice from fatal disease. In the absence of FcgammaRIIB, IVIG is not protective; this indicates that reduced FcgammaRIV expression alone is insufficient to protect animals from pathogenic IgG2b immune complexes. These results establish the significance of specific IgG subclasses and their cognate FcgammaRs in renal disease.

The relevance of antigen binding to the pathogenicity of lupus autoantibodies.

Although lupus autoantibodies provide diagnostic value, discordance between serum levels and nephritis poses mechanistic questions. Krishnan and co-workers report that only those that crossreact with basement membrane components produce immune deposits. Thus, other glomerular binding properties probably define where deposits form. Thereafter, Fc- and complement-mediated events influence disease expression. Clearly other factors determine the ultimate phenotype; however, the findings provide insights into the variable disease patterns in lupus nephritis.

Interferon-α accelerates murine systemic lupus erythematosus in a T cell-dependent manner.

OBJECTIVE: To investigate the mechanism by which interferon-α (IFNα) accelerates systemic lupus erythematosus (SLE) in (NZB×NZW)F1 (NZB/NZW) mice. METHODS: NZB/NZW mice were treated with an adenovirus expressing IFNα. In some mice, T cells were depleted with an anti-CD4 antibody. The production of anti-double-stranded DNA (anti-dsDNA) antibodies was measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assay. Germinal centers and antibody-secreting cells (ASCs) in spleens and IgG deposition and leukocyte infiltrates in kidneys were visualized by immunofluorescence staining. The phenotype of splenic cells was determined by flow cytometry. Finally, somatic hypermutation and gene usage in VH regions of IgG2a and IgG3 were studied by single-cell polymerase chain reaction. RESULTS: IFNα-accelerated lupus in NZB/NZW mice was associated with elevated serum levels of IgG2 and IgG3 anti-dsDNA antibodies and accumulation of many IgG ASCs in the spleen, which did not develop into long-lived plasma cells. Furthermore, IgG2a and IgG3 antibodies in the mice were highly somatically mutated and used distinct repertoires of VH genes. The induction of SLE in the mice was associated with an increase in B cell Toll-like receptor 7 expression, increased serum levels of BAFF, interleukin-6 (IL-6), and tumor necrosis factor α, and induction of T cells expressing IL-21. Although IFNα drove a T cell-independent increase in serum levels of IgG, autoantibody induction and the development of nephritis were both completely dependent on CD4+ T cell help. CONCLUSION: These findings demonstrate that, although IFNα activates both innate and adaptive immune responses in NZB/NZW mice, CD4+ T cells are necessary for IFNα-driven induction of anti-dsDNA antibodies and clinical SLE.

Selective blockade of BAFF for the prevention and treatment of systemic lupus erythematosus nephritis in NZM2410 mice.

OBJECTIVE: To determine whether BAFF or combined BAFF/APRIL blockade is effective in a mouse model of systemic lupus erythematosus (SLE) nephritis characterized by rapidly progressive glomerulosclerosis. METHODS: NZM2410 mice at early and late stages of SLE nephritis were treated with a short course of BAFF-R-Ig or TACI-Ig fusion protein. Proteinuria and serologic profile were evaluated every 2 weeks. Immunohistochemical, flow cytometric, and enzyme-linked immunospot analyses of the spleen, kidney, and bone marrow were performed after 8 weeks and after 33 weeks. RESULTS: A short course of selective blockade of BAFF alone was sufficient to prevent and treat SLE nephritis in NZM2410 mice, despite the formation of pathogenic autoantibodies. Decreases in spleen size and B cell depletion persisted for more than 33 weeks after treatment and resulted in secondary decreases in CD4 memory T cell formation and activation of splenic and peripheral monocytes. Immune complex deposition in the kidneys was dissociated from renal damage and from activation of renal endothelial and resident dendritic cells. CONCLUSION: Selective blockade of BAFF alone, which resulted in B cell depletion and splenic collapse, was sufficient to prevent and treat the disease in this model of noninflammatory SLE nephritis. This shows that the inflammatory microenvironment may be a determinant of the outcome of B cell modulation strategies.

Poly(ADP-ribose) polymerase-1 regulates the progression of autoimmune nephritis in males by inducing necrotic cell death and modulating inflammation.

Necrotic lesions and necrotic cell death characterize severe autoimmune nephritides, and contribute to local inflammation and to progression of the disease. Poly(ADP-ribose) polymerase-1 (PARP-1), a DNA repair enzyme, is involved in the induction of necrosis and is a key player in the acute and chronic inflammation. Therefore, we hypothesized that PARP-1 controls the severity of nephritis by mediating the induction of necrosis in the kidney. We used lupus and anti-glomerular basement membrane models of nephritis to determine the effects of PARP-1 on the inflammatory response in the kidney. We show in this study that PARP-1 is indeed activated during the course of glomerulonephritis. We also show that the absence of PARP-1 or its pharmacological inhibition results in milder nephritis, with lower blood urea nitrogen levels, reduced necrotic lesions, and higher survival rates. The relevance of PARP-1 showed a strong male sex specificity, and treatment of male mice with 17beta-estradiol prolonged their survival during the course of nephritis. PARP-1 also regulated TNF-alpha expression and up-regulation of adhesion molecules, further supporting a role of PARP-1 in the inflammatory process within the kidney. Our results demonstrate that PARP-1 activation and consequent necrotic cell death play an important role in the pathogenesis of male nephritis, and suggest that PARP-1 can be a novel therapeutic target in glomerulonephritis.