Rapamycin prevents the development of nephritis in lupus-prone NZB/W F1 mice

Immunometabolic Mechanisms of LANCL2 in CD4+ T Cells and Phagocytes Provide Protection from Systemic Lupus Erythematosus

Lanthionine synthetase C-like 2 (LANCL2) is an immunoregulatory therapeutic target for autoimmune diseases. NIM-1324 is an investigational new drug aimed at addressing the unmet clinical needs of patients with systemic lupus erythematosus (SLE) by targeting the LANCL2 immunometabolic pathway. In R848 and bm12 adoptive transfer models of systemic inflammation that share pathologies with SLE, Lancl2-/- mice experienced greater mortality, increased spleen weight, and reduced CD25hi FOXP3+ CD4+ regulatory T cells compared with the wild type. Conversely, treatment with NIM-1324 in the wild type increased CD25hi FOXP3+ regulatory T cells while reducing inflammatory IL-17+ and IL-21+ CD4+ T cell subsets in the spleen. In traditional mouse models of SLE (NZB/W F1 and MRL/lpr), oral treatment with NIM-1324 protected against weight loss and proteinuria, decreased anti-dsDNA titers, and provided similar changes to the CD4+ T cell compartment in the spleen. The pharmacological activation of LANCL2 by NIM-1324 rescued hypocomplementemia, reduced kidney histopathological scores, and decreased blood IFN response genes and inflammatory cytokines. The loss of LANCL2 in phagocytes impairs phagosome processing, leading to increased uptake of material and inflammatory cytokine production, yet decreased markers of endosomal maturation, phagosome turnover, and lysozyme activity. Treatment with NIM-1324 increases metabolic and lysozyme activity in the phagosome, providing support for increased markers of early phagosome function. This efficacy translated to human PBMCs from patients with SLE, because ex vivo treatment with NIM-1324 resulted in reduced levels of IFN-α, IL-6, and IL-8. Consequently, the activation of LANCL2 effectively modulates CD4+ T cell differentiation and phagocyte activation, supporting immune tolerance in SLE.

Therapeutic prime/pull vaccination of HSV-2-infected guinea pigs with the ribonucleotide reductase 2 (RR2) protein and CXCL11 chemokine boosts antiviral local tissue-resident and effector memory CD4+ and CD8+ T cells and protects against recurrent genital herpes

Following acute herpes simplex virus type 2 (HSV-2) infection, the virus undergoes an asymptomatic latent infection of sensory neurons of dorsal root ganglia (DRG). Chemical and physical stress cause intermittent virus reactivation from latently infected DRG and recurrent virus shedding in the genital mucosal epithelium causing genital herpes in symptomatic patients. While T cells appear to play a role in controlling virus reactivation from DRG and reducing the severity of recurrent genital herpes, the mechanisms for recruiting these T cells into DRG and the vaginal mucosa (VM) remain to be fully elucidated. The present study investigates the effect of CXCL9, CXCL10, and CXCL11 T-cell-attracting chemokines on the frequency and function of DRG- and VM-resident CD4+ and CD8+ T cells and its effect on the frequency and severity of recurrent genital herpes in the recurrent herpes guinea pig model. HSV-2 latent-infected guinea pigs were immunized intramuscularly with the HSV-2 ribonucleotide reductase 2 (RR2) protein (Prime) and subsequently treated intravaginally with the neurotropic adeno-associated virus type 8 expressing CXCL9, CXCL10, or CXCL11 chemokines to recruit CD4+ and CD8+ T cells into the infected DRG and VM (Pull). Compared to the RR2 therapeutic vaccine alone, the RR2/CXCL11 prime/pull therapeutic vaccine significantly increased the frequencies of functional tissue-resident and effector memory CD4+ and CD8+ T cells in both DRG and VM tissues. This was associated with less virus in the healed genital mucosal epithelium and reduced frequency and severity of recurrent genital herpes. These findings confirm the role of local DRG- and VM-resident CD4+ and CD8+ T cells in reducing virus shedding at the vaginal site of infection and the severity of recurrent genital herpes and propose the novel prime-pull vaccine strategy to protect against recurrent genital herpes.IMPORTANCEThe present study investigates the novel prime/pull therapeutic vaccine strategy to protect against recurrent genital herpes using the latently infected guinea pig model. In this study, we used the strategy that involves immunization of herpes simplex virus type 2-infected guinea pigs using a recombinantly expressed herpes tegument protein-ribonucleotide reductase 2 (RR2; prime), followed by intravaginal treatment with the neurotropic adeno-associated virus type 8 expressing CXCL9, CXCL10, or CXCL11 T-cell-attracting chemokines to recruit T cells into the infected dorsal root ganglia (DRG) and vaginal mucosa (VM) (pull). We show that the RR2/CXCL11 prime-pull therapeutic vaccine strategy elicited a significant reduction in virus shedding in the vaginal mucosa and decreased the severity and frequency of recurrent genital herpes. This protection was associated with increased frequencies of functional tissue-resident (TRM cells) and effector (TEM cells) memory CD4+ and CD8+ T cells infiltrating latently infected DRG tissues and the healed regions of the vaginal mucosa. These findings shed light on the role of tissue-resident and effector memory CD4+ and CD8+ T cells in DRG tissues and the VM in protection against recurrent genital herpes and propose the prime-pull therapeutic vaccine strategy in combating genital herpes.

B cell metabolism in autoimmune diseases: signaling pathways and interventions

Autoimmune diseases are heterogeneous disorders believed to stem from the immune system's inability to distinguish between auto- and foreign- antigens. B lymphocytes serve a crucial role in humoral immunity as they generate antibodies and present antigens. Dysregulation of B cell function induce the onset of autoimmune disorders by generating autoantibodies and pro-inflammatory cytokines, resulting in an imbalance in immune regulation. New research in immunometabolism shows that cellular metabolism plays an essential role in controlling B lymphocytes immune reactions by providing the energy and substrates for B lymphocytes activation, differentiation, and function. However, dysregulated immunometabolism lead to autoimmune diseases by disrupting self-tolerance mechanisms. This review summarizes the latest research on metabolic reprogramming of B lymphocytes in autoimmune diseases, identifying crucial pathways and regulatory factors. Moreover, we consider the potential of metabolic interventions as a promising therapeutic strategy. Understanding the metabolic mechanisms of B cells brings us closer to developing novel therapies for autoimmune disorders.

Role of T cells in the pathogenesis of systemic lupus erythematous: Focus on immunometabolism dysfunctions

Evidence demonstrates that T cells are implicated in developing SLE, and each of them dominantly uses distinct metabolic pathways. Indeed, intracellular enzymes and availability of specific nutrients orchestrate fate of T cells and lead to differentiation of regulatory T cells (Treg), memory T cells, helper T cells, and effector T cells. The function of T cells in inflammatory and autoimmune responses is determined by metabolic processes and activity of their enzymes. Several studies were conducted to determine metabolic abnormalities in SLE patients and clarify how these modifications could control the functions of the involved T cells. Metabolic pathways such as glycolysis, mitochondrial pathways, oxidative stress, mTOR pathway, fatty acid and amino acid metabolisms are dysregulated in SLE T cells. Moreover, immunosuppressive drugs used in treating autoimmune diseases, including SLE, could affect immunometabolism. Developing drugs to regulate autoreactive T cell metabolism could be a promising therapeutic approach for SLE treatment. Accordingly, increased knowledge about metabolic processes paves the way to understanding SLE pathogenesis better and introduces novel therapeutic options for SLE treatment. Although monotherapy with metabolic pathways modulators might not be sufficient to prevent autoimmune disease, they may be an ideal adjuvant to reduce administration doses of immunosuppressive drugs, thus reducing drug-associated adverse effects. This review summarized emerging data about T cells that are involved in SLE pathogenesis, focusing on immunometabolism dysregulation and how these modifications could affect the disease development.

Lupus Nephritis: Current Perspectives and Moving Forward

Lupus nephritis is a severe organ manifestation of systemic lupus erythematosus, and its pathogenesis involves complex etiology and mechanisms. Despite significant knowledge gains and extensive efforts put into understanding the development and relapsing disease activity, lupus nephritis remains a substantial cause of morbidity and mortality in lupus patients. Current therapies retain a significant unmet medical need regarding rates of complete response, preventing relapse of lupus nephritis, progression of chronic kidney disease to kidney failure, drug toxicity, and pill burden-related drug non-adherence. Connected to progression of chronic kidney disease are the associated risks for disabling or even lethal cardiovascular events, as well as chronic kidney disease-related secondary immunodeficiency and serious infections. In this regard, biomarkers are needed that can predict treatment response to specific drugs to enable personalized precision medicine. A series of clinical trials with innovative immunomodulatory drugs are ongoing and raise expectations for improvements in the management of lupus nephritis. Here, we review how new developments in pathogenesis connect with current and future perspectives for the management of lupus nephritis.

Novel and emerging treatment strategies for lupus nephritis

INTRODUCTION

Lupus nephritis (LN) is a key predictor for kidney failure and death in patients with systemic lupus erythematosus (SLE). While conventional immunosuppressive treatments have improved the outcome of LN, novel therapies continue to emerge. These new agents target specific immune-reactive cells (B cell repertoire or T lymphocytes) and crucial cytokines/signalling pathways in LN pathogenesis.

AREAS COVERED

New therapeutic approaches that target specific immune-reactive cells (B cell repertoire or T lymphocytes), crucial cytokines and their signalling pathways in LN pathogenesis.

EXPERT OPINION

Although earlier studies of rituximab fail to show benefit, a newer generation anti-CD20 biologic, obinutuzumab, is promising in LN. Inhibition of B-cell activating factor by belimumab confers superior renal response when added to the standard of care (SOC) regimens, leading to its recent approval for LN. Therapies targeting plasma cells (proteasome inhibitors, anti-CD38) in LN are being developed. A newer generation calcineurin inhibitor, voclosporin, when combined with SOC, results in better renal responses in LN. Other innovative strategies include targeting type I interferon, co-stimulatory signals, complement cascade (anti-C5b) and intracellular proliferation signals (e.g. mTOR, JAK1/2, BTK). While these novel agents improve the short-term renal responses without increased toxicities, long-term data on disease progression and safety remain to be established. Patient stratification by clinical phenotypes, biomarkers and molecular profiles helps enhance the efficacy and cost-effectiveness of novel therapies of LN.

Lupus nephritis: new progress in diagnosis and treatment

Systemic lupus erythematosus (SLE) is a chronic multifactorial autoimmune disease that affects many organs, including the kidney. Lupus nephritis (LN) is a common manifestation characterized by heterogeneous clinical and histopathological findings, and often associates with poor prognosis. The diagnosis and treatment of LN is challenging, depending largely on renal biopsy, and there is no reliable non-invasive LN biomarker. Up to now, the complete remission rate of LN is only 20%∼30% after receiving six months of standard treatment, which is far from satisfactory. Moreover, adverse reactions to immunosuppressants, especially glucocorticoids, further compromise the prognosis of LN. Biological reagents targetting autoimmune responses and inflammatory pathways, bring hope to the treatment of intractable lupus. The European Renal Association-European Dialysis and Transplant Association (EULAR/ERA-EDTA) and KDIGO (Kidney Disease: Improving Global Outcomes) have been working on and launched the recommendations for the management of LN. In this review, we update our knowledge in the pathogenesis, diagnosis, and management of LN and prospect for the future potential targets in the management of LN.

Mitochondrial impairment and repair in the pathogenesis of systemic lupus erythematosus

Nucleic acid autoantibodies, increase type I interferon (IFN-α) levels, and immune cell hyperactivation are hallmarks of systemic lupus erythematosus (SLE). Notably, immune cell activation requires high level of cellular energy that is predominately generated by the mitochondria. Mitochondrial reactive oxygen species (mROS), the byproduct of mitochondrial energy generation, serves as an essential mediator to control the activation and differentiation of cells and regulate the antigenicity of oxidized nucleoids within the mitochondria. Recently, clinical trials on normalization of mitochondrial redox imbalance by mROS scavengers and those investigating the recovery of defective mitophagy have provided novel insights into SLE prophylaxis and therapy. However, the precise mechanism underlying the role of oxidative stress-related mitochondrial molecules in skewing the cell fate at the molecular level remains unclear. This review outlines distinctive mitochondrial functions and pathways that are involved in immune responses and systematically delineates how mitochondrial dysfunction contributes to SLE pathogenesis. In addition, we provide a comprehensive overview of damaged mitochondrial function and impaired metabolic pathways in adaptive and innate immune cells and lupus-induced organ tissues. Furthermore, we summarize the potential of current mitochondria-targeting drugs for SLE treatment. Developing novel therapeutic approaches to regulate mitochondrial oxidative stress is a promising endeavor in the search for effective treatments for systemic autoimmune diseases, particularly SLE.

Effect of Combined Mycophenolate and Rapamycin Treatment on Kidney Fibrosis in Murine Lupus Nephritis

Background: A significant proportion of lupus nephritis patients develop chronic kidney disease (CKD) and progressive kidney fibrosis, for which there is no specific treatment. We previously reported that mycophenolate or rapamycin monotherapy showed comparable efficacy in suppressing kidney fibrosis in a murine model of lupus nephritis through their direct action on mesangial cells. We extended our study to investigate the effect of combined mycophenolate and rapamycin treatment (MR) on kidney fibrosis in NZBWF1/J mice.

Methods: Female NZBWF1/J mice with active nephritis were randomized to receive vehicle or treatment with mycophenolate (50 mg/kg/day) and rapamycin (1.5 mg/kg/day) (MR) for up to 12 weeks, and the effect of treatment on clinical parameters, kidney histology, and fibrotic processes was investigated.

Results: Progression of nephritis in untreated mice was accompanied by mesangial proliferation, glomerulosclerosis, tubular atrophy, protein cast formation, increased mTOR and ERK phosphorylation, and induction of TGF-β1, IL-6, α-smooth muscle actin, fibronectin, and collagen expression. Combined MR treatment prolonged survival, improved kidney function, decreased anti-dsDNA antibody level, and ameliorated histopathological changes. The effect of combined MR treatment on kidney histology and function was comparable to that of mycophenolate or rapamycin monotherapy. In vitro studies in human mesangial cells showed that exogenous TGF-β1 and IL-6 both induced mTOR and ERK phosphorylation and downstream fibrotic processes. Both mycophenolic acid and rapamycin inhibited inflammatory and fibrotic processes induced by TGF-β1 or IL-6 by downregulating mTOR and ERK phosphorylation.

Conclusions: Our findings indicate that combined mycophenolate and rapamycin, at reduced dose, improves kidney fibrosis in murine lupus nephritis through their distinct effect on mTOR and ERK signaling in mesangial cells.

Pharmacologically Inferred Glycolysis and Glutaminolysis Requirement of B Cells in Lupus-Prone Mice

Several studies have shown an enhanced metabolism in the CD4⁺ T cells of lupus patients and lupus-prone mice. Little is known about the metabolism of B cells in lupus. In this study, we compared the metabolism of B cells between lupus-prone B6.Sle1.Sle2.Sle3 triple-congenic mice and C57BL/6 controls at steady state relative to autoantibody production, as well as during T cell-dependent (TD) and T cell-independent (TI) immunizations. Starting before the onset of autoimmunity, B cells from triple-congenic mice showed an elevated glycolysis and mitochondrial respiration, which were normalized in vivo by inhibiting glycolysis with a 2-deoxy-d-glucose (2DG) treatment. 2DG greatly reduced the production of TI-Ag-specific Abs, but showed minimal effect with TD-Ags. In contrast, the inhibition of glutaminolysis with 6-diazo-5-oxo-l-norleucine had a greater effect on TD than TI-Ag-specific Abs in both strains. Analysis of the TI and TD responses in purified B cells in vitro suggests, however, that the glutaminolysis requirement is not B cell-intrinsic. Thus, B cells have a greater requirement for glycolysis in TI than TD responses, as inferred from pharmacological interventions. B cells from lupus-prone and control mice have different intrinsic metabolic requirements or different responses toward 2DG and 6-diazo-5-oxo-l-norleucine, which mirrors our previous results obtained with follicular Th cells. Overall, these results predict that targeting glucose metabolism may provide an effective therapeutic approach for systemic autoimmunity by eliminating both autoreactive follicular Th and B cells, although it may also impair TI responses.

Successful treatment of sirolimus in a Chinese patient with refractory LN and APS: a case report

It has been reported that the mammalian target of rapamycin (mTOR) pathway is involved in the pathogenesis of systemic lupus erythematosus (SLE), and increasing evidence has shown the effect of mTOR-targeted therapies with sirolimus in SLE. The objective of this study was to report the successful treatment of sirolimus in a Chinese patient with refractory lupus nephritis (LN) and anti-phospholipid antibody syndrome (APS). A 44-year-old female with a previous diagnosis of autoimmune hemolytic anemia (AIHA) and APS secondary to SLE presented with lupus nephritis refractory to cyclophosphamide and mycophenolate. Renal biopsy met the criteria of WHO class III LN complicated by acute tubular injury and immunofluorescence confirmed the activation of the mTOR pathway. Treatment with the mTOR inhibitor sirolimus was initiated in this patient. Complete remission (CR) was achieved after 6 months, and flare-free remission was maintained for the next 3.5 years. The literature on the efficacy of sirolimus in patients with LN was reviewed. Although the available evidence is limited to retrospective studies with small sample sizes, sirolimus appeared to be efficacious in some patients with refractory LN. Well-designed clinical trials are warranted, and pathology-guided precision medicine might assist in guiding physicians’ treatment decisions.

Renal mTORC1 activation is associated with disease activity and prognosis in lupus nephritis

OBJECTIVE

This study was initiated to evaluate mammalian target of rapamycin (mTOR) activation in renal tissue of lupus nephritis (LN) patients.

METHODS

This retrospective study included 187 LN patients, 20 diabetic nephropathy (DN) patients, 10 minimal change disease (MCD) patients, and 10 normal controls (NCs). 7 of 187 LN patients had repeated renal biopsies. mTORC1/2 activation was evaluated by immunohistochemistry and multiplexed immunofluorescence. The association of mTORC1/2 activation with the clinicopathologic indices and prognostic outcomes was analysed among 187 LN patients. Proteomics was performed in renal biopsies of 20 LN patients. Proteomics was employed to comprehensively evaluate the impact of mTOR activation on intrarenal gene expression.

RESULTS

mTORC1/2 was significantly activated in podocytes, mesangial cells, endothelial cells and tubular epithelial cells of LN patients as compared with those with MCD or NC. The glomerular mTORC1 activation was higher in LN patients compared with DN patients. mTORC1, but not mTORC2, activation strongly correlated with serum albumin, complement C3, proteinuria, and the following pathological biomarkers of LN: crescent formation, interstitial inflammation and fibrosis. Moreover, mTORC1 activation was identified as a prognostic marker in LN patients. Bioinformatic analyses of proteomics and immunohistochemical data unveiled increased complement activation, antigen presentation, and phagocytosis in LN patients with mTORC1 activation.

CONCLUSION

Renal mTORC1 activation could be a biomarker to reveal disease activity and predict clinical prognosis in LN patients.

Improvement of renal and non-renal SLE outcome measures on sirolimus therapy - A 21-year follow-up study of 73 patients

The safety, tolerance, and selected renal and non-renal outcome measures were evaluated in 73 SLE patients who received sirolimus therapy for more than 3 months in our institution over the past 21 years. In 12 patients who had lupus nephritis, proteinuria (p = 0.0287), hematuria (p = 0.0232), anti-DNA antibody levels (p = 0.0028) and steroid use were reduced (p = 0.0200). In the non-renal cohort of 61 patients, anti-DNA antibody levels (p = 0.0332) and steroid use were reduced (p = 0.0163). Both in the renal and non-renal cohorts, C3 (renal p = 0.0070; non-renal p = 0.0021) and C4 complement levels were increased (renal p = 0.0063; non-renal p = 0.0042) Adverse effects of mouth sores (2/73), headaches (1/73), and gastrointestinal discomfort were noted in a minority of patients (6/73). Sirolimus was only discontinued in two of 73 patients due to headache and recurrent infections, respectively. This study suggests that sirolimus is well tolerated and exerts long-term therapeutic efficacy in controlling renal and non-renal manifestations of SLE.

B Cell Metabolism and Autophagy in Autoimmunity

B cells are central to the pathogenesis of multiple autoimmune diseases, through antigen presentation, cytokine secretion, and the production of autoantibodies. During development and differentiation, B cells undergo drastic changes in their physiology. It is emerging that these are accompanied by equally significant shifts in metabolic phenotype, which may themselves also drive and enforce the functional properties of the cell. The dysfunction of B cells during autoimmunity is characterised by the breaching of tolerogenic checkpoints, and there is developing evidence that the metabolic state of B cells may contribute to this. Determining the metabolic phenotype of B cells in autoimmunity is an area of active study, and is important because intervention by metabolism-altering therapeutic approaches may represent an attractive treatment target.

Immunometabolism in systemic lupus erythematosus: Relevant pathogenetic mechanisms and potential clinical applications

Systemic lupus erythematosus (SLE) is a complex, heterogeneous, systemic autoimmune disease involving a wide array of aberrant innate and adaptive immune responses. The immune microenvironment of SLE promotes the metabolic reprogramming of immune cells, leading to immune dyshomeostasis and triggering autoimmune inflammation. Different immune subsets switch from a resting state to a highly metabolic active state by alternating the redox-sensitive signaling pathway and the involved metabolic intermediates to amplify the inflammatory response, which is critical in SLE pathogenesis. In this review, we discuss abnormal metabolic changes in glucose metabolism, tricarboxylic acid cycle, and lipid and amino acid metabolism as well as mitochondrial dysfunction in immune cells in SLE. We also review studies focused on the potential targets for key molecules of metabolic pathways in SLE, such as hypoxia-inducible factor-1α, mammalian target of rapamycin, and AMP-activated protein kinase. We highlight the therapeutic rationale for targeting these pathways in treating SLE and summarize their recent clinical applications in SLE.

Rapamycin Eyedrops Increased CD4+Foxp3+ Cells and Prevented Goblet Cell Loss in the Aged Ocular Surface

Dry eye disease (DED), one of the most prevalent conditions among the elderly, is a chronic inflammatory disorder that disrupts tear film stability and causes ocular surface damage. Aged C57BL/6J mice spontaneously develop DED. Rapamycin is a potent immunosuppressant that prolongs the lifespan of several species. Here, we compared the effects of daily instillation of eyedrops containing rapamycin or empty micelles for three months on the aged mice. Tear cytokine/chemokine profile showed a pronounced increase in vascular endothelial cell growth factor-A (VEGF-A) and a trend towards decreased concentration of Interferon gamma (IFN)-γ in rapamycin-treated groups. A significant decrease in inflammatory markers in the lacrimal gland was also evident (IFN-γ, IL-12, CIITA and Ctss); this was accompanied by slightly diminished Unc-51 Like Autophagy Activating Kinase 1 (ULK1) transcripts. In the lacrimal gland and draining lymph nodes, we also observed a significant increase in the CD45⁺CD4⁺Foxp3⁺ cells in the rapamycin-treated mice. More importantly, rapamycin eyedrops increased conjunctival goblet cell density and area compared to the empty micelles. Taken together, evidence from these studies indicates that topical rapamycin has therapeutic efficacy for age-associated ocular surface inflammation and goblet cell loss and opens the venue for new investigations on its role in the aging process of the eye.

Immunometabolic Pathways and Its Therapeutic Implication in Autoimmune Diseases

Autoimmune diseases (AIDs) are characterized with aberrant immune responses and their respective signaling pathways controlling cell differentiation, death, and survival. Cell metabolism is also an indispensable biochemical process that provides the very fundamental energy and materials. Accumulating evidences implicate that metabolism pathways have critical roles in determining the function of different immune subsets. Mechanisms of how immunometabolism participate in the pathogenesis of AIDs were also under intensive exploration. Here, in this review, we summarize the metabolic features of immune cells in AIDs and also the individual function of immunometabolism pathways, including glucose metabolism and tricarboxylic acid (TCA) cycle, in the setting of AIDs, mainly focusing on the potential targets for intervention. We also review studies that explore the intervention strategies targeting key molecules of metabolic pathways, such as mammalian target of rapamycin (mTOR), AMP-activated protein kinase (AMPK), and hypoxia-inducible factor 1a (HIF1a), in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). The highlight of this review is to provide a comprehensive summary of the status quo of immunometabolism studies in AIDs and the potential translatable drug targets.

A review of advances in the understanding of lupus nephritis pathogenesis as a basis for emerging therapies

Lupus nephritis is an important cause of both acute kidney injury and chronic kidney disease that can result in end-stage renal disease. Its pathogenic mechanisms are characterized by aberrant activation of both innate and adaptive immune responses, dysregulation of inflammatory signaling pathways, and increased cytokine production. Treatment of lupus nephritis remains a challenging issue in the management of systemic lupus erythematosus since the clinical presentation, response to treatment, and prognosis all vary considerably between patients and are influenced by ethnicity, gender, the degree of chronic kidney damage, pharmacogenomics, and non-immunological modulating factors. Elucidation of the various immunopathogenic pathways in lupus nephritis has resulted in the development of novel therapies, including biologics that target specific antigens on B lymphocytes to achieve B cell depletion, agents that modulate B cell proliferation and development, drugs that block co-stimulatory pathways, drugs that target T lymphocytes primarily, and therapies that target complement activation, signaling pathways, pro-inflammatory cytokines, and neutrophil extracellular traps. This review will discuss recent advances in the understanding of disease pathogenesis in lupus nephritis in the context of potential emerging therapies.

Rapamycin inhibits B-cell activating factor (BAFF)-stimulated cell proliferation and survival by suppressing Ca2+-CaMKII-dependent PTEN/Akt-Erk1/2 signaling pathway in normal and neoplastic B-lymphoid cells

B-cell activating factor (BAFF) is a crucial survival factor for B cells, and excess BAFF contributes to development of autoimmune diseases. Recent studies have shown that rapamycin can prevent BAFF-induced B-cell proliferation and survival, but the underlying mechanism remains to be elucidated. Here we found that rapamycin inhibited human soluble BAFF (hsBAFF)-stimulated cell proliferation by inducing G₁-cell cycle arrest, which was through downregulating the protein levels of CDK2, CDK4, CDK6, cyclin A, cyclin D1, and cyclin E. Rapamycin reduced hsBAFF-stimulated cell survival by downregulating the levels of anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-xL and survivin) and meanwhile upregulating the levels of pro-apoptotic proteins (BAK and BAX). The cytostatic and cytotoxic effects of rapamycin linked to its attenuation of hsBAFF-elevated intracellular free Ca²⁺ ([Ca²⁺]_i). In addition, rapamycin blocked hsBAFF-stimulated B-cell proliferation and survival by preventing hsBAFF from inactivating PTEN and activating the Akt-Erk1/2 pathway. Overexpression of wild type PTEN or ectopic expression of dominant negative Akt potentiated rapamycin's suppression of hsBAFF-induced Erk1/2 activation and proliferation/viability in Raji cells. Interestingly, PP242 (mTORC1/2 inhibitor) or Akt inhibitor X, like rapamycin (mTORC1 inhibitor), reduced the basal or hsBAFF-induced [Ca²⁺]_i elevations. Chelating [Ca²⁺]_i with BAPTA/AM, preventing [Ca²⁺]_i elevation using EGTA, 2-APB or verapamil, inhibiting CaMKII with KN93, or silencing CaMKII strengthened rapamycin's inhibitory effects. The results indicate that rapamycin inhibits BAFF-stimulated B-cell proliferation and survival by blunting mTORC1/2-mediated [Ca²⁺]_i elevations and suppressing Ca²⁺-CaMKII-dependent PTEN/Akt-Erk1/2 signaling pathway. Our finding underscores that rapamycin may be exploited for prevention of excessive BAFF-induced aggressive B-cell malignancies and autoimmune diseases.

B Cell Abnormalities in Systemic Lupus Erythematosus and Lupus Nephritis-Role in Pathogenesis and Effect of Immunosuppressive Treatments

Abnormalities in B cells play pivotal roles in the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis (LN). Breach in central and peripheral tolerance mechanisms generates autoreactive B cells which contribute to the pathogenesis of SLE and LN. Dysregulation of B cell transcription factors, cytokines and B cell-T cell interaction can result in aberrant B cell maturation and autoantibody production. These immunological abnormalities also lead to perturbations in circulating and infiltrating B cells in SLE and LN patients. Conventional and novel immunosuppressive medications confer differential effects on B cells which have important clinical implications. While cyclophosphamide and mycophenolate mofetil (MMF) showed comparable clinical efficacy in active LN, MMF induction was associated with earlier reduction in circulating plasmablasts and plasma cells. Accumulating evidence suggests that MMF maintenance is associated with lower risk of disease relapse than azathioprine, which may be explained by its more potent and selective suppression of B cell proliferation. Novel therapeutic approaches targeting the B cell repertoire include B cell depletion with monoclonal antibodies binding to cell surface markers, inhibition of B cell cytokines, and modulation of costimulatory signals in B cell-T cell interaction. These biologics, despite showing improvements in serological parameters and proteinuria, did not achieve primary endpoints when used as add-on therapy to standard treatments in active LN patients. Other emerging treatments such as calcineurin inhibitors, mammalian target of rapamycin inhibitors and proteasome inhibitors also show distinct inhibitory effects on the B cell repertoire. Advancement in the knowledge on B cell biology has fueled the development of new therapeutic strategies in SLE and LN. Modification in background treatments, study endpoints and selective recruitment of subjects showing aberrant B cells or its signaling pathways when designing future clinical trials may better elucidate the roles of these novel therapies for SLE and LN patients.

Effect of mycophenolate and rapamycin on renal fibrosis in lupus nephritis

Lupus nephritis (LN) leads to chronic kidney disease (CKD) through progressive fibrosis. Mycophenolate inhibits inosine monophosphate dehydrogenase and is a standard treatment for LN. The mammalian or mechanistic target of rapamycin (mTOR) pathway is activated in LN. Rapamycin inhibits mTOR and is effective in preventing kidney transplant rejection, with the additional merits of reduced incidence of malignancies and viral infections. The effect of mycophenolate or rapamycin on kidney fibrosis in LN has not been investigated. We investigated the effects of mycophenolate and rapamycin in New Zealand Black and White first generation (NZB/W F1) murine LN and human mesangial cells (HMCs), focusing on mechanisms leading to kidney fibrosis. Treatment of mice with mycophenolate or rapamycin improved nephritis manifestations, decreased anti-double stranded (ds) DNA antibody titer and reduced immunoglobulin G (IgG) deposition in the kidney. Both mycophenolate and rapamycin, especially the latter, decreased glomerular mTOR Ser2448 phosphorylation. Renal histology in untreated mice showed mesangial proliferation and progressive glomerulosclerosis with tubular atrophy, and increased expression of transforming growth factor β1 (TGF-β1), monocyte chemoattractant protein-1 (MCP-1), α-smooth muscle actin (α-SMA), fibronectin (FN) and collagen. Both mycophenolate and rapamycin ameliorated the histopathological changes. Results from in vitro experiments showed that both mycophenolate and rapamycin decreased mesangial cell proliferation and their binding with anti-dsDNA antibodies. Mycophenolate and rapamycin also down-regulated mTOR and extracellular signal-regulated kinase (ERK) phosphorylation and inhibited fibrotic responses in mesangial cells that were induced by anti-dsDNA antibodies or TGF-β1. Our findings suggest that, in addition to immunosuppression, mycophenolate and rapamycin may reduce fibrosis in LN, which has important implications in preventing CKD in patients with LN.

In the Right Place, at the Right Time: Spatiotemporal Conditions Determining Plasma Cell Survival and Function

Plasma cells (PCs), the B lineage cells responsible for producing and secreting antibodies (Abs), are critical cellular components of the humoral immune system. While most of the antibody-secreting cells in the body have a rather short lifetime of a few days, some of them can become long-lived and persist in the body over the entire life span of an individual. The majority of these long-lived plasma cells secretes protective antibodies against pathogens, and are thereby crucial for the humoral component of immunological memory. The generation of these protective antibody-secreting cells can be triggered by an exposure to pathogens, and also by vaccination. Although the majority of plasma cells are protective, sometimes long-lived plasma cells produce autoreactive antibodies, which contribute to the pathogenesis and perpetuation of chronic autoimmune diseases, including lupus erythematosus, rheumatoid arthritis, or multiple sclerosis. In order to promote the formation of protective antibody-secreting cells and to target pathogenic plasma cells, it is crucial to understand the signals which promote their longevity and allow them to exert their function. In recent years, it has become clear that plasma cells depend on extrinsic factors for their survival, leading to the concept that certain tissue microenvironments promote plasma cell retention and longevity. However, these niches are not static structures, but also have dynamic features with respect to their cellular composition. Here, we review what is known about the molecular and cellular composition of the niches, and discuss the impact of dynamic changes within these microenvironments on plasma cell function. As plasma cell metabolism is tightly linked to their function, we present new tools, which will allow us to analyze metabolic parameters in the plasma cell niches in vivo over time.

Clinical Experience of Sirolimus Regarding Efficacy and Safety in Systemic Lupus Erythematosus

New treatment options constitute unmet needs for patients diagnosed with systemic lupus erythematosus (SLE). Inhibition of the mammalian target of rapamycin (mTOR) pathway by sirolimus, a drug approved and in clinical use to prevent transplant rejection, has shown promising effects in lupus animal models as well as in patients with both antiphospholipid syndrome and SLE. Sirolimus inhibits antigen-induced T cell proliferation and increases the number of circulating regulatory T cells. Recently, sirolimus was tested in an open label phase 1/2 trial, including 43 patients with active SLE, resistant or intolerant to conventional medications. The results were encouraging showing a progressive improvement, including mucocutaneous and musculoskeletal manifestations. At our university unit, we have more than 16 years' experience of sirolimus as treatment for non-renal manifestations of SLE. Herein, we retrospectively evaluated data on tolerance, dosage, affected organ systems, disease activity measures, corticosteroid reduction, concomitant immunosuppressive therapies, and patient-reported outcome measures (PROMs) such as pain intensity, fatigue, well-being and quality-of-life (QoL) in 27 Caucasian patients with mildly active SLE. Musculoskeletal manifestation was the main reason for sirolimus treatment followed by skin involvement and leukocytopenia. Mean time on sirolimus was 47.1 (range 2-140) months. Decreasing global disease activity was observed, as measured by the clinical SLE disease activity index-2000, with a mean reduction of 2.5 points (range -10 to 0) and a corresponding mean reduction of the physician's global assessment (0-4) of 0.64 (range -2 to 0). The mean daily dose of corticosteroids (prednisolone) was reduced by 3.3 mg (-12.5 to 0). Non-significant trends toward improvements of QoL and pain intensity were found. Serious side-effects were not seen during sirolimus treatment, but early withdrawal due to nausea (n = 4) and non-serious infections (n = 2) appeared. This observational study, including longtime real-life use of sirolimus in SLE, is the largest to date and it essentially confirms the results of the recent phase 1/2 trial. Our data indicate that sirolimus is efficient in patients with musculoskeletal SLE manifestations, particularly arthritis and tendinitis. Further randomized controlled trials evaluating the potential benefits of sirolimus in SLE are warranted, but should aim to enroll patients with shorter disease duration, less accrued damage, and more diverse ethnicities.

Longterm Data on Sirolimus Treatment in Patients with Lupus Nephritis

Objective.

To expand the limited longterm data on sirolimus treatment in patients with lupus nephritis (LN). Our pilot short-term data suggested efficacy of sirolimus treatment in these patients.

Methods.

We retrospectively reviewed 16 class III/IV/V patients with LN who have received prednisolone (PSL) and sirolimus either as initial or maintenance treatment.

Results.

Sixteen patients received sirolimus treatment (9 because of intolerance to standard immunosuppressants and 7 because of a history of malignancy) for 45.3 ± 36.5 months. In 5 patients, sirolimus and PSL were given as induction for active nephritis, and they showed improvements in proteinuria (2.8 ± 1.9 g/day at baseline, 0.1 ± 0.1 g/day after 36 mos, p = 0.011), anti-dsDNA (107.7 ± 91.9 IU/ml and 37.0 ± 55.4 IU/ml, respectively, p = 0.178), and C3 (54.8 ± 26.1 mg/dl and 86.3 ± 18.6 mg/dl, respectively, p = 0.081). Eleven patients received sirolimus and low-dose PSL as longterm maintenance, and they showed continued improvement in C3 (90.4 ± 18.1 mg/dl and 117.7 ± 25.1 mg/dl at commencement and after 36 mos, respectively, p = 0.025), stable renal function (estimated glomerular filtration rate 58.6 ± 25.8 ml/min and 63.0 ± 29.6 ml/min, respectively, p = 0.239), and proteinuria (0.8 ± 0.7 g/day and 0.7 ± 0.7 g/day respectively, p = 0.252). Renal flare occurred in 1 patient, and another patient who had stage 4 chronic kidney disease when sirolimus was started developed endstage renal failure after 27 months. Sirolimus was discontinued in 5 patients, in 4 cases related to drug side effects. Deterioration of dyslipidemia occurred in 4 patients, but was adequately controlled with statin therapy.

Conclusion.

The preliminary evidence suggests that sirolimus may serve as an alternative treatment for patients with LN who do not tolerate standard treatment or who had a history of malignancy, and it has an acceptable longterm safety profile.

Metabolism as a Target for Modulation in Autoimmune Diseases

Metabolic pathways are now well recognized as important regulators of immune differentiation and activation, and thus influence the development of autoimmune diseases such as systemic lupus erythematosus (SLE). The mechanistic target of rapamycin (mTOR) has emerged as a key sensor of metabolic stress and an important mediator of proinflammatory lineage specification. Metabolic pathways control the production of mitochondrial reactive oxygen species (ROS), which promote mTOR activation and also modulate the antigenicity of proteins, lipids, and DNA, thus placing ROS at the heart of metabolic disturbances during pathogenesis of SLE. Therefore, we review here the pathways that control ROS production and mTOR activation and identify targets for safe therapeutic modulation of the signaling network that underlies autoimmune diseases, focusing on SLE.

The influence of exposure to immunosuppressive treatment during pregnancy on renal function and rate of apoptosis in native kidneys of female Wistar rats

Pregnancy puts a significant additional strain on kidneys. The aim of our study was to investigate the impact of immunosuppressive drugs on changes in native kidneys in female Wistar rats after exposure during pregnancy. The study was conducted on 32 dams, subjected to immunosuppressive regimens commonly used in the therapy of human kidney transplant recipients (cyclosporine A, mycophenolate mofetil and prednisone; tacrolimus, mycophenolate mofetil and prednisone; cyclosporine A, everolimus and prednisone). The animals received drugs for 2 weeks before pregnancy and during 3 weeks of pregnancy. In all treated dams lower body weight (but not kidney mass) and alterations in serum sodium and chloride ions were found; serum creatinine concentration was increased in dams treated with cyclosporine A, everolimus and prednisone. All treatment groups of dams showed increased apoptosis in the distal tubules. In histological examination the changed intensity of acidophilic or basophilic cytoplasm of epithelial cells was found in kidneys of rats treated with calcineurin inhibitors, mycophenolate mofetil and prednisone. All immunosuppressive regimens caused abnormalities affecting nephron tubules. Regimens containing calcineurin inhibitors and mycophenolate mofetil caused higher rate of apoptosis and more pronounced histopathological changes. Regimen based on everolimus despite the lower rate of apoptosis in the proximal tubules and lower accumulation of kidney injury markers revealed higher serum creatinine concentration. Thus, interpretation which combination of drugs is better or worse for long-lasting functioning of kidneys in pregnant females requires further studies.

Rapamycin attenuates BAFF-extended proliferation and survival via disruption of mTORC1/2 signaling in normal and neoplastic B-lymphoid cells

B cell activating factor from the TNF family (BAFF) stimulates B-cell proliferation and survival, but excessive BAFF promotes the development of aggressive B cells leading to malignant and autoimmune diseases. Recently, we have reported that rapamycin, a macrocyclic lactone, attenuates human soluble BAFF (hsBAFF)-stimulated B-cell proliferation/survival by suppressing mTOR-mediated PP2A-Erk1/2 signaling pathway. Here, we show that the inhibitory effect of rapamycin on hsBAFF-promoted B cell proliferation/survival is also related to blocking hsBAFF-stimulated phosphorylation of Akt, S6K1, and 4E-BP1, as well as expression of survivin in normal and B-lymphoid (Raji and Daudi) cells. It appeared that both mTORC1 and mTORC2 were involved in the inhibitory activity of rapamycin, as silencing raptor or rictor enhanced rapamycin's suppression of hsBAFF-induced survivin expression and proliferation/viability in B cells. Also, PP242, an mTORC1/2 kinase inhibitor, repressed survivin expression, and cell proliferation/viability more potently than rapamycin (mTORC1 inhibitor) in B cells in response to hsBAFF. Of interest, ectopic expression of constitutively active Akt (myr-Akt) or constitutively active S6K1 (S6K1-ca), or downregulation of 4E-BP1 conferred resistance to rapamycin's attenuation of hsBAFF-induced survivin expression and B-cell proliferation/viability, whereas overexpression of dominant negative Akt (dn-Akt) or constitutively hypophosphorylated 4E-BP1 (4EBP1-5A), or downregulation of S6K1, or co-treatment with Akt inhibitor potentiated the inhibitory effects of rapamycin. The findings indicate that rapamycin attenuates excessive hsBAFF-induced cell proliferation/survival via blocking mTORC1/2 signaling in normal and neoplastic B-lymphoid cells. Our data underscore that rapamycin may be a potential agent for preventing excessive BAFF-evoked aggressive B-cell malignancies and autoimmune diseases.

Activation of the Mechanistic Target of Rapamycin in SLE: Explosion of Evidence in the Last Five Years

The mechanistic target of rapamycin (mTOR) is a central regulator in cell growth, activation, proliferation, and survival. Activation of the mTOR pathway underlies the pathogenesis of systemic lupus erythematosus (SLE). While mTOR activation and its therapeutic reversal were originally discovered in T cells, recent investigations have also uncovered roles in other cell subsets including B cells, macrophages, and "non-immune" organs such as the liver and the kidney. Activation of mTOR complex 1 (mTORC1) precedes the onset of SLE and associated co-morbidities, such as anti-phospholipid syndrome (APS), and may act as an early marker of disease pathogenesis. Six case reports have now been published that document the development of SLE in patients with genetic activation of mTORC1. Targeting mTORC1 over-activation with N-acetylcysteine, rapamycin, and rapalogs provides an opportunity to supplant current therapies with severe side effect profiles such as prednisone or cyclophosphamide. In the present review, we will discuss the recent explosion of findings in support for a central role for mTOR activation in SLE.

mTOR has distinct functions in generating versus sustaining humoral immunity

Little is known about the role of mTOR signaling in plasma cell differentiation and function. Furthermore, for reasons not understood, mTOR inhibition reverses antibody-associated disease in a murine model of systemic lupus erythematosus. Here, we have demonstrated that induced B lineage-specific deletion of the gene encoding RAPTOR, an essential signaling adaptor for rapamycin-sensitive mTOR complex 1 (mTORC1), abrogated the generation of antibody-secreting plasma cells in mice. Acute treatment with rapamycin recapitulated the effects of RAPTOR deficiency, and both strategies led to the ablation of newly formed plasma cells in the spleen and bone marrow while also obliterating preexisting germinal centers. Surprisingly, although perturbing mTOR activity caused a profound decline in serum antibodies that were specific for exogenous antigen or DNA, frequencies of long-lived bone marrow plasma cells were unaffected. Instead, mTORC1 inhibition led to decreased expression of immunoglobulin-binding protein (BiP) and other factors needed for robust protein synthesis. Consequently, blockade of antibody synthesis was rapidly reversed after termination of rapamycin treatment. We conclude that mTOR signaling plays critical but diverse roles in early and late phases of antibody responses and plasma cell differentiation.

Combination therapy for inhibitor reversal in haemophilia A using monoclonal anti-CD20 and rapamycin

Development of antibodies (inhibitors) against coagulation factor VIII (FVIII) is a major complication of intravenous replacement therapy in haemophilia A (HA). Current immune tolerance induction (ITI) regimens are not universally effective. Rituximab, a B cell-depleting antibody against CD20, has shown mixed results for inhibitor reversal in patients. This study aims to develop a combinatorial therapy for inhibitor reversal in HA, using anti-murine CD20 (anti-mCD20) antibody and rapamycin, which targets both B and T cell responses. Additionally, it extensively characterises the role of the IgG backbone in B cell depletion by anti-CD20 antibodies. For this, inhibitors were generated in BALB/c-HA mice by weekly IV injection of FVIII. Subsequently, anti-mCD20 (18B12) with IgG2a or IgG1 backbone was injected IV in two doses three weeks apart and B cell depletion and recovery was characterised. Rapamycin was administered orally 3x/week (for 1 month) while continuing FVIII injections. Altering the IgG backbone of anti-mCD20 from IgG2a to IgG1 reduced overall depletion of B cells (including memory B cells), and marginal zone, B-10, and B-1b cells were specifically unaffected. While neither antibody was effective alone, in combination with rapamycin, anti-mCD20 IgG2a but not IgG1 was able to reverse inhibitors in HA mice. This regimen was particularly effective for starting titres of ~10 BU. Although IgG1 anti-mCD20 spared potentially tolerogenic B cell subsets, IgG2a directed sustained hyporesponsiveness when administered in conjunction with rapamycin. This regimen represents a promising treatment for inhibitor reversal in HA, as both of these compounds have been extensively used in human patients.

Roles of mTOR complexes in the kidney: implications for renal disease and transplantation

The mTOR pathway has a central role in the regulation of cell metabolism, growth and proliferation. Studies involving selective gene targeting of mTOR complexes (mTORC1 and mTORC2) in renal cell populations and/or pharmacologic mTOR inhibition have revealed important roles of mTOR in podocyte homeostasis and tubular transport. Important advances have also been made in understanding the role of mTOR in renal injury, polycystic kidney disease and glomerular diseases, including diabetic nephropathy. Novel insights into the roles of mTORC1 and mTORC2 in the regulation of immune cell homeostasis and function are helping to improve understanding of the complex effects of mTOR targeting on immune responses, including those that impact both de novo renal disease and renal allograft outcomes. Extensive experience in clinical renal transplantation has resulted in successful conversion of patients from calcineurin inhibitors to mTOR inhibitors at various times post-transplantation, with excellent long-term graft function. Widespread use of this practice has, however, been limited owing to mTOR-inhibitor- related toxicities. Unique attributes of mTOR inhibitors include reduced rates of squamous cell carcinoma and cytomegalovirus infection compared to other regimens. As understanding of the mechanisms by which mTORC1 and mTORC2 drive the pathogenesis of renal disease progresses, clinical studies of mTOR pathway targeting will enable testing of evolving hypotheses.

Effect of Immunosuppressive Therapy on Proteinogram in Rats

BACKGROUND It has been observed that the use of immunosuppressive drugs in patients after transplantation of vascularized organs may be associated with changes in the concentration of certain fractions of plasma proteins. The concentration of these proteins was correlated with an increased risk of occurrence of stage 3 chronic kidney disease (CKD). This article examines the effect of the most commonly used immunosuppressive drugs on the concentration of plasma proteins in Wistar rats. MATERIAL AND METHODS The study involved 36 rats grouped according to the immunosuppressive regimen used (tacrolimus, mycophenolate mofetil, cyclosporine A, rapamycin, and prednisone). The rats in all study groups were treated with a 3-drug protocol for 6 months. The treatment dose was adjusted based on available data in the literature. No drugs were administered to the control group. The rats were sacrificed and blood samples collected to determine the concentration of plasma proteins using electrophoresis technique. RESULTS Statistically significant differences were observed between protein concentrations within the studied groups. The differences related to the proteins with masses of 195 kDa, 170 kDa, 103 kDa, and 58 kDa. CONCLUSIONS (1) Immunosuppressive drugs caused changes in the proteinogram of plasma proteins. (2) The strongest effect on rat plasma proteins was exerted by a regimen based on rapamycin. Intermediate, weak, and weakest effects were observed in regimens based on cyclosporine A, tacrolimus, and mycophenolate mofetil, respectively.

Activation of mTOR (mechanistic target of rapamycin) in rheumatic diseases

Mechanistic target of rapamycin (mTOR, also known as mammalian target of rapamycin) is a ubiquitous serine/threonine kinase that regulates cell growth, proliferation and survival. These effects are cell-type-specific, and are elicited in response to stimulation by growth factors, hormones and cytokines, as well as to internal and external metabolic cues. Rapamycin was initially developed as an inhibitor of T-cell proliferation and allograft rejection in the organ transplant setting. Subsequently, its molecular target (mTOR) was identified as a component of two interacting complexes, mTORC1 and mTORC2, that regulate T-cell lineage specification and macrophage differentiation. mTORC1 drives the proinflammatory expansion of T helper (TH) type 1, TH17, and CD4(-)CD8(-) (double-negative, DN) T cells. Both mTORC1 and mTORC2 inhibit the development of CD4(+)CD25(+)FoxP3(+) T regulatory (TREG) cells and, indirectly, mTORC2 favours the expansion of T follicular helper (TFH) cells which, similarly to DN T cells, promote B-cell activation and autoantibody production. In contrast to this proinflammatory effect of mTORC2, mTORC1 favours, to some extent, an anti-inflammatory macrophage polarization that is protective against infections and tissue inflammation. Outside the immune system, mTORC1 controls fibroblast proliferation and chondrocyte survival, with implications for tissue fibrosis and osteoarthritis, respectively. Rapamycin (which primarily inhibits mTORC1), ATP-competitive, dual mTORC1/mTORC2 inhibitors and upstream regulators of the mTOR pathway are being developed to treat autoimmune, hyperproliferative and degenerative diseases. In this regard, mTOR blockade promises to increase life expectancy through treatment and prevention of rheumatic diseases.

Tuberous sclerosis and fulminant lupus in a young woman

Tuberous sclerosis is an autosomal dominant disorder characterized by involvement of skin, nervous system, kidneys, and lungs. It results from mutations in 1 of 2 genes: TSC1 (encoding hamartin) or TSC2 (encoding tuberin), leading to dysregulation and activation of the mammalian target of rapamycin (mTOR) pathway. Constitutive activation of mTOR signaling has recently been reported in systemic lupus erythematosus (SLE), and inhibition of this pathway may benefit patients with SLE nephritis. We report a case of a young woman with tuberous sclerosis who developed fulminant SLE, with lower extremity edema, massive proteinuria, and class IV lupus glomerulonephritis. She died despite treatment with high-dose steroids, plasmapheresis, and cyclophosphamide. Although there are no prior reports of coexistence of these 2 rare diseases, this case is of considerable interest because of the possibility that activation of mTOR by the TSC mutations may have led to activation of the immune system and the development of unusually severe SLE.

Small molecules in the treatment of systemic lupus erythematosus

Advances in the understanding of the cellular biological events that underlie systemic lupus erythematosus (SLE) have led to the identification of key molecules and signaling pathways that are aberrantly expressed. The parallel development of small molecule drugs that inhibit or interfere with the specific perturbations identified, offers perspective for more rational, effective and less toxic therapy. In this review, we present data from preclinical and clinical studies of such emerging novel therapies with a particular focus on kinase inhibitors and other compounds that modulate signal transduction. Moreover, we highlight the use of chromatin-modifying medications, bringing attention to the central role of epigenetics in SLE pathogenesis.

Rapamycin ameliorates proteinuria and restores nephrin and podocin expression in experimental membranous nephropathy

Objective. Recent studies have shown a beneficial effect of rapamycin in passive and active Heymann Nephritis (HN). However, the mechanisms underlying this beneficial effect have not been elucidated. Methods. Passive Heymann Nephritis (PHN) was induced by a single intravenous infusion of anti-Fx1 in 12 Sprague-Dawley male rats. One week later, six of these rats were commenced on daily treatment with subcutaneous rapamycin 0.5 mgr/kg (PHN-Rapa). The remaining six rats were used as the proteinuric control group (PHN) while six more rats without PHN were given the rapamycin solvent and served as the healthy control group (HC). All rats were sacrificed at the end of the 7th week. Results. Rapamycin significantly reduced proteinuria during the autologous phase of PHN. Histological lesions were markedly improved by rapamycin. Immunofluorescence revealed attenuated deposits of autologous alloantibodies in treated rats. Untreated rats showed decreased glomerular content of both nephrin and podocin whereas rapamycin restored their expression. Conclusions. Rapamycin monotherapy significantly improves proteinuria and histological lesions in experimental membranous nephropathy. This beneficial effect may be mediated by inhibition of the alloimmune response during the autologous phase of PHN and by restoration of the normal expression of the podocyte proteins nephrin and podocin.

Metabolic regulation of organelle homeostasis in lupus T cells

Abnormal T-cell signaling and activation are characteristic features in systemic lupus erythematosus (SLE). Lupus T cells are shifted toward an over-activated state, important signaling pathways are rewired, and signaling molecules are replaced. Disturbances in metabolic and organelle homeostasis, importantly within the mitochondrial, endosomal, and autophagosomal compartments, underlie the changes in signal transduction. Mitochondrial hyperpolarization, enhanced endosomal recycling, and dysregulated autophagy are hallmarks of pathologic organelle homeostasis in SLE. This review is focused on the metabolic checkpoints of endosomal traffic that control immunological synapse formation and mitophagy and may thus serve as targets for treatment in SLE.

Rapamycin induced ultrastructural and molecular alterations in glomerular podocytes in healthy mice

BACKGROUND

In the normal kidney, rapamycin is considered to be non-nephrotoxic. In the present study, we investigated whether rapamycin is indeed non-nephrotoxic by examining the ultrastructural and molecular alterations of podocytes in healthy mice.

METHODS

Balb/c mice were given three different intraperitoneal doses of rapamycin for 1 week (dose model)-low-dose group: 1 mg/kg/day, intermediate-dose (ID) group: 1.5 mg/kg/day and high-dose (HD) group: 3 mg/kg/day; four mice in each group. An ID of rapamycin was also given for three different periods (time model): 1, 4 and 8 weeks; four mice were in each group. Mice treated with dimethyl sulphoxide served as controls. Body weight was measured weekly. Renal function was assessed by serum creatinine at the time of sacrifice. For estimation of albuminuria, 24-h urine collections were performed before treatment and weekly thereafter. Glomerular content of nephrin, podocin, Akt and Ser473-phospho-Akt was estimated by western blot and immunofluorescence. Nephrin and podocin messenger RNA (mRNA) were measured by real-time polymerase chain reaction. Mean podocyte foot process width (FPW) was measured by electron microscopy.

RESULTS

Urine albumin levels increased in the HD and 4-week groups. Renal function was modestly deteriorated in the HD group. The mean FPW increased in a dose-dependant manner at Week 1, further deteriorated at Week 4 and finally improved at Week 8. Nephrin and podocin mRNA levels showed a significant decrease at Week 1 and were restored at Week 4 and 8. Nephrin and podocin protein levels were reduced at Week 4 and recovered at Week 8. Ser473-phospho-Akt significantly increased in all rapamycin-treated groups.

CONCLUSIONS

Rapamycin induced significant ultrastructural and molecular alterations in podocytes in association with albuminuria. These alterations happened early during treatment and they tended to improve over an 8-week treatment period.

Treatment of systemic lupus erythematosus: new advances in targeted therapy

Treatment for systemic lupus erythematosus (SLE) has traditionally been restricted to broad-based immunosuppression, with glucocorticoids being central to care. Recent insights into lupus pathogenesis promise new, selective therapies with more favorable side effect profiles. The best example of this is belimumab, which targets the B cell cytokine BLyS and has now received Food and Drug Administration (FDA) approval for its use in SLE. Strategies targeting other cytokines, such as interleukin 6 (IL-6) and interferon (IFN)-α, are also on the horizon. Blockade of costimulatory interactions between immune cells offers another opportunity for therapeutic intervention, as do small molecule inhibitors that interfere with cell signaling pathways. We review here the current strategies for SLE treatment, with particular focus on therapies now in active pharmaceutical development. We will also discuss new understandings in lupus pathogenesis that may lead to future advances in therapy.