Up-regulation of tubular epithelial interleukin-12 in autoimmune MRL-Fas(lpr) mice with renal injury

Synovial tissue metabolomics analysis of the therapeutic effects of stir-fried Xanthii Fructus on rheumatoid arthritis in rats

Rheumatoid arthritis (RA) is a rheumatic disease that easily causes synovial hyperplasia and joint damage. Comprehensive metabolomic profiling of synovial tissue can reveal local pathological changes during RA and identify metabolites as candidate biomarkers. Detecting metabolites in synovial tissue can more directly reflect the pathological state and disease activity associated with it. stir-fried Xanthii Fructus has demonstrated efficacy in treating RA, but its pharmacodynamic property and mechanism of action are unclear. In this study, the molecular composition of the extract of stir-fried Xanthium Fructus was determined through HPLC. The major components that exert anti-inflammatory and analgesic effects were speculated to be phenolic acids. Next, the effect of stir-fried Xanthii Fructus extracts in RA treatment was comprehensively evaluated using rat body weight, foot volume, inflammatory factors, and histopathological sections of the ankle joint as evaluation indicators. The results showed that the extract of stir-fried Xanthii Fructus could significantly reduce the inflammatory response and improve the degree of joint swelling and the imbalance between pro-inflammatory and anti-inflammatory in adjuvant arthritis rats. Finally, non-targeted metabolomics based on UPLC-Q-TOF/MS and multivariate statistical analysis were used to explore the changes of endogenous metabolites in synovium tissues and to search for potential biomarkers and related metabolic pathways in stir-fried Xanthii Fructus extract-treated AA rats. The results showed that stir-fried Xanthii Fructus mainly treated RA by regulating energy metabolism, hormone metabolism, amino acid metabolism and oxidative stress response in adjuvant arthritis rats. This study provides a theoretical basis for the mechanism of action of stir-fried Xanthii Fructus extract in treating RA.

Immunomodulatory Activity of Mesenchymal Stem Cells in Lupus Nephritis: Advances and Applications

Lupus nephritis (LN) is a significant cause of various acute and chronic renal diseases, which can eventually lead to end-stage renal disease. The pathogenic mechanisms of LN are characterized by abnormal activation of the immune responses, increased cytokine production, and dysregulation of inflammatory signaling pathways. LN treatment is an important issue in the prevention and treatment of systemic lupus erythematosus. Mesenchymal stem cells (MSCs) have the advantages of immunomodulation, anti-inflammation, and anti-proliferation. These unique properties make MSCs a strong candidate for cell therapy of autoimmune diseases. MSCs can suppress the proliferation of innate and adaptive immune cells, such as natural killer cells (NKs), dendritic cells (DCs), T cells, and B cells. Furthermore, MSCs suppress the functions of various immune cells, such as the cytotoxicity of T cells and NKs, maturation and antibody secretion of B cells, maturation and antigen presentation of DCs, and inhibition of cytokine secretion, such as interleukins (ILs), tumor necrosis factor (TNF), and interferons (IFNs) by a variety of immune cells. MSCs can exert immunomodulatory effects in LN through these immune functions to suppress autoimmunity, improve renal pathology, and restore kidney function in lupus mice and LN patients. Herein, we review the role of immune cells and cytokines in the pathogenesis of LN and the mechanisms involved, as well as the progress of research on the immunomodulatory role of MSCs in LN.

Proteomic and Mechanistic Analysis of Spironolactone in Patients at Risk for HF

OBJECTIVES

This study sought to further understand the mechanisms underlying effect of spironolactone and assessed its impact on multiple plasma protein biomarkers and their respective underlying biologic pathways.

BACKGROUND

In addition to their beneficial effects in established heart failure (HF), mineralocorticoid receptor antagonists may act upstream on mechanisms, preventing incident HF. In people at risk for developing HF, the HOMAGE (Heart OMics in AGEing) trial showed that spironolactone treatment could provide antifibrotic and antiremodeling effects, potentially slowing the progression to HF.

METHODS

Baseline, 1-month, and 9-month (or last visit) plasma samples of HOMAGE participants were measured for protein biomarkers (n = 276) by using Olink Proseek-Multiplex cardiovascular and inflammation panels (Olink, Uppsala, Sweden). The effect of spironolactone on biomarkers was assessed by analysis of covariance and explored by knowledge-based network analysis.

RESULTS

A total of 527 participants were enrolled; 265 were randomized to spironolactone (25 to 50 mg/day) and 262 to standard care ("control"). The median (interquartile range) age was 73 years (69 to 79 years), and 26% were female. Spironolactone reduced biomarkers of collagen metabolism (e.g., COL1A1, MMP-2); brain natriuretic peptide; and biomarkers related to metabolic processes (e.g., PAPPA), inflammation, and thrombosis (e.g., IL17A, VEGF, and urokinase). Spironolactone increased biomarkers that reflect the blockade of the mineralocorticoid receptor (e.g., renin) and increased the levels of adipokines involved in the anti-inflammatory response (e.g., RARRES2) and biomarkers of hemostasis maintenance (e.g., tPA, UPAR), myelosuppressive activity (e.g., CCL16), insulin suppression (e.g., RETN), and inflammatory regulation (e.g., IL-12B).

CONCLUSIONS

Proteomic analyses suggest that spironolactone exerts pleiotropic effects including reduction in fibrosis, inflammation, thrombosis, congestion, and vascular function improvement, all of which may mediate cardiovascular protective effects, potentially slowing progression toward heart failure. (HOMAGE [Bioprofiling Response to Mineralocorticoid Receptor Antagonists for the Prevention of Heart Failure]; NCT02556450).

Linarin Protects the Kidney against Ischemia/Reperfusion Injury via the Inhibition of Bioactive ETS2/IL-12

Ischemia/reperfusion injury (IRI), a participant in acute kidney injury (AKI), can occur as a series of pathological processes such as inflammation. Linarin (LIN) has been widely used for different diseases. To confirm the anti-inflammatory value and relevant mechanism of LIN during IRI, in vivo and vitro models were established. LIN or dissolvent was given, and histologic analysis, quantitative (q)RT-PCR, serum creatinine and blood urea nitrogen testing were used to evaluate kidney injury. Microarray analysis, protein-protein interaction (PPI) analysis and molecular docking were used to identify the target protein of LIN, and small interfering RNA (siRNA) transfection was applied to explore the crucial role of identified protein. First, we found that LIN inhibited kidney injury in an in vivo IRI model and decreased the expression of interleukin-12 (IL-12) p40 in vivo and in vitro IRI models. To explore the mechanism of LIN, we collected raw data from a public microarray database and identified E26 oncogene homolog 2 (ETS2) as a crucial protein of LIN according to microarray analysis and PPI. Meanwhile, qRT-PCR indicated that IL-12 p40 showed no significant difference between ETS2 knock down group and LIN treated ETS2 knock down group after hypoxia reoxygenation treatment. In addition, according to molecular docking the contact area is highly conserved and located on a PPI domain of ETS2 which indicates that LIN may alter the interaction with synergistic proteins in the regulation of IL-12 p40 expression. Our study demonstrated the anti-inflammatory effect of LIN during IRI-AKI, broadening the medicinal value of LIN and the therapeutic options for IRI-AKI.

Epoxyeicosatrienoic Acid Analog EET-A Blunts Development of Lupus Nephritis in Mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that causes life threatening renal disease and current therapies are limited with serious side-effects. CYP epoxygenase metabolites of arachidonic acid epoxyeicosatrienoic acids (EETs) demonstrate strong anti-inflammatory and kidney protective actions. We investigated the ability of an orally active EET analog, EET-A to prevent kidney injury in a mouse SLE model. Twenty-weeks old female NZBWF1 (SLE) and age-matched NZW/LacJ (Non SLE) were treated with vehicle or EET-A (10 mg/kg/d, p.o.) for 14 weeks and urine and kidney tissues were collected at the end of the protocol. SLE mice demonstrated marked renal chemotaxis with 30-60% higher renal mRNA expression of CXC chemokine receptors (CXCR) and CXC chemokines (CXCL) compared to Non SLE mice. In SLE mice, the elevated chemotaxis is associated with 5-15-fold increase in cytokine mRNA expression and elevated inflammatory cell infiltration in the kidney. SLE mice also had elevated BUN, serum creatinine, proteinuria, and renal fibrosis. Interestingly, EET-A treatment markedly diminished renal CXCR and CXCL renal mRNA expression in SLE mice. EET-A treatment also reduced renal TNF-α, IL-6, IL-1β, and IFN-γ mRNA expression by 70-80% in SLE mice. Along with reductions in renal chemokine and cytokine mRNA expression, EET-A reduced renal immune cell infiltration, BUN, serum creatinine, proteinuria and renal fibrosis in SLE mice. Overall, we demonstrate that an orally active EET analog, EET-A prevents renal injury in a mouse model of SLE by reducing inflammation.

Carbon monoxide inhibits T cell activation in target organs during systemic lupus erythematosus

Systemic lupus erythematosus is characterized by the presence of circulating anti-nuclear antibodies (ANA) and systemic damage that includes nephritis, haematological manifestations and pulmonary compromise, among others. Although major progress has been made in elucidating the molecular mechanisms responsible for autoimmunity, current therapies for lupus have not improved considerably. Because the exposure of carbon monoxide (CO) has been shown to display beneficial immunoregulatory properties in different immune-mediated diseases, we investigated whether CO therapy improves lupus-related kidney injury in lupus mice. MRL-Fas(lpr) lupus mice were exposed to CO and disease progression was evaluated. ANA, leucocyte-infiltrating populations in spleen, kidney and lung and kidney lesions, were measured. CO therapy significantly decreased the frequency of activated B220(+) CD4(-) CD8(-) T cells in kidneys and lungs, as well as serum levels of ANA. Furthermore, we observed that CO therapy reduced kidney injury by decreasing proliferative glomerular damage and immune complexes deposition, decreased proinflammatory cytokine production and finally delayed the impairment of kidney function. CO exposure ameliorates kidney and lung leucocyte infiltration and delays kidney disease in MRL-Fas(lpr) lupus mice. Our data support the notion that CO could be explored as a potential new therapy for lupus nephritis.

The pathological role of IL-18Rα in renal ischemia/reperfusion injury

Interleukin (IL)-18 is a proinflammatory cytokine produced by leukocytes and parenchymal cells (eg, tubular epithelial cells (TECs), mesangial cells, and podocytes). IL-18 receptor (IL-18R) is expressed on these cells in the kidney during ischemia/reperfusion injury (IRI), but its role in this injury is unknown. Fas/Fas ligand (FasL) is also involved in the pathogenesis of renal IRI via tubular apoptosis. In addition, IL-18 enhances the expression of FasL on TECs, but the mechanism underlying this enhancement is not known. Here we used IL-18Rα-deficient mice to explore the pathological role of IL-18Rα in renal IRI. We found that compared to wild-type (WT) mice with renal IRI as an acute kidney injury (AKI), the IL-18Rα-deficient mice demonstrated decreased renal function (as represented by blood urea nitrogen), tubular damage, an increased accumulation of leukocytes (CD4+ T cells, neutrophils, and macrophages), upregulated early AKI biomarkers (ie, urinary kidney injury molecule-1 levels), and increased mRNA expressions of proinflammatory cytokines (IL-1β, IL-12p40, and IL-18) and chemokines (intercellular adhesion molecule-1 and CCL2/monocyte chemoattractant protein-1). The mRNA expression of FasL in the kidney was increased in the IL-18Rα-deficient mice compared to the WT mice. The adoptive transfer of splenocytes by WT mice led to decreased renal IRI compared to the IL-18Rα-deficient mice. In vitro, the mRNA expression of FasL on TECs was promoted in the presence of recombinant IL-18. These data reveal that IL-18Rα has an anti-inflammatory effect in IRI-induced AKI. Above all, IL-18 enhanced the inflammatory mechanisms and the apoptosis of TECs through the Fas/FasL pathway by blocking IL-18Rα.

Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients.

The multi-faceted influences of estrogen on lymphocytes: toward novel immuno-interventions strategies for autoimmunity management

Early studies of the immune system disclosed that, generally, females exhibit stronger responses to a variety of antigens than males. Perhaps as a result of this response, women are more prone to developing autoimmune diseases than men. Yet, the precise cellular and molecular mechanisms remain under investigation. Recently, interferon-gamma and the related pro-inflammatory interleukin-12 were found to be under effects of sex steroid hormones, with potential implications in regulating immune cells and autoimmune responses. In B lymphocytes, functional binding sites for estrogen receptors were identified in the promoter of the gene encoding activation-induced deaminase, an enzyme required for somatic hypermutation, and class-switch recombination. The observation that estrogen exerts direct impacts on antibody affinity-maturation provides a potential mechanism that could account for generating pathogenic high-affinity auto-antibodies. Further deciphering the multi-faceted influences of sex hormones on the responsiveness of immune cells could lead to novel therapeutic interventions for autoimmunity management.

Targeting transcription factor Stat4 uncovers a role for interleukin-18 in the pathogenesis of severe lupus nephritis in mice

Polymorphisms in the transcription factor Stat4 gene have been implicated as risk factors for systemic lupus erythematosus. Although some polymorphisms have a strong association with autoantibodies and nephritis, their impact on pathophysiology is still unknown. To explore this further we used signal transducers and activators of transcription 4 (Stat4) knockout MRL/MpJ-Fas(lpr)/Fas(lpr) (MRL-Fas(lpr)) mice and found that they did not differ in survival or renal function from Stat4-intact MRL-Fas(lpr) mice. Circulating interleukin (IL)-18 levels, however, were elevated in Stat4-deficient compared to Stat4-intact mice, suggesting that this interleukin might contribute to the progression of lupus nephritis independent of Stat4. In a second approach, Stat4 antisense or missense oligonucleotides or vehicle were given to MRL-Fas(lpr) mice with advanced nephritis. Each of these treatments temporarily ameliorated disease, although IL-18 was increased in each setting. Based on these findings, studies using gene transfer to overexpress IL-18 in MRL-Fas(lpr) and IL-12p40/IL-23 knockout MRL-Fas(lpr) mice reveal a critical role for IL-18 in mediating disease. Thus, the Stat4 and IL-12 (an activator of Stat4)-independent factor, IL-18, can drive autoimmune lupus nephritis in MRL-Fas(lpr) mice. Temporarily blocking Stat4 during advanced nephritis ameliorates disease, suggesting a time-dependent compensatory proinflammatory mechanism.

Cytokine overproduction, T-cell activation, and defective T-regulatory functions promote nephritis in systemic lupus erythematosus

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is mostly attributable to the glomerular deposition of immune complexes and overproduction of T helper- (Th-) 1 cytokines. In this context, the high glomerular expression of IL-12 and IL-18 exerts a major pathogenetic role. These cytokines are locally produced by both macrophages and dendritic cells (DCs) which attract other inflammatory cells leading to maintenance of the kidney inflammation. However, other populations including T-cells and B-cells are integral for the development and worsening of renal damage. T-cells include many pathogenetic subsets, and the activation of Th-17 in keeping with defective T-regulatory (Treg) cell function regards as further event contributing to the glomerular damage. These populations also activate B-cells to produce nephritogenic auto-antibodies. Thus, LN includes a complex pathogenetic mechanism that involves different players and the evaluation of their activity may provide an effective tool for monitoring the onset of the disease.

STAT4 associates with systemic lupus erythematosus through two independent effects that correlate with gene expression and act additively with IRF5 to increase risk

OBJECTIVES

To confirm and define the genetic association of STAT4 and systemic lupus erythematosus (SLE), investigate the possibility of correlations with differential splicing and/or expression levels, and genetic interaction with IRF5.

METHODS

30 tag SNPs were genotyped in an independent set of Spanish cases and controls. SNPs surviving correction for multiple tests were genotyped in five new sets of cases and controls for replication. STAT4 cDNA was analysed by 5'-RACE PCR and sequencing. Expression levels were measured by quantitative PCR.

RESULTS

In the fine mapping, four SNPs were significant after correction for multiple testing, with rs3821236 and rs3024866 as the strongest signals, followed by the previously associated rs7574865, and by rs1467199. Association was replicated in all cohorts. After conditional regression analyses, two major independent signals, represented by SNPs rs3821236 and rs7574865, remained significant across the sets. These SNPs belong to separate haplotype blocks. High levels of STAT4 expression correlated with SNPs rs3821236, rs3024866 (both in the same haplotype block) and rs7574865 but not with other SNPs. Transcription of alternative tissue-specific exons 1, indicating the presence of tissue-specific promoters of potential importance in the expression of STAT4, was also detected. No interaction with associated SNPs of IRF5 was observed using regression analysis.

CONCLUSIONS

These data confirm STAT4 as a susceptibility gene for SLE and suggest the presence of at least two functional variants affecting levels of STAT4. The results also indicate that the genes STAT4 and IRF5 act additively to increase the risk for SLE.

Oversecretion of cytokines and chemokines in lupus nephritis is regulated by intraparenchymal dendritic cells: a review

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is attributed to the glomerular deposition of immune complexes as well as to imbalance of the cytokine homeostasis. In this context, high production of cytokines and chemokines by dendritic cells (DCs) may concur to LN. In addition, urinary cytokine excretion may reflect the accumulation of DCs within glomeruli. DCs are differentiated in both myeloid and plasmacytoid (p) subsets in relation to their typical antigen and chemokine expression. Both subsets migrate in response to chemotactic stimuli because pDCs are susceptible to IL-18 expressed by resident glomerular cells. pDCs bear the IL-18R, and it is conceivable that DCs migrate to the kidney under the attraction of IL-18. Therefore, the depletion of DCs reflects the inflammation severity in LN, whereas measurement of Th1 cytokines may represent an effective tool for monitoring the onset of LN.

Cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can form immune complexes and deposit in tissues, causing inflammation and organ damage. There is evidence that interferons and some interleukins can have an active role in the pathogenesis of SLE and can contribute significantly to the immune imbalance in the disease, whereas the role of some cytokines (such as TNF) is still debated. This review discusses the activity of several cytokines in SLE, their effects on the immune cells in relation to the disease pathogenesis, and the promise and limitations of cytokine-based therapies in clinical trials for lupus patients.

Cytokines in Glomerulonephritis

Cytokines play central roles in both innate and adaptive immune responses that lead to renal inflammation. They are involved systemically in cross-talk between antigen-presenting cells, leukocytes, and regulatory cells to initiate and modulate nephritogenic immunity. Within the kidney, cytokines play a central role in signaling between infiltrating leukocytes and intrinsic renal cells and orchestrate the effector responses that lead to renal damage. Glomerulonephritis (GN) is an important cause of renal inflammation leading to renal failure that results from adaptive responses targeted at the kidney. Animal models of GN have shown that cytokines play critical roles in initiation and modulation of renal inflammatory responses through their ability to modulate the T helper 1/T helper 2 balance of nephritogenic immune responses. Evidence from clinical studies is now confirming the importance of this paradigm in directing the inflammatory mechanisms, histologic patterns, and clinical consequences of human GN. Cytokines also have critical intrarenal effector roles in the development, perpetuation, and resolution of GN. The proinflammatory role of intrarenal cytokine production by leukocytes in GN is well recognized, but, more recently, the role of intrinsic renal cell cytokine production in amplifying renal inflammation has been shown in animal models of GN. Studies showing benefits of specific anticytokine therapies directed at tumor necrosis factor in human GN are now appearing.

Macrophage migration inhibitory factor deficiency attenuates macrophage recruitment, glomerulonephritis, and lethality in MRL/lpr mice

Systemic lupus erythematosus (SLE) is a serious systemic autoimmune disease of unknown etiology. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is operative in innate and adaptive immunity and important in immune-mediated diseases such as rheumatoid arthritis and atherosclerosis. The functional relevance of MIF in systemic autoimmune diseases such as SLE is unknown. Using the lupus-prone MRL/lpr mice, we aim to examine the expression and function of MIF in this murine model of systemic autoimmune disease. These experiments revealed that renal MIF expression was significantly higher in MRL/lpr mice compared with nondiseased control mice (MRL/MpJ), and MIF was also markedly up-regulated in skin lesions of MRL/lpr mice. To examine the effect of MIF on development of systemic autoimmune disease, we generated MRL/lpr mice with a targeted disruption of the MIF gene (MIF(-/-)MRL/lpr), and compared their disease manifestations to MIF(+/+)MRL/lpr littermates. MIF(-/-)MRL/lpr mice exhibited significantly prolonged survival, and reduced renal and skin manifestations of SLE. These effects occurred in the absence of major changes in T and B cell markers or alterations in autoantibody production. In contrast, renal macrophage recruitment and glomerular injury were significantly reduced in MIF(-/-)MRL/lpr mice, and this was associated with reduction in the monocyte chemokine MCP-1. Taken together, these data suggest MIF as a critical effector of organ injury in SLE.

Anti-inflammatory effect of all-trans-retinoic acid in inflammatory arthritis

OBJECTIVE

To determine whether all-trans-retinoic acid (ATRA) improves the destruction of joints and the effect of cytokines on DBA/1J mice with collagen-induced arthritis (CIA).

METHODS

Starting from the time of type II collagen injection, DBA/1J mice were injected intraperitoneally with PBS or 0.5 mg of ATRA 3 times per week for 35 days. The effects of treatment were monitored by determining arthritis and histological scores and measuring cellular proliferation, production of cytokines (IL-2, IL-10, IL-12, IL-6, IFN-gamma, and TNF-alpha) and IgG, and the expression of mRNAs for inducible nitric oxide synthase (iNOS), monocyte chemoattractant protein-1 (MCP-1), and CXCR3.

RESULTS

The arthritis score and incidence of arthritis were lower in the mice treated with ATRA than in those treated with PBS. Histopathologic evidence of joint damage was 34% lower, and the infiltrations of macrophages were reduced in the mice treated with ATRA compared with those treated with PBS. Type II collagen- and ConA-stimulated proliferation of spleen cells, the production of cytokines (IL-6, IL-12, and TNF-alpha), the serum levels of total IgG and IgG1 anti-collagen antibodies, and the expression of mRNAs for MCP-1 were significantly reduced in the mice treated with ATRA than in those treated with PBS.

CONCLUSION

ATRA improved the clinical course and reduced the production of inflammatory cytokines, immunoglobulin, and chemokines in murine CIA. These data suggest that ATRA might be also effective for the treatment of inflammatory arthritis like human rheumatoid arthritis.

The beneficial effects of treatment with all-trans-retinoic acid plus corticosteroid on autoimmune nephritis in NZB/WF mice

Corticosteroids are highly effective anti-inflammatory or immunosuppressive drugs used commonly to treat human systemic lupus erythematosus (SLE). All-trans-retinoic acid (ATRA), which belongs to a class of retinoids that exert immunomodulatory and anti-inflammatory functions, can also suppress the development of lupus nephritis in an animal model. However, both agents can inflict serious adverse effects. Here, we have asked whether ATRA can serve as a steroid-sparing drug in the treatment of lupus nephritis. To examine the efficacy of combining predonisolone (PSL) with ATRA, we treated intraperitoneally New Zealand black/white F1 (NZB/W F1) mice with PSL, ATRA or both agents. Survival rate and proteinuria were determined once a month. Cytokine and anti-DNA antibody production were determined by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). Renal histopathology was observed by haematoxylin and periodic acid Schiff (PAS), immunoperoxidase and immunohistochemical assay. Survival rate and proteinuria were improved in all experimental groups, and were much improved in the mice receiving the combination of ATRA and PSL (P <0.05). A single administration of ATRA reduced the Th1 [interleukin (IL)-2, interferon (IFN)-gamma and IL-12], and a Th2 (IL-4) cytokine level, as effectively as administration of PSL. ATRA also suppressed the expression of inducible nitric oxide synthetase (iNOS) and monocyte chemoattractant protein-1 (MCP-1) in the kidney. The combination of PSL and ATRA significantly reduced IgG2 (especially IgG2b)-specific anti-DNA antibody levels in comparison with administration of either agent alone. These data suggest that ATRA might have the potential to act as a new therapeutic and steroid-sparing drug against lupus nephritis.

Nephritogenic autoantibodies but absence of nephritis in Il-12p35-deficient mice with pristane-induced lupus

BACKGROUND

There is strong evidence that Th1 cytokines are essential for disease in murine models of lupus. Interleukin-12 (IL-12) is essential for Th1 cell differentiation and induces interferon-gamma (IFN-gamma) production. Paradoxically, it has been suggested that an IL-12 defect drives the pathogenesis of lupus, although its precise role remains unclear. We investigated the role of IL-12 for lupus-like disease induced by pristane. IL-12p35-deficient (-/-) and control (+/+) BALB/c mice were treated with pristane or phosphate-buffered saline (PBS).

METHODS

Proteinuria was measured and renal pathology evaluated 10 months after treatment. Sera were analyzed for autoantibodies and total immunoglobulin levels. Cytokine expression and production was analyzed.

RESULTS

Pristane induced nephritogenic autoantibodies and renal immunoglobulin and complement deposition in both IL-12 -/- and +/+ mice. However, proliferative pathology and proteinuria were absent in IL-12-/- mice, whereas pristane induced severe nephritis in one third of the +/+ mice. As expected, cytokine balance was skewed toward a Th2 response in pristane-treated IL-12 -/- mice.

CONCLUSION

These data indicate that renal immune complex deposition can occur in the absence of IL-12p35, but that structural renal damage requires the presence of IL-12p35 or mediators induced by this molecule, such as IFN-gamma. In contrast to the abrogation of nephritogenic autoantibodies by the lack of IFN-gamma, such antibodies are induced by pristane in IL-12p35-deficient mice. Absence of structural renal disease, despite the presence of nephritogenic autoantibodies in pristane-treated IL-12-/- mice, indicates that antibody deposition alone is not sufficient for the development of lupus nephritis in this model.

IL-12 deficiency in MRL-Fas(lpr) mice delays nephritis and intrarenal IFN-gamma expression, and diminishes systemic pathology

Autoimmune disease in MRL-Fas(lpr) mice is characterized by fatal nephritis, systemic pathology, and autoantibodies, mimicking human lupus. We previously reported that 1) intrarenal IL-12 elicits nephritis by fostering the accumulation of intrarenal IFN-gamma-secreting T cells, and 2) MRL-Fas(lpr) mice deficient in the IFN-gamma receptor were spared from nephritis. Therefore, we hypothesized that eliminating IL-12 in MRL-Fas(lpr) mice reduces IFN-gamma-secreting cells and thereby prevents systemic pathology. For this purpose, we constructed an IL-12p40-deficient MRL-Fas(lpr)(IL-12(-/-)) strain. We determined that glomerular and interstitial, but not perivascular, renal pathology were decreased in IL-12(-/-) mice vs the wild-type (WT) strain (5 mo of age). Similarly, systemic pathology (lung, lacrimal and salivary glands, skin, and lymphadenopathy) was diminished. The intrarenal accumulation of T cells (CD4(+), CD8(+), CD4(-)CD8(-)B220(+)) and macrophages was dramatically reduced in IL-12(-/-) MRL-Fas(lpr) kidneys. We determined that there were fewer IFN-gamma transcripts (>70%) in the IL-12(-/-) protected kidneys compared with the WT kidneys. Similarly, cells propagated from IL-12(-/-) MRL-Fas(lpr) kidneys generated substantially less IFN-gamma when stimulated with IL-12 and IL-18 compared with those from WT kidneys, and we detected fewer CD8 and B220 T cells producing IFN-gamma in these IL-12(-/-) MRL-Fas(lpr) kidneys. Of note, survival was modestly extended in the IL-12(-/-) MRL-Fas(lpr) mice. While lung and lacrimal and salivary gland pathology remained reduced in moribund IL-12(-/-) MRL-Fas(lpr) mice, renal pathology and IFN-gamma expression were equivalent to those in the WT strain. Thus, we suggest that IL-12 is a therapeutic target for multiple tissues in lupus; however blocking IL-12 alone is not sufficient to confer enduring protection from lupus nephritis.

Correlation of renal tubular epithelial cell-derived interleukin-18 up-regulation with disease activity in MRL-Faslpr mice with autoimmune lupus nephritis

OBJECTIVE

MRL-Fas(lpr) mice spontaneously develop an autoimmune disease that mimics systemic lupus erythematosus in humans. Infiltrating T cells expressing interferon-gamma (IFNgamma) are responsible for the autoimmune kidney destruction in MRL-Fas(lpr) mice, and interleukin-18 (IL-18) released by mononuclear phagocytes stimulates T cells to produce the IFNgamma. Since MRL-Fas(lpr) T cells are characterized by an overexpression of the IL-18 receptor accessory chain, we sought to determine the impact of IL-18 on the progression of lupus nephritis in MRL-Fas(lpr) mice.

METHODS

IL-18 expression in sera and kidney tissues from MRL-Fas(lpr) mice was determined by enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blotting. IL-18 production by primary cultured tubular epithelial cells (TECs) from MRL-Fas(lpr) and BALB/c mice were examined by RT-PCR, ELISA, and Western blotting. The interactions of TEC-derived IL-18 and MRL-Fas(lpr) T cells were studied in coculture assays. IL-18-related effects on TEC viability and adhesion molecule expression were determined by fluorescence-activated cell sorting and cell proliferation assays.

RESULTS

Up-regulation of mature IL-18 was restricted to nephritic MRL-Fas(lpr) kidneys and increased in parallel with the severity of lupus nephritis. IL-18 expression was not confined to infiltrating monocytes but was primarily detected in TECs. Similarly, interleukin-1beta-converting enzyme expression, which is required for the processing of precursor IL-18, was localized in TECs. De novo synthesis of IL-18 by MRL-Fas(lpr) TECs was confirmed by RT-PCR and Western blotting. Functional assays revealed that activated TECs induced IFNgamma production in MRL-Fas(lpr) T cells through IL-18. IL-18, in turn, increased apoptotic TEC death and up-regulation of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1.

CONCLUSION

Taken together, our findings suggest that IL-18-producing TECs may directly be involved in the pathogenesis of lupus nephritis.

Inflammatory skin disease in K14/p40 transgenic mice: evidence for interleukin-12-like activities of p40

The proinflammatory cytokine interleukin-12, a p35/p40 heterodimer, is produced by resident cells in skin and has been implicated as a pathogenetic factor in T-cell-mediated skin diseases. Secretion of heterodimeric interleukin-12 is always accompanied by production of p40 monomer and p40/p40 homodimer. To investigate the possible in vivo role of p40 per se, we generated mice that constitutively express monomeric and homodimeric p40 in basal keratinocytes. These mice spontaneously developed an eczematous skin disease that was characterized by hyperkeratosis, focal epidermal spongiosis, and a mixed inflammatory infiltrate composed of T cells (CD4+), macrophages, eosinophils, mast cells, and few neutrophils. Fluorescence-activated cell sorter analysis of transgenic epidermal cell suspensions revealed induction of major histocompatibility complex class II molecules on keratinocytes and a 2-3-fold increase in the content of Langerhans cells. Cytokines produced by these activated epidermal cells include interleukin-1alpha and tumor necrosis factor alpha. The skin disease in K14/p40 mice was similar to that of littermate mice that received injections of interleukin-12, suggesting overlapping in vivo functional properties. As induction of interferon-gamma is a major function of interleukin-12, we tested the in vitro ability of transgenic p40 to induce interferon-gamma. In contrast to interleukin-12, transgenic p40 did not stimulate interferon-gamma secretion by cultured splenocytes. We conclude that transgenic p40 and interleukin-12 are equally capable of initiating cutaneous inflammation. Despite these in vivo similarities, there is a clear functional difference between interleukin-12 and transgenic p40 in vitro, suggesting that interferon-gamma is not a major factor contributing to interleukin-12-like activities of transgenic p40.

Interleukin-12 from intrinsic cells is an effector of renal injury in crescentic glomerulonephritis

Interleukin-12 (IL-12) directs the cognate nephritogenic T helper type 1 responses that initiate renal injury in murine crescentic glomerulonephritis (GN). The recent demonstration of IL-12 production by intrinsic renal cells, including mesangial and proximal tubular cells, raises the possibility that IL-12 from nonimmune cells may contribute to inflammatory renal injury. To address this possibility, the development of sheep anti-mouse glomerular basement membrane globulin-induced crescentic GN was studied in C57BL/6 wild-type (WT), IL-12-deficient (IL-12 -/-), and IL-12 "chimeric" mice. IL-12 chimeric mice were produced by transplantation of WT bone marrow into IL-12 -/- mice to restore IL-12 production by immune cells, while leaving them deficient in renal IL-12 production. WT and "sham" chimeric mice (normal bone marrow transplanted into WT mice) developed crescentic GN with glomerular T-cell and macrophage recruitment and impaired renal function (elevated proteinuria and serum creatinine) 10 d after initiation of GN. IL-12 -/- mice showed significant protection from GN. Chimeric IL-12 mice showed significant attenuation of crescent formation, glomerular T-cell and macrophage accumulation, and renal impairment, compared with WT and sham chimeric mice, but were not protected to the same extent as IL-12 -/- mice. IL-12 chimeric mice showed no attenuation of their systemic cognate immune response to the nephritogenic antigen (sheep globulin), indicated by antigen-specific circulating antibody and cutaneous delayed-type hypersensitivity. These studies indicate that IL-12 produced by non-bone marrow derived intrinsic renal cells contributes to immune renal injury. They provide the first in vivo demonstration of a proinflammatory role for an intrinsic renal cell-derived cytokine in renal inflammation.

The role of IFN-gamma in systemic lupus erythematosus: a challenge to the Th1/Th2 paradigm in autoimmunity

The classification of T helper cells into type 1 (Th1) and type 2 (Th2) led to the hypothesis that Th1 cells and their cytokines (interleukin [IL]-2, interferon [IFN]-gamma) are involved in cell-mediated autoimmune diseases, and that Th2 cells and their cytokines (IL-4, IL-5, IL-10, IL-13) are involved in autoantibody(humoral)-mediated autoimmune diseases. However, this paradigm has been refuted by recent studies in several induced and spontaneous mouse models of systemic lupus erythematosus, which showed that IFN-gamma is a major effector molecule in this disease. These and additional findings, reviewed here, suggest that these two cross-talking classes of cytokines can exert autoimmune disease-promoting or disease-inhibiting effects without predictability or strict adherence to the Th1-versus-Th2 dualism.

Accumulating monocytes in the vasculature of rat renal allografts: phenotype, cytokine, inducible no synthase, and tissue factor mRNA expression

BACKGROUND

Necrotic patches and hemorrhagic lesions develop in the renal tissue between day 4 and day 5 after transplantation of fully allogeneic DA rat kidneys to LEW recipients. These lesions are at least in part due to destruction and obstruction of blood vessels. Damage of graft endothelial cells and blood coagulation are likely to be mediated by intravascular graft leukocytes. However, this cell population has not been thoroughly characterized before.

METHODS

We perfused untreated control kidneys, renal isografts, and allografts on day 4 after transplantation with phosphate-buffered saline/ethylenediaminetetraacetic acid to harvest leukocytes from both the blood stream as well as from the marginal intravascular pool. The mRNA expression of typical products of activated monocytes was analyzed in reverse-transcriptase polymerase chain reaction experiments. Graft monocytes were purified and their immunophenotype was investigated by flow cytometry.

RESULTS

Allograft rejection led to a 10-fold increase in the number of intravascular graft leukocytes compared to isografts. A mean number of about 100x10(6) leukocytes was harvested from a single allogeneic kidney, about 73% of these cells were monocytes and most of them displayed an activated phenotype. Compared to isografts, intravascular allograft leukocytes displayed an increased expression of tumor necrosis factor-alpha, inducible NO synthase and tissue factor.

CONCLUSIONS

Our study shows that large numbers of activated monocytes accumulate inside allograft vessels. As they express genes the products of which might damage the allograft by inducing cell death or thrombosis, we speculate that they directly participate in allograft destruction.

Calorie restriction decreases proinflammatory cytokines and polymeric Ig receptor expression in the submandibular glands of autoimmune prone (NZB x NZW)F1 mice

Calorie restriction or fish oil (enriched in n-3 fatty acids) supplementation ameliorates glomerulonephritis and Sjögren's syndrome lesions in (NZB x NZW)F1(B/W) mice. Enhanced proinflammatory cytokine expression and deposition of immune complexes are the important pathological events in the development of Sjögren's syndrome. In the present study, we have examined the effect of calorie restriction and fish oil supplementation on the expression of key inflammatory cytokines [gamma interferon (INF-gamma), interleukin-10 (IL-10), and IL-12] and polymeric immunoglobulin (Ig) receptor (pIgR) (receptor for IgA and IgM) and the secretion of Ig in the submandibular glands (SMG) of B/W mice. Weanling B/W mice were fed either ad libitum (AL) or calorie restricted (CR) (40% less calories than AL) diet supplemented with 5% corn oil (CO) or 5% fish oil (FO) until 4 or 9 months of age. The SMGs were removed and a portion of the tissue used for semiquantitive determinations of IFN-gamma, IL-10, IL-12 (p40), and pIgR mRNA. The remaining SMG tissue was fragmented and cultured for 7 days and the culture supernatants assayed for IgA, IgM, and IgG2a levels by enzyme-linked immunosorbent assay. Results revealed a significant increase in the expression of IFN-gamma, IL-10, and IL-12 mRNA with age in AL fed mice, whereas CR fed mice maintained their levels to near those seen in young animals regardless of the dietary fat. PIgR mRNA expression also remained unaltered in CR animals irrespective of age and dietary fat, while it was found significantly increased in AL fed mice. CR significantly inhibited the elevated levels of IgA and IgG2a seen in aged mice. Interestingly, CR also influenced the Ig level in young animals. In summary, these results indicate that amelioration of autoimmune disease by CR in B/W mice is possibly mediated by the lowered mRNA expression of IFN-gamma, IL-10, IL-12, and pIgR and the reduced Ig secretion.

Treatment of lupus in NZB/W F1 mice with monoclonal antibody against Fas ligand

Since Fas ligand (FasL) can induce apoptosis of Fas-bearing cells, Fas/FasL interactions can play a critical role in maintaining self-tolerance. Fas/FasL interactions in lupus-like autoimmune disease have been well characterized in studies using either Fas or FasL mutant mice. However, the effect of the defective FasL-mediated signaling on the establishment of lupus in other mouse strains, such as NZB/W (B/W) F1, remains uncertain. In the present study, we examined the effect of anti-FasL monoclonal antibody (mAb) on the development of lupus. Treatment of B/W F1 mice with anti-FasL mAb augmented IgG1- and IgG2a-type anti-dsDNA Ab production. However, treatment of B/W F1 mice with anti-FasL mAb also significantly prevented the development of lupus nephritis. These results indicate that Fas/FasL interactions not only regulate IgG-type autoantibody production, but also influence the development of lupus nephritis in B/W F1 mice.

IL-12 Drives IFN-γ-Dependent Autoimmune Kidney Disease in MRL-Fas lpr Mice

IL-12 is secreted by kidney tubular epithelial cells in autoimmune MRL-Faslpr mice before renal injury and increases with advancing disease. Because IL-12 is a potent inducer of IFN-γ, the purpose of this study was to determine whether local provision of IL-12 elicits IFN-γ-secreting T cells within the kidney, which, in turn, incites injury in MRL-Faslpr mice. We used an ex vivo retroviral gene transfer strategy to construct IL-12-secreting MRL-Faslpr tubular epithelial cells (IL-12 “carrier cells”), which were implanted under the kidney capsule of MRL-Faslpr mice before renal disease for a sustained period (28 days). IL-12 “carrier cells” generated intrarenal and systemic IL-12. IL-12 fostered a marked, well-demarcated accumulation of CD4, CD8, and double negative (CD4−CD8− B220+) T cells adjacent to the implant site. We detected more IFN-γ-producing T cells (CD4 &gt; CD8 &gt; CD4−CD8− B220+) at 28 days (73 ± 14%) as compared with 7 days (20 ± 8%) after implanting the IL-12 “carrier cells;” the majority of these cells were proliferating (60–70%). By comparison, an increase in systemic IL-12 resulted in a diffuse acceleration of pathology in the contralateral (unimplanted) kidney. IFN-γ was required for IL-12-incited renal injury, because IL-12 “carrier cells” failed to elicit injury in MRL-Faslpr kidneys genetically deficient in IFN-γ receptors. Furthermore, IFN-γ “carrier cells” elicited kidney injury in wild-type MRL-Faslpr mice. Taken together, IL-12 elicits autoimmune injury by fostering the accumulation of IFN-γ-secreting CD4, CD8, and CD4−CD8− B220+ T cells within the kidney, which, in turn, promote a cascade of events culminating in autoimmune kidney disease in MRL-Faslpr mice.

Mycophenolate mofetil ameliorates perivascular T lymphocyte inflammation and reduces the double-negative T cell population in SLE-prone MRLlpr/lpr mice

Effects on T lymphocyte mediated pathology, phenotypes, and functions in MRLlpr/lpr mice given mycophenolate mofetil (MMF) (100 mg/kg/day) via drinking water or controls given ip cyclophosphamide (CYC) injections (1.8 mg/mouse/week) or water were described. Both MMF and CYC treatment diminished kidney and large salivary gland perivascular cell infiltrates, reduced profoundly double-negative (DN) T cell frequencies, decreased total lymphocyte number in spleen, and increased in vitro proliferative response to Con A. IFN-gamma and IL-10 in supernatants from Con A stimulated spleen cells were augmented after MMF but not CYC treatment. MMF treatment increased whereas CYC reduced IL-12 in serum. Kidney expressions of IFN-gamma, IL-10, and IL-12 mRNA were unaffected by MMF but decreased by CYC. Our results demonstrate that MMF and CYC suppress perivascular T lymphocyte inflammation by reducing the DN T cell population and by amelioration of T cell function. The varying cytokine patterns suggest different mechanisms of the two drugs.

Granulocyte-Colony Stimulating Factor Treatment of Lupus Autoimmune Disease in MRL-lpr/lpr Mice

G-CSF not only functions as an endogenous hemopoietic growth factor for neutrophils, but also displays pro-Th2 and antiinflammatory properties that could be of therapeutic benefit in autoimmune settings. We evaluated the effect of treatment with G-CSF in a murine model of spontaneous systemic lupus erythematosus, a disease in which G-CSF is already administered to patients to alleviate neutropenia, a common complication. Chronic treatment of lupus-prone MRL-lpr/lpr mice with low doses (10 μg/kg) of recombinant human G-CSF, despite the induction of a shift toward the Th2 phenotype of the autoimmune response, increased glomerular deposition of Igs and accelerated lupus disease. Conversely, high-dose (200 μg/kg) treatment with G-CSF induced substantial protection, prolonging survival by &gt;2 mo. In the animals treated with these high doses of G-CSF, neither the Th1/Th2 profile nor the serum levels of TNF-α and IL-10 were modified. Despite the presence of immune complexes in their kidney glomeruli, no inflammation ensued, and serum IL-12 and soluble TNF receptors remained at pre-disease levels. This uncoupling of immune complex deposition and kidney damage resulted from a local down-modulation of FcγRIII (CD16) expression within the glomeruli by G-CSF. Our results demonstrate a beneficial effect of high doses of G-CSF in the prevention of lupus nephritis that may hold promise for future clinical applications, provided caution is taken in dose adjustment.

The central and multiple roles of B cells in lupus pathogenesis

A standard view of B cells in systemic autoimmunity is that they promote lupus by producing autoantibodies (autoAb). However, this view is incomplete because recent studies have revealed that autoimmune disease can be dissociated from autoAb deposition. Furthermore, the spontaneous T-cell activation and organ infiltration in systemic lupus erythematosus patients and animal models are difficult to explain entirely via a direct autoAb-mediated mechanism. In this review, we describe work addressing the B-cell functions of autoantigen presentation and autoAb production in lupus pathogenesis. In the JHD-MRL-Faslpr strain (JHD/lpr), a B-cell-deficient version of the lupus-prone MRL-Faslpr (MRL/lpr) mouse, spontaneous nephritis and dermatitis is abrogated, demonstrating that B cells have a primary role in disease. B cells play a similar role in Fas-intact, lupus-prone MRL mice. To address the role of autoantigen presentation, we analyzed transgenic mice which have B cells that cannot secrete immunoglobulin (mIgM transgenic mice). The restoration of B cells without antibody caused substantial interstitial nephritis and vasculitis although less marked than the intact MRL/lpr controls. To address the role of autoAb, we infused serum from aged MRL/lpr mice into JHD/lpr mice. At most, mild to no nephritis was observed in the infused mice. These results indicate that B cells are promoting autoimmunity in mechanisms other than autoAb secretion, and we describe a model depicting these B-cell roles in the context of other inflammatory events in lupus.

Ischemia/Reperfusion-Induced IFN-γ Up-Regulation: Involvement of IL-12 and IL-18

Tissue injury as a consequence of ischemia followed by reperfusion is characterized by early as well as late signs of inflammation. The latter, among others, involves IFN-γ-dependent up-regulation of MHC class I and II Ag expression. Employing a murine model of renal ischemia, we show that renal IL-18 mRNA up-regulation coincides with caspase-1 activation at day 1 following ischemia. IFN-γ and IL-12 mRNA are subsequently up-regulated at day 6 following ischemia. Combined, but not separate, in vivo neutralization of the IFN-γ inducing cytokines IL-12 and IL-18 reduces IFN-γ-dependent MHC class I and II up-regulation to a similar extent as IFN-γ neutralization, suggesting the involvement of functional IL-12, IL-18, and IFN-γ protein. These results reveal a novel relationship between tissue injury of nonmicrobial origin and the induction of IL-12 as well as IL-18. The collaboration observed between endogenous IL-12 and IL-18 in the induction of IFN-γ after renal ischemia/reperfusion, resembles the immune response to bacterial infections.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.

Interleukin-12 is synthesized by mesangial cells and stimulates platelet-activating factor synthesis, cytoskeletal reorganization, and cell shape change

Preliminary studies indicate the involvement of interleukin (IL)-12 in experimental renal pathology. In the present study, we evaluated whether cultured glomerular mesangial cells are able to produce IL-12 and whether IL-12 may regulate some of their functions, including the cytoskeletal reorganization, the change in cell shape, and the production of platelet-activating factor (PAF). The results obtained indicate that pro-inflammatory stimuli, such as tumor necrosis factor-alpha and bacterial polysaccharides, induce the expression of IL-12 mRNA and the synthesis of the protein by cultured mesangial cells. Moreover, cultured mesangial cells were shown to bind IL-12 and to express the human low-affinity IL-12 beta1-chain receptor. When challenged with IL-12, mesangial cells produced PAF in a dose- and time-dependent manner and superoxide anions. No production of tumor necrosis factor-alpha and IL-8 was observed. Moreover, we demonstrate that IL-12 induced a delayed and sustained shape change of mesangial cells that reached its maximum between 90 and 120 minutes of incubation. The changes in cell shape occurred concomitantly with cytoskeletal rearrangements and may be consistent with cell contraction. As IL-12-dependent shape change of mesangial cells was concomitant with the synthesis of PAF, which is known to promote mesangial cell contraction, we investigated the role of PAF using two chemically different PAF receptor antagonists. Both antagonists inhibited almost completely the cell shape change induced by IL-12, whereas they were ineffective on angiotensin-II-induced cell shape change. In conclusion, our results suggest that mesangial cells can either produce IL-12 or be stimulated by this cytokine to synthesize PAF and to undergo shape changes compatible with cell contraction.

IL-12 directs severe renal injury, crescent formation and Th1 responses in murine glomerulonephritis

Glomerular crescent formation characterizes severe glomerulonephritis (GN). Evidence suggests that crescent formation results from a delayed-type hypersensitivity-like Th1 response. As IL-12 directs Th1 responses, we tested the hypothesis that IL-12 is important in crescentic GN. Neutralization of IL-12 attenuated crescent formation and cell-mediated injury in C57BL/6 mice sensitized to and challenged with sheep anti-mouse glomerular basement membrane (GBM) globulin. Recombinant IL-12 induced severe crescentic GN with enhanced Th1 responses in C57BL/6 mice in which non-crescentic GN was induced by injecting anti-GBM globulin into naive mice. BALB/c mice do not develop significant crescent formation in these models, due either to regulatory effects of IL-4, or to deficits in IL-12 production/responsiveness. Administering IL-12 to BALB/c mice with GN induced Th1 responses and crescent formation, whereas IL-4-deficient BALB/c mice did not develop cell-mediated crescentic injury when GN was induced in sensitized mice. These results establish a central role for IL-12 in severe crescentic GN.

Augmentation of natural killer cell activity in mice by oral administration of transforming growth factor-beta

The latent form of transforming growth factor-beta (TGF-beta) in human milk and platelets was converted to the active form when conscious, pylorus-ligated mice were given human milk and platelets by intragastric intubation. Oral administration of TGF-beta exerted enhancing effects on the natural killer (NK)-cell activities in spleen and liver. Augmentation of NK-cell activities in spleen was observed for 7 days after oral administration of TGF-beta. TGF-beta at concentrations of 5 and 20 ng produced the greatest augmentation of NK-cell activities in spleen. However, NK-cell activities in spleen were unaffected when TGF-beta was given intravenously. Interleukin (IL)-12 production in spleen was enhanced by oral administration of TGF-beta, but not by intravenous administration of TGF-beta. These findings suggest that large amounts of TGF-beta in human milk are involved in early antiviral protection through the augmentation of NK-cell activities.

IFN-γ Limits Macrophage Expansion in MRL-Fas lpr Autoimmune Interstitial Nephritis: A Negative Regulatory Pathway

IFN-γ is capable of enhancing and limiting inflammation. Therefore, an increase in IFN-γ in autoimmune MRL-Faslpr mice could exacerbate or thwart renal injury. We have established a retroviral gene transfer approach to incite interstitial nephritis in MRL-Faslpr mice that is rapid, enduring, and circumscribed. Renal tubular epithelial cells (TEC) were genetically modified to secrete macrophage (Mφ) growth factors (CSF-1-TEC, GM-CSF-1-TEC) and infused under the renal capsule. To determine the impact of IFN-γ in Mφ growth factor-incited renal injury, we constructed a MRL-Faslpr IFN-γ-receptor (IFN-γR)-deficient strain. Gene transfer of CSF-1 or GM-CSF incited more severe interstitial nephritis in IFN-γR-deficient than in IFN-γR-intact MRL-Faslpr mice, consisting of an increase of Mφ. To determine the mechanism responsible for the increase in Mφ in IFN-γR-deficient MRL-Faslpr mice, we evaluated Mφ proliferation, apoptosis, and recruitment. Proliferation of bone marrow Mφ from IFN-γR-intact MRL-Faslpr costimulated with CSF-1 or GM-CSF and IFN-γ was reduced twofold, while the IFN-γR-deficient MRL-Faslpr bone marrow Mφ remained stable. Furthermore, we detected more proliferating and fewer apoptotic Mφ within the interstitium in IFN-γR-deficient MRL-Faslpr mice. Using unilateral ureteral ligation we established that IFN-γR signaling does not alter Mφ recruitment into the kidney. Thus, the increase in Mφ elicited by Mφ growth factors in IFN-γR-deficient MRL-Faslpr mice is a result of enhanced proliferation and decreased apoptosis, and is independent of recruitment. Taken together, we suggest that IFN-γ provides a negative regulatory pathway capable of limiting Mφ-mediated renal inflammation.

Prostaglandin E2 and tumor necrosis factor alpha cooperate to activate human dendritic cells: synergistic activation of interleukin 12 production

Interleukin (IL)-12 is a proinflammatory cytokine that contributes to innate resistance and to the development of antigen-specific T cell responses. Among other effects, prostaglandin E2 (PGE2) inhibits the production of IL-12 by macrophages activated with lipopolysaccharide (LPS). Here we investigated the effects of PGE2 on human dendritic cells (DCs) which develop in the presence of GM-CSF and IL-4. We demonstrate that in the absence of LPS, PGE2 dose dependently stimulated the production of IL-12 by DCs. Although PGE2 alone stimulated the production of low amounts of IL-12 only, it synergized with tumor necrosis factor (TNF)-alpha to induce high levels of IL-12 production by DCs. Addition of TNF-alpha in the absence of PGE2 had no effect on IL-12 production. Conversely, in the presence of LPS, PGE2 inhibited IL-12 production by DCs in a dose-dependent manner. The combination of PGE2 and TNF-alpha efficiently silenced mannose receptor-mediated endocytosis in DCs and readily induced neo-expression of the CD83 antigen. In addition, the expression of various surface antigens such as major histocompatibility complex class I and II, adhesion, as well as costimulatory molecules was upregulated by this treatment. The effects of PGE2 on IL-12 synthesis and CD83 expression could be mimicked by dibutyryl-cAMP and forskolin, indicating that they were due to the intracellular elevation of cAMP levels. DC treated with PGE2 and TNF-alpha were most potent in stimulating allogeneic T cell proliferation. Our data demonstrate that PGE2 contributes to the maturation of human DCs and that PGE2 can be a potent enhancer of IL-12 production by human DCs.