Lupus nephritis: low urinary DNase I levels reflect loss of renal DNase I and may be utilized as a biomarker of disease progression.

Renal DNase I is lost in advanced stages of lupus nephritis. Here, we determined if loss of renal DNase I reflects a concurrent loss of urinary DNase I, and whether absence of urinary DNase I predicts disease progression. Mouse and human DNase I protein and DNase I endonuclease activity levels were determined by western blot, gel, and radial activity assays at different stages of the murine and human forms of the disease. Cellular localization of DNase I was analyzed by immunohistochemistry, immunofluorescence, confocal microscopy, and immunoelectron microscopy. We further compared DNase I levels in human native and transplanted kidneys to determine if the disease depended on autologous renal genes, or whether the nephritic process proceeded also in transplanted kidneys. The data indicate that reduced renal DNase I expression level relates to serious progression of lupus nephritis in murine, human native, and transplanted kidneys. Notably, silencing of renal DNase I correlated with loss of DNase I endonuclease activity in the urine samples. Thus, urinary DNase I levels may therefore be used as a marker of lupus nephritis disease progression and reduce the need for renal biopsies.

Lipid degradation promotes prostate cancer cell survival.

Prostate cancer is the most common male cancer and androgen receptor (AR) is the major driver of the disease. Here we show that Enoyl-CoA delta isomerase 2 (ECI2) is a novel AR-target that promotes prostate cancer cell survival. Increased ECI2 expression predicts mortality in prostate cancer patients (p = 0.0086). ECI2 encodes for an enzyme involved in lipid metabolism, and we use multiple metabolite profiling platforms and RNA-seq to show that inhibition of ECI2 expression leads to decreased glucose utilization, accumulation of fatty acids and down-regulation of cell cycle related genes. In normal cells, decrease in fatty acid degradation is compensated by increased consumption of glucose, and here we demonstrate that prostate cancer cells are not able to respond to decreased fatty acid degradation. Instead, prostate cancer cells activate incomplete autophagy, which is followed by activation of the cell death response. Finally, we identified a clinically approved compound, perhexiline, which inhibits fatty acid degradation, and replicates the major findings for ECI2 knockdown. This work shows that prostate cancer cells require lipid degradation for survival and identifies a small molecule inhibitor with therapeutic potential.

Impact of the tumor necrosis factor receptor-associated protein 1 (Trap1) on renal DNaseI shutdown and on progression of murine and human lupus nephritis.

Recent findings show that transformation of mild glomerulonephritis into end-stage disease coincides with shutdown of renal DNaseI expression in (NZBxNZW)F1 mice. Down-regulation of DNaseI results in reduced chromatin fragmentation and deposition of extracellular chromatin fragments in glomerular basement membranes where they appear in complex with IgG antibodies. Here, we implicate the anti-apoptotic and survival protein, tumor necrosis factor receptor-associated protein 1 (Trap1) in the disease process, based on the observation that annotated transcripts from this gene overlap with transcripts from the DNaseI gene. Furthermore, we translate these observations to human lupus nephritis. In this study, mouse and human DNaseI and Trap1 mRNA levels were determined by real-time quantitative PCR and compared with protein expression levels and clinical data. Cellular localization was analyzed by immune electron microscopy, IHC, and in situ hybridization. Data indicate that silencing of DNaseI gene expression correlates inversely with expression of the Trap1 gene. Our observations suggest that the mouse model is relevant for the aspects of disease progression in human lupus nephritis. Acquired silencing of the renal DNaseI gene has been shown to be important for progression of disease in both the murine and human forms of lupus nephritis. Early mesangial nephritis initiates a cascade of inflammatory signals that lead to up-regulation of Trap1 and a consequent down-regulation of renal DNaseI by transcriptional interference.

Autoantibodies in lupus: culprits or passive bystanders?

Several autoantibodies are culprits in the pathogenesis of organ damage in systemic lupus erythematosus, by means of established or postulated mechanisms, whereby inducing a perturbation of cell structure and function, with consequent tissue-organ impairment. Common autoantibody-mediated mechanisms of damage include cell surface binding with or without cytolysis, immune complex-mediated damage, penetration into living cells, binding to cross-reactive extracellular molecules. Experimental data from both murine models and humans have recently clarified the key role of autoantibodies in severe organ involvements, including nephritis, neuropsychiatric (NP) dysfunction, and cerebrovascular disease (CVD). In lupus nephritis early and late phases are distinguishable and mediated by different processes in which anti-chromatin antibodies are both inducing and perpetuating agents, by immune-complex formation and massive deposition in mesangial matrix at first, and in glomerular basement membrane at end-stage. Also NP abnormalities occur very early, much earlier than other systemic manifestations, and exacerbate with the increase in autoantibody titers. Among the autoantibodies mainly implicated in neurolupus, anti-ß2 glycoprotein I (ß2GPI) antibodies are preferentially involved in focal NP events which are a consequence of non-inflammatory microangiopathy; otherwise, anti-ribosomal P protein antibodies and N-methyl-d-aspartate receptor (NMDAR) antibodies cause diffuse NP events through a direct cytotoxic effect on neuronal cells at specific brain zones.

Deposition of chromatin-IgG complexes in skin of nephritic MRL-lpr/lpr mice is associated with increased local matrix metalloprotease activities.

Chromatin-IgG complexes appear as electron dense structures (EDS) in glomerular basement membranes in lupus nephritis. Here, we present results of comparative analyses of the composition of EDS in murine lupus dermatitis and nephritis. One focus was to perform an analytical approach to understand why such complex structures bind skin basement membrane components. Transcription of skin membrane-encoding genes was analysed to see if expression of such genes was increased, eventually indicating that binding capacity of immune complexes increased when dermatitis developed. Variations in matrix metalloprotease 2 (MMP2), MMP9 and Dnase1 mRNA levels and enzymatic activities were correlated with circulatory chromatin-IgG complexes and deposition in skin. We also examined if glomerular deposits of EDS predicted similar deposits in skin of (NZB x NZW)F1 or MRL-lpr/lpr mice, as we observed chromatin-IgG complexes in capillary lumina in skin and glomeruli in both strains. EDS consisting of chromatin fragments and IgG were found sub-epidermally in skin with LE-like lesions of end-stage nephritic MRL-lpr/lpr mice. Dermal MMP-encoding genes were up-regulated during disease progression, and gelatinolytic activity was increased in affected skin. Dnase1 mRNA level and total nuclease activity remained stable in skin during the disease, in contrast to progressive loss of renal Dnase1 mRNA and total renal nuclease activity during development of nephritis. Loss of renal Dnase1 may explain release of chromatin fragments, while increased MMP activity may disrupt membranes making them accessible for chromatin fragment-IgG complexes. Circulatory chromatin-IgG complexes, and up-regulated intradermal MMP activity may be crucial for deposition of immune complexes in skin of lupus-prone mice.