Genetic susceptibility to diabetic kidney disease is linked to promoter variants of XOR

The lifetime risk of kidney disease in people with diabetes is 10-30%, implicating genetic predisposition in the cause of diabetic kidney disease (DKD). Here we identify an expression quantitative trait loci (QTLs) in the cis-acting regulatory region of the xanthine dehydrogenase, or xanthine oxidoreductase (Xor), a binding site for C/EBPβ, to be associated with diabetes-induced podocyte loss in DKD in male mice. We examine mouse inbred strains that are susceptible (DBA/2J) and resistant (C57BL/6J) to DKD, as well as a panel of recombinant inbred BXD mice, to map QTLs. We also uncover promoter XOR orthologue variants in humans associated with high risk of DKD. We introduced the risk variant into the 5'-regulatory region of XOR in DKD-resistant mice, which resulted in increased Xor activity associated with podocyte depletion, albuminuria, oxidative stress and damage restricted to the glomerular endothelium, which increase further with type 1 diabetes, high-fat diet and ageing. Therefore, differential regulation of Xor contributes to phenotypic consequences with diabetes and ageing.

Gene expression profiles in sporadic ALS fibroblasts define disease subtypes and the metabolic effects of the investigational drug EH301

Metabolic alterations shared between the nervous system and skin fibroblasts have emerged in ALS. Recently, we found that a subgroup of sporadic ALS (sALS) fibroblasts (sALS1) is characterized by metabolic profiles distinct from other sALS cases (sALS2) and controls, suggesting that metabolic therapies could be effective in sALS. The metabolic modulators nicotinamide riboside and pterostilbene (EH301) are under clinical development for the treatment of ALS. Here, we studied the transcriptome and metabolome of sALS cells to understand the molecular bases of sALS metabotypes and the impact of EH301. Metabolomics and transcriptomics were investigated at baseline and after EH301 treatment. Moreover, weighted gene co-expression network analysis (WGCNA) was used to investigate the association of metabolic and clinical features. We found that the sALS1 transcriptome is distinct from sALS2 and that EH301 modifies gene expression differently in sALS1, sALS2, and controls. Furthermore, EH301 had strong protective effects against metabolic stress, an effect linked to anti-inflammatory and antioxidant pathways. WGCNA revealed that ALS functional rating scale and metabotypes are associated with gene modules enriched for cell cycle, immunity, autophagy, and metabolism genes, which are modified by EH301. Meta-analysis of publicly available transcriptomics data from induced motor neurons by Answer ALS confirmed functional associations of genes correlated with disease traits. A subset of genes differentially expressed in sALS fibroblasts was used in a machine learning model to predict disease progression. In conclusion, multi-omics analyses highlighted differential metabolic and transcriptomic profiles in patient-derived fibroblast sALS, which translate into differential responses to the investigational drug EH301.

Identification of MALT1 feedback mechanisms enables rational design of potent antilymphoma regimens for ABC-DLBCL

MALT1 inhibitors are promising therapeutic agents for B-cell lymphomas that are dependent on constitutive or aberrant signaling pathways. However, a potential limitation for signal transduction-targeted therapies is the occurrence of feedback mechanisms that enable escape from the full impact of such drugs. Here, we used a functional genomics screen in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) cells treated with a small molecule irreversible inhibitor of MALT1 to identify genes that might confer resistance or enhance the activity of MALT1 inhibition (MALT1i). We find that loss of B-cell receptor (BCR)- and phosphatidylinositol 3-kinase (PI3K)-activating proteins enhanced sensitivity, whereas loss of negative regulators of these pathways (eg, TRAF2, TNFAIP3) promoted resistance. These findings were validated by knockdown of individual genes and a combinatorial drug screen focused on BCR and PI3K pathway-targeting drugs. Among these, the most potent combinatorial effect was observed with PI3Kδ inhibitors against ABC-DLBCLs in vitro and in vivo, but that led to an adaptive increase in phosphorylated S6 and eventual disease progression. Along these lines, MALT1i promoted increased MTORC1 activity and phosphorylation of S6K1-T389 and S6-S235/6, an effect that was only partially blocked by PI3Kδ inhibition in vitro and in vivo. In contrast, simultaneous inhibition of MALT1 and MTORC1 prevented S6 phosphorylation, yielded potent activity against DLBCL cell lines and primary patient specimens, and resulted in more profound tumor regression and significantly improved survival of ABC-DLBCLs in vivo compared with PI3K inhibitors. These findings provide a basis for maximal therapeutic impact of MALT1 inhibitors in the clinic, by disrupting feedback mechanisms that might otherwise limit their efficacy.

Raloxifene is a Female-specific Proteostasis Therapeutic in the Spinal Cord

Several neurodegenerative disorders are characterized by proteasome dysfunctions leading to protein aggregations and pathogenesis. Since we showed that estrogen receptor alpha (ERα) activates the proteasome, drugs able to stimulate ERα in the central nervous system (CNS) could hold potential for therapeutic intervention. However, the transcriptional effects of selective estrogen receptor modulators (SERMs), such as tamoxifen and raloxifene, can be tissue specific. A direct comparison of the effects of different SERMs on gene transcription in the CNS has never been performed. Here, we report an RNA-seq analysis of the spinal cord treated with estrogen, tamoxifen, or raloxifene. We find stark SERM and sex-specific differences in gene expression profiles in the spinal cord. Notably, raloxifene, but not estrogen or tamoxifen, modulates numerous deubiquitinating enzymes, proteasome subunits and assembly factors, and these effects translate into decreased protein aggregates. In the SOD1-G93A mouse model of amyotrophic lateral sclerosis, we found that even a low dose of raloxifene causes a significant decrease in mutant SOD1 aggregates in the spinal cord, accompanied by a delay in the decline of muscle strength in females, but not in males. These results strongly indicate SERM-selective as well as sex-specific effects, and emphasize the importance of sex as a biological variable to be considered for the careful selection of specific SERM for use in clinical trials for neurodegenerative diseases.

Proteasome mapping reveals sexual dimorphism in tissue-specific sensitivity to protein aggregations

Defects in the proteasome can result in pathological proteinopathies. However, the pathogenic role of sex‐ and tissue‐specific sensitivity to proteotoxic stress remains elusive. Here, we map the proteasome activity across nine tissues, in male and female mice, and demonstrate strong sexual dimorphism in proteasome activity, where females have significantly higher activity in several tissues. Further, we report drastic differences in proteasome activity among tissues, independently of proteasome concentration, which are exacerbated under stress conditions. Sexual dimorphism in proteasome activity is confirmed in a SOD1 ALS mouse model, in which the spinal cord, a tissue with comparatively low proteasome activity, is severely affected. Our results offer mechanistic insight into tissue‐specific sensitivities to proteostasis stress and into sex differences in the progression of neurodegenerative proteinopathies.

Quinoline and thiazolopyridine allosteric inhibitors of MALT1

Quinolines and thiazolopyridines were developed as allosteric inhibitors of MALT1, with good cellular potency and exquisite selectivity. Mouse pharmacokinetic (PK) profiling showed these to have low in vivo clearance, and moderate oral exposure. The thiazolopyridines were less lipophilic than the quinolines, and one thiazolopyridine example was active in our hIL10 mouse pharmacodynamic (PD) model upon oral dosing.

Specific covalent inhibition of MALT1 paracaspase suppresses B cell lymphoma growth

The paracaspase MALT1 plays an essential role in activated B cell-like diffuse large B cell lymphoma (ABC DLBCL) downstream of B cell and TLR pathway genes mutated in these tumors. Although MALT1 is considered a compelling therapeutic target, the development of tractable and specific MALT1 protease inhibitors has thus far been elusive. Here, we developed a target engagement assay that provides a quantitative readout for specific MALT1-inhibitory effects in living cells. This enabled a structure-guided medicinal chemistry effort culminating in the discovery of pharmacologically tractable, irreversible substrate-mimetic compounds that bind the MALT1 active site. We confirmed that MALT1 targeting with compound 3 is effective at suppressing ABC DLBCL cells in vitro and in vivo. We show that a reduction in serum IL-10 levels exquisitely correlates with the drug pharmacokinetics and degree of MALT1 inhibition in vitro and in vivo and could constitute a useful pharmacodynamic biomarker to evaluate these compounds in clinical trials. Compound 3 revealed insights into the biology of MALT1 in ABC DLBCL, such as the role of MALT1 in driving JAK/STAT signaling and suppressing the type I IFN response and MHC class II expression, suggesting that MALT1 inhibition could prime lymphomas for immune recognition by cytotoxic immune cells.

Abstract LB-303: Substrate-mimetic covalent inhibitor of MALT1 is most effective against CARD11 mutant ABC-DLBCL

Diffuse Large B-cell lymphoma is the most common subtype of B-cell non Hodgkin Lymphoma (B-NHL) representing 30% of all B-NHL. There are three molecular subtypes: germinal center B cell-like (GCB) DLBCL, activated B cell-like (ABC) DLBCL, and primary mediastinal B cell lymphoma (PMBL). Of those, Activated B-cell like Diffuse Large B-cell Lymphoma (ABC-DLBCL) represents a third of the patients and is characterized by constitutive NF-κB activity due to mutations in various proteins of the B-cell receptor (BCR) as well as Toll-like receptor (TLR) pathways. Mutations in the BCR pathway include: activating mutations of CD79A/B (20% of ABC-DLBCLs) and CARD11 (10%) and deletion or inactivating mutation of A20 (20-30%). In the TLR pathway, MYD88 is mutated in 37% of ABC-DLBCL patients. Given this scenario, numerous therapeutic strategies targeting proteins signaling downstream of the BCR pathway have been proposed for ABC-DLBCL -including inhibitors targeting kinases SYK, BTK, PI3K, PKC, MAPKs and AKT or the protease MALT1. MALT1 inhibition provides advantages to other targets because it is downstream of most of the BCR pathway mutations present in patients, including CARD11. Patients with CARD11 mutations do not respond to BTK inhibitors. However, none of the MALT1 inhibitors reported to date are good candidates for clinical use.

Here we report a new class of substrate mimetic MALT1 inhibitors based on Z-VRPR-fmk. Our lead compound, SCM-02-138 displayed nanomolar potency in biochemical and cellular MALT1 protease reporter assays. Crystallography shows covalent binding of the compound to MALT1 active site Cys residue. SCM-02-138 was highly selective for MALT1 and showed over 100-fold differential killing in sensitive vs resistant cell lines. MALT1 inhibition was most effective in CARD11 mutant cells. SCM-02-138 was active in vivo, as assessed by hIL10 inhibition in xenografted models of ABC-DLBCL cell lines. Moreover it was effective against ABC-DLBCL xenografts and PDX DLBCL ex vivo. Combination of SCM-02-138 with other BCR inhibitors revealed PI3K delta inhibition as the most synergistic combination. Combination of SCM-02-138 and CAL-101 potentiated both proliferation inhibition and apoptosis.

In summary, we have developed a new class of MALT1 peptidic inhibitor characterized by nanomolar potency, irreversibility and high specificity. This inhibitor will be particularly useful against CARD11 mutant ABC-DLBCL, which are resistant to BTK inhibitors.

Citation Format: Lorena Fontan, David Scott, John Hatcher, Qi Qiao, Ilkay Us, Gabriella Casalena, Mariette Bekkers, Ulrike Philippar, Matthew Durant, Spandan Chennamadhavuni, Hao Wu, Nathaniel Gray, Ari Melnick. Substrate-mimetic covalent inhibitor of MALT1 is most effective against CARD11 mutant ABC-DLBCL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-303. doi:10.1158/1538-7445.AM2017-LB-303

Glomerular Endothelial Mitochondrial Dysfunction Is Essential and Characteristic of Diabetic Kidney Disease Susceptibility

The molecular signaling mechanisms between glomerular cell types during initiation/progression of diabetic kidney disease (DKD) remain poorly understood. We compared the early transcriptome profile between DKD-resistant C57BL/6J and DKD-susceptible DBA/2J (D2) glomeruli and demonstrated a significant downregulation of essential mitochondrial genes in glomeruli from diabetic D2 mice, but not in C57BL/6J, with comparable hyperglycemia. Diabetic D2 mice manifested increased mitochondrial DNA lesions (8-oxoguanine) exclusively localized to glomerular endothelial cells after 3 weeks of diabetes, and these accumulated over time in addition to increased urine secretion of 8-oxo-deoxyguanosine. Detailed assessment of glomerular capillaries from diabetic D2 mice demonstrated early signs of endothelial injury and loss of fenestrae. Glomerular endothelial mitochondrial dysfunction was associated with increased glomerular endothelin-1 receptor type A (Ednra) expression and increased circulating endothelin-1 (Edn1). Selective Ednra blockade or mitochondrial-targeted reactive oxygen species scavenging prevented mitochondrial oxidative stress of endothelial cells and ameliorated diabetes-induced endothelial injury, podocyte loss, albuminuria, and glomerulosclerosis. In human DKD, increased urine 8-oxo-deoxyguanosine was associated with rapid DKD progression, and biopsies from patients with DKD showed increased mitochondrial DNA damage associated with glomerular endothelial EDNRA expression. Our studies show that DKD susceptibility was linked to mitochondrial dysfunction, mediated largely by Edn1-Ednra in glomerular endothelial cells representing an early event in DKD progression, and suggest that cross talk between glomerular endothelial injury and podocytes leads to defects and depletion, albuminuria, and glomerulosclerosis.

TGFβ-Induced Actin Cytoskeleton Rearrangement in Podocytes Is Associated with Compensatory Adaptation of Mitochondrial Energy Metabolism

BACKGROUND/AIMS

In podocytes, the overexpression of TGFβ ligands and receptors during glomerulosclerosis could be a causal factor for injury induction and perpetuation in glomerular tufts. Mitochondrial dysfunction and oxidative stress are emerging as potential therapeutic targets in glomerular injury, and TGFβ has been shown to modulate mitochondrial metabolism in different cell types. This study aims at investigating the role of TGFβ in podocyte energy metabolism and cytoskeleton dynamics.

METHODS

Mitochondrial function and cytoskeleton dynamics were analyzed in TGFβ-treated WT and Smad2/3 double KO podocytes.

RESULTS

TGFβ treatment in podocytes induced a significant Smad-dependent increase of mitochondrial oxygen consumption rate (OCR). ATP content was unchanged and increased respiration was not associated with increased mitochondrial mass. Increased cellular reactive oxygen species induced by Smad-mediated TGFβ signaling were reverted by NADPH oxidase inhibitor apocynin. TGFβ treatment did not induce mitochondrial oxidative stress, and Smad2/3-dependent TGFβ signaling and increased mitochondrial OCR were found to be associated with actin cytoskeleton dynamics. The role of motor proteins myosin II and dynamin in TGFβ-induced actin polymerization was demonstrated by specific inhibition, resulting in actin stabilization and normalization of mitochondrial OCR.

CONCLUSION

TGFβ-induced rearrangements of actin cytoskeleton are controlled by Smad2/3 signaling pathways and coupled with the activation of mitochondrial ATP synthesis as bioenergetic adaptation to ATP consumption by ATP- and GTP-dependent motor proteins, myosin II and dynamin.

Endothelial mitochondrial oxidative stress determines podocyte depletion in segmental glomerulosclerosis

Focal segmental glomerular sclerosis (FSGS) is a primary kidney disease that is commonly associated with proteinuria and progressive loss of glomerular function, leading to development of chronic kidney disease (CKD). FSGS is characterized by podocyte injury and depletion and collapse of glomerular capillary segments. Progression of FSGS is associated with TGF-β activation in podocytes; however, it is not clear how TGF-β signaling promotes disease. Here, we determined that podocyte-specific activation of TGF-β signaling in transgenic mice and BALB/c mice with Adriamycin-induced glomerulosclerosis is associated with endothelin-1 (EDN1) release by podocytes, which mediates mitochondrial oxidative stress and dysfunction in adjacent endothelial cells via paracrine EDN1 receptor type A (EDNRA) activation. Endothelial dysfunction promoted podocyte apoptosis, and inhibition of EDNRA or scavenging of mitochondrial-targeted ROS prevented podocyte loss, albuminuria, glomerulosclerosis, and renal failure. We confirmed reciprocal crosstalk between podocytes and endothelial cells in a coculture system. Biopsies from patients with FSGS exhibited increased mitochondrial DNA damage, consistent with EDNRA-mediated glomerular endothelial mitochondrial oxidative stress. Our studies indicate that segmental glomerulosclerosis develops as a result of podocyte-endothelial crosstalk mediated by EDN1/EDNRA-dependent mitochondrial dysfunction and suggest that targeting the reciprocal interaction between podocytes and endothelia may provide opportunities for therapeutic intervention in FSGS.

Transforming growth factor-β, bioenergetics, and mitochondria in renal disease

The transforming growth factor-β (TGF-β) family comprises more than 30 family members that are structurally related secreted dimeric cytokines, including TGF-β, activins, and bone morphogenetic proteins/growth and differentiation factors. TGF-β are pluripotent regulators of cell proliferation, differentiation, apoptosis, migration, and adhesion of many different cell types. TGF-β pathways are highly evolutionarily conserved and control embryogenesis, tissue repair, and tissue homeostasis in invertebrates and vertebrates. Aberrations in TGF-β activity and signaling underlie a broad spectrum of developmental disorders and major pathologies in human beings, including cancer, fibrosis, and autoimmune diseases. Recent observations have indicated an emerging role for TGF-β in the regulation of mitochondrial bioenergetics and oxidative stress responses characteristic of chronic degenerative diseases and aging. Conversely, energy and metabolic sensory pathways cross-regulate mediators of TGF-β signaling. Here, we review TGF-β and regulation of bioenergetic and mitochondrial functions, including energy and oxidant metabolism and apoptotic cell death, as well as their emerging relevance in renal biology and disease.

Sex differences in brain proteomes of neuron-specific STAT3-null mice after cerebral ischemia/reperfusion

Signal transduction and activator of transcription-3 (STAT3) plays an important role in neuronal survival, regeneration and repair after brain injury. We previously demonstrated that STAT3 is activated in brain after cerebral ischemia specifically in neurons. The effect was sex-specific and modulated by sex steroids, with higher activation in females than males. In the current study, we used a proteomics approach to identify downstream proteins affected by ischemia in male and female wild-type (WT) and neuron-specific STAT3 knockout (KO) mice. We established four comparison groups based on the transgenic condition and the hemisphere analyzed, respectively. Moreover, the sexual variable was taken into account and male and female animals were analyzed independently. Results support a role for STAT3 in metabolic, synaptic, structural and transcriptional responses to cerebral ischemia, indeed the adaptive response to ischemia/reperfusion injury is delayed in neuronal-specific STAT3 KO mice. The differences observed between males and females emphasize the importance of sex-specific neuronal survival and repair mechanisms, especially those involving antioxidant and energy-related activities, often caused by sex hormones.

Involvement of Stat3 in mouse brain development and sexual dimorphism: a proteomics approach

Although the role of STAT3 in cell physiology and tissue development has been largely investigated, its involvement in the development and maintenance of nervous tissue and in the mechanisms of neuroprotection is not yet known. The potentially wide range of STAT3 activities raises the question of tissue- and gender-specificity as putative mechanisms of regulation. To explore the function of STAT3 in the brain and the hypothesis of a gender-linked modulation of STAT3, we analyzed a neuron-specific STAT3 knockout mouse model investigating the influence of STAT3 activity in brain protein expression pattern in both males and females in the absence of neurological insult. We performed a proteomic study aimed to reveal the molecular pathways directly or indirectly controlled by STAT3 underscoring its role in brain development and maintenance. We identified several proteins, belonging to different neuronal pathways such as energy metabolism or synaptic transmission, controlled by STAT3 that confirm its crucial role in brain development and maintenance. Moreover, we investigated the different processes that could contribute to the sexual dimorphic behavior observed in the incidence of neurological and mental disease. Interestingly both STAT3 KO and gender factors influence the expression of several mitochondrial proteins conferring to mitochondrial activity high importance in the regulation of brain physiology and conceivable relevance as therapeutic target.

A novel deletion in the GTPase domain of OPA1 causes defects in mitochondrial morphology and distribution, but not in function

Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is caused by mutations in the ubiquitously expressed gene optic atrophy 1 (OPA1), involved in fusion and biogenesis of the inner membrane of mitochondria. Bioenergetic failure, mitochondrial network abnormalities and increased apoptosis have all been proposed as possible causal factors. However, their relative contribution to pathogenesis as well as the prominent susceptibility of the retinal ganglion cell (RGC) in this disease remains uncertain. Here we identify a novel deletion of OPA1 gene in the GTPase domain in three patients affected by ADOA. Muscle biopsy of the patients showed neurogenic atrophy and abnormal morphology and distribution of mitochondria. Confocal microscopy revealed increased mitochondrial fragmentation in fibroblasts as well as in myotubes, where mitochondria were also unevenly distributed, with clustered organelles alternating with areas where mitochondria were sparse. These abnormalities were not associated with altered bioenergetics or increased susceptibility to pro-apoptotic stimuli. Therefore, changes in mitochondrial shape and distribution can be independent of other reported effects of OPA1 mutations, and therefore may be the primary cause of the disease. The arrangement of mitochondria in RGCs, which degenerate in ADOA, may be exquisitely sensitive to disturbance, and this may lead to bioenergetic crisis and/or induction of apoptosis. Our results highlight the importance of mitochondrial dynamics in the disease per se, and point to the loss of the fine positioning of mitochondria in the axons of RGCs as a possible explanation for their predominant degeneration in ADOA.

Biochemical phenotypes associated with the mitochondrial ATP6 gene mutations at nt8993

Two point mutations (T>G and T>C) at the same 8993 nucleotide of mitochondrial DNA (at comparable mutant load), affecting the ATPase 6 subunit of the F1F0-ATPase, result in neurological phenotypes of variable severity in humans. We have investigated mitochondrial function in lymphocytes from individuals carrying the 8993T>C mutation: the results were compared with data from five 8993T>G NARP (Neuropathy, Ataxia and Retinitis Pigmentosa) patients. Both 8993T>G and 8993T>C mutations led to energy deprivation and ROS overproduction. However, the relative contribution of the two pathogenic components is different depending on the mutation considered. The 8993T>G change mainly induces an energy deficiency, whereas the 8993T>C favours an increased ROS production. These results possibly highlight the different pathogenic mechanism generated by the two mutations at position 8993 and provide useful information to better characterize the biochemical role of the highly conserved Leu-156 in ATPase 6 subunit of the mitochondrial ATP synthase complex.

Angiographic diagnosis of jugular venous system dilatation in children. A report of five cases

We report five children with a soft mass in the neck due to congenital jugular venous ectasia. Three had fusiform dilatation of the internal jugular vein, which in one case was associated with dilatation of the ipselateral external jugular vein. Two children had aneurysmal dilatation of the superficial cervical communicating vein. The first four cases required angiographic studies for final diagnosis. Venography via the femoral vein was most valuable for visualization of the dilated segments of internal jugular veins but failed to show the vascular mass communicating with the superficial vein of the neck. These were best visualized by direct injection of the contrast medium into the vessel. In the fifth case a correct diagnosis was obtained with xeroradiography alone.