Kashyap, Sonu

Autosomal dominant polycystic kidney disease is the most common inherited kidney disorder and a leading monogenic cause of kidney failure. Reduction or loss of polycystin-1 and polycystin-2 function disrupts ciliary calcium signaling, elevates cyclic AMP (cAMP), reprograms cellular metabolism, and activates proliferative cascades that drive cyst expansion. Tolvaptan, a vasopressin V2 receptor antagonist, established cAMP modulation as a disease-modifying strategy but is limited by aquaretic effects and hepatotoxicity risk. This review highlights emerging therapeutic strategies in clinical trial development that extend beyond vasopressin antagonism. Gene-directed therapies aim to restore polycystin dosage, including anti–miR-17 oligonucleotides ( e.g ., farabursen) and pharmacochaperones that rescue misfolded polycystin-1 and restore trafficking in select PKD1 missense variants ( e.g ., VX-407). Paracrine signaling can be modulated with anti–pregnancy-associated plasma protein A antibodies that reduce insulin-like growth factor-1 bioavailability in cystic microenvironments. Metabolic reprogramming is targeted by agents such as metformin, bempedoic acid, glucagon-like peptide-1 receptor agonists, and structured dietary interventions. Sodium-glucose cotransporter 2 inhibitors hold theoretical promise but await definitive results from ongoing trials. A novel cAMP-lowering strategy through phosphodiesterase-4 activation is advancing toward clinical testing. Looking ahead, gene therapy, and genome editing offer the potential to raise polycystin levels above the threshold for cystogenesis, although challenges in vector capacity, kidney-specific delivery, and durability remain. Artificial intelligence–guided discovery, coupled with human organoid platforms, is accelerating therapeutic repurposing and rational combination design. Collectively, these advances signal a transition toward a layered, mechanism-guided framework in which vasopressin blockade is integrated with metabolic, other signaling, and genotype-specific therapies. As biomarkers and risk stratification tools mature, autosomal dominant polycystic kidney disease management is poised to become increasingly precise, tolerable, and effective.

ABSTRACT Nicotinamide adenine dinucleotide (NAD) is a key coenzyme involved in energy metabolism, DNA repair, and cellular signaling. While the effects of acute NAD depletion have been better characterized, the consequences of chronic NAD deficiency remain unclear. Here, we investigated the impact of chronic NAD depletion in cultured cells by removing the availability of nicotinamide (NAM), a key precursor for NAD synthesis, from the culture media. In NIH3T3 fibroblasts, NAM depletion caused a dramatic drop in intracellular NAD levels within 2 days. Remarkably, the cells remained viable even after 7–14 days of NAM depletion, despite NAD + levels falling to less than 10% of control conditions. This chronic NAD depletion led to distinct metabolic alterations. Mitochondrial basal respiration remained unchanged, but cells exhibited reduced spare respiratory and maximal capacities, along with significantly impaired glycolysis. Notably, NAD depletion triggered an interferon‐dependent inflammatory response, resembling viral infections. This was driven by cytosolic leakage of mitochondrial DNA (mtDNA) through voltage‐dependent anion channel 1 (VDAC1), which activated the cGAS‐STING signaling pathway. Inhibition of VDAC oligomerization with VBIT‐4, STING signaling with H‐151, or mtDNA depletion blocked the upregulation of interferon genes induced by NAM depletion. Similar interferon responses triggered by NAD depletion were observed in IMR90 human fibroblasts and HS5 stromal cells. Our findings reveal a novel link between chronic NAD deficiency, VDAC‐mediated mtDNA release to the cytoplasm, and the activation of the inflammatory response, providing new insight into how NAD decline affects cellular metabolic and inflammatory processes.

AbstractBackgroundThe efficacy of Calorie Restriction (CR) in enhancing cognition, promoting healthy aging, and extending lifespan is well‐established. Yet, it remains unclear whether the apolipoprotein E (APOE) genotype, a known modifier for aging and age‐related disorders, influences the beneficial effects of CR in countering aging.MethodsTo investigate this question, we utilized humanized APOE mouse models, which express APOE2, APOE3, or APOE4 alleles systematically (refer to as E2, E3, and E4 mice). These mice were subjected to either ad libitum (AL) feeding or 30% CR feeding, starting from 12 months and continuing up to 20 months of age (N = 11‐20/ genotype /group, mixed sex). We monitored energy expenditure using the Comprehensive Laboratory Animal Monitoring System (CLAMS). Additionally, we evaluated anxiety levels and memory capabilities through various behavioral tests. Finally, we collected brain, blood, and feces samples for transcriptomic, lipidomic, and microbiomic analyses.ResultsCLAMS measurements showed that CR significantly decreased the metabolic rate in E3 and E4 mice, but not E2 mice, during the non‐feeding period of the CR group, compared to the AL group. Furthermore, CR reduced anxiety and enhanced associative memory in E3 and E4 mice relative to the AL group. Brain transcriptomics revealed that CR upregulated the cholesterol synthesis pathway, potentially improving myelination‐related pathways in E3 and E4 mice. This finding was further validated by the increased staining intensity of myelin basic protein (MBP) observed in E3 and E4 mice from an independent cohort. In contrast, these effects were not pronounced in E2 mice. Additionally, while CR’s impact on the brain lipid profile was minor across all APOE genotypes, it significantly altered blood lipid profile of E2 mice, with minimal changes observed in E3 and E4 mice. Finally, in microbiomics, CR led to notable changes in the abundance of Bifidobacterium species in E3 and E4 mice and Lactobacillus species in E2 mice.ConclusionsOur study highlights the role of APOE genotypes in modulating the diverse effects of CR on cognition, brain transcriptomics, lipid metabolism, and the microbiome, providing a crucial foundation for considering APOE genotypes in developing prevention strategies for aging and age‐related disorders.

Abstract Aims Doxorubicin (DXR) is a chemotherapeutic agent that causes dose-dependent cardiotoxicity. Recently, it has been proposed that the NADase CD38 may play a role in doxorubicin-induced cardiotoxicity (DIC). CD38 is the main NAD+-catabolizing enzyme in mammalian tissues. Interestingly, in the heart, CD38 is mostly expressed as an ecto-enzyme that can be targeted by specific inhibitory antibodies. The goal of the present study is to characterize the role of CD38 ecto-enzymatic activity in cardiac metabolism and the development of DIC. Methods and results Using both a transgenic animal model and a non-cytotoxic enzymatic anti-CD38 antibody, we investigated the role of CD38 and its ecto-NADase activity in DIC in pre-clinical models. First, we observed that DIC was prevented in the CD38 catalytically inactive (CD38-CI) transgenic mice. Both left ventricular systolic function and exercise capacity were decreased in wild-type but not in CD38-CI mice treated with DXR. Second, blocking CD38-NADase activity with the specific antibody 68 (Ab68) likewise protected mice against DIC and decreased DXR-related mortality by 50%. A reduction of DXR-induced mitochondrial dysfunction, energy deficiency, and inflammation gene expression were identified as the main mechanisms mediating the protective effects. Conclusion NAD+-preserving strategies by inactivation of CD38 via a genetic or a pharmacological-based approach improve cardiac energetics and reduce cardiac inflammation and dysfunction otherwise seen in an acute DXR cardiotoxicity model.

Renal artery stenosis (RAS) is a common public health problem, affecting up to 7% of individuals over 65 years of age. Optimal therapy for patients with RAS is controversial, as recent studies have indicated that revascularization via stenting fails to improve renal function or patient survival. Medical therapy is associated with high morbidity and mortality, primarily due to cardiovascular disease. However, morphologic correlates for reversibility following restoration of blood flow have not been adequately defined. The purpose of this study was to standardize an experimental model for the restoration of blood flow, employing a well characterized murine RAS model. Total N=10 C57B/6J male mice were used. RAS was induced on the right renal artery by putting a polytetrafluoroethylene cuff (N=6) and sham surgery was performed without cuff placement (N=4). To determine the feasibly of restoring the blood flow to the stenotic kidney, cuff was taken off at day 7 following the RAS surgery. Blood pressure measurements were done using tail cuff method at baseline, before taking cuff off and then every week until harvest. MRI images were captured using an Avance DRX 700WB spectrometer with a vertical 16.4 T wide bore magnet connected with the imaging tools at baseline, 3 days after putting the cuff on or sham surgery, and at 3 weeks after cuff off. The animals were harvested at day 28 following surgery and kidney weights are obtained. Baseline renal perfusion (1018±41.6 ml/100g/min) was significantly reduced (634.7±141.3 ml/100g/min, p=0.01) following cuff placement. Perfusion was restored to normal (955±59.8 ml/100g/min) at 28 days following cuff removal at 7 days after RAS. Similarly, volume of the stenotic kidney was significantly reduced (at day 3 after RAS 172±8.6 mm 3 ) compared to baseline (206.3±4.4 mm 3 , p=0.0007). There was no significant difference in perfusion and volume after cuff off compared to baseline and sham groups. There was no significant difference in kidney weight between cuff‐off (167± 4.7 mg) and sham groups (163±9.95 mg). Also, there was no difference in heart weight between cuff off (150±3.7mg) and sham groups (148±6.7mg). We conclude that this model will provide the basis for determining the latest time point associated with recovery of renal structure and potential histopathologic markers that predict preservation of renal structure following cuff removal. Also, this model would provide the basis for determining efficacy of additional therapies to target inflammation, etc. to widen the “therapeutic window” during which restoration of renal blood flow is beneficial. Support or Funding Information This project is funded by National Institutes of health, NIAID R01 AI100911.

CX3CR1 is a chemokine receptor widely expressed on inflammatory cells which recognizes CX3CL1 (fractalkine) a membrane bound chemokine that can function as an adhesion receptor. Blockade of CX3CR1 has been shown to reduce inflammation and chronic renal injury in a variety of models. We sought to determine whether CX3CR1 deficient mice are protected from chronic renal injury in experimental renal artery stenosis (RAS). RAS was established in CX3CR1 knockout (KO) and wild‐type C57BLK/6 mice (WT) through placement of a cuff on the right renal artery. Sham mice underwent manipulation of the right renal artery without placement of a cuff. As assessed by MRI, mean flow reduction was 65.3% in the WT mice and 66.5% in the KO mice (p=ns) subjected to RAS. Both KO and WT mice developed hypertension, which persisted throughout the 4 week study. KO and WT mice developed a similar degree of cardiac hypertrophy (166 mg WT, 172 mg KO, p=ns; 117 mg sham). Stenotic kidney weights were reduced to a similar extent in KO and WT mice (sham 148 mg, WT 83 mg, KO 53 mg) with compensatory hypertrophy of the contralateral kidney (sham 136 mg, WT 170 mg, KO 206 mg, p=0.0016 KO vs WT). The stenotic kidney of both KO and WT mice developed severe atrophy, characterized by flattening and simplification of tubular epithelium and influx of interstitial T cells and macrophages (32.8 % cortical surface area for WT and 76.4% cortical surface area for KO, p=0.01). The contralateral kidney was without significant histopathologic abnormality. We conclude that development of severe atrophy is not prevented in CX3CR1 KO mice, indicating that alternative pathways contribute to chronic renal damage in this model. Support or Funding Information This work is supported by NIH Grant R01 AI100911.

Nicotinamide adenine dinucleotide (NAD) acts as a cofactor in several oxidation-reduction (redox) reactions and is a substrate for a number of nonredox enzymes. NAD is fundamental to a variety of cellular processes including energy metabolism, cell signaling, and epigenetics. NAD homeostasis appears to be of paramount importance to health span and longevity, and its dysregulation is associated with multiple diseases. NAD metabolism is dynamic and maintained by synthesis and degradation. The enzyme CD38, one of the main NAD-consuming enzymes, is a key component of NAD homeostasis. The majority of CD38 is localized in the plasma membrane with its catalytic domain facing the extracellular environment, likely for the purpose of controlling systemic levels of NAD. Several cell types express CD38, but its expression predominates on endothelial cells and immune cells capable of infiltrating organs and tissues. Here we review potential roles of CD38 in health and disease and postulate ways in which CD38 dysregulation causes changes in NAD homeostasis and contributes to the pathophysiology of multiple conditions. Indeed, in animal models the development of infectious diseases, autoimmune disorders, fibrosis, metabolic diseases, and age-associated diseases including cancer, heart disease, and neurodegeneration are associated with altered CD38 enzymatic activity. Many of these conditions are modified in CD38-deficient mice or by blocking CD38 NADase activity. In diseases in which CD38 appears to play a role, CD38-dependent NAD decline is often a common denominator of pathophysiology. Thus, understanding dysregulation of NAD homeostasis by CD38 may open new avenues for the treatment of human diseases.

During the COVID-19 pandemic, efforts have been made worldwide to develop effective therapies to address the devastating immune-mediated effects of SARS-CoV-2. With the exception of monoclonal antibody-mediated therapeutics and preventive approaches such as mass immunization, most experimental or repurposed drugs have failed in large randomized clinical trials ( https://www.who.int/publications/i/item/therapeutics-and-covid-19-living-guideline ). The worldwide spread of SARS-CoV-2 virus revealed specific susceptibilities to the virus among the elderly and individuals with age-related syndromes. These populations were more likely to experience a hyperimmune response characterized by a treatment-resistant acute lung pathology accompanied by multiple organ failure. These observations underscore the interplay between the virus, the biology of aging, and outcomes observed in the most severe cases of SARS-CoV-2 infection. The ectoenzyme CD38 has been implicated in the process of “inflammaging” in aged tissues. In a current publication, Horenstein et al. present evidence to support the hypothesis that CD38 plays a central role in altered immunometabolism resulting from COVID-19 infection. The authors discuss a critical but underappreciated trifecta of CD38-mediated NAD + metabolism, aging, and COVID-19 immune response and speculate that the CD38/NAD + axis is a promising therapeutic target for this disease.

Aim Th1 cells have potent pro‐inflammatory properties and have been shown to play an important role in the development and progression of acute renal injury to chronic renal disease. The aim of this study is to test the hypothesis that chronic renal damage in mice with renal artery stenosis (RAS) would be ameliorated in mice with homozygous deletion of the Th1 transcription factor T‐bet. Methods C57BL6/J (WT) and C57BL6/J mice with homozygous deletion of T‐bet (KO) were obtained from Jackson Laboratory. Renal artery stenosis surgery (RAS) was performed by placement of a polytetrafluoroethylene cuff on the right renal artery of KO (KO RAS group, n =5) and WT mice (WT RAS group, n =6). Sham (SH) surgery was performed with manipulation of the right renal artery without cuff placement in KO (KO SH group, n =4) and WT mice (WT SH group, n =5). Renal blood perfusion and oxygenation (R2*) were measured using 16.4T MRI. Blood pressure measurements were done using tail‐cuff method. Kidneys were harvested at 28 days after RAS for assessment of histology. Results Baseline intra‐renal perfusion in both KO RAS and WT RAS mice was reduced to a similar extent following cuff placement. In KO RAS group, baseline intra‐renal perfusion (795 ± 57 ml/100g/min) was reduced to 234 ± 22 ml/100g/min ( p <0.0001 vs baseline, mean reduction 71%) and in WT RAS group, baseline intra‐renal perfusion (836 ± 87 ml/100g/min) was reduced to 220 ± 21 ml/100g/min ( p =0.002 vs baseline, mean reduction 74%). Both KO RAS and WT RAS mice developed hypertension, which persisted throughout the 4 week study. WT RAS group showed significant elevation in cortical R2*, a measure of hypoxia, following RAS compared to their baseline ( p =0.002). KO RAS mice showed slightly higher R2* value, which was not significantly different from their baseline values. The weight of the stenotic kidney of the KO RAS group (105 ± 11.6 mg) was significantly lower than the KO SH mice (178 ± 14.1 mg, p =0.0021) but significantly higher than the WT RAS group (51.7 ± 7.9 mg, p =0.0010). On histologic and immune‐histochemical analysis, we observed that the stenotic kidney of the KO RAS group had significantly lower (%) cortical tubular atrophy (15% ± 6.7, p <0.0001) compared to WT RAS mice (81.7% ± 7). KO RAS group had significantly lower macrophage (MQ) ( p =0.0016) and T cell influx ( p =0.0052) compared to the WT RAS, as assessed by the % of cortical surface areas staining positive for F4/80 (MQ) and CD3 (T cell). When compared to their respective shams, KO RAS showed no significant differences in the % cortical tubular atrophy, MQ and CD3+ T cell influx. Conclusion We conclude that deficiency of Th1 transcription factor T‐bet, protects against chronic renal injury as evidenced by the less cortical atrophy in KO RAS compared to WT RAS group, despite a similar elevation in blood pressure and reduction in perfusion. This model may provide a novel therapeutic target to prevent renal disease progression in patients with renovascular hypertension. Support or Funding Information National Institutes of Health Grant AI 100911 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .