Publications by authors named "Samir M Parikh"

Article Synopsis
  • Disturbances in kidney tubular cell metabolism are significant in acute kidney injury (AKI), particularly affecting NAD metabolism.
  • Recent studies show that these metabolic shifts during AKI can lead to lasting changes, increasing the risk of developing chronic kidney disease (CKD).
  • The review discusses the molecular mechanisms of this metabolic dysfunction in AKI and suggests how these acute changes in NAD metabolism can have long-term impacts on kidney health.
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The vascular endothelial barrier maintains intravascular volume and metabolic homeostasis. Although plasma fluids and proteins extravasate continuously from tissue microvasculature (capillaries, post-capillary venules), systemic vascular leakage increases in critical illness associated with sepsis, burns and trauma, among others, or in association with certain drugs or toxin exposures. Systemically dysregulated fluid homeostasis, which can lead to hypovolaemia, hypotensive shock and widespread tissue oedema, has been termed systemic capillary leak syndrome (SCLS) when overt secondary causes (for example, heart or liver failure) are excluded.

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Article Synopsis
  • Vascular leakage is a serious complication of severe infections like septicemia and malaria, leading to shock and multi-organ dysfunction, with a specific syndrome (MG-CLS) causing recurrent severe episodes triggered by minor infections.
  • Researchers identified loss-of-function mutations in the PARP15 gene present in MG-CLS patients, linked to reduced enzyme function and increased vascular leakage.
  • The PARP15 enzyme plays a crucial role in protecting blood vessel integrity during inflammation by inhibiting certain pathways, indicating a genetic factor influencing susceptibility to MG-CLS-related vascular issues.
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Introduction: Mesoamerican nephropathy (MeN) is a chronic kidney disease (CKD) which may be caused by recurrent acute kidney injury (AKI). We investigated urinary quinolinate-to-tryptophan ratio (Q/T), a validated marker of nicotinamide adenine dinucleotide (NAD+) biosynthesis that is elevated during ischemic and inflammatory AKI, in a sugarcane worker population in Nicaragua with high rates of MeN.

Methods: Among 693 male sugarcane workers studied, we identified 45 who developed AKI during the harvest season.

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Background: Despite the availability of effective therapies for patients with chronic kidney disease, type 2 diabetes, and hypertension (the kidney-dysfunction triad), the results of large-scale trials examining the implementation of guideline-directed therapy to reduce the risk of death and complications in this population are lacking.

Methods: In this open-label, cluster-randomized trial, we assigned 11,182 patients with the kidney-dysfunction triad who were being treated at 141 primary care clinics either to receive an intervention that used a personalized algorithm (based on the patient's electronic health record [EHR]) to identify patients and practice facilitators to assist providers in delivering guideline-based interventions or to receive usual care. The primary outcome was hospitalization for any cause at 1 year.

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Clarkson disease, or monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS), is a rare, relapsing-remitting disorder featuring the abrupt extravasation of fluids and proteins into peripheral tissues, which in turn leads to hypotensive shock, severe hemoconcentration, and hypoalbuminemia. The specific leakage factor(s) and pathways in ISCLS are unknown, and there is no effective treatment for acute flares. Here, we characterize an autonomous vascular endothelial defect in ISCLS that was recapitulated in patient-derived endothelial cells (ECs) in culture and in a mouse model of disease.

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High-density lipoprotein (HDL) nanoparticles promote endothelial cell (EC) function and suppress inflammation, but their utility in treating EC dysfunction has not been fully explored. Here, we describe a fusion protein named ApoA1-ApoM (A1M) consisting of apolipoprotein A1 (ApoA1), the principal structural protein of HDL that forms lipid nanoparticles, and ApoM, a chaperone for the bioactive lipid sphingosine 1-phosphate (S1P). A1M forms HDL-like particles, binds to S1P, and is signaling competent.

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Experimental models suggest an important role for mitochondrial dysfunction in the pathogenesis of chronic kidney disease (CKD) and acute kidney injury (AKI), but little is known regarding the impact of common mitochondrial genetic variation on kidney health. We sought to evaluate associations of inherited mitochondrial DNA (mtDNA) variation with risk of CKD and AKI in a large population-based cohort. We categorized UK Biobank participants who self-identified as white into eight distinct mtDNA haplotypes, which were previously identified based on their associations with phenotypes associated with mitochondrial DNA copy number, a measure of mitochondrial function.

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Nicotinamide adenine dinucleotide (NAD+) levels decline in experimental models of acute kidney injury (AKI). Attenuated enzymatic conversion of tryptophan to NAD+ in tubular epithelium may contribute to adverse cellular and physiological outcomes. Mechanisms underlying defense of tryptophan-dependent NAD+ production are incompletely understood.

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Article Synopsis
  • Chronic liver injury from cholestasis leads to significant tissue damage, fibrosis, and kidney complications; IRF3 plays a key role in regulating inflammation and cell death in this process.
  • In studies with patients and mice models of cholestasis, increased phosphorylation of IRF3 was linked to higher tissue damage in the liver and kidneys, while IRF3 knockout mice showed reduced damage and inflammation.
  • The study highlights a potential mechanism where bile acids activate IRF3, which then upregulates ZBP1, suggesting that the IRF3-ZBP1 pathway could be crucial in understanding and addressing cholestatic liver and kidney injuries.
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Most cases of preterm labor have unknown cause, and the burden of preterm birth is immense. Placental aging has been proposed to promote labor onset, but specific mechanisms remain elusive. We report findings stemming from unbiased transcriptomic analysis of mouse placenta, which revealed that hypoxia-inducible factor 1 (HIF-1) stabilization is a hallmark of advanced gestational timepoints, accompanied by mitochondrial dysregulation and cellular senescence; we detected similar effects in aging human placenta.

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Nicotinamide adenine dinucleotide (NAD) is a redox cofactor critical for oxidative phosphorylation. Nicotinamide (NAM) and nicotinamide riboside (NR) are NAD precursors widely used as nutritional supplements to augment oxidative phosphorylation. Indeed, NAD precursors have been reported to improve outcomes in ischemic stroke when administered as a rescue therapy after stroke onset.

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Kidney injury is common and associated with worse outcomes in patients with septic shock. Mitochondrial resuscitation with thiamine (vitamin B1) may attenuate septic kidney injury. To assess whether thiamine supplementation attenuates kidney injury in septic shock.

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Article Synopsis
  • Mesoamerican nephropathy (MeN) is a kidney disease mainly affecting young men in Mesoamerica who work really hard in agriculture, especially sugarcane.
  • Researchers studied the urine of sugarcane workers in Nicaragua and compared it with people doing easier jobs or living in other countries.
  • They found that the high-risk workers had different chemicals in their urine that may suggest problems with inflammation and how their bodies use energy.
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Endothelial cells (ECs) normally form an anticoagulant surface under physiological conditions, but switch to support coagulation following pathogenic stimuli. This switch promotes thrombotic cardiovascular disease. To generate thrombin at physiologic rates, coagulation proteins assemble on a membrane containing anionic phospholipid, most notably phosphatidylserine (PS).

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Introduction: Quinolinic acid is an intermediate compound derived from the metabolism of dietary tryptophan. Its accumulation has been reported in patients suffering a broad spectrum of diseases and conditions. In this manuscript, we present the results of a systematic review of research studies assessing urinary quinolinic acid in health and disease.

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Acute kidney injury (AKI) occurs in approximately 13% of hospitalized patients and predisposes patients to chronic kidney disease (CKD) through the AKI-to-CKD transition. Studies from our laboratory and others have demonstrated that maladaptive repair of proximal tubule cells (PTCs), including induction of dedifferentiation, G2/M cell cycle arrest, senescence, and profibrotic cytokine secretion, is a key process promoting AKI-to-CKD transition, kidney fibrosis, and CKD progression. The molecular mechanisms governing maladaptive repair and the relative contribution of dedifferentiation, G2/M arrest, and senescence to CKD remain to be resolved.

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Acute kidney injury (AKI) is a serious and highly prevalent disease, yet only supportive treatment is available. Nicotinamide adenine dinucleotide (NAD+) is a cofactor necessary for adenosine triphosphate (ATP) production and cell survival. Changes in renal NAD+ biosynthesis and energy utilization are features of AKI.

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The perivascular sphingosine 1-phosphate signaling axis may be an emerging therapeutic target for treating chronic kidney disease (Tanaka ).

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Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients.

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