Post hoc analysis of the SONAR trial indicates that the endothelin receptor antagonist atrasentan is associated with less pain in patients with type 2 diabetes and chronic kidney disease

The role of endothelin receptor antagonists in kidney disease

Kidney diseases are among the most prevalent conditions worldwide, impacting over 850 million individuals. They are categorized into acute kidney injury and chronic kidney disease. Current preclinical and clinical trials have demonstrated that endothelin (ET) is linked to the onset and progression of kidney disease. In kidney diseases, pathological conditions such as hyperglycemia, acidosis, insulin resistance, and elevated angiotensin II levels lead to an increase in ET. This elevation activates endothelin receptor type A, resulting in harmful effects like proteinuria and a reduced glomerular filtration rate (GFR). Therefore, to slow the progression of kidney disease, endothelin receptor antagonists (ERAs) have been proposed as promising new therapies. Numerous studies have demonstrated the efficacy of ERAs in significantly reducing proteinuria and improving GFR, thereby slowing the progression of kidney diseases. This review discusses the mechanisms of action of ERAs in treating kidney disease, their efficacy and safety in preclinical and clinical studies, and explores future prospects for ERAs.

Ion Channels and G-Protein-Coupled Receptors Involved in the Development of Chronic Post-ischemic Pain (CPIP): A Model of Complex Regional Pain Syndrome (CRPS-I)

Chronic pain is a physical and emotional sensation that exceeds biological necessity. Complex regional pain syndrome (CRPS) is considered a chronic primary pain condition that can arise after limb trauma, such as surgery, ischemia, and fractures. This type of pain is a multifactorial disorder that predominantly affects one body extremity and occurs either without initial nerve injury (CRPS-I) or with partial or complete nerve injury (CRPS-II). Therefore, CRPS-I is still a painful and debilitating condition without a complete understanding of its underlying mechanisms. This gap in knowledge about CRPS-I pathophysiology contributes to patient suffering, as there is still no standard pharmacological treatment. Preclinical research uses diverse models of CRPS-I, such as chronic post-ischemia pain (CPIP), to better understand its pain activation pathways. Various mechanisms continue to emerge in CPIP, including the role of different G-protein-coupled receptors (GPCRs) and ion channels. In this review, we will focus on the mechanisms surrounding these different GPCRs and ion channels in a model of CRPS-I-induced nociception in rodents (the CPIP model). To date, the primary targets studied in CPIP pathophysiology include transient receptor potential (TRP) and N-methyl-D-aspartate (NMDA) ion channels, as well as cannabinoid, bradykinin, adenosine, adrenergic, and endothelin GPCRs.

Endothelin receptor antagonists in chronic kidney disease

Endothelin-1 is a potent vasoconstrictor that has diverse physiological functions in the kidney, including in the regulation of blood flow and glomerular filtration, electrolyte homeostasis and endothelial function. Overexpression of endothelin-1 contributes to the pathophysiology of both diabetic and non-diabetic chronic kidney disease (CKD). Selective endothelin receptor antagonists (ERAs) that target the endothelin A (ETA) receptor have demonstrated benefits in animal models of kidney disease and in clinical trials. In patients with type 2 diabetes and CKD, the selective ETA ERA, atrasentan, reduced albuminuria and kidney function decline. Concerns about the increased risks of fluid retention and heart failure with ERA use have led to the design of further trials to optimize dosing and patient selection. More recent studies have shown that the dual ETA receptor and angiotensin receptor blocker, sparsentan, preserved kidney function with minimal fluid retention in patients with IgA nephropathy. Moreover, combined administration of a low dose of the ETA-selective ERA, zibotentan, with the sodium-glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin, enhanced albuminuria reduction and mitigated fluid retention in patients with CKD. Notably, sparsentan and aprocitentan have received FDA approval for the treatment of IgA nephropathy and treatment-resistant hypertension, respectively. This Review describes our current understanding of the use of ERAs in patients with CKD to guide their optimal safe and effective use in clinical practice.

Targeting endothelin signaling in podocyte injury and diabetic nephropathy-diabetic kidney disease

Despite advances in diabetes management, there is an urgent need for novel therapeutic strategies since the current treatments remain insufficient in halting the progression of diabetic nephropathy-diabetic kidney disease (DN-DKD). This review is mainly addressed on the pivotal role of endothelin-1 in the pathophysiology of DN, with a specific focus on its effects on podocytes and the glomerular filtration barrier. Endothelin-1 promotes mesangial cell proliferation, sclerosis, and direct podocyte injury via the activation of endothelin type A and B receptors, that drive the progression of glomerulosclerosis in DN-DKD. Endothelin receptor antagonists, including drugs like atrasentan and sparsentan, have demonstrated nephroprotective effects in experimental models by reducing proteinuria and podocyte injury. The therapeutic potential to slow the progression of DN to end-stage kidney disease (ESKD) of these endothelin receptor antagonists in clinical practice is currently under evaluation. However, fluid retention and increased risk of heart failure associated with endothelin receptor antagonists need careful consideration. This review aims to provide an in-depth analysis of the pathophysiological role of endothelin and the emerging therapeutic implications of targeting this pathway in DN-DKD and discusses efficacy, safety, and the possibility of combining the new generation of endothelin receptor antagonists with the standard treatment of CKD and DN-DKD.

Utilization of Reimbursed Acupuncture Therapy for Low Back Pain

Importance

Treating low back pain (LBP) often involves a combination of pharmacologic, nonpharmacologic, and interventional treatments; one approach is acupuncture therapy, which is safe, effective, and cost-effective. How acupuncture is used within pain care regimens for LBP has not been widely studied.

Objective

To document trends in reimbursed acupuncture between 2010 and 2019 among a large sample of patients with LBP, focusing on demographic, socioeconomic, and clinical characteristics associated with acupuncture use and the nonpharmacologic, pharmacologic, and interventional treatments used by patients who utilize acupuncture.

Design, Setting, and Participants

This cross-sectional study included insurance claims of US adults in a deidentified database. The study sample included patients diagnosed with LBP between 2010 and 2019. Data were analyzed between September 2023 and June 2024.

Main Outcomes and Measures

Changes in rates of reimbursed acupuncture utilization between 2010 and 2019, including electroacupuncture use, which involves the electrical stimulation of acupuncture needles. Covariates included age, sex, race and ethnicity, income, educational attainment, region, and a chronic LBP indicator. Secondary analyses tracked other nonpharmacologic treatments (eg, physical therapy, chiropractic care), pharmacologic treatments (eg, opioids, gabapentinoids), and interventional treatments (eg, epidural steroid injections).

Results

The total sample included 6 840 497 adults with LBP (mean [SD] age, 54.6 [17.8] years; 3 916 766 female [57.3%]; 802 579 Hispanic [11.7%], 258 087 non-Hispanic Asian [3.8%], 804 975 non-Hispanic Black [11.8%], 4 974 856 non-Hispanic White [72.7%]). Overall, 106 485 (1.6%) had 1 or more acupuncture claim, while 61 503 (0.9%) had 1 or more electroacupuncture claim. The rate of acupuncture utilization increased consistently, from 0.9% in 2010 to 1.6% in 2019; electroacupuncture rates were relatively stable. Patients who were female (male: odds ratio [OR], 0.68; 99% CI, 0.67-0.70), Asian (OR, 3.26; 99% CI, 3.18-3.35), residing in the Pacific region (New England: OR, 0.26; 99% CI, 0.25-0.28), earning incomes of over $100 000 (incomes less than $40 000: OR, 0.59; 99% CI, 0.57-0.61), college educated (high school or less: OR, 0.32; 99% CI, 0.27-0.35), and with chronic LBP (OR, 2.39; 99% CI, 2.35-2.43) were more likely to utilize acupuncture. Acupuncture users were more likely to engage in other nonpharmacologic pain care like physical therapy (39.2%; 99% CI, 38.9%-39.5% vs 29.3%; 99% CI, 29.3%-29.3%) and less likely to utilize prescription drugs, including opioids (41.4%; 99% CI, 41.1%-41.8% vs 52.5%; 99% CI, 52.4%-52.5%), compared with nonusers.

Conclusions and Relevance

In this cross-sectional study, we found that acupuncture utilization among patients with LBP was rare but increased over time. Demographic, socioeconomic, and clinical characteristics were associated with acupuncture utilization, and acupuncture users were more likely to utilize other nonpharmacologic treatments and less likely to utilize pharmacologic treatments.

Comprehensive analysis of the endothelin system in the kidneys of mice, rats, and humans

The intrarenal endothelin (ET) system is an established moderator of kidney physiology and mechanistic contributor to the pathophysiology and progression of chronic kidney disease in humans and rodents. The aim of the present study was to characterize ET system by combining single cell RNA sequencing (scRNA-seq) data with immunolocalization in human and rodent kidneys of both sexes. Using publicly available scRNA-seq data, we assessed sex and kidney disease status (human), age and sex (rats), and diurnal expression (mice) on the kidney ET system expression. In normal human biopsies of both sexes and in rodent kidney samples, the endothelin-converting enzyme-1 (ECE1) and ET-1 were prominent in the glomeruli and endothelium. These data agreed with the scRNA-seq data from these three species, with ECE1/Ece1 mRNA enriched in the endothelium. However, the EDN1/Edn1 gene (encodes ET-1) was rarely detected, even though it was immunolocalized within the kidneys, and plasma and urinary ET-1 excretion are easily measured. Within each species, there were some sex-specific differences. For example, in kidney biopsies from living donors, men had a greater glomerular endothelial cell endothelin receptor B (Ednrb) compared with women. In mice, females had greater kidney endothelial cell Ednrb than male mice. As commercially available antibodies did not work in all species, and RNA expression did not always correlate with protein levels, multiple approaches should be considered to maintain required rigor and reproducibility of the pre- and clinical studies evaluating the intrarenal ET system.

Endothelin System in Hypertension and Chronic Kidney Disease

ET (endothelin) is a powerful vasoconstrictor 21-amino acid peptide present in many tissues, which exerts many physiological functions across the body and participates as a mediator in many pathological conditions. ETs exert their effects through ETA and ETB receptors, which can be blocked by selective receptor antagonists. ETs were shown to play important roles among others, in systemic hypertension, particularly when resistant or difficult to control, and in pulmonary hypertension, atherosclerosis, cardiac hypertrophy, subarachnoid hemorrhage, chronic kidney disease, diabetic cardiovascular disease, scleroderma, some cancers, etc. To date, ET antagonists are only approved for the treatment of primary pulmonary hypertension and recently for IgA nephropathy and used in the treatment of digital ulcers in scleroderma. However, they may soon be approved for the treatment of patients with resistant hypertension and different types of nephropathy. Here, the role of ETs is reviewed with a special emphasis on participation in and treatment of hypertension and chronic kidney disease.

Endothelin receptor antagonists in diabetic and non-diabetic chronic kidney disease

Chronic kidney disease (CKD) is one of the major causes of morbidity and mortality, affecting >800 million persons globally. While we still lack efficient, targeted therapies addressing the major underlying pathophysiologic processes in CKD, findings of several recent trials have brought about a shifting landscape of promising therapies. The endothelin system has been implicated in the pathophysiology of CKD and endothelin receptor antagonists are one class of drugs for which we have increasing evidence of efficacy in these patients. In this review we summarize the most recent findings on the safety and efficacy of endothelin receptor antagonists in diabetic and non-diabetic CKD, future directions of research and upcoming treatments.

Post hoc analysis of the SONAR trial: potential analgesic effects of atrasentan?

Chan et al. conducted a post hoc analysis of the Study of Diabetic Nephropathy with Atrasentan (SONAR) to demonstrate that atrasentan reduced chronic pain-related adverse events reported by investigators and the initiation of analgesics. This study creates an interesting hypothesis, but it is limited in that the pain information was collected as part of the adverse events and the presence/absence of pain at baseline was unknown. Thus, prospective clinical trials are required to confirm these findings.