Identification of HSP90 inhibitors as a novel class of senolytics.

Aging is the main risk factor for many chronic degenerative diseases and cancer. Increased senescent cell burden in various tissues is a major contributor to aging and age-related diseases. Recently, a new class of drugs termed senolytics were demonstrated to extending healthspan, reducing frailty and improving stem cell function in multiple murine models of aging. To identify novel and more optimal senotherapeutic drugs and combinations, we established a senescence associated ß-galactosidase assay as a screening platform to rapidly identify drugs that specifically affect senescent cells. We used primary Ercc1 -/- murine embryonic fibroblasts with reduced DNA repair capacity, which senesce rapidly if grown at atmospheric oxygen. This platform was used to screen a small library of compounds that regulate autophagy, identifying two inhibitors of the HSP90 chaperone family as having significant senolytic activity in mouse and human cells. Treatment of Ercc1 -/∆ mice, a mouse model of a human progeroid syndrome, with the HSP90 inhibitor 17-DMAG extended healthspan, delayed the onset of several age-related symptoms and reduced p16INK4a expression. These results demonstrate the utility of our screening platform to identify senotherapeutic agents as well as identified HSP90 inhibitors as a promising new class of senolytic drugs.The accumulation of senescent cells is thought to contribute to the age-associated decline in tissue function. Here, the authors identify HSP90 inhibitors as a new class of senolytic compounds in an in vitro screening and show that administration of a HSP90 inhibitor reduces age-related symptoms in progeroid mice.

Calcium supplementation during sepsis exacerbates organ failure and mortality via calcium/calmodulin-dependent protein kinase kinase signaling.

BACKGROUND: Calcium plays an essential role in nearly all cellular processes. As such, cellular and systemic calcium concentrations are tightly regulated. During sepsis, derangements in such tight regulation frequently occur, and treating hypocalcemia with parenteral calcium administration remains the current practice guideline. OBJECTIVE: We investigated whether calcium administration worsens mortality and organ dysfunction using an experimental murine model of sepsis and explored the mechanistic role of the family of calcium/calmodulin-dependent protein kinases in mediating these physiological effects. To highlight the biological relevance of these observations, we conducted a translational study of the association between calcium administration, organ dysfunction, and mortality among a cohort of critically ill septic ICU patients. DESIGN: Prospective, randomized controlled experimental murine study and observational clinical cohort analysis. SETTING: University research laboratory and eight ICUs at a tertiary care center. PATIENTS: A cohort of 870 septic ICU patients. SUBJECTS: C57Bl/6 and CaMKK mice. INTERVENTIONS: Mice underwent cecal ligation and puncture polymicrobial sepsis and were administered with calcium chloride (0.25 or 0.25 mg/kg) or normal saline. MEASUREMENTS AND MAIN RESULTS: Administering calcium chloride to septic C57Bl/6 mice heightened systemic inflammation and vascular leak, exacerbated hepatic and renal dysfunction, and increased mortality. These events were significantly attenuated in CaMKK mice. In a risk-adjusted analysis of septic patients, calcium administration was associated with an increased risk of death, odds ratio 1.92 (95% CI, 1.00-3.68; p = 0.049), a significant increase in the risk of renal dysfunction, odds ratio 4.74 (95% CI, 2.48-9.08; p < 0.001), and a significant reduction in ventilator-free days, mean decrease 3.29 days (0.50-6.08 days; p = 0.02). CONCLUSIONS: Derangements in calcium homeostasis occur during sepsis that is sensitive to calcium administration. This altered calcium signaling, transduced by the calmodulin-dependent protein kinase kinase cascade, mediates heightened inflammation and vascular leak that culminates in elevated organ dysfunction and mortality. In the clinical management of septic patients, calcium supplementation provides no benefit and may impose harm.