ObjectiveTo determine that 1) an age-dependent loss of inducible autophagy underlies the failure to recover from AKI in older, adult animals during endotoxemia, and 2) pharmacologic induction of autophagy, even after established endotoxemia, is of therapeutic utility in facilitating renal recovery in aged mice.DesignMurine model of endotoxemia and cecal ligation and puncture (CLP) induced acute kidney injury (AKI).SettingAcademic research laboratory.SubjectsC57Bl/6 mice of 8 (young) and 45 (adult) weeks of age.InterventionLipopolysaccharide (1.5 mg/kg), Temsirolimus (5 mg/kg), AICAR (100 mg/kg). Measurements and Main Results: Herein we report that diminished autophagy underlies the failure to recover renal function in older adult mice utilizing a murine model of LPS-induced AKI. The administration of the mTOR inhibitor temsirolimus, even after established endotoxemia, induced autophagy and protected against the development of AKI.ConclusionsThese novel results demonstrate a role for autophagy in the context of LPS-induced AKI and support further investigation into like interventions that have potential to alter the natural history of disease.

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 physiologic 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. Observational clinical cohort analysis. Setting University research laboratory. Eight ICUs at a tertiary care center. Patients 870 septic ICU patients. Subjects C57BL/6 and CaMKK−/− mice. Interventions Mice underwent cecal ligation and puncture polymicrobial sepsis and were administered 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, OR 1.92 (95% CI 1.00–3.68, p=0.049), a significant increase in the risk of renal dysfunction, OR 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 are sensitive to calcium administration. This altered calcium signaling, transduced by the CaMKK 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.

Dysregulated Ca(2+) handling is prevalent during sepsis and postulated to perpetuate the aberrant inflammation underlying subsequent organ dysfunction and death. The signal transduction cascades mediating these processes are unknown. Here, we identify that CaMKIα mediates the Mϕ response to LPS in vitro and the inflammation and organ dysfunction of sepsis in vivo. We show that LPS induced active pThr(177)-CaMKIα in RAW 264.7 cells and murine peritoneal Mϕ, which if inhibited biochemically with STO609 (CaMKK inhibitor) or by RNAi, reduces LPS-induced production of IL-10. Transfection of constitutively active CaMKIα (CaMKI293), but not a kinase-deficient mutant (CaMKI293(K49A)), induces IL-10 release. This production of IL-10 is mediated by CaMKIα-dependent regulation of p38 MAPK activation. CaMKIα activity also mediates the cellular release of HMGB1 by colocalizing with and regulating the packaging of HMGB1 into secretory lysosomes. During endotoxemia, mice receiving in vivo CaMKIα(RNAi) display reduced systemic concentrations of IL-10 and HMGB1 in comparison with mice receiving NT(RNAi). These data support the biological relevance of CaMKIα-dependent IL-10 production and HMGB1 secretion. In a CLP model of sepsis, CaMKIα(RNAi) mice display reduced systemic concentrations of IL-10, IL-6, TNF-α, and HMGB1 in comparison with NT(RNAi) mice, which correlate with reductions in the development of renal dysfunction. These data support that CaMKIα signaling is integral to the Mϕ responding to LPS and may also be operant in vivo in regulating the inflammation and organ dysfunction consequent to sepsis.

Autophagy is an evolutionarily conserved cytoplasmic process regulated by the energy rheostats mTOR and AMPK that recycles damaged or unused proteins and organelles. It has been described as an important effector arm of immune cells. We have shown that the cytoplasmically oriented calcium/calmodulin-dependent protein kinase I α (CaMKIα) regulates the inflammatory phenotype of the macrophage (Mφ). Here, we hypothesize that CaMKIα mediates Mφ autophagy. LPS induced autophagy in RAW 264.7 cells and murine peritoneal Mφ that was attenuated with biochemical CaMK inhibition or CaMKIα siRNA. Inhibition of CaMKIα reduced LPS-induced p-Thr172AMPK and TORC1 activity, and expression of a constitutively active CaMKIα but not a kinase-deficient mutant induced p-Thr172AMPK and autophagy that was attenuated by the AMPK inhibitor Compound C. Co-immunoprecipitation and in vitro kinase assays demonstrated that CaMKIα activates AMPK, thereby inducing ATG7, which also localizes to this CaMKIα-AMPK complex. During LPS-induced lung inflammation, C57Bl/6 mice receiving CaMKIαsiRNA displayed reduced lung and bronchoalveolar immune cell autophagy that correlated with reduced neutrophil recruitment, myeloperoxidase activity, and air space cytokine concentration. Independently inhibiting autophagy, using siRNA targeting the PI3 kinase VPS34, yielded similar reductions in lung autophagy and neutrophil recruitment. Thus, a novel CaMKIα-AMPK pathway is rapidly activated in Mφ exposed to LPS and regulates an early autophagic response, independent of TORC1 inhibition. These mechanisms appear to be operant in vivo in orchestrating LPS-induced lung neutrophil recruitment and inflammation.

Autophagy, an evolutionarily conserved homeostasis process regulating biomass quantity and quality, plays a critical role in the host response to sepsis. Recent studies show its calcium dependence, but the calcium sensitive regulatory cascades have not been defined. Here we describe a novel mechanism in which CaMKIV, through inhibitory serine phosphorylation of GSK-3β and inhibition of FBXW7 recruitment, prevents ubiquitin proteosomal degradation of mTOR, and thereby augments autophagy in both the Mφ and the kidney. Under the conditions of sepsis studied, mTOR expression and activity were requisite for autophagy, a paradigm countering the current perspective that prototypically, mTOR inhibition induces autophagy. CaMKIV-mTOR dependent autophagy was fundamentally important for IL-6 production in vitro and in vivo. Similar mechanisms were operant in the kidney during endotoxemia and served a cytoprotective role in mitigating acute kidney injury. Thus, CaMKIV-mTOR-dependent autophagy is conserved in both immune and non-immune/parenchymal cells and is fundamental for the respective functional and adaptive responses to septic insult.