SIRT1 inhibition during the hypoinflammatory phenotype of sepsis enhances immunity and improves outcome

Abstract

Mechanism-based sepsis treatments are unavailable, and their incidence is rising worldwide. Deaths occur during the early acute phase of hyperinflammation or subsequent postacute hypoinflammatory phase with sustained organ failure. The acute sepsis phase shifts rapidly, and multiple attempts to treat early excessive inflammation have uniformly failed. We reported in a sepsis cell model and human sepsis blood leukocytes that nuclear NAD+ sensor SIRT1 deacetylase remodels chromatin at specific gene sets to switch the acute-phase proinflammatory response to hypoinflammatory. Importantly, SIRT1 chromatin reprogramming is reversible, suggesting that inhibition of SIRT1 might reverse postacute-phase hypoinflammation. We tested this concept in septic mice, using the highly specific SIRT1 inhibitor EX-527, a small molecule that closes the NAD+ binding site of SIRT1. Strikingly, when administered 24 h after sepsis, all treated animals survived, whereas only 40% of untreated mice survived. EX-527 treatment reversed the inability of leukocytes to adhere at the small intestine MVI, reversed in vivo endotoxin tolerance, increased leukocyte accumulation in peritoneum, and improved peritoneal bacterial clearance. Mechanistically, the SIRT1 inhibitor restored repressed endothelial E-selectin and ICAM-1 expression and PSGL-1 expression on the neutrophils. Systemic benefits of EX-527 treatment included stabilized blood pressure, improved microvascular blood flow, and a shift toward proimmune macrophages in spleen and bone marrow. Our findings reveal that modifying the SIRT1 NAD+ axis may provide a novel way to treat sepsis in its hypoinflammatory phase.

Sequential Actions of SIRT1-RELB-SIRT3 Coordinate Nuclear-Mitochondrial Communication during Immunometabolic Adaptation to Acute Inflammation and Sepsis

“…Remarkably, we found in mice that inhibiting SIRT1 activity after the switch to adaptation improves peripheral circulation, restores immune competence, and markedly improves survival (20). That study, however, did not address whether SIRT1 inhibition rebalanced glucose and fatty acid mitochondrial oxidation or altered mitochondrial bioenergetics.…”

“…Using our established model of murine sepsis (cecal ligation and puncture) (20), we found that treating sepsis splenocytes ex vivo for 24 h with the SIRT1 inhibitor EX-527 significantly decreased mRNA levels of Relb, Sirt3, Idh 2 , Sod 2 , and Vdac (Fig. 8D).…”

“…All mice were obtained from Jackson Laboratories (Bar Harbor, ME), and the standard CLP procedure (two punctures with 22-gauge needles) was performed under anesthesia as described (20). Animals that received laparotomy without CLP served as sham controls.…”

“…We also used the SIRT-specific inhibitor EX-527 (8,15,20) to test whether SIRT1 activation is indispensable for reprogramming mitochondrial bioenergetics in TLR4-adapted primary human monocytes. Adding EX-527 ex vivo 8 h after LPS stimulation decreased the mRNA level of all genes except SOD 2 after normalizing against untreated cells (Fig.…”

“…Increases in NAD ϩ availability and the cooperative actions of nuclear SIRT1, SIRT6, and RELB are required to move from initiation to adaptation (15,19). When NAD ϩ or SIRT1 levels decrease in cell models of sepsis and sepsis mice, the initial acute inflammatory response is amplified by allowing excessive NFB RelA/p65 activation (19,20). To adapt to acute inflammation, nuclear SIRT1 guides RELB to generate silent heterochromatin at pro-immune genes like TNF-␣ and IL-1␤ (21) and to activate the euchromatin of genes responsible for fatty acid uptake and oxidation.…”