Abstract
Sepsis is one of the most common comorbidities observed in diabetic patients, associated with a deficient innate immune response. Recently, we have shown that glucagon possesses anti-inflammatory properties. In this study, we investigated if hyperglucagonemia triggered by diabetes might reduce the migration of neutrophils, increasing sepsis susceptibility. 21 days after diabetes induction by intravenous injection of alloxan, we induced moderate sepsis in Swiss-Webster mice through cecum ligation and puncture (CLP). The glucagon receptor (GcgR) antagonist des-his1-[Glu9]-glucagon amide was injected intraperitoneally 24h and 1h before CLP. We also tested the effect of glucagon on CXCL1/KC-induced neutrophil migration to the peritoneal cavity in mice. Neutrophil chemotaxis in vitro was tested using transwell plates, and the expression of total PKA and phospho-PKA was evaluated by western blot. GcgR antagonist restored neutrophil migration, reduced CFU numbers in the peritoneal cavity and improved survival rate of diabetic mice after CLP procedure, however, the treatment did no alter hyperglycemia, CXCL1/KC plasma levels and blood neutrophilia. In addition, glucagon inhibited CXCL1/KC-induced neutrophil migration to the peritoneal cavity of non-diabetic mice. Glucagon also decreased the chemotaxis of neutrophils triggered by CXCL1/KC, PAF, or fMLP in vitro. The inhibitory action of glucagon occurred in parallel with the reduction of CXCL1/KC-induced actin polymerization in neutrophils in vitro, but not CD11a and CD11b translocation to cell surface. The suppressor effect of glucagon on CXCL1/KC-induced neutrophil chemotaxis in vitro was reversed by pre-treatment with GcgR antagonist and adenylyl cyclase or PKA inhibitors. Glucagon also increased PKA phosphorylation directly in neutrophils in vitro. Furthermore, glucagon impaired zymosan-A-induced ROS production by neutrophils in vitro. Human neutrophil chemotaxis and adherence to endothelial cells in vitro were inhibited by glucagon treatment. According to our results, this inhibition was independent of CD11a and CD11b translocation to neutrophil surface or neutrophil release of CXCL8/IL-8. Altogether, our results suggest that glucagon may be involved in the reduction of neutrophil migration and increased susceptibility to sepsis in diabetic mice. This work collaborates with better understanding of the increased susceptibility and worsening of sepsis in diabetics, which can contribute to the development of new effective therapeutic strategies for diabetic septic patients.
Highlights
Diabetes is frequently associated with the development and worsening of sepsis, with about 22% of septic patients presenting a medical history of diabetes [1, 2]
Diabetic mice subjected to cecum ligation and puncture (CLP) showed decreased accumulation of total leukocytes, mainly neutrophils, into the peritoneal cavity compared to non-diabetic mice subjected to CLP (Figure 1A)
Glucagon receptor (GcgR) antagonism improved bacterial clearance in the peritoneal cavity of diabetic mice subjected to CLP in a dose-dependent manner as colony-forming units (CFU) counts were consistently decreased by GcgR treatment (Figure 1B)
Summary
Diabetes is frequently associated with the development and worsening of sepsis, with about 22% of septic patients presenting a medical history of diabetes [1, 2]. The high risk of infections observed in diabetic patients has been linked with defects in the innate and adaptive immune system [3], the mechanisms behind immune deficiency in diabetes are still unknown. It was shown that the greater severity of sepsis in type 1 diabetic mice is related to reduce neutrophil migration to the focus of infection [7, 8]. The severity, organ dysfunction, and mortality were seen in patients with severe sepsis who have a close relationship with high plasma glucagon levels [10], suggesting an association between glucagon overproduction and diabetes immune deficiency. We previously demonstrated that glucagon reduced lipopolysaccharide (LPS)-induced neutrophil migration to airways, increasing the evidence of its anti-inflammatory performance [11]. Glucagon is a stimulatory hormone which acts through a 7TM receptor coupled to a Gs protein, inducing an increase in the intracellular levels of cyclic adenosine monophosphate (cAMP) with consequent stimulation of the protein kinase A (PKA)/cAMP response element-binding (CREB) signaling pathway [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
