Adenosine receptor antagonists effect on plasma-enhanced killing

Improvement of the sepsis survival rate by adenosine 2a receptor antagonists depends on immune regulatory functions of regulatory T-cells

Adenosine shows a significant immunosuppressive effect in sepsis via binding to the adenosine 2a receptor (A2aR). Both genetic deletion and pharmacological inhibition of the A2aR may improve survival in sepsis. However, available research on this protective mechanism is quite limited. We used an A2aR antagonist (ZM241385) to treat a cecal ligation and puncture model of normal mice or regulatory T-cell (Treg)-depletion mice and found that the protective effect of ZM241385 is dependent on Tregs. Mechanically, A2aR inactivation was associated with decreased frequencies and reduced function of Foxp3+ Tregs, as evidenced by Foxp3 and CTLA-4 expression and classical effector T-cell proliferative assays, suggesting Treg modulation is a potential protective mechanism against sepsis. Simultaneously, the function and quantity of abdominal neutrophils were improved with ZM241385 treatment. To see if a link exists between them, Tregs and neutrophils were co-cultured, and it was found that ZM241385 blocked the inhibitory effect of Tregs on neutrophils. According to our research, Tregs play a key role in how A2aR antagonists improve sepsis prognosis and bacterial clearance.

Machine learning and murine models explain failures of clinical sepsis trials

BACKGROUND

Multiple clinical trials failed to demonstrate the efficacy of hydrocortisone, ascorbic acid, and thiamine (HAT) in sepsis. These trials were dominated by patients with pulmonary sepsis and have not accounted for differences in the inflammatory responses across varying etiologies of injury/illness. Hydrocortisone, ascorbic acid, and thiamine have previously revealed tremendous benefits in animal peritonitis sepsis models (cecal ligation and puncture [CLP]) in contradiction to the various clinical trials. The impact of HAT remains unclear in pulmonary sepsis. Our objective was to investigate the impact of HAT in pneumonia, consistent with the predominate etiology in the discordant clinical trials. We hypothesized that, in a pulmonary sepsis model, HAT would act synergistically to reduce end-organ dysfunction by the altering the inflammatory response, in a unique manner compared with CLP.

METHODS

Using Pseudomonas aeruginosa pneumonia, a pulmonary sepsis model (pneumonia [PNA]) was compared directly to previously investigated intra-abdominal sepsis models. Machine learning applied to early vital signs stratified animals into those predicted to die (pDie) versus predicted to live (pLive). Animals were then randomized to receive antibiotics and fluids (vehicle [VEH]) vs. HAT). Vitals, cytokines, vitamin C, and markers of liver and kidney function were assessed in the blood, bronchoalveolar lavage, and organ homogenates.

RESULTS

PNA was induced in 119 outbred wild-type Institute of Cancer Research mice (predicted mortality approximately 50%) similar to CLP. In PNA, interleukin 1 receptor antagonist in 72-hour bronchoalveolar lavage was lower with HAT (2.36 ng/mL) compared with VEH (4.88 ng/mL; p = 0.04). The remaining inflammatory cytokines and markers of liver/renal function showed no significant difference with HAT in PNA. PNA vitamin C levels were 0.62 mg/dL (pDie HAT), lower than vitamin C levels after CLP (1.195 mg/dL). Unlike CLP, PNA mice did not develop acute kidney injury (blood urea nitrogen: pDie, 33.5 mg/dL vs. pLive, 27.6 mg/dL; p = 0.17). Furthermore, following PNA, HAT did not significantly reduce microscopic renal oxidative stress (mean gray area: pDie, 16.64 vs. pLive, 6.88; p = 0.93). Unlike CLP where HAT demonstrated a survival benefit, HAT had no impact on survival in PNA.

CONCLUSION

Hydrocortisone, ascorbic acid, and thiamine therapy has minimal benefits in pneumonia. The inflammatory response induced by pulmonary sepsis is unique compared with the response during intra-abdominal sepsis. Consequently, different etiologies of sepsis respond differently to HAT therapy.

The immunomodulatory function of adenosine in sepsis

Sepsis is an unsolved clinical condition with a substantial mortality rate in the hospital. Despite decades of research, no effective treatments for sepsis exists. The role of adenosine in the pathogenesis of sepsis is discussed in this paper. Adenosine is an essential endogenous molecule that activates the A1, A2a, A2b, and A3 adenosine receptors to regulate tissue function. These receptors are found on a wide range of immune cells and bind adenosine, which helps to control the immune response to inflammation. The adenosine receptors have many regulatory activities that determine the onset and progression of the disease, which have been discovered via the use of animal models. A greater understanding of the role of adenosine in modulating the immune system has sparked hope that an adenosine receptor-targeted treatment may be used one day to treat sepsis.