The immunomodulatory function of adenosine in sepsis

Sex differences in adenosine deaminase activity associate with disparities in SARS-CoV-2 innate immunity

Females demonstrate elevated type-I interferon production and a stronger antiviral immune response; however, the mechanisms underlying sex-based differences in antiviral immunity are incompletely understood. We previously reported that low adenosine deaminase (ADA) activity perturbs the methylation-based transcriptional silencing of endogenous retroviral elements (hERV), which stimulates IFN-Stimulated Genes (ISG) and primes antiviral immunity. Here we demonstrate lower ADA activity in females compared to their male counterparts, which correlated with higher hERV and ISG expression in female lungs. Sex differences in ADA2 were linked to the number and expression profiles of blood and lung-derived monocyte populations. Single-cell RNA sequencing of respiratory cells from patients with COVID-19 showed a significant female bias in hERV-ISG signatures, and implicated IL-18 as a driver of sex-specific ADA2 expression. Observations in healthy and COVID-19 cohorts indicate that higher ADA activity is associated with suppressed antiviral innate immunity in the male respiratory tract, which may drive adverse COVID-19 outcomes.

Region-specific neuroprotective effects of meldonium pretreatment in two models of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a common yet poorly understood complication of sepsis, which poses a burden in clinical settings, as its management relies on supportive care without targeted pharmacological interventions. Meldonium is a drug approved for ischemic heart disease but has also gained attention for its neuroprotective effects. In animal models of sepsis, meldonium pretreatment exerted antioxidative, antiapoptotic, and anti-inflammatory effects, but its neurological effects have not been studied in SAE. In the present study, rats were pretreated with meldonium for 4 weeks, before sepsis was induced via a faecal intraperitoneal injection (FIP) or a lipopolysaccharide (LPS) injection. The cerebellum, medulla oblongata, and prefrontal cortex were examined due to their involvement in functions that are often impaired in sepsis. Eight hours post-sepsis induction, markers of brain injury were assessed, including reflexes scores, dry to wet brain mass ratio, prooxidant-antioxidant balance (PAB), advanced oxidation protein products (AOPP), lipid peroxidation (LPO), phosphatidylcholine (PC) to lysophosphatidylcholine (LPC) ratio, HMGB1 and haptoglobin protein expression, and CD73 activity. Meldonium-pretreated FIP-septic rats showed an earlier decline in reflex scores compared to the sepsis-only group, accompanied by a slight brain water accumulation. However, in both models of sepsis, meldonium pretreatment prevented alterations in the PAB, AOPP, and LPO in a region-specific manner. It also preserved the PC/LPC ratio in the prefrontal cortex of FIP-septic rats and in all regions of LPS-septic rats. Haptoglobin protein content was altered only in FIP-septic rats, and preserved by meldonium pretreatment in the cerebellum and medulla oblongata of these rats. Additionally, meldonium pretreatment preserved CD73 activity in the medulla oblongata and prefrontal cortex of FIP-septic rats and in the cerebellum and prefrontal cortex of LPS-septic rats. In conclusion, our study is the first to demonstrate that pretreatment with meldonium, a drug that has shown neuroprotective effects in other invasive models can also provide benefits in SAE, with the extent of protection depending on both the model of sepsis induction and the specific brain region investigated. Our findings support the discussion on the importance of selecting the right sepsis model and studying individual brain regions when investigating SAE and potential therapeutic approaches.

Trauma patients with type O blood exhibit unique multiomics signature with decreased lectin pathway of complement levels

BACKGROUND

Patients with type O blood may have an increased risk of hemorrhagic complications because of lower baseline levels of von Willebrand factor and factor VIII, but the transition to a mortality difference in trauma is less clear. We hypothesized that type O trauma patients will have differential proteomic and metabolomic signatures in response to trauma beyond von Willebrand factor and factor VIII alone.

METHODS

Patients meeting the highest level of trauma activation criteria were prospectively enrolled. Blood samples were collected upon arrival to the emergency department. Proteomic and metabolomic (multiomics) analyses of these samples were performed using liquid chromatography-mass spectrometry. Demographic, clinical, and multiomics data were compared between patients with type O blood versus all other patients.

RESULTS

There were 288 patients with multiomics data; 146 (51%) had type O blood. Demographics, injury patterns, and initial vital signs and laboratory measurements were not different between groups. Type O patients had increased lengths of stay (7 vs. 6 days, p = 0.041) and a trend toward decreased mortality secondary to traumatic brain injury compared with other causes (traumatic brain injury, 44.4% vs. 87.5%; p = 0.055). Type O patients had decreased levels of mannose-binding lectin and mannose-binding lectin-associated serine proteases 1 and 2, which are required for the initiation of the lectin pathway of complement activation. Type O patients also had metabolite differences signifying energy metabolism and mitochondrial dysfunction.

CONCLUSION

Blood type O patients have a unique multiomics signature, including decreased levels of proteins required to activate the lectin complement pathway. This may lead to overall decreased levels of complement activation and decreased systemic inflammation in the acute phase, possibly leading to a survival advantage, especially in traumatic brain injury. However, this may later impair healing. Future work will need to confirm these associations, and animal studies are needed to test therapeutic targets.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Chemical constituent characterization and determination of Quisqualis fructus based on UPLC-Q-TOF-MS and HPLC combined with fingerprint and chemometric analysis

Quisqualis fructus (QF) is a traditional Chinese medicine (TCM) that it has a long history in the therapeutic field of killing parasites, eliminating accumulation, and stopping diarrhea. However, the therapeutic material basis of QF is remaining ambiguous nowadays. The geographical origin differences of QF are also usually ignored in the process of medication. In this study, the alcohol-aqueous soluble constituents in QF from different origins were systematically characterized and accurately measured by ultra-high performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and high-performance liquid chromatography (HPLC) respectively. Chemometric analysis was performed for origin differentiation and screening of potential quality marker (Q-marker). Finally, A total of 106 constituents were tentatively characterized in positive and negative ion modes, including 29 fatty acids, 26 organic acids, 11 amino acids and derivatives, 10 glycosides, 9 alkaloids and derivatives, and 21 other constituents. QF from different origins were effectively distinguished and 16 constituents were selected as the potential Q-markers subsequently. Four representative components (trigonelline, adenosine, ellagic acid, and 3,3'-di-O-methylellagic acid) in QF samples were simultaneously determined. HPLC fingerprint analysis indicated that the similarity between 16 batches of QF was in the range of 0.870-0.999. The above results provide some insights for the research on the pharmacodynamic constituents, quality control, and geographical discrimination of QF.

Suppression by central adenosine A3 receptors of the cholinergic defense against cardiovascular aberrations of sepsis: role of PI3K/MAPKs/NFκB signaling

Introduction: Despite the established role of peripheral adenosine receptors in sepsis-induced organ dysfunction, little or no data is available on the interaction of central adenosine receptors with sepsis. The current study tested the hypothesis that central adenosine A3 receptors (A3ARs) modulate the cardiovascular aberrations and neuroinflammation triggered by sepsis and their counteraction by the cholinergic antiinflammatory pathway. Methods: Sepsis was induced by cecal ligation and puncture (CLP) in rats pre-instrumented with femoral and intracisternal (i.c.) catheters for hemodynamic monitoring and central drug administration, respectively. Results: The CLP-induced hypotension, reduction in overall heart rate variability (HRV) and sympathovagal imbalance towards parasympathetic predominance were abolished by i.v. nicotine (100 μg/kg) or i.c. VUF5574 (A3AR antagonist, 2 µg/rat). In addition, the selective A3AR agonist, 3-iodobenzyl-5'-N-methylcarboxamidoadenosine IB-MECA, 4 µg/rat, i.c.) exaggerated the hypotension and cardiac autonomic dysfunction induced by sepsis and opposed the favorable nicotine actions against these septic manifestations. Immunohistochemically, IB-MECA abolished the nicotine-mediated downregulation of NFκB and NOX2 expression in rostral ventrolateral medullary areas (RVLM) of brainstem of septic rats. The inhibitory actions of IB-MECA on nicotine responses disappeared after i.c. administration of PD98059 (MAPK-ERK inhibitor), SP600125 (MAPK-JNK inhibitor) or wortmannin (PI3K inhibitor). Moreover, infliximab (TNFα inhibitor) eliminated the IB-MECA-induced rises in RVLM-NFκB expression and falls in HRV, but not blood pressure. Conclusion: Central PI3K/MAPKs pathway mediates the A3AR counteraction of cholinergic defenses against cardiovascular and neuroinflammatory aberrations in sepsis.

ADENOSINE INFLUENCES FOXP3 EXPRESSION OF T REGS VIA THE A2AR/CREB PATHWAY IN A MOUSE MODEL OF SEPSIS

ABSTRACT

The adenosine concentration and forkhead box protein (Foxp3) expression in T regulatory cells (T regs ) are increased during sepsis. However, the mechanism by which adenosine induces Foxp3 expression is incompletely understood. A cecal ligation and puncture (CLP) model was constructed using C57BL/J mice. The plasma adenosine concentration and Foxp3 expression in splenic T regs were increased consistently for 15 days after sepsis onset. Analysis of the mean fluorescence intensity of Foxp3 and adenosine concentration in the same mice revealed a linear correlation. In the CLP model, adenosine 2a receptor (A2aR) blockade inhibited Foxp3 expression in T regs . In vitro activation of A2aR promoted Foxp3 expression in T regs and facilitated secretion of extracellular vesicles. Transcriptome sequencing revealed that A2aR blockade led to changes in cyclic adenosine monophosphate response element-binding protein (CREB) transcription in T regs in our sepsis model. Use of adenosine or A2aR agonists promoted CREB expression, CREB phosphorylation at S133, T reg expression of Foxp3, and enhanced inhibition of proliferation of cluster of differentiation (CD)4+ lymphocytes. A2aR blockade or inhibition of CREB expression inhibited Foxp3 expression in T regs . In the CLP model, use of CREB inhibitors could inhibit Foxp3 expression and reduce the bacterial load. In summary, adenosine in sepsis promotes CREB phosphorylation via A2aR which, in turn, upregulates Foxp3 expression in T regs .

Plasma Metabolomics Reveals Distinct Biological and Diagnostic Signatures for Melioidosis

Rationale: The global burden of sepsis is greatest in low-resource settings. Melioidosis, infection with the gram-negative bacterium Burkholderia pseudomallei, is a frequent cause of fatal sepsis in endemic tropical regions such as Southeast Asia. Objectives: To investigate whether plasma metabolomics would identify biological pathways specific to melioidosis and yield clinically meaningful biomarkers. Methods: Using a comprehensive approach, differential enrichment of plasma metabolites and pathways was systematically evaluated in individuals selected from a prospective cohort of patients hospitalized in rural Thailand with infection. Statistical and bioinformatics methods were used to distinguish metabolomic features and processes specific to patients with melioidosis and between fatal and nonfatal cases. Measurements and Main Results: Metabolomic profiling and pathway enrichment analysis of plasma samples from patients with melioidosis (n = 175) and nonmelioidosis infections (n = 75) revealed a distinct immuno-metabolic state among patients with melioidosis, as suggested by excessive tryptophan catabolism in the kynurenine pathway and significantly increased levels of sphingomyelins and ceramide species. We derived a 12-metabolite classifier to distinguish melioidosis from other infections, yielding an area under the receiver operating characteristic curve of 0.87 in a second validation set of patients. Melioidosis nonsurvivors (n = 94) had a significantly disturbed metabolome compared with survivors (n = 81), with increased leucine, isoleucine, and valine metabolism, and elevated circulating free fatty acids and acylcarnitines. A limited eight-metabolite panel showed promise as an early prognosticator of mortality in melioidosis. Conclusions: Melioidosis induces a distinct metabolomic state that can be examined to distinguish underlying pathophysiological mechanisms associated with death. A 12-metabolite signature accurately differentiates melioidosis from other infections and may have diagnostic applications.

Staphylococcus aureus suppresses the pentose phosphate pathway in human neutrophils via the adenosine receptor A2aR to enhance intracellular survival

IMPORTANCE

Staphylococcus aureus is one of the leading causes of antimicrobial-resistant infections whose success as a pathogen is facilitated by its massive array of immune evasion tactics, including intracellular survival within critical immune cells such as neutrophils, the immune system's first line of defense. In this study, we describe a novel pathway by which intracellular S. aureus can suppress the antimicrobial capabilities of human neutrophils by using the anti-inflammatory adenosine receptor, adora2a (A2aR). We show that signaling through A2aR suppresses the pentose phosphate pathway, a metabolic pathway used to fuel the antimicrobial NADPH oxidase complex that generates reactive oxygen species (ROS). As such, neutrophils show enhanced ROS production and reduced intracellular S. aureus when treated with an A2aR inhibitor. Taken together, we identify A2aR as a potential therapeutic target for combatting intracellular S. aureus infection.

The Immune Regulatory Role of Adenosine in the Tumor Microenvironment

Adenosine, an immunosuppressive metabolite, is produced by adenosine triphosphate (ATP) released from dying or stressed cells and is found at high levels in the tumor microenvironment of most solid tumors. It mediates pro-tumor activities by inducing tumor cell proliferation, migration or invasion, tumor tissue angiogenesis, and chemoresistance. In addition, adenosine plays an important role in regulating anti-tumor immune responses and facilitating tumor immune escape. Adenosine receptors are broadly expressed by tumor-infiltrated immune cells, including suppressive tumor-associated macrophages and CD4+ regulatory T cells, as well as effector CD4+ T cells and CD8+ cytotoxic T lymphocytes. Therefore, adenosine is indispensable in down-regulating anti-tumor immune responses in the tumor microenvironment and contributes to tumor progression. This review describes the current progress on the role of adenosine/adenosine receptor pathway in regulating the tumor-infiltrating immune cells that contribute to tumor immune evasion and aims to provide insights into adenosine-targeted tumor immunotherapy.

Pharmacology of Adenosine Receptors: Recent Advancements

Adenosine receptors (ARs) are widely acknowledged pharmacological targets yet are still underutilized in clinical practice. Their ubiquitous distribution in almost all cells and tissues of the body makes them, on the one hand, excellent candidates for numerous diseases, and on the other hand, intrinsically challenging to exploit selectively and in a site-specific manner. This review endeavors to comprehensively depict the substantial advancements witnessed in recent years concerning the development of drugs that modulate ARs. Through preclinical and clinical research, it has become evident that the modulation of ARs holds promise for the treatment of numerous diseases, including central nervous system disorders, cardiovascular and metabolic conditions, inflammatory and autoimmune diseases, and cancer. The latest studies discussed herein shed light on novel mechanisms through which ARs exert control over pathophysiological states. They also introduce new ligands and innovative strategies for receptor activation, presenting compelling evidence of efficacy along with the implicated signaling pathways. Collectively, these emerging insights underscore a promising trajectory toward harnessing the therapeutic potential of these multifaceted targets.

CD39/CD73/A2AR pathway and cancer immunotherapy

Cancer development is closely associated with immunosuppressive tumor microenvironment (TME) that attenuates antitumor immune responses and promotes tumor cell immunologic escape. The sequential conversion of extracellular ATP into adenosine by two important cell-surface ectonucleosidases CD39 and CD73 play critical roles in reshaping an immunosuppressive TME. The accumulated extracellular adenosine mediates its regulatory functions by binding to one of four adenosine receptors (A1R, A2AR, A2BR and A3R). The A2AR elicits its profound immunosuppressive function via regulating cAMP signaling. The increasing evidence suggests that CD39, CD73 and A2AR could be used as novel therapeutic targets for manipulating the antitumor immunity. In recent years, monoclonal antibodies or small molecule inhibitors targeting the CD39/CD73/A2AR pathway have been investigated in clinical trials as single agents or in combination with anti-PD-1/PD-L1 therapies. In this review, we provide an updated summary about the pathophysiological function of the adenosinergic pathway in cancer development, metastasis and drug resistance. The targeting of one or more components of the adenosinergic pathway for cancer therapy and circumvention of immunotherapy resistance are also discussed. Emerging biomarkers that may be used to guide the selection of CD39/CD73/A2AR-targeting treatment strategies for individual cancer patients is also deliberated.

Low-Dose Colchicine Attenuates Sepsis-Induced Liver Injury: A Novel Method for Alleviating Systemic Inflammation

Sepsis is a significant public health challenge. The immune system underlies the pathogenesis of the disease. The liver is both an active player and a target organ in sepsis. Targeting the gut immune system using low-dose colchicine is an attractive method for alleviating systemic inflammation in sepsis without inducing immunosuppression. The present study aimed to determine the use of low-dose colchicine in LPS-induced sepsis in mice. C67B mice were injected intraperitoneal with LPS to induce sepsis. The treatment group received 0.02 mg/kg colchicine daily by gavage. Short and extended models were performed, lasting 3 and 5 days, respectively. We followed the mice for biochemical markers of end-organ injury, blood counts, cytokine levels, and liver pathology and conducted proteomic studies on liver samples. Targeting the gut immune system using low-dose colchicine improved mice's well-being measured by the murine sepsis score. Treatment alleviated the liver injury in septic mice, manifested by a significant decrease in their liver enzyme levels, including ALT, AST, and LDH. Treatment exerted a trend to reduce creatinine levels. Low-dose colchicine improved liver pathology, reduced inflammation, and reduced the pro-inflammatory cytokine TNFα and IL1-β levels. A liver proteomic analysis revealed low-dose colchicine down-regulated sepsis-related proteins, alpha-1 antitrypsin, and serine dehydratase. Targeting the gut immune system using low-dose colchicine attenuated liver injury in LPS-induced sepsis, reducing the pro-inflammatory cytokine levels. Low-dose colchicine provides a safe method for immunomodulation for multiple inflammatory disorders.