The inhibition of GLUT1-induced glycolysis in macrophage by phloretin participates in the protection during acute lung injury

GLUT1 Promotes NLRP3 Inflammasome Activation of Airway Epithelium in Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a devastating clinical disease caused by different factors, with high morbidity and mortality. It has been shown that lung injury and inflammation caused by lipopolysaccharide (LPS) can be modulated by NLRP3 inflammasome activation, yet its exact function within the airway epithelium is still unknown. Meanwhile, glucose transporter protein 1 (GLUT1) has been shown to contribute to a number of inflammatory illnesses, including ALI. The present study aimed to assess GLUT1's function in NLRP3 inflammasome activation of airway epithelium in LPS-induced acute lung injury. BALB/c mice and BEAS-2B cells were exposed to LPS (5 mg/kg and 200 μg/mL, respectively), with or without GLUT1 antagonists (WZB117 or BAY876). LPS up-regulated pulmonary expression of NLRP3 and GLUT1 in mice, which could be blocked by WZB117 or BAY876. Pharmacological inhibition of GLUT1 in vivo significantly attenuated lung tissue damage, neutrophil accumulation, and proinflammatory factors release (TNF-α, IL-6, and IL-1β) in LPS-exposed mice. Meanwhile, the activation markers of NLRP3 inflammasome (ASC, caspase-1, IL-1β, and IL-18) induced by LPS were also suppressed. In cultured BEAS-2B cells, LPS induced an increase in GLUT1 expression and triggered activation of the NLRP3 inflammasome, both of which were inhibited by GLUT1 antagonists. These results illustrate that GLUT1 participates in LPS-induced ALI and promotes the activation of the NLRP3 inflammasome in airway epithelial cells.

Metabolism-driven glycosylation represents therapeutic opportunities in interstitial lung diseases

Metabolic changes are coupled with alteration in protein glycosylation. In this review, we will focus on macrophages that are pivotal in the pathogenesis of pulmonary fibrosis and sarcoidosis and thanks to their adaptable metabolism are an attractive therapeutic target. Examples presented in this review demonstrate that protein glycosylation regulates metabolism-driven immune responses in macrophages, with implications for fibrotic processes and granuloma formation. Targeting proteins that regulate glycosylation, such as fucosyltransferases, neuraminidase 1 and chitinase 1 could effectively block immunometabolic changes driving inflammation and fibrosis, providing novel avenues for therapeutic interventions.

Phloretin targets SIRT1 to alleviate oxidative stress, apoptosis, and inflammation in deep venous thrombosis

Deep vein thrombosis (DVT) is a type of venous thromboembolism posing a serious threat to health on a global scale. Phloretin is a potential natural product that has a variety of pharmacological activities. Besides, some Chinese medicines reported that deacetylase sirtuin (SIRT)1 treats DVT by anti-inflammatory and anti-platelet production. However, the specific binding targets and binding modes have not been elaborated. The present study was to investigate whether phloretin attenuates DVT in model rats and oxidized low‑density lipoprotein (ox‑LDL) induced human umbilical vein endothelial cells (HUVECs), and to explore its potential target. The results revealed that the treatment of phloretin, especially pretreatment of it elevated tissue plasminogen activator (t-PA), superoxide dismutase (SOD), prothrombin time (PT), thrombin time (TT), activated partial thromboplastin time (APTT), and cell apoptosis proteins whereas it suppressed plasminogen activator inhibitor (PAI), malondialdehyde (MDA), reactive oxygen species (ROS), fibrinogen (FIB) in DVT rats and cells. Concurrently, phloretin inhibited collagen type I alpha 1 (COL1A1), transforming growth factor-β1 (TGF-β1), and inflammatory factors while it enhanced nuclear factor erythroid 2-related factor 2 (Nrf-2), heme oxygenase 1 (HO-1). In addition, 20 μM phloretin exerted powerful effective protection in HUVECs with DVT model. Later, the surface plasmon resonance (SPR) confirmed that phloretin has a high affinity with SIRT1. Furthermore, siRNA-SIRT1 transfection abolished the protective effect of phloretin against ox‑LDL‑induced DVT in HUVECs, indicating that phloretin targets SIRT1 to alleviate oxidative stress, cell apoptosis, and inflammation in DVT rats and HUVECs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-023-00207-y.

GLUT1 contributes to impaired epithelial tight junction in the late phase of acute lung injury

Dysfunction of epithelial barrier is crucial for the development of acute lung injury (ALI). This study was aimed to evaluate the role of glucose transporter 1 (GLUT1) in dysregulation of epithelial tight junction in ALI. GLUT1 was inhibited with specific antagonists WZB117 or BAY876 to see the effects on epithelial tight junction in a well-established LPS-induced mouse ALI model as well as in vitro cultured epithelial cells. Pharmacological inhibition of GLUT1 with WZB117 at either a low or high dose had no effects on lung injury and inflammation 24 h after LPS challenge, but significantly decreased the pulmonary inflammatory responses induced by LPS at 72 h with a high dose, which was verified by treatment with BAY876. WZB117 or BAY876 also recovered the expression of epithelial tight junction proteins ZO-1 and occludin. In cultured BEAS-2B and A549 cells, LPS induced increased GLUT1 expression, accompanied by decreased expression of tight junction protein ZO-1 and occludin. Blockade of GLUT1 restored LPS-induced disruption of ZO-1 and occludin in BEAS-2B rather than A549. Taken together, our results showed that GLUT1 is responsible for dysfunction of epithelial tight junctions in the late phase of LPS-induced ALI.

Cellular metabolism hijacked by viruses for immunoevasion: potential antiviral targets

Cellular metabolism plays a central role in the regulation of both innate and adaptive immunity. Immune cells utilize metabolic pathways to modulate the cellular differentiation or death. The intricate interplay between metabolism and immune response is critical for maintaining homeostasis and effective antiviral activities. In recent years, immunometabolism induced by viral infections has been extensively investigated, and accumulating evidence has indicated that cellular metabolism can be hijacked to facilitate viral replication. Generally, virus-induced changes in cellular metabolism lead to the reprogramming of metabolites and metabolic enzymes in different pathways (glucose, lipid, and amino acid metabolism). Metabolic reprogramming affects the function of immune cells, regulates the expression of immune molecules and determines cell fate. Therefore, it is important to explore the effector molecules with immunomodulatory properties, including metabolites, metabolic enzymes, and other immunometabolism-related molecules as the antivirals. This review summarizes the relevant advances in the field of metabolic reprogramming induced by viral infections, providing novel insights for the development of antivirals.

Iso-seco-tanapartholide from Artemisia argyi inhibits the PFKFB3-mediated glycolytic pathway to attenuate airway inflammation in lipopolysaccharide-induced acute lung injury mice

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese folk medicine, Artemisia argyi H.Lév. & Vaniot (A. argyi) has been used for thousands of years, and it is clinically used to treat bronchitis and asthma. However, the mechanism of action of A. argyi on respiratory tract inflammation is not clear. Accumulating evidence that phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) is actively expressed in inflammation. Here, we found that iso-seco-tanapartholide (IST), a sesquiterpene isolated from A. argyi, exhibited potent anti-inflammatory activity and significant inhibition of PFKFB3 expression. Therefore, we evaluated the effect of IST on airway inflammation and revealed its possible mechanisms.

AIM OF THE STUDY

This study aimed to investigate the protective effect and possible mechanism of IST in lipopolysaccharide (LPS)-induced acute lung injury in mice.

MATERIALS AND METHODS

In vitro, RAW264.7 cells and BMDMs were stimulated with LPS, and the level of NO and inflammatory factors TNF-α, IL-1β, and IL-6 were detected by Griess reagent and ELISA, respectively. The effect of IST on the levels of PFKFB3 and its downstream proteins (p-STAT3, p-p65) in cells was assayed by western blotting. Lactate and glycolytic phenotypes were detected by lactate kit and Seahorse assay. In vivo, a mouse model of acute lung injury was induced by LPS, and the levels of inflammatory factors were measured by ELISA. Expression of PFKFB3 and its downstream proteins (p-STAT3, p-p65) in mouse alveolar macrophages by western blotting analysis. Lung permeability assessment by Evans Blue dye assay. H&E staining and Immunocytochemistry were used to observe the protection of IST against lung injury.

RESULTS

IST significantly reduced LPS-induced expression of PFKFB3 and its downstream proteins (p-STAT3, p-p65). The inhibition of PFKFB3 has an impact on the glycolytic phenotype, such as a reduction in the rate of extracellular acidification (ECAR) and elevated lactate levels, and an increase in the rate of cellular oxygen consumption (OCR). Furthermore, IST inhibited LPS-induced NO release and increased the expression of pro-inflammatory factors TNF-α, IL-1β, and IL-6. In vivo, IST reduced pulmonary edema in LPS-induced acute lung injury, improved lung function, and reduced levels of inflammatory factors and lactate secretion.

CONCLUSIONS

These results suggest that IST improves the characteristics of ALI by inhibiting the expression of the PFKFB3-mediated glycolytic pathway and may be a potential anti-inflammatory agent for inflammation-related lung diseases.

The Molecular Pharmacology of Phloretin: Anti-Inflammatory Mechanisms of Action

The isolation of phlorizin from the bark of an apple tree in 1835 led to a flurry of research on its inhibitory effect on glucose transporters in the intestine and kidney. Using phlorizin as a prototype drug, antidiabetic agents with more selective inhibitory activity towards glucose transport at the kidney have subsequently been developed. In contrast, its hydrolysis product in the body, phloretin, which is also found in the apple plant, has weak antidiabetic properties. Phloretin, however, displays a range of pharmacological effects including antibacterial, anticancer, and cellular and organ protective properties both in vitro and in vivo. In this communication, the molecular basis of its anti-inflammatory mechanisms that attribute to its pharmacological effects is scrutinised. These include inhibiting the signalling pathways of inflammatory mediators' expression that support its suppressive effect in immune cells overactivation, obesity-induced inflammation, arthritis, endothelial, myocardial, hepatic, renal and lung injury, and inflammation in the gut, skin, and nervous system, among others.