Human P2X7 receptors - Properties of single ATP-gated ion channels

Overexpression or knockdown of the P2X7 receptor regulates the progression of non-small cell lung cancer, involving GSK-3β and JNK signaling pathways

Studies have indicated that P2X7 receptor are involved in the progression of non-small cell lung cancer (NSCLC). Therefore, this study sought to explore how modulating P2X7 receptor expression levels affect the biological function of NSCLC and its underlying mechanisms. Recombinant plasmids with P2X7 receptor overexpression or knockdown were constructed and transfected into LLC and LA795 cells, and the biological function changes of these two cells were assessed in vitro. Subsequently, stable cell lines (overexpression or knockdown of P2X7 receptor) were screened, and their tumorigenicity was detected in vivo. The findings of this study demonstrate that both LLC and LA795 cells expressed functional P2X7 receptors, and overexpression of P2X7 receptors promoted the migration and invasion of LLC and LA795 cells. Conversely, the knockdown of the P2X7 receptor yielded contrasting effects. The mechanism involved phosphatidylinositol 3-kinase/protein kinase B/glycogen synthase kinase 3 beta (PI3K/Akt/GSK-3β), c-Jun N-terminal kinase (JNK) signaling pathway and epithelial-mesenchymal transition (EMT). In addition, the knockdown of the P2X7 receptor suppressed cell proliferation and promoted apoptosis in both cells (LLC and LA795). In vivo experiments corroborated these findings, demonstrating that overexpression of the P2X7 receptor promoted tumor growth while its knockdown inhibited tumor growth. The expression levels of related signaling proteins (PI3K/Akt/GSK-3β, JNK, and EMT) in vivo were consistent with the trends observed in vitro. In conclusion, our results suggest that downregulating P2X7 receptor expression can effectively suppress tumor growth, invasion, and migration in NSCLC. Our results suggest that the P2X7 receptor has the potential as a therapeutic target for NSCLC.

Crosstalk of pyroptosis and cytokine in the tumor microenvironment: from mechanisms to clinical implication

In the realm of cancer research, the tumor microenvironment (TME) plays a crucial role in tumor initiation and progression, shaped by complex interactions between cancer cells and surrounding non-cancerous cells. Cytokines, as essential immunomodulatory agents, are secreted by various cellular constituents within the TME, including immune cells, cancer-associated fibroblasts, and cancer cells themselves. These cytokines facilitate intricate communication networks that significantly influence tumor initiation, progression, metastasis, and immune suppression. Pyroptosis contributes to TME remodeling by promoting the release of pro-inflammatory cytokines and sustaining chronic inflammation, impacting processes such as immune escape and angiogenesis. However, challenges remain due to the complex interplay among cytokines, pyroptosis, and the TME, along with the dual effects of pyroptosis on cancer progression and therapy-related complications like cytokine release syndrome. Unraveling these complexities could facilitate strategies that balance inflammatory responses while minimizing tissue damage during therapy. This review delves into the complex crosstalk between cytokines, pyroptosis, and the TME, elucidating their contribution to tumor progression and metastasis. By synthesizing emerging therapeutic targets and innovative technologies concerning TME, this review aims to provide novel insights that could enhance treatment outcomes for cancer patients.

Burning down the house: Pyroptosis in the tumor microenvironment of hepatocellular carcinoma

A high mortality rate makes hepatocellular carcinoma (HCC) a difficult cancer to treat. When surgery is not possible, liver cancer patients are treated with chemotherapy. However, HCC management and treatment are difficult. Sorafenib, which is a first-line treatment for hepatocellular carcinoma, initially slows disease progression. However, sorafenib resistance limits patient survival. Recent studies have linked HCC to programmed cell death, which has increased researcher interest in therapies targeting cell death. Pyroptosis, which is an inflammatory mode of programmed cell death, may be targeted to treat HCC. Pyroptosis pathways, executors, and effects are examined in this paper. This review summarizes how pyroptosis affects the tumor microenvironment (TME) in HCC, including the role of cytokines such as IL-1β and IL-18 in regulating immune responses. The use of chemotherapies and their ability to induce cancer cell pyroptosis as alternative treatments and combining them with other drugs to reduce side effects is also discussed. In conclusion, we highlight the potential of inducing pyroptosis to treat HCC and suggest ways to improve patient outcomes. Studies on cancer cell pyroptosis may lead to new HCC treatments.

Functional role of P2X7 purinergic receptor in cancer and cancer-related pain

Numerous studies have revealed that the ATP-gated ion channel purinergic 2X7 receptor (P2X7R) plays an important role in tumor progression and the pathogenesis of cancer pain. P2X7R requires activation by extracellular ATP to perform its regulatory role functions. During tumor development or cancer-induced pain, ATP is released from tumor cells or other cells in the tumor microenvironment (such as tumor-associated immune cells), which activates P2X7R, opens ion channels on the cell membrane, affects intracellular molecular metabolism, and regulates the activity of tumor cells. Furthermore, peripheral organs and receptors can be damaged during tumor progression, and P2X7R expression in nerve cells (such as microglia) is significantly upregulated, enhancing sensory afferent information, sensitizing the central nervous system, and inducing or exacerbating pain. These findings reveal that the ATP-P2X7R signaling axis plays a key regulatory role in the pathogenesis of tumors and cancer pain and also has a therapeutic role. Accordingly, in this study, we explored the role of P2X7R in tumors and cancer pain, discussed the pharmacological properties of inhibiting P2X7R activity (such as the use of antagonists) or blocking its expression in the treatment of tumor and cancer pain, and provided an important evidence for the treatment of both in the future.

Differential effects of purines and prostaglandins on hypoxia induced dilatation of porcine retinal vessels at different branching level ex vivo

The metabolic pathways leading from hypoxia to retinal vasodilatation can involve effects of both purines and prostaglandins, but the effects of these compounds at different vascular branching levels are unknown. The purpose of the present study was to investigate differential effects of purines and prostaglandins in hypoxia-induced dilatation of retinal arterioles, precapillary arterioles and capillaries ex vivo. Porcine hemiretinas were mounted in a tissue chamber while monitoring temperature, pH, and oxygen tension. The effect of hypoxia on the diameter of larger arterioles, precapillary arterioles and capillaries was studied in the presence of the ecto-nucleotidase inhibitor AOPCP, the nonselective P2 purinoreceptor antagonist PPADS, the A2B adenosine receptor antagonist MRS 1754, the A3 adenosine receptor antagonist MRS 1523, the EP1 receptor antagonist SC-19220, the EP2 receptor antagonist PF-04418948, the EP3 receptor antagonist L-798,106, the EP4 receptor antagonist L-161-982, the prostaglandin synthesis inhibitor ibuprofen, and ibuprofen combined with AOPCP or ATP. Hypoxia-induced dilatation in arterioles was reduced by the A2B adenosine receptor antagonist (p < 0.01) and increased by the EP2 and the EP3 receptor antagonists (p < 0.01 for both comparisons). In precapillary arterioles the dilatation was reduced by the EP2 receptor antagonist (p < 0.04) and increased by the EP1 receptor antagonist (p < 0.03), whereas in capillaries the dilatation was increased by both the A3 adenosine receptor antagonist (p < 0.01), by ibuprofen in combination with the unspecific ecto-nucleotidase inhibitor AOPCP (p = 0.04) and by the prostaglandin EP3 receptor antagonist. Hypoxia-induced dilatation of retinal vessels is influenced by adenosine A2B and A3 receptors, and by the prostaglandin EP1, EP2 and EP3 receptors. The effects mediated by these receptors differ at different branching levels of the resistance vessels.

Role of NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are a common group of neurological disorders characterized by progressive loss of neuronal structure and function leading to cognitive impairment. Recent studies have shown that neuronal pyroptosis mediated by the NLRP3 inflammasome plays a crucial role in the pathogenesis of neurodegenerative diseases.

OBJECTIVE AND METHOD

The NLRP3 inflammasome is a multiprotein complex that, when activated within cells, triggers an inflammatory response, ultimately leading to pyroptotic cell death of neurons. Pyroptosis is a typical pro-inflammatory programmed cell death process occurring downstream of NLRP3 inflammasome activation, characterized by the formation of pores on the cell membrane by the GSDMD protein, leading to cell lysis and the release of inflammatory factors. It has been found that NLRP3 inflammasome-mediated neuronal pyroptosis is closely associated with the development of various neurodegenerative diseases, such as Alzheimer's disease, traumatic brain injury, and Parkinson's disease. Therefore, inhibiting NLRP3 inflammasome activation and attenuating neuronal pyroptosis could potentially serve as novel strategies for the treatment of neurodegenerative diseases.

RESULTS

The aim of this review is to explore the role of NLRP3 activation-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases. Firstly, we extensively discuss the relationship between NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in various neurodegenerative diseases. Subsequently, we further explore the mechanisms driving NLRP3 activation and assembly, as well as the post-translational modifications regulating NLRP3 inflammasome activation.

CONCLUSION

Understanding these mechanisms will contribute to a deeper understanding of the link between neuronal pyroptosis and neurodegenerative diseases, and hold significant implications for the treatment and prevention of neurodegenerative diseases.

The inhibitory effect of Yam polysaccharides on acrylamide-induced programmed cell death in RAW 264.7 cells

Acrylamide has been well known for its neurotoxicity, genotoxicity, carcinogenicity, etc. Recently, the immunotoxicity of acrylamide has been reported by different research groups, although the underlying mechanisms of acrylamide endangering immune systems have not been fully elucidated. In this study, mouse monocyte-macrophage cells model was used to clarify the toxic mechanism of acrylamide and the inhibitory effect of Yam polysaccharides (YPS) on acrylamide-induced damage. We found that acrylamide induced RAW 264.7 cell death in a time- and concentration-dependent manner. After acrylamide (2.0, 3.0, 4.0 mmol/L) treatment for 24 h, cell apoptosis, autophagy, and pyroptosis were observed. However, the levels of autophagy and pyroptosis decreased at a high concentration of acrylamide (4.0 mmol/L). Acrylamide upregulated P2X7 expression, but the P2X7 level was not showing a monotone increasing trend. When the P2X7 antagonist was applied, the effect of acrylamide on autophagy and pyroptosis was weakened. Additionally, acrylamide triggered the occurrence of oxidative stress and a decreased nitric oxide (NO) level. However, reactive oxygen species (ROS) generation, the decrease of heme oxygenase-1 (HO-1) expression, and the increase of inducible nitric oxide synthase (iNOS) expression were reversed by the inhibition of P2X7. Yam polysaccharides (50.0 μg/ml) significantly inhibited acrylamide-induced oxidative stress and cell death (including apoptosis, autophagy, and pyroptosis). Yam polysaccharides also effectively reversed the increase of iNOS expression induced by acrylamide. However, Yam polysaccharides promoted the expression of P2X7 rather than prohibit it. These results indicated that acrylamide caused RAW 264.7 cell death due to pro-apoptosis as well as excessive autophagy and pyroptosis. Apoptosis might be more predominant than autophagy and pyroptosis under a higher concentration of acrylamide (4.0 mmol/L). P2X7-stimulated oxidative stress was responsible for acrylamide-induced programmed cell death (PCD), but P2X7 showed limited regulatory effect on apoptosis. Yam polysaccharides with antioxidant activity inhibited acrylamide-induced cell death (apoptosis, autophagy, and pyroptosis), but exerted limited effect on the acrylamide-induced P2X7 expression. These findings would offer an insight into elucidating the immunotoxic mechanism of acrylamide and the potential approaches to control its toxicity.

Progesterone Reduces ATP-Induced Pyroptosis of SH-SY5Y Cells

Aim

To investigate the mechanism of progesterone inhibiting the scorch death of SH-SY5Y cells induced by exogenous adenosine triphosphate (ATP).

Methods

SH-SY5Y cells with good logarithmic growth were used in the experiment. The cells were randomly divided into 5 groups: normal control group, DMSO group, BBG group, ATP group, and ATP+progesterone group. The cell survival rate of each group was measured by CCK-8 method. The expressions of P2X7 receptor, caspase-1, caspase-11, and IL-1β were detected by western blotting.

Results

(1) After SH-SY5Y cells were treated with ATP at different concentrations (1, 3, 6, and 9 mmol/L) for 2 hours, the cell survival rate decreased in a concentration-dependent manner compared with the normal blank group. The results showed that the optimal lethal concentration of ATP was 6 mmol/L. SH-SY5Y cells were preincubated with progesterone at different concentrations (3, 10, 30, and 100 nmol/L) for 30 minutes and then incubated with 6 mmol/L ATP. The cell survival rate of this group was significantly improved (P < 0.01). The optimal concentration of progesterone to improve cell survival and inhibit cell death was 30 nmol/L. (2) Compared to the control group, there was no significant difference (P > 0.05) in P2X7 receptor, caspase-1, caspase-11, and IL-1β with the DMSO group (0.001% DMSO, 24 h) and BBG group (bbg1 mmol/L, 24 h). (3) In the ATP group, the expression of P2X7 receptor and caspase-1 (the key protein of classical cell death pathway) increased significantly (P < 0.01), which was related to inflammatory factor IL-1β with consistent performance (P < 0.01). There was no significant change in caspase-11 (the key protein of nonclassical focal death pathway) (P > 0.05). (4) The expression of P2X7 receptor, caspase-1, and inflammatory factor IL-1β in the progesterone+ATP group was significantly downregulated (P < 0.01). There was no significant change in caspase-11 (P > 0.05).

Conclusion

Certain dose of progesterone can inhibit the focal death of SH-SY5Y cells induced by extracellular high concentration ATP. It can reduce the expression of P2X7 receptor, inhibit the conduction pathway of cell death, reduce the release of inflammatory factor IL-1β, and improve cell survival.

Effects of Anthraquinones on Immune Responses and Inflammatory Diseases

The anthraquinones (AQs) and derivatives are widely distributed in nature, including plants, fungi, and insects, with effects of anti-inflammation and anti-oxidation, antibacterial and antiviral, anti-osteoporosis, anti-tumor, etc. Inflammation, including acute and chronic, is a comprehensive response to foreign pathogens under a variety of physiological and pathological processes. AQs could attenuate symptoms and tissue damages through anti-inflammatory or immuno-modulatory effects. The review aims to provide a scientific summary of AQs on immune responses under different pathological conditions, such as digestive diseases, respiratory diseases, central nervous system diseases, etc. It is hoped that the present paper will provide ideas for future studies of the immuno-regulatory effect of AQs and the therapeutic potential for drug development and clinical use of AQs and derivatives.

The Purinergic Landscape of Type 2 Diabetes Mellitus

Adenosine triphosphate (ATP) is the key energy intermediate of cellular metabolic processes and a ubiquitous extracellular messenger. As an extracellular messenger, ATP acts at plasma membrane P2 receptors (P2Rs). The levels of extracellular ATP (eATP) are set by both passive and active release mechanisms and degradation processes. Under physiological conditions, eATP concentration is in the low nanomolar range but can rise to tens or even hundreds of micromoles/L at inflammatory sites. A dysregulated eATP homeostasis is a pathogenic factor in several chronic inflammatory diseases, including type 2 diabetes mellitus (T2DM). T2DM is characterized by peripheral insulin resistance and impairment of insulin production from pancreatic β-cells in a landscape of systemic inflammation. Although various hypoglycemic drugs are currently available, an effective treatment for T2DM and its complications is not available. However, counteracting systemic inflammation is anticipated to be beneficial. The postulated eATP increase in T2DM is understood to be a driver of inflammation via P2X7 receptor (P2X7R) activation and the release of inflammatory cytokines. Furthermore, P2X7R stimulation is thought to trigger apoptosis of pancreatic β-cells, thus further aggravating hyperglycemia. Targeting eATP and the P2X7R might be an appealing novel approach to T2DM therapy.

Inherent P2X7 Receptors Regulate Macrophage Functions during Inflammatory Diseases

Macrophages are mononuclear phagocytes which derive either from blood-borne monocytes or reside as resident macrophages in peripheral (Kupffer cells of the liver, marginal zone macrophages of the spleen, alveolar macrophages of the lung) and central tissue (microglia). They occur as M1 (pro-inflammatory; classic) or M2 (anti-inflammatory; alternatively activated) phenotypes. Macrophages possess P2X7 receptors (Rs) which respond to high concentrations of extracellular ATP under pathological conditions by allowing the non-selective fluxes of cations (Na⁺, Ca²⁺, K⁺). Activation of P2X7Rs by still higher concentrations of ATP, especially after repetitive agonist application, leads to the opening of membrane pores permeable to ~900 Da molecules. For this effect an interaction of the P2X7R with a range of other membrane channels (e.g., P2X4R, transient receptor potential A1 [TRPA1], pannexin-1 hemichannel, ANO6 chloride channel) is required. Macrophage-localized P2X7Rs have to be co-activated with the lipopolysaccharide-sensitive toll-like receptor 4 (TLR4) in order to induce the formation of the inflammasome 3 (NLRP3), which then activates the pro-interleukin-1β (pro-IL-1β)-degrading caspase-1 to lead to IL-1β release. Moreover, inflammatory diseases (e.g., rheumatoid arthritis, Crohn’s disease, sepsis, etc.) are generated downstream of the P2X7R-induced upregulation of intracellular second messengers (e.g., phospholipase A2, p38 mitogen-activated kinase, and rho G proteins). In conclusion, P2X7Rs at macrophages appear to be important targets to preserve immune homeostasis with possible therapeutic consequences.

The Tyrosine Phosphatase hPTPRβ Controls the Early Signals and Dopaminergic Cells Viability via the P2X7 Receptor

ATP, one of the signaling molecules most commonly secreted in the nervous system and capable of stimulating multiple pathways, binds to the ionotropic purinergic receptors, in particular, the P2X₇ receptor (P2X₇R) and stimulates neuronal cell death. Given this effect of purinergic receptors on the viability of dopaminergic neurons model cells and that Ras GTPases control Erk1/2-regulated mitogen-activated cell proliferation and survival, we have investigated the role of the small GTPases of the Ras superfamily, together with their regulatory and effector molecules as the potential molecular intermediates in the P2X₇R-regulated cell death of SN4741 dopaminergic neurons model cells. Here, we demonstrate that the neuronal response to purinergic stimulation involves the Calmodulin/RasGRF1 activation of the small GTPase Ras and Erk1/2. We also demonstrate that tyrosine phosphatase PTPRβ and other tyrosine phosphatases regulate the small GTPase activation pathway and neuronal viability. Our work expands the knowledge on the intracellular responses of dopaminergic cells by identifying new participating molecules and signaling pathways. In this sense, the study of the molecular circuitry of these neurons is key to understanding the functional effects of ATP, as well as considering the importance of these cells in Parkinson’s Disease.

Quercetin as a protective agent for liver diseases: A comprehensive descriptive review of the molecular mechanism

Quercetin is the major representative of the flavonoid subgroup of flavones, with good pharmacological activities for the treatment of liver diseases, including liver steatosis, fatty hepatitis, liver fibrosis, and liver cancer. It can significantly influence the development of liver diseases via multiple targets and multiple pathways via antifat accumulation, anti-inflammatory, and antioxidant activity, as well as the inhibition of cellular apoptosis and proliferation. Despite extensive research on understanding the mechanism of quercetin in the treatment of liver diseases, there are still no targeted therapies available. Thus, we have comprehensively searched and summarized the different targets of quercetin in different stages of liver diseases and concluded that quercetin inhibited inflammation of the liver mainly through NF-κB/TLR/NLRP3, reduced PI3K/Nrf2-mediated oxidative stress, mTOR activation in autophagy, and inhibited the expression of apoptotic factors associated with the development of liver diseases. In addition, quercetin showed different mechanisms of action at different stages of liver diseases, including the regulation of PPAR, UCP, and PLIN2-related factors via brown fat activation in liver steatosis. The compound inhibited stromal ECM deposition at the liver fibrosis stage, affecting TGF1β, endoplasmic reticulum stress (ERs), and apoptosis. While at the final liver cancer stage, inhibiting cancer cell proliferation and spread via the hTERT, MEK1/ERK1/2, Notch, and Wnt/β-catenin-related signaling pathways. In conclusion, quercetin is an effective liver protectant. We hope to explore the pathogenesis of quercetin in different stages of liver diseases through the review, so as to provide more accurate targets and theoretical basis for further research of quercetin in the treatment of liver diseases.