Inhibition Of Panx1 Research Articles

Blocking Pannexin-1 Channels Alleviates Thalamic Hemorrhage-Induced Pain and Inflammatory Depolarization of Microglia in Mice.

Central post-stroke pain (CPSP) is a neuropathic pain syndrome that frequently occurs following cerebral stroke. The pathogenesis of CPSP is mainly due to thalamic injury caused by ischemia and hemorrhage. However, its underlying mechanism is far from clear. In the present study, a thalamic hemorrhage (TH) model was established in young male mice by microinjection of 0.075 U of type IV collagenase into the unilateral ventral posterior lateral nucleus and ventral posterior medial nucleus of the thalamus. We found that TH led to microglial pannexin (Panx)-1, a large-pore ion channel, opening within the thalamus accompanied with thalamic tissue injury, pain sensitivities, and neurological deficit, which were significantly prevented by either intraperitoneal injection of the Panx1 blocker carbenoxolone or intracerebroventricular perfusion of the inhibitory mimetic peptide 10Panx. However, inhibition of Panx1 has no additive effect on pain sensitivities upon pharmacological depletion of microglia. Mechanistically, we found that carbenoxolone alleviated TH-induced proinflammatory factors transcription, neuronal apoptosis, and neurite disassembly within the thalamus. In summary, we conclude that blocking of microglial Panx1 channels alleviates CPSP and neurological deficit through, at least in part, reducing neural damage mediated by the inflammatory response of thalamic microglia after TH. Targeting Panx1 might be a potential strategy in the treatment of CPSP.

Pannexin1 inhibits autophagy of cisplatin-resistant testicular cancer cells by mediating ATP release

ABSTRACT Pannexin1 (Panx-1) is a gap junction channel protein that mediates the release of intracellular ATP during autophagy, and thus plays an important role in tumor cell apoptosis and chemo-resistance. However, the role of Panx-1 in cisplatin-resistance of testicular cancer cells remains unclear. We found that cisplatin-resistant I-10 testicular cancer cell lines (I-10/CDDP) autophagy-associated proteins (p62, p-mTOR, mTOR and LC3) exhibited high levels of autophagy in their expression, while LC3-II expression was more significantly in the presence of lysosomal degradation blocked by chloroquine (CQ). Xenograft models using I-10/CDDP cells with knockdown ATG5 and ATG7 were established in mouse models and showed blockade of autophagic flux and inhibition of tumor growth. In addition, inhibition of Panx-1 by carbenoxolone (CBX) and probenecid (PBN), as well as shRNA-mediated knockdown promoted autophagy in the I-10/CDDP cells, which was accompanied by a decrease in the levels of extracellular ATP. In contrast, overexpression of Panx-1 decreased autophagy of I-10/CDDP cells and increased extracellular ATP levels. To further determine the effect of panx-1-mediated ATP release on the autophagy of I-10/CDDP cells, apyrase was used to hydrolyze the extracellular ATP. Apyrase promoted autophagy in I-10/CDDP cells city by decreasing extracellular ATP, regardless of Panx-1 expression. This study demonstrated for the first time that Panx-1-mediated ATP release inhibits autophagy of I-10/CDDP cells, which provides a potential therapeutic strategy for cisplatin-resistant testicular cancer.

In vitro effect of Pannexin 1 channel on the invasion and migration of I-10 testicular cancer cells via ERK1/2 signaling pathway

Pannexin (Panx) plays a crucial role in several cellular processes such as immune cell death, cell proliferation, invasion, and migration, apoptosis, and autophagy. However, the role of Panx in regulating cell migration and invasion in testicular cancer remains to be elucidated. In the present study, we determined the correlation between Panx-1 channel function and migration and invasion in I-10 testicular cancer cells. Transwell and wound healing assays showed that inhibition of Panx-1 by carbenoxolone (CBX) and probenecid (PBN) attenuated the migration and invasion of testicular cancer cells in vitro. Moreover, knockdown of Panx-1 with short hairpin RNA (shRNA) remarkably decreased the migration and invasion ability of I-10 cells. In shRNA-transfected cells, extracellular ATP (released through Panx channel) was also found to be decreased. Similarly, overexpression of Panx-1 with mPanx-1 increased the migration and invasion ability of I-10 cells. Moreover, we found that in mPanx-1-transfected cells treated with U0126 (inhibitor of p-ERK1/2), the migration and invasion of I-10 cells were remarkably attenuated. Overall, increased Panx-1 promotes migration and invasion in testicular cancer cells, and the effect is probably be related with ERK1/2 kinase activity. Thus, Panx-1 can serve as a potential therapeutic target for the treatment of testicular cancer.

Hematopoietic pannexin 1 function is critical for neuropathic pain

Neuropathic pain symptoms respond poorly to available therapeutics, with most treated patients reporting unrelieved pain and significant impairment in daily life. Here, we show that Pannexin 1 (Panx1) in hematopoietic cells is required for pain-like responses following nerve injury in mice, and a potential therapeutic target. Panx1 knockout mice (Panx1−/−) were protected from hypersensitivity in two sciatic nerve injury models. Bone marrow transplantation studies show that expression of functional Panx1 in hematopoietic cells is necessary for mechanical hypersensitivity following nerve injury. Reconstitution of irradiated Panx1 knockout mice with hematopoietic Panx1−/− cells engineered to re-express Panx1 was sufficient to recover hypersensitivity after nerve injury; this rescue required expression of a Panx1 variant that can be activated by G protein-coupled receptors (GPCRs). Finally, chemically distinct Panx1 inhibitors blocked development of nerve injury-induced hypersensitivity and partially relieved this hypersensitivity after it was established. These studies indicate that Panx1 expressed in immune cells is critical for pain-like effects following nerve injury in mice, perhaps via a GPCR-mediated activation mechanism, and suggest that inhibition of Panx1 may be useful in treating neuropathic pain.

The role of Pannexin1 in the inflammation and its prospect as a therapeutic target for sepsis

Background Pannexin(Panx)1 belongs to Panx family and has been regarded as a group of newly discovered gap junction proteins. Panx1 is ubiquitously expressed on various cell types and is involved in the transportation of intracellular metabolites and signal transmitters. Objective This review aims to discuss the role of Panx1 in the inflammatory responses and immune responses of sepsis as well as its therapeutic potentials as a new target for sepsis treatment. Content This review discusses Panx1 as a key player mediating ATP release from apoptotic and dying cells in the activation of innate and adaptive immune response, particularly its pathophysiological relations to the development of sepsis. Furthermore, pharmacological inhibition of Panx1 by using small molecules for the treatment of sepsis is highlighted. Trend Panx1 is pathophysiologically linked to a variety of diseases such as inflammation, seizure and cancer. Emerging evidences also reveal a critical role of Panx1 in sepsis, making Panx1 a promising therapeutic candidate for sepsis treatment. Key words: Pannexin1 channel; Inflammation; Immune response; Sepsis

Modulation of the endocannabinoid system and PanX1-mediated neuroinflammation in an in vitro model of Alzheimer's disease

Alzheimer's disease is an age-related neurodegenerative disease characterized by the progressive deterioration of cognition andmemory resulting from synaptic loss and neuronal death. The accumulation of toxic amyloid-beta oligomers results in chronic neuroinflammation leading to synaptic dysfunction and severe neurodegeneration. Modulation of the endocannabinoid system has been shown to confer neuroprotection against amyloid-beta-induced neurotoxicity through the inhibition of Ca permeable channels, apoptotic cascades and blocking the activation and subsequent release of pro-inflammatory cytokines from microglia. A recently identified membrane channel, PanX1, has been implicated in the release of ATP from damaged cells as well as activation of the NLRP3 inflammasome and the resulting processing of IL-1beta in immune cells. The aim of this study was to investigate the involvement of PanX1 in cannabinoid-mediated neuroprotection against amyloid-beta. Cultured primary rat cortical neurons treated with amyloid-beta release chemoattractant signals that induced the migration of BV2 microglial cells using a Boyden chamber assay. Both the pharmacological inhibition of PanX1 by mimetic peptide panx and treatment with URB597, an inhibitor of cannabinoid degradation, significantly reduced the microglial migration that is stimulated by amyloid-betaprimed neuronal media. Furthermore, no additive effect from cotreating neurons with both panx and URB597 on microglial migration was found indicating a possible overlap in the two pathways. Amyloid-beta has no effect on total neuronal expression of PanX1, however increased levels of mature membrane bound PanX1 have been observed. Application of URB597 or probenecid, an inhibitor of PanX1 gating, reduced membrane PanX1 to control levels. Current experiments are aimed at investigating the link between the endocannabinoid systems anti-apoptotic effects and neuronal PanX1 regulation as well as elucidating the involvement of PanX1 in microglial activation. Funding received from the Higher Education Authority (HEA) under the Program for Research in Third Level Institutes (PRTLI) cycle 5 and co-funded by the Irish government and the European Union.

ATP and potassium ions: a deadly combination for astrocytes

The ATP release channel Pannexin1 (Panx1) is self-regulated, i.e. the permeant ATP inhibits the channel from the extracellular space. The affinity of the ATP binding site is lower than that of the purinergic P2X7 receptor allowing a transient activation of Panx1 by ATP through P2X7R. Here we show that the inhibition of Panx1 by ATP is abrogated by increased extracellular potassium ion concentration ([K+]o) in a dose-dependent manner. Since increased [K+]o is also a stimulus for Panx1 channels, it can be expected that a combination of ATP and increased [K+]o would be deadly for cells. Indeed, astrocytes did not survive exposure to these combined stimuli. The death mechanism, although involving P2X7R, does not appear to strictly follow a pyroptotic pathway. Instead, caspase-3 was activated, a process inhibited by Panx1 inhibitors. These data suggest that Panx1 plays an early role in the cell death signaling pathway involving ATP and K+ ions. Additionally, Panx1 may play a second role once cells are committed to apoptosis, since Panx1 is also a substrate of caspase-3.

Assessing a Potential Role of Host Pannexin 1 during Chlamydia trachomatis Infection

Pannexin 1 (Panx1) is a plasma membrane channel glycoprotein that plays a role in innate immune response through association with the inflammasome complex. Probenecid, a classic pharmacological agent for gout, has also been used historically in combination therapy with antibiotics to prevent cellular drug efflux and has been reported to inhibit Panx1. As the inflammasome has been implicated in the progression of Chlamydia infections, and with chlamydial infections at record levels in the US, we therefore investigated whether probenecid would have a direct effect on Chlamydia trachomatis development through inhibition of Panx1. We found chlamydial development to be inhibited in a dose-dependent, yet reversible manner in the presence of probenecid. Drug treatment induced an aberrant chlamydial morphology consistent with persistent bodies. Although Panx1 was shown to localize to the chlamydial inclusion, no difference was seen in chlamydial development during infection of cells derived from wild-type and Panx1 knockout mice. Therefore, probenecid may inhibit C. trachomatis growth by an as yet unresolved mechanism.

Purinergic signaling integrates local excitation and global inhibition signals that regulate neutrophil chemotaxis

Neutrophil chemotaxis requires local excitatory signals at the front and inhibitory signals at the back of cells. The mechanisms that link these signals are unknown. We previously showed that chemoattractants induce ATP release and excitatory purinergic feedback mechanisms at the front. Here we show that pannexin‐1 (panx1) is responsible for ATP release and that chemotaxis requires translocation of panx1 to the front and A2a adenosine receptors (A2aR) to the back. Panx1 provides both, ATP and adenosine, to elicit the excitatory and inhibitory signals at the front and back of cells. Inhibition of panx1 with carbenoxolone (CBX) completely abolished chemotaxis, while inhibition of A2aR with the antagonist CSC reduced migration speed (Fig. 1). Our findings demonstrate that panx1 is the molecular link that integrates the excitatory and inhibitory purinergic feedback mechanisms that regulate chemotaxis at the front and back of cells.This work was funded by grants from the National Institutes of Health and the Congressionally Directed Medical Research Program.