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The key role of transient receptor potential melastatin-2 channels in amyloid-?-induced neurovascular dysfunction.

ABSTRACT: Alzheimer's dementia is a devastating and incurable disease afflicting over 35 million people worldwide. Amyloid-? (A?), a key pathogenic factor in this disease, has potent cerebrovascular effects that contribute to brain dysfunction underlying dementia by limiting the delivery of oxygen and glucose to the working brain. However, the downstream pathways responsible for the vascular alterations remain unclear. Here we report that the cerebrovascular dysfunction induced by A? is mediated by DNA damage caused by vascular oxidative-nitrosative stress in cerebral endothelial cells, which, in turn, activates the DNA repair enzyme poly(ADP)-ribose polymerase. The resulting increase in ADP ribose opens transient receptor potential melastatin-2 (TRPM2) channels in endothelial cells leading to intracellular Ca(2+) overload and endothelial dysfunction. The findings provide evidence for a previously unrecognized mechanism by which A? impairs neurovascular regulation and suggest that TRPM2 channels are a potential therapeutic target to counteract cerebrovascular dysfunction in Alzheimer's dementia and related pathologies.

SUBMITTER: Park L

PROVIDER: S-EPMC4283829 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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The key role of transient receptor potential melastatin-2 channels in amyloid-β-induced neurovascular dysfunction.

Park L L Wang G G Moore J J Girouard H H Zhou P P Anrather J J Iadecola C C

Nature communications 20141029

Alzheimer's dementia is a devastating and incurable disease afflicting over 35 million people worldwide. Amyloid-β (Aβ), a key pathogenic factor in this disease, has potent cerebrovascular effects that contribute to brain dysfunction underlying dementia by limiting the delivery of oxygen and glucose to the working brain. However, the downstream pathways responsible for the vascular alterations remain unclear. Here we report that the cerebrovascular dysfunction induced by Aβ is mediated by DNA da ...[more]

PMID: 25351853

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Project description:BackgroundMyalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is hallmarked by a significant reduction in natural killer (NK) cell cytotoxicity, a mechanism tightly regulated by calcium (Ca2+). Interestingly, interleukin-2 (IL-2) increases NK cell cytotoxicity. Transient receptor potential melastatin 2 (TRPM2) ion channels are fundamental for Ca2+ signalling in NK cells. This pilot investigation aimed to characterise TRPM2 and CD38 surface expression in vitro on NK cells in ME/CFS patients. This investigation furthermore examined the pharmaceutical effect of 8-bromoadenosine phosphoribose (8-Br-ADPR) and N6-Benzoyladenosine-3',5'-cyclic monophosphate (N6-Bnz-cAMP) on TRPM2 and CD38 surface expression and NK cell cytotoxicity between ME/CFS and healthy control (HC) participants.MethodsTen ME/CFS patients (43.45 ± 12.36) and 10 HCs (43 ± 12.27) were age and sex-matched. Isolated NK cells were labelled with fluorescent antibodies to determine baseline and drug-treated TRPM2 and CD38 surface expression on NK cell subsets. Following IL-2 stimulation, NK cell cytotoxicity was measured following 8-Br-ADPR and N6-Bnz-cAMP drug treatments by flow cytometry.ResultsBaseline TRPM2 and CD38 surface expression was significantly higher on NK cell subsets in ME/CFS patients compared with HCs. Post IL-2 stimulation, TRPM2 and CD38 surface expression solely decreased on the CD56DimCD16+ subset. 8-Br-ADPR treatment significantly reduced TRPM2 surface expression on the CD56BrightCD16Dim/- subset within the ME/CFS group. Baseline cell cytotoxicity was significantly reduced in ME/CFS patients, however no changes were observed post drug treatment in either group.ConclusionOverexpression of TRPM2 on NK cells may function as a compensatory mechanism to alert a dysregulation in Ca2+ homeostasis to enhance NK cell function in ME/CFS, such as NK cell cytotoxicity. As no improvement in NK cell cytotoxicity was observed within the ME/CFS group, an impairment in the TRPM2 ion channel may be present in ME/CFS patients, resulting in alterations in [Ca2+]i mobilisation and influx, which is fundamental in driving NK cell cytotoxicity. Differential expression of TRPM2 between NK cell subtypes may provide evidence for their role in the pathomechanism involving NK cell cytotoxicity activity in ME/CFS.

Project description:Transient receptor potential melastatin 3 (TRPM3) is a nonselective cation channel that is inhibited by Gβγ subunits liberated following activation of Gαi/o protein-coupled receptors. Here, we demonstrate that TRPM3 channels are also inhibited by Gβγ released from Gαs and Gαq Activation of the Gs-coupled adenosine 2B receptor and the Gq-coupled muscarinic acetylcholine M1 receptor inhibited the activity of TRPM3 heterologously expressed in HEK293 cells. This inhibition was prevented when the Gβγ sink βARK1-ct (C terminus of β-adrenergic receptor kinase-1) was coexpressed with TRPM3. In neurons isolated from mouse dorsal root ganglion (DRG), native TRPM3 channels were inhibited by activating Gs-coupled prostaglandin-EP2 and Gq-coupled bradykinin B2 (BK2) receptors. The Gi/o inhibitor pertussis toxin and inhibitors of PKA and PKC had no effect on EP2- and BK2-mediated inhibition of TRPM3, demonstrating that the receptors did not act through Gαi/o or through the major protein kinases activated downstream of G-protein-coupled receptor (GPCR) activation. When DRG neurons were dialyzed with GRK2i, which sequesters free Gβγ protein, TRPM3 inhibition by EP2 and BK2 was significantly reduced. Intraplantar injections of EP2 or BK2 agonists inhibited both the nocifensive response evoked by TRPM3 agonists, and the heat hypersensitivity produced by Freund's Complete Adjuvant (FCA). Furthermore, FCA-induced heat hypersensitivity was completely reversed by the selective TRPM3 antagonist ononetin in WT mice and did not develop in Trpm3-/- mice. Our results demonstrate that TRPM3 is subject to promiscuous inhibition by Gβγ protein in heterologous expression systems, primary neurons and in vivo, and suggest a critical role for this ion channel in inflammatory heat hypersensitivity.SIGNIFICANCE STATEMENT The ion channel TRPM3 is widely expressed in the nervous system. Recent studies showed that Gαi/o-coupled GPCRs inhibit TRPM3 through a direct interaction between Gβγ subunits and TRPM3. Since Gβγ proteins can be liberated from other Gα subunits than Gαi/o, we examined whether activation of Gs- and Gq-coupled receptors also influence TRPM3 via Gβγ. Our results demonstrate that activation of Gs- and Gq-coupled GPCRs in recombinant cells and sensory neurons inhibits TRPM3 via Gβγ liberation. We also demonstrated that Gs- and Gq-coupled receptors inhibit TRPM3 in vivo, thereby reducing pain produced by activation of TRPM3, and inflammatory heat hypersensitivity. Our results identify Gβγ inhibition of TRPM3 as an effector mechanism shared by the major Gα subunits.

Project description:BackgroundMyalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe multisystemic condition associated with post-infectious onset, impaired natural killer (NK) cell cytotoxicity and impaired ion channel function, namely Transient Receptor Potential Melastatin 3 (TRPM3). Long-term effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has resulted in neurocognitive, immunological, gastrointestinal, and cardiovascular manifestations recently recognised as post coronavirus disease 2019 (COVID-19) condition. The symptomatology of ME/CFS overlaps significantly with post COVID-19; therefore, this research aimed to investigate TRPM3 ion channel function in post COVID-19 condition patients.MethodsWhole-cell patch-clamp technique was used to measure TRPM3 ion channel activity in isolated NK cells of N = 5 ME/CFS patients, N = 5 post COVID-19 patients, and N = 5 healthy controls (HC). The TRPM3 agonist, pregnenolone sulfate (PregS) was used to activate TRPM3 function, while ononetin was used as a TRPM3 antagonist.ResultsAs reported in previous research, PregS-induced TRPM3 currents were significantly reduced in ME/CFS patients compared with HC (p = 0.0048). PregS-induced TRPM3 amplitude was significantly reduced in post COVID-19 condition compared with HC (p = 0.0039). Importantly, no significant difference was reported in ME/CFS patients compared with post COVID-19 condition as PregS-induced TRPM3 currents of post COVID-19 condition patients were similar of ME/CFS patients currents (p > 0.9999). Isolated NK cells from post COVID-19 condition and ME/CFS patients were resistant to ononetin and differed significantly with HC (p < 0.0001).ConclusionThe results of this investigation suggest that post COVID-19 condition patients may have impaired TRPM3 ion channel function and provide further evidence regarding the similarities between post COVID-19 condition and ME/CFS. Impaired TRPM3 channel activity in post COVID-19 condition patients suggest impaired ion mobilisation which may consequently impede cell function resulting in chronic post-infectious symptoms. Further investigation into TRPM3 function may elucidate the pathomechanism, provide a diagnostic and therapeutic target for post COVID-19 condition patients and commonalities with ME/CFS patients.

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The key role of transient receptor potential melastatin-2 channels in amyloid-?-induced neurovascular dysfunction.

Publications

The key role of transient receptor potential melastatin-2 channels in amyloid-β-induced neurovascular dysfunction.

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