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Fan YY, Li Y, Tian XY, Wang YJ, Huo J, Guo BL, Chen R, Yang CH, Li Y, Zhang HF, Niu BL, Zhang MS. Delayed Chronic Acidic Postconditioning Improves Poststroke Motor Functional Recovery and Brain Tissue Repair by Activating Proton-Sensing TDAG8. Transl Stroke Res 2024; 15:620-635. [PMID: 36853417 DOI: 10.1007/s12975-023-01143-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/13/2022] [Accepted: 02/17/2023] [Indexed: 03/01/2023]
Abstract
Acidic postconditioning by transient CO2 inhalation applied within minutes after reperfusion has neuroprotective effects in the acute phase of stroke. However, the effects of delayed chronic acidic postconditioning (DCAPC) initiated during the subacute phase of stroke or other acute brain injuries are unknown. Mice received daily DCAPC by inhaling 5%/10%/20% CO2 for various durations (three cycles of 10- or 20-min CO2 inhalation/10-min break) at days 3-7, 7-21, or 3-21 after photothrombotic stroke. Grid-walk, cylinder, and gait tests were used to assess motor function. DCAPC with all CO2 concentrations significantly promoted motor functional recovery, even when DCAPC was delayed for 3-7 days. DCAPC enhanced the puncta density of GAP-43 (a marker of axon growth and regeneration) and synaptophysin (a marker of synaptogenesis) and reduced the amoeboid microglia number, glial scar thickness and mRNA expression of CD16 and CD32 (markers of proinflammatory M1 microglia) compared with those of the stroke group. Cerebral blood flow (CBF) increased in response to DCAPC. Furthermore, the mRNA expression of TDAG8 (a proton-activated G-protein-coupled receptor) was increased during the subacute phase of stroke, while DCAPC effects were blocked by systemic knockout of TDAG8, except for those on CBF. DCAPC reproduced the benefits by re-expressing TDAG8 in the peri-infarct cortex of TDAG8-/- mice infected with HBAAV2/9-CMV-TDAG8-3flag-ZsGreen. Taken together, we first showed that DCAPC promoted functional recovery and brain tissue repair after stroke with a wide therapeutic time window of at least 7 days after stroke. Brain-derived TDAG8 is a direct target of DCAPC that induces neuroreparative effects.
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Affiliation(s)
- Yan-Ying Fan
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China.
- Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan, 030001, China.
| | - Yu Li
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Xiao-Ying Tian
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Ying-Jing Wang
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Jing Huo
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Bao-Lu Guo
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Ru Chen
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Cai-Hong Yang
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Yan Li
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Hui-Feng Zhang
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China
| | - Bao-Long Niu
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China.
- College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
| | - Ming-Sheng Zhang
- Department of Pharmacology, Basic Medical Sciences Center, Shanxi Medical University, Taiyuan, 030001, China.
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Glitsch MD. Recent advances in acid sensing by G protein coupled receptors. Pflugers Arch 2024; 476:445-455. [PMID: 38340167 PMCID: PMC11006784 DOI: 10.1007/s00424-024-02919-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/12/2024]
Abstract
Changes in extracellular proton concentrations occur in a variety of tissues over a range of timescales under physiological conditions and also accompany virtually all pathologies, notably cancers, stroke, inflammation and trauma. Proton-activated, G protein coupled receptors are already partially active at physiological extracellular proton concentrations and their activity increases with rising proton concentrations. Their ability to monitor and report changes in extracellular proton concentrations and hence extracellular pH appears to be involved in a variety of processes, and it is likely to mirror and in some cases promote disease progression. Unsurprisingly, therefore, these pH-sensing receptors (pHR) receive increasing attention from researchers working in an expanding range of research areas, from cellular neurophysiology to systemic inflammatory processes. This review is looking at progress made in the field of pHRs over the past few years and also highlights outstanding issues.
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Affiliation(s)
- Maike D Glitsch
- Medical School Hamburg, Am Sandtorkai 1, 20457, Hamburg, Germany.
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Hajjar S, Zhou X. pH sensing at the intersection of tissue homeostasis and inflammation. Trends Immunol 2023; 44:807-825. [PMID: 37714775 PMCID: PMC10543622 DOI: 10.1016/j.it.2023.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/13/2023] [Accepted: 08/13/2023] [Indexed: 09/17/2023]
Abstract
pH is tightly maintained at cellular, tissue, and systemic levels, and altered pH - particularly in the acidic range - is associated with infection, injury, solid tumors, and physiological and pathological inflammation. However, how pH is sensed and regulated and how it influences immune responses remain poorly understood at the tissue level. Applying conceptual frameworks of homeostatic and inflammatory circuitries, we categorize cellular and tissue components engaged in pH regulation, drawing parallels from established cases in physiology. By expressing various intracellular (pHi) and extracellular pH (pHe)-sensing receptors, the immune system may integrate information on tissue and cellular states into the regulation of homeostatic and inflammatory programs. We introduce the novel concept of resistance and adaptation responses to rationalize pH-dependent immunomodulation intertwined with homeostatic equilibrium and inflammatory control. We discuss emerging challenges and opportunities in understanding the immunological roles of pH sensing, which might reveal new strategies to combat inflammation and restore tissue homeostasis.
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Affiliation(s)
- Stephanie Hajjar
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, 300 Longwood Ave, Boston, MA 02115, USA
| | - Xu Zhou
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, 300 Longwood Ave, Boston, MA 02115, USA.
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Yang H, Verhoeve VI, Chandler CE, Nallar S, Snyder GA, Ernst RK, Gillespie JJ. Structural determination of Rickettsia lipid A without chemical extraction confirms shorter acyl chains in later-evolving Spotted Fever Group pathogens. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.06.547954. [PMID: 37461656 PMCID: PMC10350050 DOI: 10.1101/2023.07.06.547954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2024]
Abstract
Rickettsiae are Gram-negative obligate intracellular parasites of numerous eukaryotes. Human pathogens of the Transitional Group (TRG), Typhus Group (TG), and Spotted Fever Group (SFG) rickettsiae infect blood-feeding arthropods, have dissimilar clinical manifestations, and possess unique genomic and morphological attributes. Lacking glycolysis, rickettsiae pilfer numerous metabolites from host cytosol to synthesize peptidoglycan and lipopolysaccharide (LPS). For LPS, O-antigen immunogenicity varies between SFG and TG pathogens; however, lipid A proinflammatory potential is unknown. We previously demonstrated that R. akari (TRG), R. typhi (TG), and R. montanensis (SFG) produce lipid A with long 2' secondary acyl chains (C16 or C18) compared to short 2' secondary acyl chains (C12) in R. rickettsii (SFG) lipid A. To further probe this structural heterogeneity and estimate a time point when shorter 2' secondary acyl chains originated, we generated lipid A structures for two additional SFG rickettsiae ( R. rhipicephali and R. parkeri ) utilizing Fast Lipid Analysis Technique adopted for use with tandem mass spectrometry (FLAT n ). FLAT n allowed analysis of lipid A structure directly from host cell-purified bacteria, providing substantial improvement over lipid A chemical extraction. FLAT n -derived structures indicate SFG rickettsiae diverging after R. rhipicephali evolved shorter 2' secondary acyl chains. Bioinformatics analysis of Rickettsia LpxL late acyltransferases revealed discrete active sites and hydrocarbon rulers for long versus short 2' secondary acyl chain addition. While the significance of different lipid A structures for diverse Rickettsia pathogens is unknown, our success using FLAT n will facilitate determining how structural heterogeneity impacts interactions with host lipid A receptors and overall inflammatory potential. IMPORTANCE Deforestation, urbanization, and homelessness lead to spikes in Rickettsioses. Vector-borne human pathogens of Transitional Group (TRG), Typhus Group (TG), and Spotted Fever Group (SFG) rickettsiae differ by clinical manifestations, immunopathology, genome composition, and morphology. We previously showed that lipid A (or endotoxin), the membrane anchor of Gram-negative bacterial lipopolysaccharide (LPS), structurally differs in R. rickettsii (later-evolving SFG) relative to R. montanensis (basal SFG), R. typhi (TG), and R. akari (TRG). As lipid A structure influences recognition potential in vertebrate LPS sensors, further assessment of Rickettsia lipid A structural heterogeneity is needed. Here, we sidestepped the difficulty of ex vivo lipid A chemical extraction by utilizing FLAT n , a new procedure for generating lipid A structures directly from host cell-purified bacteria. These data confirm later-evolving SFG pathogens synthesize structurally distinct lipid A. Our findings impact interpreting immune responses to different Rickettsia pathogens and utilizing lipid A adjuvant or anti-inflammatory properties in vaccinology.
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Koshmanova E, Berger A, Beckers E, Campbell I, Mortazavi N, Sharifpour R, Paparella I, Balda F, Berthomier C, Degueldre C, Salmon E, Lamalle L, Bastin C, Egroo MV, Phillips C, Maquet P, Collette F, Muto V, Chylinski D, Jacobs HI, Talwar P, Sherif S, Vandewalle G. In vivo Locus Coeruleus activity while awake is associated with REM sleep quality in healthy older individuals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.10.527974. [PMID: 36993680 PMCID: PMC10054994 DOI: 10.1101/2023.02.10.527974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The locus coeruleus (LC) is the primary source of norepinephrine (NE) in the brain, and the LC-NE system is involved in regulating arousal and sleep. It plays key roles in the transition between sleep and wakefulness, and between slow wave sleep (SWS) and rapid eye movement sleep (REMS). However, it is not clear whether the LC activity during the day predicts sleep quality and sleep properties during the night, and how this varies as a function of age. Here, we used 7 Tesla functional Magnetic Resonance Imaging (7T fMRI), sleep electroencephalography (EEG) and a sleep questionnaire to test whether the LC activity during wakefulness was associated with sleep quality in 52 healthy younger (N=33; ~22y; 28 women) and older (N=19; ~61y; 14 women) individuals. We find that, in older, but not in younger participants, higher LC activity, as probed during an auditory mismatch negativity task, is associated with worse subjective sleep quality and with lower power over the EEG theta band during REMS (4-8Hz), which are two sleep parameters significantly correlated in our sample of older individuals. The results remain robust even when accounting for the age-related changes in the integrity of the LC. These findings suggest that the activity of the LC may contribute to the perception of the sleep quality and to an essential oscillatory mode of REMS, and that the LC may be an important target in the treatment of sleep disorders and age-related diseases.
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Dinh MN, Hitomi M, Al-Turaihi ZA, Scott JG. Alamar Blue assay optimization to minimize drug interference and inter-assay viability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.16.532999. [PMID: 36993631 PMCID: PMC10055072 DOI: 10.1101/2023.03.16.532999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Alamar Blue (AB) has become an increasingly popular reagent of choice for cell viability assays. We chose AB over other reagents such as MTT and Cell-Titer Glo due to its cost effectiveness and its ability to be a nondestructive assay. While analyzing the effect of osimertinib, an EGFR inhibitor on the non-small cell lung cancer cell line, PC-9, we noticed unexpected right-shifts of dose response curves as compared to the curve obtained by Cell Titer Glo assay. Here, we describe our modified AB assay method to avoid right shift right shift in dose response curve. Unlike some of the redox drugs that were reported to directly affected AB reading, osimertinib itself did not directly increase AB reading. Yet, the removal of the drug containing medium prior to AB addition eliminated falsely increased reading giving comparable dose response curve as the one determined by Cell Titer Glo assay. When a panel of 11 drugs were assessed, we found that this modified AB assay eliminated unexpected similar right shifts detected in other epidermal growth factor receptor (EGFR) inhibitors. We also found that plate-to-plate variability can be minimized by adding an appropriate concentration of rhodamine B solution to the assay plates to calibrate fluorimeter sensitivity. This calibration method also enables a continuous longitudinal assay to monitor cell growth or recovery from drug toxicity over time. Our new modified AB assay is expected to provide accurate in vitro measurement of EGFR targeted therapies.
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Affiliation(s)
- Mina N. Dinh
- Department of Translational Hematology & Oncology Research, Cleveland Clinic, Cleveland, OH
| | - Masahiro Hitomi
- Department of Translational Hematology & Oncology Research, Cleveland Clinic, Cleveland, OH
| | - Zahraa A. Al-Turaihi
- Department of Translational Hematology & Oncology Research, Cleveland Clinic, Cleveland, OH
| | - Jacob G. Scott
- Department of Translational Hematology & Oncology Research, Cleveland Clinic, Cleveland, OH
- Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH
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Abstract
Extracellular proton concentration is at 40 nM when pH is 7.4. In disease conditions such as brain ischemia, proton concentration can reach µM range. To respond to this increase in extracellular proton concentration, the mammalian brain expresses at least three classes of proton receptors. Acid-sensing ion channels (ASICs) are the main neuronal cationic proton receptor. The proton-activated chloride channel (PAC), which is also known as (aka) acid-sensitive outwardly rectifying anion channel (ASOR; TMEM206), mediates acid-induced chloride currents. Besides proton-activated channels, GPR4, GPR65 (aka TDAG8, T-cell death-associated gene 8), and GPR68 (aka OGR1, ovarian cancer G protein-coupled receptor 1) function as proton-sensitive G protein-coupled receptors (GPCRs). Though earlier studies on these GPCRs mainly focus on peripheral cells, we and others have recently provided evidence for their functional importance in brain injury. Specifically, GPR4 shows strong expression in brain endothelium, GPR65 is present in a fraction of microglia, while GPR68 exhibits predominant expression in brain neurons. Here, to get a better view of brain acid signaling and its contribution to ischemic injury, we will review the recent findings regarding the differential contribution of proton-sensitive GPCRs to cerebrovascular function, neuroinflammation, and neuronal injury following acidosis and brain ischemia.
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Affiliation(s)
- Xiang-ming Zha
- Division of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO, USA
- Xiang-ming Zha, Division of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte St, Kansas City, MO 64108, USA.
| | - Zhi-Gang Xiong
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Roger P Simon
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
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Sisignano M, Fischer MJM, Geisslinger G. Proton-Sensing GPCRs in Health and Disease. Cells 2021; 10:cells10082050. [PMID: 34440817 PMCID: PMC8392051 DOI: 10.3390/cells10082050] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/05/2021] [Accepted: 08/06/2021] [Indexed: 12/17/2022] Open
Abstract
The group of proton-sensing G-protein coupled receptors (GPCRs) consists of the four receptors GPR4, TDAG8 (GPR65), OGR1 (GPR68), and G2A (GPR132). These receptors are cellular sensors of acidification, a property that has been attributed to the presence of crucial histidine residues. However, the pH detection varies considerably among the group of proton-sensing GPCRs and ranges from pH of 5.5 to 7.8. While the proton-sensing GPCRs were initially considered to detect acidic cellular environments in the context of inflammation, recent observations have expanded our knowledge about their physiological and pathophysiological functions and many additional individual and unique features have been discovered that suggest a more differentiated role of these receptors in health and disease. It is known that all four receptors contribute to different aspects of tumor biology, cardiovascular physiology, and asthma. However, apart from their overlapping functions, they seem to have individual properties, and recent publications identify potential roles of individual GPCRs in mechanosensation, intestinal inflammation, oncoimmunological interactions, hematopoiesis, as well as inflammatory and neuropathic pain. Here, we put together the knowledge about the biological functions and structural features of the four proton-sensing GPCRs and discuss the biological role of each of the four receptors individually. We explore all currently known pharmacological modulators of the four receptors and highlight potential use. Finally, we point out knowledge gaps in the biological and pharmacological context of proton-sensing GPCRs that should be addressed by future studies.
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Affiliation(s)
- Marco Sisignano
- Institute of Clinical Pharmacology, Pharmazentrum Frankfurt/ZAFES, University Hospital of Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany;
- Fraunhofer Institute for Translational Medicine and Pharmacology (ITMP), Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
- Correspondence:
| | - Michael J. M. Fischer
- Center for Physiology and Pharmacology, Institute of Physiology, Medical University of Vienna, Schwarzspanierstrasse 17, 1090 Vienna, Austria;
| | - Gerd Geisslinger
- Institute of Clinical Pharmacology, Pharmazentrum Frankfurt/ZAFES, University Hospital of Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany;
- Fraunhofer Institute for Translational Medicine and Pharmacology (ITMP), Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
- Fraunhofer Cluster of Excellence for Immune-Mediated Diseases (CIMD), Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
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Bie F, Wang K, Xu T, Yuan J, Ding H, Lv B, Liu Y, Lan M. The potential roles of circular RNAs as modulators in traumatic spinal cord injury. Biomed Pharmacother 2021; 141:111826. [PMID: 34328121 DOI: 10.1016/j.biopha.2021.111826] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 06/07/2021] [Accepted: 06/11/2021] [Indexed: 02/08/2023] Open
Abstract
Spinal cord injury (SCI) may cause long-term physical impairment and bring a substantial burden to both the individual patient and society. Existing therapeutic approaches for SCI have proven inadequate. This is mainly owing to the incomplete understanding of the cellular and molecular events post-injury. Circular RNAs (circRNAs) represent a new class of non-coding RNAs with a covalently closed annular structure that participates in regulating the transcription of certain genes and are linked to various biological processes and diseases. Mounting evidence is indicative that circRNAs are highly expressed in the spinal cord and they play key roles in multiple processes of neurological diseases. Recently, a role for circRNAs as effectors of SCI has emerged, leading to the continuity of relevant research. In this review, we presented current studies with regards to the abnormality of circRNAs mediating SCI by affecting mechanisms of autophagy, apoptosis, inflammation, and neural regeneration. Furthermore, the potential clinical value of circRNAs as therapeutic targets of SCI was also analyzed.
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Affiliation(s)
- Fan Bie
- Department of Rehabilitation Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu 212002, China.
| | - Kaiyang Wang
- Department of Orthopedics, Shanghai Jiao Tong University Sixth People's Hospital, Shanghai 200233, China.
| | - Tao Xu
- Department of Orthopedics, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
| | - Jishan Yuan
- Department of Orthopedics, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu 212002, China.
| | - Hua Ding
- Department of Orthopedics, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu 212002, China.
| | - Bin Lv
- Department of Orthopedics, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu 212002, China; Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
| | - Yuwen Liu
- Department of Orthopedics, Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu 210008, China.
| | - Min Lan
- Department of Rehabilitation Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu 212002, China.
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Zhou G, Zha XM. GPR68 Contributes to Persistent Acidosis-Induced Activation of AGC Kinases and Tyrosine Phosphorylation in Organotypic Hippocampal Slices. Front Neurosci 2021; 15:692217. [PMID: 34113235 PMCID: PMC8185064 DOI: 10.3389/fnins.2021.692217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 04/29/2021] [Indexed: 12/28/2022] Open
Abstract
Persistent acidosis occurs in ischemia and multiple neurological diseases. In previous studies, acidic stimulation leads to rapid increase in intracellular calcium in neurons. However, it remains largely unclear how a prolonged acidosis alters neuronal signaling. In our previous study, we found that GPR68-mediated PKC activities are protective against acidosis-induced injury in cortical slices. Here, we first asked whether the same principle holds true in organotypic hippocampal slices. Our data showed that 1-h pH 6 induced PKC phosphorylation in a GPR68-dependent manner. Go6983, a PKC inhibitor worsened acidosis-induced neuronal injury in wild type (WT) but had no effect in GPR68−/− slices. Next, to gain greater insights into acid signaling in brain tissue, we treated organotypic hippocampal slices with pH 6 for 1-h and performed a kinome profiling analysis by Western blot. Acidosis had little effect on cyclin-dependent kinase (CDK) or casein kinase 2 activity, two members of the CMGC family, or Ataxia telangiectasia mutated (ATM)/ATM and RAD3-related (ATR) activity, but reduced the phosphorylation of MAPK/CDK substrates. In contrast, acidosis induced the activation of CaMKIIα, PKA, and Akt. Besides these serine/threonine kinases, acidosis also induced tyrosine phosphorylation. Since GPR68 is widely expressed in brain neurons, we asked whether GPR68 contributes to acidosis-induced signaling. Deleting GPR68 had no effect on acidosis-induced CaMKII phosphorylation, attenuated that of phospho-Akt and phospho-PKA substrates, while abolishing acidosis-induced tyrosine phosphorylation. These data demonstrate that prolonged acidosis activates a network of signaling cascades, mediated by AGC kinases, CaMKII, and tyrosine kinases. GPR68 is the primary mediator for acidosis-induced activation of PKC and tyrosine phosphorylation, while both GPR68-dependent and -independent mechanisms contribute to the activation of PKA and Akt.
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Affiliation(s)
- Guokun Zhou
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, AL, United States
| | - Xiang-Ming Zha
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, AL, United States
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Zhou G, Wang T, Zha XM. RNA-Seq analysis of knocking out the neuroprotective proton-sensitive GPR68 on basal and acute ischemia-induced transcriptome changes and signaling in mouse brain. FASEB J 2021; 35:e21461. [PMID: 33724568 PMCID: PMC7970445 DOI: 10.1096/fj.202002511r] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/14/2021] [Accepted: 02/04/2021] [Indexed: 12/17/2022]
Abstract
Brain acid signaling plays important roles in both physiological and disease conditions. One key neuronal metabotropic proton receptor in the brain is GPR68, which contributes to hippocampal long-term potentiation (LTP) and mediates neuroprotection in acidotic and ischemic conditions. Here, to gain greater understanding of GPR68 function in the brain, we performed mRNA-Seq analysis in mice. First, we studied sham-operated animals to determine baseline expression. Compared to wild type (WT), GPR68-/- (KO) brain downregulated genes that are enriched in Gene Ontology (GO) terms of misfolding protein binding, response to organic cyclic compounds, and endoplasmic reticulum chaperone complex. Next, we examined the expression profile following transient middle cerebral artery occlusion (tMCAO). tMCAO-upregulated genes cluster to cytokine/chemokine-related functions and immune responses, while tMCAO-downregulated genes cluster to channel activities and synaptic signaling. For proton-sensitive receptors, tMCAO downregulated ASIC1a and upregulated GPR4 and GPR65, but had no effect on ASIC2, PAC, or GPR68. GPR68 deletion did not alter the expression of these proton receptors, either at baseline or after ischemia. Lastly, we performed GeneVenn analysis of differential genes at baseline and post-tMCAO. Ischemia upregulated the expression of three hemoglobin genes, along with H2-Aa, Ppbp, Siglece, and Tagln, in WT but not in KO. Immunostaining showed that tMCAO-induced hemoglobin localized to neurons. Western blot analysis further showed that hemoglobin induction is GPR68-dependent. Together, these data suggest that GPR68 deletion at baseline disrupts chaperone functions and cellular signaling responses and imply a contribution of hemoglobin-mediated antioxidant mechanism to GPR68-dependent neuroprotection in ischemia.
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Affiliation(s)
- Guokun Zhou
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, AL, USA
| | - Tao Wang
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, AL, USA
| | - Xiang-Ming Zha
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, AL, USA
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