Browsing by Author "Obukhov, Alexander G."
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Item 459 Caspase-1 mediated inflammatory response - a critical player in concussive mild traumatic brain injury (mTBI) associated long term pain(Cambridge University Press, 2023-04-24) Nguyen, Tyler; Talley, Sarah; Nguyen, Natalie; Cochran, Ashlyn G.; Al-Juboori, Mohammed; Smith, Jared A.; Saxena, Saahil; Campbell, Edward M.; Obukhov, Alexander G.; White, Fletcher A.; Anesthesia, School of MedicineOBJECTIVES/GOALS: Patients who have experienced conjunctive mild traumatic brain injuries (mTBIs) suffer from a number of comorbidities, including chronic pain. Despite extensive studies investigating the underlying mechanisms of mTBI-associated chronic pain, the role of inflammation after mTBI and its contribution to long-term pain are still poorly understood. METHODS/STUDY POPULATION: Given the shifting dynamics of inflammation, it is important to understand the spatial-longitudinal changes and their effects on TBI-related pain. Utilizing a recently developed transgenic caspase-1 luciferase reporter mouse, we characterized the bioluminescence signal evident in both in vivo and ex vivo tissues following repetitive closed head mTBIs. This allowed us to reveal the spatiotemporal dynamics of caspase-1 activation in individual animals over time. Furthermore, we utilize various proteomic and behavioral assays to evaluate the role of caspase-1 mediated inflammation in the development and progression of injury-associated chronic pain. Lastly, by blocking inflammasome caspase-1 activation with a specific inhibitor, we assess its clinical potential as the next therapeutic approach to pain. RESULTS/ANTICIPATED RESULTS: We established that there were significant increases in bioluminescent signals upon protease cleavage in the brain, thorax, abdomen, and paws in vivo, which lasted for at least one week after each injury. Enhanced inflammation was also observed in ex vivo brain slice preparations following injury events that lasted for at least 3 days. Concurrent with the in vivo detection of the bioluminescent signal were persistent decreases in mouse hind paw withdrawal thresholds that lasted for more than two months postinjury. Using MCC950, a potent small molecule inhibitor of NLRP3 inflammasome-caspase 1 activity, we observed reductions in both caspase-1 bioluminescent signals in vivo and caspase-1 p45 expression by immunoblotting and an increase in hind paw withdrawal thresholds. DISCUSSION/SIGNIFICANCE: Overall, these findings suggest that neuroinflammation in the brain following repeated mTBIs is coincidental with a chronic nociplastic pain state, and repeated mTBI-associated events can be ameliorated by a highly specific small molecule inhibitor of NLRP3 inflammasome activation.Item Angiotensin Converting Enzyme 2 in Cardiopulmonary Diseases: Ramifications for the Control of SARS-CoV-2(American Heart Association, 2020-09) Sharma, Ravindra K.; Stevens, Bruce R.; Obukhov, Alexander G.; Grant, Maria B.; Oudit, Gavin Y.; Li, Qiuhong; Richards, Elaine M.; Pepine, Carl J.; Raizada, Mohan K.; Anatomy and Cell Biology, School of MedicineDiscovery of angiotensin converting enzyme 2 (ACE2) revealed that the renin angiotensin system (RAS) has two counterbalancing arms. ACE2 is a major player in the protective arm, highly expressed in lungs and gut with the ability to mitigate cardiopulmonary diseases such as inflammatory lung disease. ACE2 also exhibits activities involving gut microbiome, nutrition, and as a chaperone stabilizing the neutral amino acid transporter, B0AT1, in gut. But the current interest in ACE2 arises because it is the cell surface receptor for the novel coronavirus, SARS-CoV-2, to infect host cells, similar to SARS-CoV. This suggests that ACE2 be considered harmful, however because of its important other roles, it is paradoxically a potential therapeutic target for cardiopulmonary diseases including COVID-19, caused by SARS-CoV-2. This review describes the discovery of ACE2, its physiological functions, and its place in the RAS. It illustrates new analyses of the structure of ACE2 that provides better understanding of its actions particularly in lung and gut, shedding of ACE2 by ADAM17 and role of TMPRSS2 in SARS-CoV-2 entry into host cells. Cardiopulmonary diseases are associated with decreased ACE2 activity and the mitigation by increasing ACE2 activity along with its therapeutic relevance are addressed. Finally, the potential use of ACE2 as a treatment target in COVID-19, despite its role to allow viral entry into host cells, is suggested.Item Bone Marrow-Derived Cells Restore Functional Integrity of the Gut Epithelial and Vascular Barriers in a Model of Diabetes and ACE2 Deficiency(AHA, 2019-11-08) Duan, Yaqian; Prasad, Ram; Feng, Dongni; Beli, Eleni; Calzi, Sergio Li; Longhini, Ana Leda F.; Lamendella, Regina; Floyd, Jason L.; Dupont, Mariana; Noothi, Sunil K.; Sreejit, Gopal Krishan; Athmanathan, Baskaran; Wright, Justin; Jensen, Amanda R.; Oudit, Gavin Y.; Markel, Troy A.; Nagareddy, Prabhakara R; Obukhov, Alexander G.; Grant, Maria B.; Anatomy and Cell Biology, School of MedicineRationale: There is incomplete knowledge of the impact of bone marrow (BM) cells on the gut microbiome and gut barrier function. Objective: We postulated that diabetes and systemic angiotensin-converting enzyme 2 (ACE2) deficiency would synergize to adversely impact both the microbiome and gut barrier function. Methods and Results: Bacterial 16S rRNA sequencing and metatranscriptomic analysis were performed on fecal samples from WT, ACE2−/y, Akita (type 1 diabetic, T1D), and ACE2−/y-Akita mice. Gut barrier integrity was assessed by immunofluorescence, and BM cell extravasation into the small intestine was evaluated by flow cytometry. In the ACE2−/y-Akita or Akita mice, the disrupted barrier was associated with reduced levels of myeloid angiogenic cells (MACs), but no increase in inflammatory monocytes was observed within the gut parenchyma. Genomic and metatranscriptomic analysis of the microbiome of ACE2−/y-Akita mice demonstrated a marked increase in peptidoglycan (PGN) producing bacteria. When compared to control cohorts treated with saline, intraperitoneal administration of MACs significantly decreased the microbiome gene expression associated with PGN biosynthesis and restored epithelial and endothelial gut barrier integrity. Also indicative of diabetic gut barrier dysfunction, increased levels of PGN and intestinal fatty acid binding protein-2 (FABP-2) were observed in plasma of human subjects with T1D (n=21) and Type 2 diabetes (T2D, n=23) compared to non-diabetic controls (n=23). Using human retinal endothelial cells, we determined that PGN activates a non-canonical Toll-like receptor-2 (TLR2) associated MyD88-ARNO-ARF6 signaling cascade, resulting in destabilization of p120-catenin and internalization of VE-cadherin as a mechanism of deleterious impact of PGN on the endothelium. Conclusion: We demonstrate for the first time that the defect in gut barrier function and dysbiosis in ACE2−/y-Akita mice can be favorably impacted by exogenous administration of MACs.Item Capsaicin and TRPV1 Channels in the Cardiovascular System: The Role of Inflammation(MDPI, 2021-12) Munjuluri, Sreepadaarchana; Wilkerson, Dru A.; Sooch, Gagandeep; Chen, Xingjuan; White, Fletcher A.; Obukhov, Alexander G.; Pharmacology and Toxicology, School of MedicineCapsaicin is a potent agonist of the Transient Receptor Potential Vanilloid type 1 (TRPV1) channel and is a common component found in the fruits of the genus Capsicum plants, which have been known to humanity and consumed in food for approximately 7000–9000 years. The fruits of Capsicum plants, such as chili pepper, have been long recognized for their high nutritional value. Additionally, capsaicin itself has been proposed to exhibit vasodilatory, antimicrobial, anti-cancer, and antinociceptive properties. However, a growing body of evidence reveals a vasoconstrictory potential of capsaicin acting via the vascular TRPV1 channel and suggests that unnecessary high consumption of capsaicin may cause severe consequences, including vasospasm and myocardial infarction in people with underlying inflammatory conditions. This review focuses on vascular TRPV1 channels that are endogenously expressed in both vascular smooth muscle and endothelial cells and emphasizes the role of inflammation in sensitizing the TRPV1 channel to capsaicin activation. Tilting the balance between the beneficial vasodilatory action of capsaicin and its unwanted vasoconstrictive effects may precipitate adverse outcomes such as vasospasm and myocardial infarction, especially in the presence of proinflammatory mediators.Item Catechol estrogens stimulate insulin secretion in pancreatic β-cells via activation of the transient receptor potential A1 (TRPA1) channel(American Society for Biochemistry and Molecular Biology, 2019-02-22) Ma, Wenzhen; Chen, Xingjuan; Cerne, Rok; Syed, Samreen K.; Ficorilli, James V.; Cabrera, Over; Obukhov, Alexander G.; Efanov, Alexander M.; Cellular and Integrative Physiology, School of MedicineEstrogen hormones play an important role in controlling glucose homeostasis and pancreatic β-cell function. Despite the significance of estrogen hormones for regulation of glucose metabolism, little is known about the roles of endogenous estrogen metabolites in modulating pancreatic β-cell function. In this study, we evaluated the effects of major natural estrogen metabolites, catechol estrogens, on insulin secretion in pancreatic β-cells. We show that catechol estrogens, hydroxylated at positions C2 and C4 of the steroid A ring, rapidly potentiated glucose-induced insulin secretion via a nongenomic mechanism. 2-Hydroxyestrone, the most abundant endogenous estrogen metabolite, was more efficacious in stimulating insulin secretion than any other tested catechol estrogens. In insulin-secreting cells, catechol estrogens produced rapid activation of calcium influx and elevation in cytosolic free calcium. Catechol estrogens also generated sustained elevations in cytosolic free calcium and evoked inward ion current in HEK293 cells expressing the transient receptor potential A1 (TRPA1) cation channel. Calcium influx and insulin secretion stimulated by estrogen metabolites were dependent on the TRPA1 activity and inhibited with the channel-specific pharmacological antagonists or the siRNA. Our results suggest the role of estrogen metabolism in a direct regulation of TRPA1 activity with potential implications for metabolic diseases.Item Dihydroceramides Derived from Bacteroidetes Species Sensitize TRPV1 Channels(MDPI, 2023-01-03) Ludwig, Nora; Demaree, Isaac S.; Yamada, Chiaki; Nusbaum, Amilia; Nichols, Frank C.; White, Fletcher A.; Movila, Alexandru; Obukhov, Alexander G.; Anatomy, Cell Biology and Physiology, School of MedicineBacterial colonization of open wounds is common, and patients with infected wounds often report significantly elevated pain sensitivity at the wound site. Transient Receptor Potential Vanilloid Type 1 (TRPV1) channels are known to play an important role in pain signaling and may be sensitized under pro-inflammatory conditions. Bacterial membrane components, such as phosphoethanolamine dihydroceramide (PEDHC), phosphoglycerol dihydroceramide (PGDHC), and lipopolysaccharide (LPS), are released in the environment from the Gram-negative bacteria of the Bacteroidetes species colonizing the infected wounds. Here, we used intracellular calcium imaging and patch-clamp electrophysiology approaches to determine whether bacterially derived PEDHC, PGDHC, or LPS can modulate the activity of the TRPV1 channels heterologously expressed in HEK cells. We found that PEDHC and PGDHC can sensitize TRPV1 in a concentration-dependent manner, whereas LPS treatment does not significantly affect TRPV1 activity in HEK cells. We propose that sensitization of TRPV1 channels by Bacteroidetes-derived dihydroceramides may at least in part underlie the increased pain sensitivity associated with wound infections.Item Endothelial Cell-Specific Deletion of P2Y2 Receptor Promotes Plaque Stability in Atherosclerosis-Susceptible ApoE-Null Mice(American Heart Association, 2017-01) Xingjuan, Chen; Qian, Shaomin; Hoggatt, April; Tang, Hongying; Hacker, Timothy A.; Obukhov, Alexander G.; Herring, Paul B.; Seye, Cheikh I.; Cellular and Integrative Physiology, School of MedicineOBJECTIVE: Nucleotide P2Y2 receptor (P2Y2R) contributes to vascular inflammation by increasing vascular cell adhesion molecule-1 expression in endothelial cells (EC), and global P2Y2R deficiency prevents fatty streak formation in apolipoprotein E null (ApoE-/-) mice. Because P2Y2R is ubiquitously expressed in vascular cells, we investigated the contribution of endothelial P2Y2R in the pathogenesis of atherosclerosis. APPROACH AND RESULTS: EC-specific P2Y2R-deficient mice were generated by breeding VEcadherin5-Cre mice with the P2Y2R floxed mice. Endothelial P2Y2R deficiency reduced endothelial nitric oxide synthase activity and significantly altered ATP- and UTP (uridine 5'-triphosphate)-induced vasorelaxation without affecting vasodilatory responses to acetylcholine. Telemetric blood pressure and echocardiography measurements indicated that EC-specific P2Y2R-deficient mice did not develop hypertension. We investigated the role of endothelial P2Y2R in the development of atherosclerotic lesions by crossing the EC-specific P2Y2R knockout mice onto an ApoE-/- background and evaluated lesion development after feeding a standard chow diet for 25 weeks. Histopathologic examination demonstrated reduced atherosclerotic lesions in the aortic sinus and entire aorta, decreased macrophage infiltration, and increased smooth muscle cell and collagen content, leading to the formation of a subendothelial fibrous cap in EC-specific P2Y2R-deficient ApoE-/- mice. Expression and proteolytic activity of matrix metalloproteinase-2 was significantly reduced in atherosclerotic lesions from EC-specific P2Y2R-deficient ApoE-/- mice. Furthermore, EC-specific P2Y2R deficiency inhibited nitric oxide production, leading to significant increase in smooth muscle cell migration out of aortic explants. CONCLUSIONS: EC-specific P2Y2R deficiency reduces atherosclerotic burden and promotes plaque stability in ApoE-/- mice through impaired macrophage infiltration acting together with reduced matrix metalloproteinase-2 activity and increased smooth muscle cell migration.Item Ex Vivo Method for Assessing the Mouse Reproductive Tract Spontaneous Motility and a MATLAB-based Uterus Motion Tracking Algorithm for Data Analysis(Journal of Visualized Experiments, 2019-09-01) Liang, Kaley L.; Bursova, Julia O.; Lam, Frank; Chen, Xingjuan; Obukhov, Alexander G.; Cellular and Integrative Physiology, School of MedicineDysmenorrhea, or painful cramping, is the most common symptom associated with menses in females and its severity can hinder women's everyday lives. Here, we present an easy and inexpensive method that would be instrumental for testing new drugs decreasing uterine contractility. This method utilizes the unique ability of the entire mouse reproductive tract to exhibit spontaneous motility when maintained ex vivo in a Petri dish containing oxygenated Krebs buffer. This spontaneous motility resembles the wave-like myometrial activity of the human uterus, referred to as endometrial waves. To demonstrate the effectiveness of the method, we employed a well-known uterine relaxant drug, epinephrine. We demonstrate that the spontaneous motility of the entire mouse reproductive tract can be quickly and reversibly inhibited by 1 µM epinephrine in this Petri dish model. Documenting the changes of uterine motility can be easily done using an ordinary smart phone or a sophisticated digital camera. We developed a MATLAB-based algorithm allowing motion tracking to quantify spontaneous uterine motility changes by measuring the rate of uterine horn movements. A major advantage of this ex vivo approach is that the reproductive tract remains intact throughout the entire experiment, preserving all intrinsic intrauterine cellular interactions. The major limitation of this approach is that up to 10-20% of uteri may exhibit no spontaneous motility. Thus far, this is the first quantitative ex vivo method for assessing spontaneous uterine motility in a Petri dish model.Item Furanocoumarins are a novel class of modulators for the transient receptor potential vanilloid type 1 (TRPV1) channel(ASBMB, 2014-04-04) Chen, Xingjuan; Sun, Weiyang; Ginaris, Nicholas G.; Riley, Ashley M.; Cummins, Theodore R.; Fehrenbacher, Jill C.; Obukhov, Alexander G.; Department of Cellular & Integrative Physiology, IU School of MedicineFuranocoumarin imperatorin is the major active component of Angelica dahurica root extracts, widely used in traditional medicine to treat headache, toothache, and orbital eye pain. In this study, we investigated the mechanisms that may underlie the pain-relieving effects of the compound. We found that imperatorin significantly inhibited formalin- and capsaicin-induced nocifensive responses but did not alter baseline thermal withdrawal thresholds in the rat. We established that imperatorin is a weak agonist of TRPV1, a channel implicated in detecting several noxious stimuli, exhibiting a 50% effective concentration (EC50) of 12.6 ± 3.2 μM. A specific TRPV1 antagonist, JNJ-17203212 (0.5 μM), potently inhibited imperatorin-induced TRPV1 activation. Site-directed mutagenesis studies revealed that imperatorin most likely acted via a site adjacent to or overlapping with the TRPV1 capsaicin-binding site. TRPV1 recovery from desensitization was delayed in the presence of imperatorin. Conversely, imperatorin sensitized TRPV1 to acid activation but did not affect the current amplitude and/or the activation-inactivation properties of Na(v)1.7, a channel important for transmission of nociceptive information. Thus, our data indicate that furanocoumarins represent a novel group of TRPV1 modulators that may become important lead compounds in the drug discovery process aimed at developing new treatments for pain management.Item HIV-Nef Protein Transfer to Endothelial Cells Requires Rac1 Activation and Leads to Endothelial Dysfunction Implications for Statin Treatment in HIV Patients(American Heart Association, 2019-08-27) Chelvanambi, Sarvesh; Gupta, Samir K.; Chen, Xingjuan; Ellis, Bradley W.; Maier, Bernhard F.; Colbert, Tyler M.; Kuriakose, Jithin; Zorlutuna, Pinar; Jolicoeur, Paul; Obukhov, Alexander G.; Clauss, Matthias; Medicine, School of MedicineRationale Even in antiretroviral therapy (ART) treated patients, HIV continues to play a pathogenic role in cardiovascular diseases. A possible cofactor may be persistence of the early HIV response gene Nef, which we have demonstrated recently to persist in the lungs of HIV+ patients on ART. Previously, we have reported that HIV strains with Nef, but not Nef-deleted HIV strains, cause endothelial proinflammatory activation and apoptosis. Objective To characterize mechanisms through which HIV-Nef leads to the development of cardiovascular diseases using ex vivo tissue culture approaches as well as interventional experiments in transgenic murine models. Methods and Results EV (extracellular vesicles) derived from both peripheral blood mononuclear cells (PBMC) and plasma from HIV+ patient blood samples induced human coronary artery endothelial cells dysfunction. Plasma derived EV from ART+ patients that were HIV-Nef+ induced significantly greater endothelial apoptosis compared to HIV-Nef- plasma EV. Both HIV-Nef expressing T cells and HIV-Nef-induced EV increased transfer of cytosol and Nef protein to endothelial monolayers in a Rac1-dependent manner, consequently leading to endothelial adhesion protein upregulation and apoptosis. HIV-Nef induced Rac1 activation also led to dsDNA breaks in endothelial colony forming cells (ECFC), thereby resulting in ECFC premature senescence and eNOS downregulation. These Rac1 dependent activities were characterized by NOX2-mediated ROS production. Statin treatment equally inhibited Rac1 inhibition in preventing or reversing all HIV-Nef-induction abnormalities assessed. This was likely due to the ability of statins to block Rac1 prenylation as geranylgeranyl transferase inhibitors were effective in inhibiting HIV-Nef-induced ROS formation. Finally, transgenic expression of HIV-Nef in endothelial cells in a murine model impaired endothelium-mediated aortic ring dilation, which was then reversed by 3-week treatment with 5mg/kg atorvastatin. Conclusion These studies establish a mechanism by which HIV-Nef persistence despite ART could contribute to ongoing HIV related vascular dysfunction which may then be ameliorated by statin treatment.