1
|
Ranjit A, Khajehpour S, Aghazadeh-Habashi A. Update on Angiotensin II Subtype 2 Receptor: Focus on Peptide and Nonpeptide Agonists. Mol Pharmacol 2021; 99:469-487. [PMID: 33795351 DOI: 10.1124/molpharm.121.000236] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 03/12/2021] [Indexed: 11/22/2022] Open
Abstract
Angiotensin II (Ang II) is the most dominant effector component of the renin-angiotensin system (RAS) that generally acts through binding to two main classes of G protein-coupled receptors, namely Ang II subtype 1 receptor (AT1R) and angiotensin II subtype 2 receptor (AT2R). Despite some controversial reports, the activation of AT2R generally antagonizes the effects of Ang II binding on AT1R. Studying AT2R signaling, function, and its specific ligands in cell culture or animal studies has confirmed its beneficial effects throughout the body. These characteristics classify AT2R as part of the protective arm of the RAS that, along with functions of Ang (1-7) through Mas receptor signaling, modulates the harmful effects of Ang II on AT1R in the activated classic arm of the RAS. Although Ang II is the primary ligand for AT2R, we have summarized other natural or synthetic peptide and nonpeptide agonists with critical evaluation of their structure, mechanism of action, and biologic activity. SIGNIFICANCE STATEMENT: AT2R is one of the main components of the RAS and has a significant prospective for mediating the beneficial action of the RAS through its protective arm on the body's homeostasis. Targeting AT2R offers substantial clinical application possibilities for modulating various pathological conditions. This review provided concise information regarding the AT2R peptide and nonpeptide agonists and their potential clinical applications for various diseases.
Collapse
Affiliation(s)
- Arina Ranjit
- College of Pharmacy, Idaho State University, Pocatello, Idaho, USA
| | - Sana Khajehpour
- College of Pharmacy, Idaho State University, Pocatello, Idaho, USA
| | | |
Collapse
|
2
|
Manicam C, Ginter N, Li H, Xia N, Goloborodko E, Zadeh JK, Musayeva A, Pfeiffer N, Gericke A. Compensatory Vasodilator Mechanisms in the Ophthalmic Artery of Endothelial Nitric Oxide Synthase Gene Knockout Mice. Sci Rep 2017; 7:7111. [PMID: 28769073 PMCID: PMC5541003 DOI: 10.1038/s41598-017-07768-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 06/29/2017] [Indexed: 01/02/2023] Open
Abstract
Nitric oxide (NO) generated by endothelial nitric oxide synthase (eNOS) plays an important role in the maintenance of ocular vascular homeostasis. Therefore, perturbations in vascular NO synthesis have been implicated in the pathogenesis of several ocular diseases. We recently reported that eNOS contributes significantly to vasodilation of the mouse ophthalmic artery. Interestingly, dilatory responses were also retained in eNOS gene-deficient mice (eNOS-/-), indicating inherent endothelial adaptive mechanism(s) that act as back-up systems in chronic absence of eNOS to preserve vasorelaxation. Thus, this study endeavoured to identify the compensatory mechanism(s) in the ophthalmic artery of eNOS-/- mice employing isolated arterial segments and pharmacological inhibitors in vitro. Endothelium removal virtually abolished acetylcholine (ACh)-induced vasodilation, suggesting an obligatory involvement of the endothelium in cholinergic control of vascular tone. However, non-NOS and non-cyclooxygenase components compensate for eNOS deficiency via endothelium-derived hyperpolarizing factors (EDHFs). Notably, arachidonic acid-derived metabolites of the 12-lipoxygenase pathway were key mediators in activating the inwardly rectifying potassium channels to compensate for chronic lack of eNOS. Conclusively, endothelium-dependent cholinergic responses of the ophthalmic artery in the eNOS-/- mice are largely preserved and, this vascular bed has the ability to compensate for the loss of normal vasodilator responses solely via EDHFs.
Collapse
Affiliation(s)
- Caroline Manicam
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany.
| | - Natalja Ginter
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Huige Li
- Institute of Pharmacology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Ning Xia
- Institute of Pharmacology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Evgeny Goloborodko
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Jenia Kouchek Zadeh
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Aytan Musayeva
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Norbert Pfeiffer
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Adrian Gericke
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| |
Collapse
|
3
|
Abstract
Hypertension affects over 25 % of the population with the incidence continuing to rise, due in part to the growing obesity epidemic. Chronic elevations in sympathetic nerve activity (SNA) are a hallmark of the disease and contribute to elevations in blood pressure through influences on the vasculature, kidney, and heart (i.e., neurogenic hypertension). In this regard, a number of central nervous system mechanisms and neural pathways have emerged as crucial in chronically elevating SNA. However, it is important to consider that "sympathetic signatures" are present, with differential increases in SNA to regional organs that are dependent upon the disease progression. Here, we discuss recent findings on the central nervous system mechanisms and autonomic regulatory networks involved in neurogenic hypertension, in both non-obesity- and obesity-associated hypertension, with an emphasis on angiotensin-II, salt, oxidative and endoplasmic reticulum stress, inflammation, and the adipokine leptin.
Collapse
|
4
|
Abstract
The renin-angiotensin system is an enzymatic cascade by which angiotensinogen is cleaved by renin and then by angiotensin-converting enzyme to produce angiotensin II (Ang II) and subsequently other angiotensins. Biochemical and neurophysiological studies have documented the presence of the reninangiotensin system and specific Ang II receptors in the brain. Also, circulating Ang II can exert some of its actions, such as blood pressure control and body fluid homeostasis, through stimulation of Ang II receptors in the circumventricular organs that lack a normal blood-brain barrier. In addition to some of the post-synaptic effects of Ang II, recent studies have revealed that Ang II regulates synaptic transmission in several brain regions, especially the nucleus of the solitary tract, hypothalamic paraventricular nucleus, and hippocampus. This review summarizes emerging new evidence on the effect of brain Ang II on glutamatergic and GABAergic synaptic transmission. This previously unrecognized presynaptic action of Ang II is important for the control of neuronal excitability and many physiological functions including autonomic control, hormone secretion, and memory. Future research on the role of brain-derived Ang II and its receptors in synaptic transmission will further enhance our understanding of the cellular mechanisms of Ang II and the relationship between the renin-angiotensin system and brain functions.
Collapse
Affiliation(s)
- Hui-Lin Pan
- Department of Anesthesiology, Pennsylvania State University College of Medicine, Hershey 17033-0850, USA.
| |
Collapse
|
5
|
Karnik SS, Unal H, Kemp JR, Tirupula KC, Eguchi S, Vanderheyden PML, Thomas WG. International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]. Pharmacol Rev 2015; 67:754-819. [PMID: 26315714 PMCID: PMC4630565 DOI: 10.1124/pr.114.010454] [Citation(s) in RCA: 215] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.
Collapse
Affiliation(s)
- Sadashiva S Karnik
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Hamiyet Unal
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Jacqueline R Kemp
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Kalyan C Tirupula
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Satoru Eguchi
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Patrick M L Vanderheyden
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| | - Walter G Thomas
- Department of Molecular Cardiology, Lerner Research Institute of Cleveland Clinic, Cleveland, Ohio (S.S.K., H.U., J.R.K., K.C.T.); Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania (S.E.); Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium (P.M.L.V.); and Department of General Physiology, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia (W.G.T.)
| |
Collapse
|
6
|
Gong WK, Lü J, Wang F, Wang B, Wang MY, Huang HP. Effects of angiotensin type 2 receptor on secretion of the locus coeruleus in stress-induced hypertension rats. Brain Res Bull 2015; 111:62-8. [PMID: 25562714 DOI: 10.1016/j.brainresbull.2014.12.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/10/2014] [Accepted: 12/24/2014] [Indexed: 02/03/2023]
Abstract
Locus coeruleus (LC) has noradrenergic nerve terminals projecting to hypothalamus that modulating cardiovascular activity. To study the dynamic characteristics of norepinephrine (NE) release in hypothalamus followed by electrical stimulation in the locus coeruleus in the stress-induced hypertension (SIH) rats, we established the hypertension model rats by stimulations combining noise and foot-shock stress. After the end of modeling, NE release in the hypothalamus by electrical stimulation in LC was studied and NE signal was recorded by carbon fiber electrode. The peak value, the time to peak and half-life period of NE signal in both group rats were analyzed. Furthermore, to clarify the role of angiotensin II type 2 receptors (AT2) in norepinephrine (NE) release and the blood pressure of rat model of stress-induced hypertension, we intraperitoneally administered the AT2 receptor antagonist PD123319 (AT2 receptor antagonist, 0.3mg/kg, i.p.) and intracerebroventricularly injection of CGP42112 (AT2 receptor agonist, 6μg/5μl, i.c.v.) to adult male rats. We found the peak value of NE signal in the hypothalamus followed by electrical stimulation in the LC in SIH rats were higher than that in controls (P<0.01). Intraperitoneal injection of PD123319 (AT2 receptor antagonist) potentiated electrical stimulation in the LC induced NE release in the hypothalamus in SIH rats and elevated blood pressure (P<0.05), whereas intracerebroventricular injection of CGP42112 (AT2 receptor agonist) inhibited the NE release and reduced the heart rate (P<0.05). These results suggest that combining noise and foot-shock stresses increased the blood pressure and the secretion of NE in the hypothalamus followed by electrical stimulation in the LC in rats. AT2 receptors can inhibit the secretion of NE from the LC to the hypothalamus. The attenuation of presynaptic action of AT2 receptor may play a role in the pathophysiological mechanism of SIH in rats.
Collapse
Affiliation(s)
- Wan-kun Gong
- Department of Physiology and Neurobiology, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Jun Lü
- Department of Biochemistry, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Feng Wang
- Department of Forensic Medicine, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Bin Wang
- Department of Physiology and Neurobiology, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Meng-ya Wang
- Department of Physiology and Neurobiology, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Hong-ping Huang
- Department of Physiology and Neurobiology, Wannan Medical College, Wuhu, Anhui 241002, China.
| |
Collapse
|
7
|
Direct angiotensin AT2 receptor stimulation using a novel AT2 receptor agonist, compound 21, evokes neuroprotection in conscious hypertensive rats. PLoS One 2014; 9:e95762. [PMID: 24752645 PMCID: PMC3994132 DOI: 10.1371/journal.pone.0095762] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 03/29/2014] [Indexed: 01/10/2023] Open
Abstract
Background In this study, the neuroprotective effect of a novel nonpeptide AT2R agonist, C21, was examined in a conscious model of stroke to verify a class effect of AT2R agonists as neuroprotective agents. Methods and Results Spontaneously hypertensive rats (SHR) were pre-treated for 5 days prior to stroke with C21 alone or in combination with the AT2R antagonist PD123319. In a separate series of experiments C21 was administered in a series of 4 doses commencing 6 hours after stroke. A focal reperfusion model of ischemia was induced in conscious SHR by administering endothelin-1 to the middle cerebral artery (MCA). Motor coordination was assessed at 1 and 3 days after stroke and post mortem analyses of infarct volumes, microglia activation and neuronal survival were performed at 72 hours post MCA occlusion. When given prior to stroke, C21 dose dependently decreased infarct volume, which is consistent with the behavioural findings illustrating an improvement in motor deficit. During the pre-treatment protocol C21 was shown to enhance microglia activation, which are likely to be evoking protection by releasing brain derived neurotrophic factor. When drug administration was delayed until 6 hours after stroke, C21 still reduced brain injury. Conclusion These results indicate that centrally administered C21 confers neuroprotection against stroke damage. This benefit is likely to involve various mechanisms, including microglial activation of endogenous repair and enhanced cerebroperfusion. Thus, we have confirmed the neuroprotective effect of AT2R stimulation using a nonpeptide compound which highlights the clinical potential of the AT2R agonists for future development.
Collapse
|
8
|
Gao L, Zucker IH. AT2 receptor signaling and sympathetic regulation. Curr Opin Pharmacol 2010; 11:124-30. [PMID: 21159555 DOI: 10.1016/j.coph.2010.11.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 11/19/2010] [Accepted: 11/22/2010] [Indexed: 11/28/2022]
Abstract
There is a growing consensus that the balance between Angiotensin Type 1 (AT1R) and Angiotensin Type 2 (AT2R) signaling in many tissues may determine the magnitude and, in some cases the direction, of the biological response. Sympatho-excitation in cardiovascular diseases is mediated by a variety of factors and is, in part, dependent on Angiotensin II signaling in the central nervous system. Recent data have provided evidence that the AT2R can modulate sympatho-excitation in animals with hypertension and heart failure. The evidence for this concept is reviewed and a model is put forward to support the rationale that therapeutic targeting of the central AT2R may be beneficial in the setting of chronic heart failure.
Collapse
Affiliation(s)
- Lie Gao
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA
| | | |
Collapse
|
9
|
Zhu M, Cho YK, Li CS. Activation of delta-opioid receptors reduces excitatory input to putative gustatory cells within the nucleus of the solitary tract. J Neurophysiol 2008; 101:258-68. [PMID: 19019978 DOI: 10.1152/jn.90648.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The rostral nucleus of the solitary tract (NST) is the first central relay in the gustatory pathway and plays a key role in processing and modulation of gustatory information. Here, we investigated the effects of opioid receptor agonists and antagonists on synaptic responses of the gustatory parabrachial nuclei (PbN)-projecting neurons in the rostral NST to electrical stimulation of the solitary tract (ST) using whole cell recordings in the hamster brain stem slices. ST-evoked excitatory postsynaptic currents (EPSCs) were significantly reduced by met-enkephalin (MetE) in a concentration-dependent fashion and this effect was eliminated by naltrexone hydrochloride, a nonselective opioid receptor antagonist. Bath application of naltrindole hydrochloride, a selective delta-opioid receptor antagonist, eliminated MetE-induced reduction of EPSCs, whereas CTOP, a selective mu-opioid receptor antagonist had no effect, indicating that delta-opioid receptors are involved in the reduction of ST-evoked EPSCs induced by MetE. SNC80, a selective delta-opioid receptor agonist, mimicked the effect of MetE. The SNC80-induced reduction of ST-evoked EPSCs was eliminated by 7-benzylidenenaltrexone, a selective delta1-opioid receptor antagonist but not by naltriben mesylate, a selective delta2-opioid receptor antagonist, indicating that delta1-opioid receptors mediate the reduction of ST-evoked EPSCs induced by SNC80. Single-cell reverse transcriptase-polymerase chain reaction analysis revealed the presence of delta1-opioid receptor mRNA in cells that responded to SNC80 with a reduction in ST-evoked EPSCs. Moreover, Western blot analysis demonstrated the presence of 40-kDa delta-opioid receptor proteins in the rostral NST tissue. These results suggest that postsynaptic delta1-opioid receptors are involved in opioid-induced reduction of ST-evoked EPSCs of PbN-projecting rostral NST cells.
Collapse
Affiliation(s)
- Mingyan Zhu
- Department of Anatomy, Southern Illinois University School of Medicine, Life Science III Room 2073, 1135 Lincoln Dr., Carbondale, IL 62901, USA
| | | | | |
Collapse
|
10
|
Gao L, Wang WZ, Wang W, Zucker IH. Imbalance of angiotensin type 1 receptor and angiotensin II type 2 receptor in the rostral ventrolateral medulla: potential mechanism for sympathetic overactivity in heart failure. Hypertension 2008; 52:708-14. [PMID: 18768398 DOI: 10.1161/hypertensionaha.108.116228] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Upregulation of angiotensin II type 1 receptors (AT(1)R) in the rostral ventrolateral medulla (RVLM) contributes to the sympathoexcitation in the chronic heart failure (CHF). However, the role of angiotensin II type 2 receptor (AT(2)R) is not clear. In this study, we measured AT(1)R and AT(2)R protein expression in the RVLM and determined their effects on renal sympathetic nerve activity, blood pressure, and heart rate in anesthetized sham and CHF rats. We found that (1) although AT(1)R expression in the RVLM was upregulated, the AT(2)R was significantly downregulated (CHF: 0.06+/-0.02 versus sham: 0.15+/-0.02, P<0.05); (2) simultaneously stimulating RVLM AT(1)R and AT(2)R by angiotensin II evoked sympathoexcitation, hypertension, and tachycardia in both sham and CHF rats with greater responses in CHF; (3) stimulating RVLM AT1R with angiotensin II plus the specific AT(2)R antagonist PD123319 induced a larger sympathoexcitatory response than simultaneously stimulating AT(1)R and AT(2)R in sham rats, but not in CHF; (4) activating RVLM AT(2)R with CGP42112 induced a sympathoinhibition, hypotension, and bradycardia only in sham rats (renal sympathetic nerve activity: 36.4+/-5.1% of baseline versus 102+/-3.9% of baseline in artificial cerebrospinal fluid, P<0.05); (5) pretreatment with 5,8,11,14-eicosatetraynoic acid, a general inhibitor of arachidonic acid metabolism, into the RVLM attenuates the CGP42112-induced sympathoinhibition. These results suggest that AT(2)R in the RVLM exhibits an inhibitory effect on sympathetic outflow, which is, at least partially, mediated by an arachidonic acid metabolic pathway. These data implicate a downregulation in the AT(2)R as a contributory factor in the sympathoexcitation in CHF.
Collapse
Affiliation(s)
- Lie Gao
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA.
| | | | | | | |
Collapse
|
11
|
Matsuura T, Harrison RA, Westwell AD, Nakamura H, Martynyuk AE, Sumners C. Basal and angiotensin II-inhibited neuronal delayed-rectifier K+ current are regulated by thioredoxin. Am J Physiol Cell Physiol 2007; 293:C211-7. [PMID: 17360810 DOI: 10.1152/ajpcell.00615.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In previous studies, we determined that macrophage migration inhibitory factor (MIF), acting intracellularly via its intrinsic thiol-protein oxidoreductase (TPOR) activity, stimulates basal neuronal delayed-rectifier K+ current ( IKv) and inhibits basal and angiotensin (ANG) II-induced increases in neuronal activity. These findings are the basis for our hypothesis that MIF is a negative regulator of ANG II actions in neurons. MIF has recently been recategorized as a member of the thioredoxin (Trx) superfamily of small proteins. In the present study we have examined whether Trx influences basal and ANG II-modulated IKv in an effort to determine whether the Trx superfamily can exert a general regulatory influence over neuronal activity and the actions of ANG II. Intracellular application of Trx (0.8–80 nM) into rat hypothalamic/brain stem neurons in culture increased neuronal IKv, as measured by voltage-clamp recordings. This effect of Trx was abolished in the presence of the TPOR inhibitor PMX 464 (800 nM). Furthermore, the mutant protein recombinant human C32S/C35S-Trx, which lacks TPOR activity, failed to alter neuronal IKv. Trx applied at a concentration (0.08 nM) that does not alter basal IKv abolished the inhibition of neuronal IKv produced by ANG II (100 nM). Given our observation that ANG II increases Trx levels in neuronal cultures, it is possible that Trx (like MIF) has a negative regulatory role over basal and ANG II-stimulated neuronal activity via modulation of IKv. Moreover, these data suggest that TPOR may be a general mechanism for negatively regulating neuronal activity.
Collapse
Affiliation(s)
- Tomokazu Matsuura
- Dept. of Physiology and Functional Genomics, College of Medicine, University of Florida, Box 100274, 1600 SW Archer Rd., Gainesville, FL 32610-0274, USA
| | | | | | | | | | | |
Collapse
|
12
|
Chen Q, Pan HL. Signaling mechanisms of angiotensin II-induced attenuation of GABAergic input to hypothalamic presympathetic neurons. J Neurophysiol 2007; 97:3279-87. [PMID: 17287434 DOI: 10.1152/jn.01329.2006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) is an important site for the regulation of sympathetic outflow. Angiotensin II (Ang II) can activate AT(1) receptors to stimulate PVN presympathetic neurons through inhibition of GABAergic input. However, little is known about the downstream pathway involved in this presynaptic action of Ang II in the PVN. In this study, using whole cell recording from retrogradely labeled PVN neurons in rat brain slices, we determined the signaling mechanisms responsible for the effect of Ang II on synaptic GABA release to spinally projecting PVN neurons. Bath application of Ang II reproducibly decreased the frequency of GABAergic miniature postsynaptic inhibitory currents (mIPSCs) in fluorescence-labeled PVN neurons. Ang II failed to change the frequency of mIPSCs in labeled PVN neurons treated with pertussis toxin. However, Ang II-induced inhibition of mIPSCs persisted in the presence of either CdCl(2), a voltage-gated Ca(2+) channel blocker, or 4-aminopyridine, a blocker of voltage-gated K(+) channels. Interestingly, inhibition of superoxide with superoxide dismutase or Mn(III) tetrakis (4-benzoic acid) prophyrin completely blocked Ang II-induced decrease in mIPSCs. By contrast, inhibition of hydroxyl radical formation with the ion chelator deferoxamine did not significantly alter the effect of Ang II. These findings suggest that the presynaptic action of Ang II on synaptic GABA release in the PVN is mediated by the pertussis toxin-sensitive G(i/o) proteins but not by voltage-gated Ca(2+) and K(+) channels. Ang II attenuates GABAergic input to PVN presympathetic neurons through reactive oxygen species, especially superoxide anions.
Collapse
Affiliation(s)
- Qian Chen
- Department of Anesthesiology and Pain Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | | |
Collapse
|
13
|
Carter CJ. Multiple genes and factors associated with bipolar disorder converge on growth factor and stress activated kinase pathways controlling translation initiation: implications for oligodendrocyte viability. Neurochem Int 2007; 50:461-90. [PMID: 17239488 DOI: 10.1016/j.neuint.2006.11.009] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Accepted: 11/27/2006] [Indexed: 02/06/2023]
Abstract
Famine and viral infection, as well as interferon therapy have been reported to increase the risk of developing bipolar disorder. In addition, almost 100 polymorphic genes have been associated with this disease. Several form most of the components of a phosphatidyl-inositol signalling/AKT1 survival pathway (PIK3C3, PIP5K2A, PLCG1, SYNJ1, IMPA2, AKT1, GSK3B, TCF4) which is activated by growth factors (BDNF, NRG1) and also by NMDA receptors (GRIN1, GRIN2A, GRIN2B). Various other protein products of genes associated with bipolar disorder either bind to or are affected by phosphatidyl-inositol phosphate products of this pathway (ADBRK2, HIP1R, KCNQ2, RGS4, WFS1), are associated with its constituent elements (BCR, DUSP6, FAT, GNAZ) or are downstream targets of this signalling cascade (DPYSL2, DRD3, GAD1, G6PD, GCH1, KCNQ2, NOS3, SLC6A3, SLC6A4, SST, TH, TIMELESS). A further pathway relates to endoplasmic reticulum-stress (HSPA5, XBP1), caused by problems in protein glycosylation (ALG9), growth factor receptor sorting (PIK3C3, HIP1R, SYBL1), or aberrant calcium homoeostasis (WFS1). Key processes relating to these pathways appear to be under circadian control (ARNTL, CLOCK, PER3, TIMELESS). DISC1 can also be linked to many of these pathways. The growth factor pathway promotes protein synthesis, while the endoplasmic reticulum stress pathway, and other stress pathways activated by viruses and cytokines (IL1B, TNF, Interferons), oxidative stress or starvation, all factors associated with bipolar disorder risk, shuts down protein synthesis via control of the EIF2 alpha and beta translation initiation complex. For unknown reasons, oligodendrocytes appear to be particularly prone to defects in the translation initiation complex (EIF2B) and the convergence of these environmental and genomic signalling pathways on this area might well explain their vulnerability in bipolar disorder.
Collapse
|
14
|
Montiel-Herrera M, Miledi R, García-Colunga J. Membrane currents elicited by angiotensin II in astrocytes from the rat corpus callosum. Glia 2006; 53:366-71. [PMID: 16288466 DOI: 10.1002/glia.20290] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The corpus callosum (CC) is the main white matter tract in the brain. It consists primarily of axons and glial cells. In the present work, membrane currents generated by angiotensin II (Ang II) in cultured astrocytes from the CC of newborn and 3-week-old rats were studied using the whole-cell voltage-clamp technique. After 4 days of culture, approximately 90% of cells were positive to glial fibrillary acidic protein (GFAP), indicating their astrocyte lineage. Ang II elicited inward currents in approximately 20% of cells and outward currents in approximately 4% of cells from the CC for newborn or 3-week-old rats. The main effect of Ang II on astrocytes from the newborn rat CC was a reduction of membrane conductance, by blocking of delayed rectifier K(+) currents in 96% of cells. However, no common action of Ang II was observed in cells from 3-week-old rat CC because the responses were quite variable, suggesting the participation of other ion currents. The partial agonist of AT(2) receptors, CGP-42112A, exerted effects on Ang II responses, whereas the AT(1) antagonist ZD7155 did not, suggesting that Ang II responses in CC astrocytes are predominantly mediated by activation of AT(2) receptors. This study is the first to show electrical responses generated by AT(2) receptors in glial cells from the rat central nervous system, and may help gain a better understanding of the functions of Ang II receptors in astrocytes from the rat CC in particular and of glial cells in general. (c) 2005 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- Marcelino Montiel-Herrera
- Instituto de Neurobiología. Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | | | | |
Collapse
|
15
|
Matsuura T, Sun C, Leng L, Kapurniotu A, Bernhagen J, Bucala R, Martynyuk AE, Sumners C. Macrophage Migration Inhibitory Factor Increases Neuronal Delayed Rectifier K+ Current. J Neurophysiol 2006; 95:1042-8. [PMID: 16267117 DOI: 10.1152/jn.00499.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Macrophage migration inhibitory factor (MIF) has widespread actions in the immune, endocrine, and nervous systems. Previously, we reported that increases in the intracellular levels of MIF depress the firing of hypothalamus/brain stem neurons in culture, including the chronotropic actions of angiotensin II. The objective of this study was to investigate the effects of MIF on delayed rectifier K+ current ( IKv), one of the component currents whose activity contributes to neuronal firing. Intracellular perfusion of MIF (80 nM) into Sprague–Dawley rat neuronal cultures caused a significant increase in IKv, as measured by patch-clamp recordings. This effect was apparent by 3 min, and was maximal after 20–30 min. IKv current density (pA/pF) increased from 31.58 ± 2.36 in controls to 41.88 ± 3.76 in MIF-treated neurons (mean ± SE; n = 9; P < 0.01). MIF that had been inactivated by boiling did not alter IKv, and MIF-neutralizing antibodies abolished the action of recombinant MIF (rMIF). The stimulatory effect of MIF on IKv current density was mimicked by intracellular application of either P1S-MIF (80 nM) or the peptide MIF-(50–65) (0.8–8 μM), both of which harbor the thiol-protein oxidoreductase (TPOR) activity of the MIF molecule. Conversely, neither C60S-MIF (80 nM) nor the MIF homologue D-dopachrome tautomerase (80 nM), both of which lack TPOR activity, altered IKv. Finally, the increase in IKv produced by rMIF was abolished by the superoxide scavenger Tiron (1 mM). These studies indicate that the neuronal action of MIF includes a stimulatory action on IKv that may be mediated by a TPOR/superoxide-scavenging mechanism.
Collapse
Affiliation(s)
- Tomokazu Matsuura
- Department of Physiology and Functional Genomics and McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0274, USA
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Sun C, Li H, Leng L, Raizada MK, Bucala R, Sumners C. Macrophage migration inhibitory factor: an intracellular inhibitor of angiotensin II-induced increases in neuronal activity. J Neurosci 2005; 24:9944-52. [PMID: 15525779 PMCID: PMC6730251 DOI: 10.1523/jneurosci.2856-04.2004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Angiotensin II (Ang II) elicits Ang II type 1 receptor (AT1-R)-mediated increases in neuronal firing within the hypothalamus and brainstem that are ultimately responsible for physiological actions such as increased blood pressure and fluid intake. Although there is a growing literature on the intracellular mechanisms that mediate the actions of Ang II via AT1-R in neurons, little is known about the mechanisms that diminish or "switch-off" the neuronal chronotropic action of Ang II. In the present study, we identified macrophage migration inhibitory factor (MIF) as an intracellular inhibitor of the actions of Ang II in neurons. The evidence is as follows. First, Ang II, acting via AT1-R, increases the intracellular levels of MIF in neurons cultured from rat hypothalamus and brainstem. Second, elevation of intracellular MIF by Ang II prevents further chronotropic actions of this peptide. Third, intracellular application of exogenous recombinant MIF abolishes the Ang II-induced chronotropic action in neurons. Finally, intracellular application of the MIF peptide fragment MIF-(50-65), which harbors the thiol oxidoreductase property of the MIF molecule, mimics the inhibitory actions of MIF on Ang II-stimulated neuronal firing. Thus, this study is the first to demonstrate the existence of an intracellular negative regulator of Ang II-induced actions in neurons and indicates that MIF may act as a physiological brake for the chronotropic effects of Ang II in rat neurons.
Collapse
Affiliation(s)
- Chengwen Sun
- Department of Physiology and Functional Genomics and McKnight Brain Institute, University of Florida, Gainesville, Florida 32610-0274, USA
| | | | | | | | | | | |
Collapse
|
17
|
Grammatopoulos TN, Ahmadi F, Jones SM, Fariss MW, Weyhenmeyer JA, Zawada WM. Angiotensin II protects cultured midbrain dopaminergic neurons against rotenone-induced cell death. Brain Res 2005; 1045:64-71. [PMID: 15910763 DOI: 10.1016/j.brainres.2005.03.038] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 03/03/2005] [Accepted: 03/15/2005] [Indexed: 12/21/2022]
Abstract
In this study, we demonstrate that angiotensin II (Ang II) protects dopamine (DA) neurons from rotenone toxicity in vitro. Primary ventral mesencephalic (VM) cultures from E15 rats were grown for 5 days and then cultured in the presence of the mitochondrial complex I inhibitor, rotenone. Acute exposure (20 h) to 20 nM rotenone reduced the number of tyrosine hydroxylase-positive (TH+) neurons by 50 +/- 6% when compared to untreated cultures. Pre-treatment of VM cultures with 100 nM Ang II decreased TH+ neuronal loss to 25 +/- 10% at the 20-nM rotenone concentration. Ang II in the presence of the angiotensin type 1 receptor (AT1R) antagonist, losartan, was even more effective in protecting DA neurons showing a loss of only 13 +/- 4% at 20 nM rotenone. Conversely, the AT2R antagonist, PD123319, abolished the protective effects of Ang II. Furthermore, both the NMDA receptor antagonist, MK801, and the antioxidant, alpha-tocopheryl succinate (vitamin E analogue), prevented rotenone-induced toxicity. Here, we show that acute exposure of VM cultures to the pesticide rotenone leads to dopaminergic neuronal cell death and that angiotensin acting through the AT2 receptor protects dopamine neurons from rotenone toxicity.
Collapse
Affiliation(s)
- Tom N Grammatopoulos
- Division of Clinical Pharmacology and Toxicology, Department of Medicine, School of Pharmacy, University of Colorado Health Sciences Center, Denver, CO 80262, USA
| | | | | | | | | | | |
Collapse
|
18
|
Li HW, Gao YX, Matsuura T, Martynyuk A, Raizada MK, Sumners C. Adenoviral-mediated neuron specific transduction of angiotensin II type 2 receptors. ACTA ACUST UNITED AC 2005; 126:213-22. [PMID: 15664669 DOI: 10.1016/j.regpep.2004.10.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Accepted: 10/05/2004] [Indexed: 10/26/2022]
Abstract
The angiotensin II (Ang II) type 2 receptor (AT2R) is localized at specific nuclei within adult rat brain. However, a lack of specific approaches for manipulating the activity of neuronal AT2R has meant that the physiological actions of these sites in the brain remain to be established. Therefore, in this study, our aim was to develop a method by which AT2R can be specifically overexpressed in neurons and in rat brain, with the ultimate goal of a producing a system where discrete increases in AT2R levels in brain nuclei could reveal (and be linked to) physiological actions. Here, we have constructed an AT2R recombinant adenoviral vector, Ad5-SYN-AT2R-IRES-EGFP, which contains the AT2R gene and an IRES-linked EGFP reporter gene, both driven by the neuron-specific synapsin I (SYN) gene promoter. This vector efficiently transduces the AT2R into neuronal cells in culture and results in the expression of high levels of AT2R. These expressed receptors are functional in terms of inhibition of Erk mitogen activated protein kinases (Erk MAPK) and stimulation of neuronal K+ current. Furthermore, microinjection of this vector into adult rat brain elicits a long lasting ( approximately 1 month) expression of AT2R within neurons. In summary, we have developed a viral vector that can be used for the efficient transduction of AT2R into neurons both in vitro and in vivo, the use of which may help to define the physiological functions of brain AT2R in adult rats.
Collapse
Affiliation(s)
- Hong-Wei Li
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, USA
| | | | | | | | | | | |
Collapse
|
19
|
Wang H, Li J, Follett PL, Zhang Y, Cotanche DA, Jensen FE, Volpe JJ, Rosenberg PA. 12-Lipoxygenase plays a key role in cell death caused by glutathione depletion and arachidonic acid in rat oligodendrocytes. Eur J Neurosci 2004; 20:2049-58. [PMID: 15450084 DOI: 10.1111/j.1460-9568.2004.03650.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oxidative injury to premyelinating oligodendrocytes (preOLs) in developing white matter has been implicated in the pathogenesis of periventricular leukomalacia, the lesion underlying most cases of cerebral palsy in premature infants. In this study, we investigated the pathways of OL death induced by intracellular glutathione (GSH) depletion. We found that the lipoxygenase (LOX) inhibitors AA-861 and BMD-122 (N-benzyl-N-hydroxy-5-phenylpentamide; BHPP), but not the cyclooxygenase (COX) inhibitor indomethacin, fully protected the cells from GSH depletion caused by cystine deprivation. Arachidonic acid (AA), the substrate for 12-LOX, potentiated the toxicity of mild cystine deprivation and at higher concentration was itself toxic. This toxicity was also blocked by 12-LOX inhibitors. Consistent with a role for 12-LOX in the cell death pathway, 12-LOX activity increased following cystine deprivation in OLs. Blocking 12-LOX with AA-861 effectively inhibited the accumulation of reactive oxygen species (ROS) induced by cystine deprivation. These data suggest that, in OLs, intracellular GSH depletion leads to activation of 12-LOX, ROS accumulation and cell death. Mature OLs were more resistant than preOLs to cystine deprivation. The difference in sensitivity was not due to a difference in 12-LOX activity but rather appeared to be related to the presence of stronger antioxidant defense mechanisms in mature OLs. These results suggest that 12-LOX activation plays a key role in oxidative stress-induced OL death.
Collapse
Affiliation(s)
- Hong Wang
- Department of Neurology, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Sun C, Du J, Raizada MK, Sumners C. Modulation of delayed rectifier potassium current by angiotensin II in CATH.a cells. Biochem Biophys Res Commun 2003; 310:710-4. [PMID: 14550259 DOI: 10.1016/j.bbrc.2003.09.069] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Angiotensin II (Ang II) modulates, via Ang II type 1 (AT(1)) receptors, the activity of brain catecholaminergic neurons. Here we utilized catecholaminergic CATH.a cells to define the effects of Ang II on delayed rectifier K(+) current (I(Kv)), one of the factors that determines changes in neuronal activation. Receptor binding analyses demonstrated the presence of AT(1) receptors in CATH.a cells. Whole cell voltage clamp experiments in these cells revealed that Ang II (100nM) produced a significant inhibition of I(Kv), that was abolished by the AT(1) receptor blocker, losartan (1 microM), or by inhibition of phospholipase C (PLC) with U73122 (10 microM). Furthermore, this action of Ang II was completely abolished by co-inhibition of protein kinase C (PKC) and calcium/calmodulin protein kinase II (CaMKII). These results demonstrate that Ang II produces an inhibition of I(Kv) in CATH.a cells, via an intracellular pathway that includes PLC, PKC, and CaMKII.
Collapse
Affiliation(s)
- Chengwen Sun
- Department of Physiology and Functional Genomics and McKnight Brain Institute, University of Florida, Gainesville 32610, USA
| | | | | | | |
Collapse
|
21
|
Redman RS, Sheehan KB, Stout RG, Rodriguez RJ, Henson JM. Thermotolerance generated by plant/fungal symbiosis. Science 2002; 298:1581. [PMID: 12446900 DOI: 10.1126/science.1072191] [Citation(s) in RCA: 385] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Two angiotensin II (Ang II)–specific receptors, AGTR1 and AGTR2, are expressed in the mammalian brain. Ang II actions on blood pressure regulation, water electrolyte balance, and hormone secretion are primarily mediated by AGTR1. The function of AGTR2 remains unclear. Here, we show that expression of the
AGTR2
gene was absent in a female patient with mental retardation (MR) who had a balanced X;7 chromosomal translocation. Additionally, 8 of 590 unrelated male patients with MR were found to have sequence changes in the
AGTR2
gene, including one frameshift and three missense mutations. These findings indicate a role for AGTR2 in brain development and cognitive function.
Collapse
Affiliation(s)
- Regina S Redman
- U.S. Geological Survey, WFRC, 6505 NE 65th Street, Seattle, WA 98115, USA
| | | | | | | | | |
Collapse
|
22
|
Abstract
Arachidonate 12-lipoxygenase introduces a molecular oxygen at carbon 12 of arachidonic acid to generate a 12-hydroperoxy derivative. The enzymes generate 12-hydroperoxy derivatives with either S- or R-configurations. There are three isoforms of 12S-lipoxygenases named after the cells where they were first identified; platelet, leukocyte and epidermis. The leukocyte-type enzyme is widely distributed among cells, but the tissue distribution varies substantially from species to species. The platelet and epidermal enzymes are present in only a relatively limited number of cell types. Although the structures and enzymatic properties of the three isoforms of 12S-lipoxygenases have been elucidated, the physiological roles of the 12S-lipoxygenases are not yet fully understood. There are important roles for the enzymes and their products in several biological systems including those involved in atherosclerosis and neurotransmission.
Collapse
Affiliation(s)
- Tanihiro Yoshimoto
- Department of Molecular Pharmacology, Kanazawa University Graduate School of Medicine, Japan.
| | | |
Collapse
|
23
|
Reddy MA, Thimmalapura PR, Lanting L, Nadler JL, Fatima S, Natarajan R. The oxidized lipid and lipoxygenase product 12(S)-hydroxyeicosatetraenoic acid induces hypertrophy and fibronectin transcription in vascular smooth muscle cells via p38 MAPK and cAMP response element-binding protein activation. Mediation of angiotensin II effects. J Biol Chem 2002; 277:9920-8. [PMID: 11786549 DOI: 10.1074/jbc.m111305200] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Evidence suggests that the arachidonic acid metabolite of 12-lipoxygenase, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), not only mediates the effects of angiotensin II (AngII), but also has direct effects on hypertrophy and matrix protein production in vascular smooth muscle cells (VSMCs). This study is aimed at identifying the signaling pathways involved in these events. Treatment of porcine VSMCs with 12(S)-HETE led to the activation of Ras and p38 MAPK. It also stimulated phosphorylation, DNA-binding activity, and transactivation of the transcription factor cAMP response element (CRE)-binding protein. In addition, 12(S)-HETE induced transcription from a fibronectin promoter containing multiple CREs. AngII also induced transactivation of CRE-binding protein and transcription from the fibronectin promoter. A specific p38 MAPK inhibitor (SB202190) as well as a dominant-negative Ras mutant (Ras-N17) blocked both 12(S)-HETE and AngII effects. In addition, inhibitors of lipoxygenase also blocked AngII effects. Both 12(S)-HETE and AngII increased cellular hypertrophy with similar potency, and this was significantly blocked by SB202190. Stable overexpression of murine leukocyte-type 12/15-lipoxygenase in VSMCs increased the levels of cell-associated 12(S)-HETE as well as basal activity of both ERK and p38 MAPKs. Furthermore, these 12-lipoxygenase-overexpressing cells displayed significantly greater cellular hypertrophy relative to mock-transfected cells. These results show for the first time that oxidized lipids such as 12(S)-HETE can induce VSMC growth and matrix gene expression and mediate growth factor effects via activation of the Ras-MAPK pathway and key target transcription factors.
Collapse
MESH Headings
- 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid/chemistry
- 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid/metabolism
- Angiotensin II/metabolism
- Animals
- Cell Nucleus/metabolism
- Cells, Cultured
- Cyclic AMP/metabolism
- Cyclic AMP Response Element-Binding Protein/metabolism
- Enzyme Activation
- Enzyme Inhibitors/pharmacology
- Fibronectins/genetics
- Fibronectins/metabolism
- Hypertrophy
- Imidazoles/pharmacology
- Immunoblotting
- Lipid Metabolism
- Lipoxygenase/metabolism
- Luciferases/metabolism
- Mice
- Mitogen-Activated Protein Kinases/metabolism
- Muscle, Smooth, Vascular/cytology
- Oxygen/metabolism
- Phosphorylation
- Promoter Regions, Genetic
- Protein Binding
- Protein Transport
- Pyridines/pharmacology
- Signal Transduction
- Swine
- Time Factors
- Transcription, Genetic
- Transfection
- p38 Mitogen-Activated Protein Kinases
- ras Proteins/metabolism
Collapse
Affiliation(s)
- Marpadga A Reddy
- Gonda Diabetes Center, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
| | | | | | | | | | | |
Collapse
|
24
|
Bushell T, Clarke C, Mathie A, Robertson B. Pharmacological characterization of a non-inactivating outward current observed in mouse cerebellar Purkinje neurones. Br J Pharmacol 2002; 135:705-12. [PMID: 11834618 PMCID: PMC1573182 DOI: 10.1038/sj.bjp.0704518] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Whole-cell patch clamp recordings were used to investigate the properties of a non-inactivating outward current observed in mouse cerebellar Purkinje neurones at a holding potential of -20 mV. Increasing the external potassium (K(+)) concentration from 3 mM to 20 mM produced a rightward shift in the observed reversal potential of approximately 30 mV or approximately 40 mV for a K(+)-or a caesium (Cs(+))-based intracellular solution respectively, indicating the outward current was a K(+) current. The outward current was partially inhibited by the K(+) channel blocker, tetraethylammonium (TEA; IC(50)=0.15 mM). Subsequently, the background or TEA-insensitive current was measured in the presence of 1 mM TEA. The background current was reversibly inhibited by barium (Ba(2+); 300 microM, 50%) and potentiated by the application of arachidonic acid (AA; 1 mM, 62%). The volatile anaesthetic, halothane (1 mM), and the neuroprotectant, riluzole (500 microM), both reversibly inhibited the background current by 54% and 36% respectively. The background current was insensitive to changes in both intracellular and extracellular acidification. The GABA(B) and mu-opioid receptor agonists, baclofen and [D-Ala(2), N-MePhe(4)-Gly-ol(5)] enkephalin (DAMGO) both reversibly potentiated the outward current by 42% and 26% respectively. In contrast, the metabotropic glutamate receptor and acetylcholine receptor agonists, (S)-3,5-dihydroxyphenylglycine (DHPG) and muscarine both reversibly inhibited the outward current by 48% and 42% respectively. These data suggest that cerebellar Purkinje neurones possess a background current which shares several properties with recently cloned two-pore K(+) channels, particularly THIK-1.
Collapse
Affiliation(s)
- Trevor Bushell
- Neuronal Excitability Group, Biochemistry Section, Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London SW7 2BW.
| | | | | | | |
Collapse
|
25
|
Zhu M, Sumners C, Gelband CH, Posner P. Chronotropic Effect of Angiotensin II via Type 2 Receptors in Rat Brain Neurons. J Neurophysiol 2001; 85:2177-83. [PMID: 11353032 DOI: 10.1152/jn.2001.85.5.2177] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously, we determined that angiotensin II (Ang II) elicits an Ang II type 2 (AT2) receptor–mediated increase of neuronal delayed rectifier K+( I KV) current in neuronal cultures from newborn rat hypothalamus and brain stem. This requires generation of lipoxygenase (LO) metabolites of arachidonic acid (AA) and activation of serine/threonine phosphatase type 2A (PP-2A). Enhancement of I KV results in a decrease in net inward current during the action potential (AP) upstroke as well as shortening of the refractory period, which may lead to alterations in neuronal firing rate. Thus, in the present study, we used whole-cell current clamp recording methods to investigate the AT2 receptor–mediated effects of Ang II on the firing rate of cultured neurons from the hypothalamus and brain stem. At room temperature, these neurons exhibited spontaneous APs with an amplitude of 77.72 ± 2.7 mV ( n = 20) and they fired at a frequency of 0.8 ± 0.1 Hz ( n = 11). Most cells had a prolonged early after-depolarization that followed an initial fully developed AP. Superfusion of Ang II (100 nM) plus losartan (LOS, 1 μM) to block Ang II type 1 receptors elicited a significant chronotropic effect that was reversed by the AT2 receptor inhibitor PD 123,319 (1 μM). LOS alone had no effect on any of the parameters measured. The chronotropic effect of Ang II was reversed by the general LO inhibitor 5,8,11,14-eicosatetraynoic acid (10 μM) or by the selective PP-2A inhibitor okadaic acid (1 nM) and was mimicked by the 12-LO metabolite of AA 12-(S)-hydroxy-(5Z, 8Z, 10E, 14Z)-eicosatetraynoic acid. These data indicate that Ang II elicits an AT2 receptor–mediated increase in neuronal firing rate, an effect that involves generation of LO metabolites of AA and activation of PP-2A.
Collapse
MESH Headings
- 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid/pharmacology
- 5,8,11,14-Eicosatetraynoic Acid/pharmacology
- Action Potentials/drug effects
- Angiotensin II/antagonists & inhibitors
- Angiotensin II/pharmacology
- Angiotensin II Type 2 Receptor Blockers
- Angiotensin Receptor Antagonists
- Animals
- Animals, Newborn
- Arachidonic Acids/metabolism
- Brain/cytology
- Cytarabine/pharmacology
- Enzyme Inhibitors/pharmacology
- Imidazoles/pharmacology
- Lipoxygenase/metabolism
- Lipoxygenase Inhibitors/pharmacology
- Losartan/pharmacology
- Nerve Tissue Proteins/drug effects
- Nerve Tissue Proteins/physiology
- Neurons/drug effects
- Neurons/physiology
- Okadaic Acid/pharmacology
- Phosphoprotein Phosphatases/antagonists & inhibitors
- Phosphoprotein Phosphatases/metabolism
- Pyridines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/drug effects
- Receptors, Angiotensin/physiology
- Signal Transduction/drug effects
- Synaptic Transmission/drug effects
- Tetrodotoxin/pharmacology
- Time Factors
Collapse
Affiliation(s)
- M Zhu
- Department of Physiology, College of Medicine and McKnight Brain Institute, University of Florida, Gainesville, Florida 32610, USA
| | | | | | | |
Collapse
|