scholarly journals The Angiotensin II Type 2 (AT2) Receptor Promotes Axonal Regeneration in the Optic Nerve of Adult Rats

1998 ◽  
Vol 188 (4) ◽  
pp. 661-670 ◽  
Author(s):  
Ralph Lucius ◽  
Stefan Gallinat ◽  
Philip Rosenstiel ◽  
Thomas Herdegen ◽  
Jobst Sievers ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Receptor Antagonist ◽  
Axonal Regeneration ◽  
At1 Receptor ◽  
At2 Receptor ◽  
Ang Ii ◽  
Adult Rats ◽  
Nerve Crush ◽  
Retinal Explants

The renin-angiotensin system (RAS) has been traditionally linked to blood pressure and volume regulation mediated through the angiotensin II (ANG II) type 1 (AT1) receptor. Here we report that ANG II via its ANG II type 2 (AT2) receptor promotes the axonal elongation of postnatal rat retinal explants (postnatal day 11) and dorsal root ganglia neurons in vitro, and, moreover, axonal regeneration of retinal ganglion cells after optic nerve crush in vivo. In retinal explants, ANG II (10−7–10−5 M) induced neurite elongation via its AT2 receptor, since the effects were mimicked by the AT2 receptor agonist CGP 42112 (10−5 M) and were entirely abolished by costimulation with the AT2 receptor antagonist PD 123177 (10−5 M), but not by the AT1 receptor antagonist losartan (10−5 M). To investigate whether ANG II is able to promote axonal regeneration in vivo, we performed optic nerve crush experiments in the adult rats. After ANG II treatment (0.6 nmol), an increased number of growth-associated protein (GAP)-43–positive fibers was detected and the regenerating fibers regularly crossed the lesion site (1.6 mm). Cotreatment with the AT2 receptor antagonist PD 123177 (6 nmol), but not with the AT1 receptor antagonist losartan (6 nmol), completely abolished the ANG II–induced axonal regeneration, providing for the first time direct evidence for receptor-specific neurotrophic action of ANG II in the central nervous system of adult mammals and revealing a hitherto unknown function of the RAS.

scholarly journals Blocking LINGO-1 in vivo reduces degeneration and enhances regeneration of the optic nerve

2016 ◽  
Vol 2 ◽  
pp. 205521731664170 ◽  
Author(s):  
Melissa M Gresle ◽  
Yaou Liu ◽  
Trevor J Kilpatrick ◽  
Dennis Kemper ◽  
Qi-Zhu Wu ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Axonal Regeneration ◽  
Antibody Therapy ◽  
Experimental Models ◽  
Therapeutic Effects ◽  
Axonal Loss ◽  
Nerve Crush ◽  
Acute Optic Neuritis ◽  
Injury Models

Background Two ongoing phase II clinical trials (RENEW and SYNERGY) have been developed to test the efficacy of anti-LINGO-1 antibodies in acute optic neuritis and relapsing forms of multiple sclerosis, respectively. Across a range of experimental models, LINGO-1 has been found to inhibit neuron and oligodendrocyte survival, axon regeneration, and (re)myelination. The therapeutic effects of anti-LINGO-1 antibodies on optic nerve axonal loss and regeneration have not yet been investigated. Objective In this series of studies we investigate if LINGO-1 antibodies can prevent acute inflammatory axonal loss, and promote axonal regeneration after injury in rodent optic nerves. Methods The effects of anti-LINGO-1 antibody on optic nerve axonal damage were assessed using rodent myelin oligodendrocyte glycoprotein experimental autoimmune encephalomyelitis (EAE), and its effects on axonal regeneration were assessed in optic nerve crush injury models. Results In the optic nerve, anti-LINGO-1 antibody therapy was associated with improved optic nerve parallel diffusivity measures on MRI in mice with EAE and reduced axonal loss in rat EAE. Both anti-LINGO-1 antibody therapy and the genetic deletion of LINGO-1 reduced nerve crush-induced axonal degeneration and enhanced axonal regeneration. Conclusion These data demonstrate that LINGO-1 blockade is associated with axonal protection and regeneration in the injured optic nerve.

Differential blockade of central effects of angiotensin II by AT2-receptor antagonists

1993 ◽  
Vol 265 (1) ◽  
pp. H226-H231 ◽  
Author(s):  
R. E. Widdop ◽  
S. M. Gardiner ◽  
P. A. Kemp ◽  
T. Bennett
Keyword(s):  
Angiotensin Ii ◽  
Receptor Antagonist ◽  
Rapid Onset ◽  
At2 Receptor ◽  
Ang Ii ◽  
Central Administration ◽  
Inhibitory Effects ◽  
Binding Studies ◽  
Receptor Antagonists

In conscious, chronically instrumented, male Long-Evans rats, we showed previously that central administration (intracerebroventricular) of the AT1-receptor antagonist EXP-3174 (1 microgram) caused a rapid-onset marked, but transient, blockade of the regional hemodynamic responses to intracerebroventricular angiotensin II (ANG II). In contrast, the AT2-receptor antagonist PD-123319 (80 micrograms) caused a slow-onset, but marked and persistent, antagonism of the effects of intracerebroventricular ANG II. In the present study we attempted to mimic the actions of PD-123319 by giving a supramaximal dose of EXP-3174 (10 micrograms), and we also assessed the effects of PD-123177 (80 micrograms), an AT2-receptor antagonist that differs from PD-123319 only by a dimethyl group. The higher dose of EXP-3174 did not exert prolonged antagonistic effects against responses to intracerebroventricular ANG II, and PD-123177 was without inhibitory effects in this model. The results indicate important functional differences between putative AT2-receptor antagonists, when assessed in vivo, that are not apparent from binding studies.

Erythropoietin promotes axonal regeneration after optic nerve crush in vivo by inhibition of RhoA/ROCK signaling pathway

2012 ◽  
Vol 63 (6) ◽  
pp. 1182-1190 ◽  
Author(s):  
Haibo Tan ◽  
Yisheng Zhong ◽  
Xi Shen ◽  
Yu Cheng ◽  
Qin Jiao ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Signaling Pathway ◽  
Axonal Regeneration ◽  
Optic Nerve Crush ◽  
Nerve Crush

scholarly journals Characterisation of angiotensin II receptors in isolated human subcutaneous resistance arteries

2001 ◽  
Vol 2 (1_suppl) ◽  
pp. S37-S41 ◽  
Author(s):  
Hoa Ytterberg ◽  
Lars Edvinsson
Keyword(s):  
Angiotensin Ii ◽  
Receptor Antagonist ◽  
At1 Receptor ◽  
Receptor Subtypes ◽  
At2 Receptor ◽  
Ang Ii ◽  
Resistance Arteries ◽  
Receptor Antagonists ◽  
Response Curves ◽  
At1 Receptor Antagonists

Subcutaneous arteries have been used as a model for resistance arteries, which are potentially involved in enhanced blood pressure (BP) regulation in man. Angiotensin II (Ang II) is an important regulator of tone, acting via type 1 (AT1-) and type 2 (AT2-) receptor subtypes. The aim of this study was to characterise the Ang II receptors in isolated human subcutaneous arteries, using pharmacological and molecular methods. Subcutaneous arteries were obtained from patients undergoing elective gut surgery and were carefully dissected from the abdominal wall. Cylindrical segments were mounted on two L-shaped metal prongs, one of which was connected to a force-displacement transducer for continuous recording of isometric tension. Concentration-response curves to Ang II were constructed in the presence and absence of various selective AT1-receptor antagonists, candesartan, EXP3174, irbesartan and losartan, and the AT2-receptor antagonist, PD 123319. Responses to Ang II were measured as increases in force (mN) and expressed as a percentage of the response to 60 mM of KCl. Ang II caused a concentration-dependent contraction (pEC50=9.45±0.48, Emax=120±13%). Candesartan and EXP3174 caused concentration-dependent depression of the Emax of Ang II without any major shift of pEC50. Losartan and irbesartan caused a significant, dose-dependent rightward shift of the Ang II contraction-response curve in human subcutaneous arteries. The results show that contractile responses of human subcutaneous arteries are mediated via the AT1-receptor. The AT1-receptor antagonists, candesartan and EXP3174, acted in an insurmountable manner, while losartan and irbesartan were surmountable AT1-receptor antagonists. The AT2-receptor antagonist, PD 123319, (10, 100 nM) had no effect on Ang II-induced contraction. This is supported by the positive identification of mRNA for the human AT 1-receptor by RT-PCR.

Renal actions of angiotensin-(1-7): in vivo and in vitro studies

1996 ◽  
Vol 270 (1) ◽  
pp. F141-F147 ◽  
Author(s):  
R. K. Handa ◽  
C. M. Ferrario ◽  
J. W. Strandhoy
Keyword(s):  
Blood Flow ◽  
Receptor Antagonist ◽  
Renal Blood Flow ◽  
Minor Component ◽  
At1 Receptor ◽  
In Vivo Studies ◽  
Ang Ii ◽  
Water Excretion

In vivo studies were conducted in Na-replete anesthetized male Wistar rats with denervated kidneys. Intrarenal injections of angiotensin-(1–7) [ANG-(1–7) at > 1 nmol/kg produced a shallow dose-dependent decrease in renal blood flow that was mediated by the AT1-type ANG II receptor. A constant intrarenal infusion of ANG-(1–7) at 0.1 and 1 nmol.min-1.kg-1 had minimal effects on renal blood flow and blood pressure and resulted in an elevated urinary excretion of Na and water compared with the time-control saline-infused group. To determine whether ANG-(1–7) may have a direct action on tubular epithelium to inhibit Na reabsorption, we examined the effect of ANG-(1–7) on transport-dependent O2 consumption (Qo2) in fresh suspensions of rat proximal tubules in vitro. ANG-(1–7) inhibited Qo2 in a concentration-dependent fashion with a threshold concentration of approximately 100 pM. Stimulating Na-K-adenosinetriphosphatase (Na-K-ATPase) activity with nystatin caused a leftward shift of the inhibitory concentration-response curve to ANG-(1–7). The 22% inhibition of Qo2 by 1 pM ANG-(1–7) was abolished by pretreatment with 5 mM ouabain (Na-K-ATPase inhibitor), unaltered by pretreatment with 1 microM PD-123319 (AT2 receptor antagonist), partially attenuated by 1 microM losartan (AT1 receptor antagonist), and abolished by 1 microM [Sar1, Thr8]ANG II (nonselective ANG receptor antagonist). Together these findings indicate that ANG-(1–7) has biological activity in the kidney and, at nonvasoconstrictor doses, results in increased Na and water excretion in vivo. One site of action is the proximal tubule, where ANG-(1–7) can inhibit an ouabain-sensitive Na-K-ATPase exit step in cellular Na transport. This novel inhibitory action of ANG-(1–7) appears to be mediated by an AT1 receptor (minor component) and a non-AT1, non-AT2 ANG receptor (major component).

Y-P30 confers neuroprotection after optic nerve crush in adult rats

Neuroreport ◽  
2011 ◽  
Vol 22 (11) ◽  
pp. 544-547 ◽  
Author(s):  
Tamar Macharadze ◽  
Peter Landgraf ◽  
Hans-Christian Pape ◽  
Petra Wahle ◽  
Michael R. Kreutz
Keyword(s):  
Optic Nerve ◽  
Optic Nerve Crush ◽  
Adult Rats ◽  
Nerve Crush

scholarly journals Angiotensin II Dilates Bovine Adrenal Cortical Arterioles: Role of Endothelial Nitric Oxide

Endocrinology ◽  
2005 ◽  
Vol 146 (8) ◽  
pp. 3319-3324 ◽  
Author(s):  
Kathryn M. Gauthier ◽  
David X. Zhang ◽  
Erik M. Edwards ◽  
Blythe Holmes ◽  
William B. Campbell
Keyword(s):  
Nitric Oxide ◽  
Endothelial Cell ◽  
Angiotensin Ii ◽  
Receptor Antagonist ◽  
Receptor Activation ◽  
At1 Receptor ◽  
Internal Diameter ◽  
No Production ◽  
At2 Receptor ◽  
Angiotensin Type

Abstract Adrenal steroidogenesis is modulated by humoral and neuronal factors and blood flow. Angiotensin II (AII) stimulates adrenal cortical aldosterone and cortisol production and medullary catecholamine release. However, AII regulation of adrenal vascular tone has not been characterized. We examined the effect of AII on diameters of cannulated bovine adrenal cortical arteries. Cortical arteries (average internal diameter = 230 μm) were constricted with U46619 and concentration-diameter responses to AII (10−13 to 10−8 mol/liter) were measured. In endothelium-intact arteries, AII induced dilations at low concentrations (maximum dilation = 25 ± 6% at 10−10 mol/liter) and constrictions at high concentrations (maximum constriction = 25 ± 18% at 10−8 mol/liter). AII constrictions were blocked by the angiotensin type 1 (AT1) receptor antagonist, losartan (10−6 mol/liter). AII dilations were enhanced by losartan (maximal dilation = 48 ± 8%), abolished by endothelial cell removal or N-nitro-l-arginine (L-NA, 3 × 10−5 mol/liter) and inhibited by the angiotensin type 2 (AT2) receptor antagonist, PD123319 (10−6 mol/liter, maximal dilation = 18 ± 4%). In a 4,5-diaminofluorescein diacetate nitric oxide (NO) assay of isolated cortical arteries, AII stimulated NO production, which was abolished by PD123319, L-NA, or endothelial cell removal. Western immunoblot of arterial homogenates and endothelial and zona glomerulosa cell lysates revealed 48-kD and 50-kD bands corresponding to AT1 and AT2 receptors, respectively, in all three and a 140-kD band corresponding to endothelial NO synthase in endothelial cells and arteries. Our results demonstrate that AII stimulates adrenal cortical arterial dilation through endothelial cell AT2 receptor activation and NO release and AT1 receptor-dependent constriction.

Converting enzyme inhibition modulates sympathetic neurotransmission in vivo via multiple mechanisms

1993 ◽  
Vol 264 (4) ◽  
pp. E631-E637 ◽  
Author(s):  
J. H. Schwieler ◽  
T. Kahan ◽  
J. Nussberger ◽  
P. Hjemdahl
Keyword(s):  
Receptor Antagonist ◽  
Ace Inhibition ◽  
Ang Ii ◽  
Converting Enzyme ◽  
Synthesis Inhibitor ◽  
Sympathetic Neurotransmission ◽  
Muscle Perfusion ◽  
Alpha Adrenoceptors ◽  
Hoe 140

We investigated the mechanism(s) by which angiotensin-converting enzyme (ACE) inhibition influences peripheral sympathetic neurotransmission. Thus effects of the angiotensin II (ANG II) receptor antagonist losartan (Du Pont 753) were compared with those of the ACE inhibitor benazeprilat on sympathetic neurotransmission in canine gracilis muscle in situ, with alpha-adrenoceptors either intact or irreversibly blocked by phenoxybenzamine. Furthermore, effects of the bradykinin receptor antagonist HOE 140 and the prostaglandin synthesis inhibitor diclofenac were studied after ACE inhibition. Losartan reduced the vasoconstrictor response to exogenous ANG II by 76 +/- 4% at the dose used and lowered muscle perfusion pressures. ACE inhibition by benazeprilat reduced plasma ANG-(1-8) octapeptide levels (from 8 +/- 2 to 2 +/- 1 pM), mean arterial pressure, and muscle perfusion pressures. After ACE inhibition, both HOE 140 (at a dose that reduced the vasodilatory response to exogenous bradykinin by 80 +/- 3%) and diclofenac elevated basal perfusion pressures. Losartan reduced the nerve stimulation-evoked overflow of endogenous norepinephrine (NE) (-14 +/- 6%) and vasoconstrictor responses (alpha-adrenoceptors intact). ACE inhibition increased NE overflow when alpha-adrenoceptors were intact (+12 +/- 5%) and tended to reduce it when alpha-adrenoceptors were blocked (-12 +/- 4%). During ACE inhibition, HOE 140 reduced and diclofenac enhanced the evoked NE overflow. In the absence of ACE inhibition, neither HOE 140 nor diclofenac influenced NE overflow. Our findings indicate that ACE inhibition influences sympathetic neurotransmission via reduced ANG II formation and enhanced bradykinin and prostaglandin accumulation. The effects of ANG II on sympathetic neurotransmission are, however, small under these in vivo conditions.

scholarly journals Regional distribution, developmental changes, and cellular localization of CNTF-mRNA and protein in the rat brain.

1991 ◽  
Vol 115 (2) ◽  
pp. 447-459 ◽  
Author(s):  
K A Stöckli ◽  
L E Lillien ◽  
M Näher-Noé ◽  
G Breitfeld ◽  
R A Hughes ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Olfactory Bulb ◽  
Cellular Localization ◽  
Time Course ◽  
Regional Distribution ◽  
Developmental Expression ◽  
Adult Rats

Ciliary neurotrophic factor (CNTF) is a potent survival molecule for a variety of embryonic neurons in culture. The developmental expression of CNTF occurs clearly after the time period of the physiological cell death of CNTF-responsive neurons. This, together with the sites of expression, excludes CNTF as a target-derived neuronal survival factor, at least in rodents. However, CNTF also participates in the induction of type 2 astrocyte differentiation in vitro. Here we demonstrate that the time course of the expression of CNTF-mRNA and protein in the rat optic nerve (as evaluated by quantitative Northern blot analysis and biological activity, respectively) is compatible with such a glial differentiation function of CNTF in vivo. We also show that the type 2 astrocyte-inducing activity previously demonstrated in optic nerve extract can be precipitated by an antiserum against CNTF. Immunohistochemical analysis of astrocytes in vitro and in vivo demonstrates that the expression of CNTF is confined to a subpopulation of type 1 astrocytes. The olfactory bulb of adult rats has comparably high levels of CNTF to the optic nerve, and here again, CNTF-immunoreactivity is localized in a subpopulation of astrocytes. However, the postnatal expression of CNTF in the olfactory bulb occurs later than in the optic nerve. In other brain regions both CNTF-mRNA and protein levels are much lower.

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