1
|
Vuong NT, Jackson TNW, Wright CE. Role of Phospholipases A 2 in Vascular Relaxation and Sympatholytic Effects of Five Australian Brown Snake, Pseudonaja spp., Venoms in Rat Isolated Tissues. Front Pharmacol 2021; 12:754304. [PMID: 34744732 PMCID: PMC8566954 DOI: 10.3389/fphar.2021.754304] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
Human envenoming by Australian brown snakes (Pseudonaja spp.) may result in potentially life-threatening hypotension and subsequent cardiovascular collapse. There have been relatively few studies of the cardiovascular and sympathetic effects of Pseudonaja spp. venoms. In this study, we have examined the effects of venom from five brown snake species-P. affinis, aspidorhyncha, inframacula, nuchalis, and textilis-on cardiac inotropic and chronotropic responses, vascular tone, and sympathetic nerve-induced vascular contractions in rat isolated tissues. The role of phospholipases A2 (PLA2s) in venom-induced effects was assessed with the sPLA2 inhibitor varespladib. In rat isolated left and right atria, there were no physiologically relevant effects of Pseudonaja venoms (0.1-30 µg/ml) on left atrial force of contraction (inotropy) or right atrial rate (chronotropy). In contrast, in isolated small mesenteric arteries precontracted with a thromboxane mimetic, each of the five brown snake venoms (at 30 µg/ml) caused marked vasorelaxation (-60 to -90% of contractile tone). Pretreatment with varespladib (1 µM) significantly inhibited the vasorelaxation caused by P. aspidorhyncha, P. nuchalis, and P. textilis venoms. Electrically induced sympathetic nerve-mediated contractions of mesenteric arteries were significantly attenuated by only P. textilis, and P. affinis venoms (30 µg/ml) and these sympatholytic effects were inhibited by varespladib (1 µM). Based on their inhibition with the sPLA2 inhibitor varespladib, we conclude that PLA2 toxins in P. aspidorhyncha, P. nuchalis, and P. textilis venoms are involved in brown snake venom-induced vasorelaxation and the sympatholytic effects of P. affinis, and P. textilis venoms. Our study supports the promising potential role of varespladib as an initial (pre-referral) and/or adjunct (in combination with antivenom) therapeutic agent for brown snake envenoming.
Collapse
Affiliation(s)
- Nhi Thuc Vuong
- Cardiovascular Therapeutics Unit, Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, VIC, Australia
| | - Timothy N. W. Jackson
- Australian Venom Research Unit, Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, VIC, Australia
| | - Christine E. Wright
- Cardiovascular Therapeutics Unit, Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, VIC, Australia
| |
Collapse
|
2
|
Mazeh AC, Angus JA, Wright CE. Cannabidiol selectively inhibits the contraction of rat small resistance arteries: Possible role for CGRP and voltage-gated calcium channels. Eur J Pharmacol 2021; 891:173767. [PMID: 33275960 DOI: 10.1016/j.ejphar.2020.173767] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 11/23/2020] [Accepted: 11/26/2020] [Indexed: 02/07/2023]
Abstract
The pharmacology of cannabidiol, the non-psychoactive major component of Cannabis sativa, is of growing interest as it becomes more widely prescribed. This study aimed to examine the effects of cannabidiol on a wide range of contractile agents in rat small resistance arteries, in comparison with large arteries, and to explore its mechanism of action. The vascular actions of cannabidiol were also contrasted with effects on the contractions of bronchial, urogenital, cardiac and skeletal muscles. Isolated small or large arteries were incubated with cannabidiol (0.3-3 μM) or vehicle and concentration-contraction response curves were completed to various agents, including endothelin-1, arginine vasopressin, methoxamine, 5-HT, α-methyl 5-HT and U46619. In small arteries, the effects of cannabidiol were tested in the presence of antagonists of CB1 or CB2 receptors, calcitonin gene-related peptide (CGRP), nitric oxide synthase, cyclooxygenase, PPARγ or a combination. The role of L-type voltage-operated calcium channels was also assessed. Cannabidiol 1-3 μM significantly inhibited the contraction of small resistance arteries to all tested agents through a combination of mechanisms that include CGRP and L-type calcium channels. However, large arteries were insensitive to cannabidiol. Cannabidiol (10-100 μM) was largely without effect in bronchi, atria and hemidiaphragm, but 100 μM attenuated maximum contractions in vasa deferentia. Cannabidiol's effects in the clinical range (1-3 μM) appear to be specific to small resistance arteries. This high sensitivity of the resistance arterial circulation to cannabidiol may offer a therapeutic opportunity in peripheral vascular disease that excludes off-target sites such as the heart and non-vascular smooth muscle.
Collapse
Affiliation(s)
- Amna C Mazeh
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria, 3010, Australia.
| | - James A Angus
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria, 3010, Australia.
| | - Christine E Wright
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Victoria, 3010, Australia.
| |
Collapse
|
3
|
Young AP, Zhu J, Bagher AM, Denovan-Wright EM, Howlett SE, Kelly MEM. Endothelin B receptor dysfunction mediates elevated myogenic tone in cerebral arteries from aged male Fischer 344 rats. GeroScience 2021; 43:1447-1463. [PMID: 33403617 DOI: 10.1007/s11357-020-00309-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 12/01/2020] [Indexed: 02/08/2023] Open
Abstract
The human brain requires adequate cerebral blood flow to meet the high demand for nutrients and to clear waste products. With age, there is a chronic reduction in cerebral blood flow in small resistance arteries that can eventually limit proper brain function. The endothelin system is a key mediator in the regulation of cerebral blood flow, but the contributions of its constituent receptors in the endothelial and vascular smooth muscle layers of cerebral arteries have not been well defined in the context of aging. We isolated posterior cerebral arteries from young and aged Fischer 344 rats, as well as ETB receptor knock-out rats and mounted the vessels in plexiglass pressure myograph chambers to measure myogenic tone in response to increasing pressure and targeted pharmacological treatments. We used an ETA receptor antagonist (BQ-123), an ETB receptor antagonist (BQ-788), endothelin-1, an endothelin-1 synthesis inhibitor (phosphoramidon), and vessel denudation to dissect the roles of each receptor in aging vasculature. Aged rats exhibited a higher myogenic tone than young rats, and the tone was sensitive to the ETA antagonist, BQ-123, but insensitive to the ETB antagonist, BQ-788. By contrast, the tone in the vessels from young rats was raised by BQ-788 but unaffected by BQ-123. When the endothelial layer that is normally enriched with ETB1 receptors was removed from young vessels, myogenic tone increased. However, denudation of the endothelial layer did not influence vessels from aged animals. This indicated that endothelial ETB1 receptors were not functional in the vessels from aged rats. There was also an increase in ETA receptor expression with age, whereas ETB receptor expression remained constant between young and aged animals. These results demonstrate that in young vessels, ETB1 receptors maintain a lower myogenic tone, but in aged vessels, a loss of ETB receptor activity allows ETA receptors in vascular smooth muscle cells to raise myogenic tone. Our findings have potentially important clinical implications for treatments to improve cerebral perfusion in older adults with diseases characterized by reduced cerebral blood flow.
Collapse
Affiliation(s)
- Alexander P Young
- Department of Pharmacology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Jiequan Zhu
- Department of Pharmacology, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Amina M Bagher
- Department of Pharmacology and Toxicology, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Susan E Howlett
- Department of Pharmacology, Dalhousie University, Halifax, NS, B3H 4R2, Canada.,Department of Medicine (Geriatric Medicine), Dalhousie University, Halifax, NS, Canada
| | - Melanie E M Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, B3H 4R2, Canada. .,Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada.
| |
Collapse
|
4
|
Ozen G, Benyahia C, Amgoud Y, Patel J, Abdelazeem H, Bouhadoun A, Yung S, Li F, Mahieddine Y, Silverstein AM, Castier Y, Cazes A, Longrois D, Clapp LH, Norel X. Interaction between PGI2 and ET-1 pathways in vascular smooth muscle from Group-III pulmonary hypertension patients. Prostaglandins Other Lipid Mediat 2020; 146:106388. [DOI: 10.1016/j.prostaglandins.2019.106388] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 09/08/2019] [Accepted: 10/24/2019] [Indexed: 12/16/2022]
|
5
|
Role of endothelin-1 clearance in the haemodynamic responses to endothelin-1 in the pulmonary and hindquarter vasculature of anaesthetised rats. Eur J Pharmacol 2019; 855:124-136. [DOI: 10.1016/j.ejphar.2019.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 11/17/2022]
|
6
|
Angus JA, Hughes RJA, Wright CE. Distortion of K B estimates of endothelin-1 ET A and ET B receptor antagonists in pulmonary arteries: Possible role of an endothelin-1 clearance mechanism. Pharmacol Res Perspect 2018; 5. [PMID: 29226623 PMCID: PMC5723704 DOI: 10.1002/prp2.374] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 10/23/2017] [Indexed: 11/08/2022] Open
Abstract
Dual endothelin ETA and ETB receptor antagonists are approved therapy for pulmonary artery hypertension (PAH). We hypothesized that ETB receptor‐mediated clearance of endothelin‐1 at specific vascular sites may compromise this targeted therapy. Concentration‐response curves (CRC) to endothelin‐1 or the ETB agonist sarafotoxin S6c were constructed, with endothelin receptor antagonists, in various rat and mouse isolated arteries using wire myography or in rat isolated trachea. In rat small mesenteric arteries, bosentan displaced endothelin‐1 CRC competitively indicative of ETA receptor antagonism. In rat small pulmonary arteries, bosentan 10 μmol L−1 left‐shifted the endothelin‐1 CRC, demonstrating potentiation consistent with antagonism of an ETB receptor‐mediated endothelin‐1 clearance mechanism. Removal of endothelium or L‐NAME did not alter the EC50 or Emax of endothelin‐1 nor increase the antagonism by BQ788. In the presence of BQ788 and L‐NAME, bosentan displayed ETA receptor antagonism. In rat trachea (ETB), bosentan was a competitive ETB antagonist against endothelin‐1 or sarafotoxin S6c. Modeling showed the importance of dual receptor antagonism where the potency ratio of ETA to ETB antagonism is close to unity. In conclusion, the rat pulmonary artery is an example of a special vascular bed where the resistance to antagonism of endothelin‐1 constriction by ET dual antagonists, such as bosentan or the ETB antagonist BQ788, is possibly due to the competition of potentiation of endothelin‐1 by blockade of ETB‐mediated endothelin‐1 clearance located on smooth muscle and antagonism of ETA‐ and ETB‐mediated contraction. This conclusion may have direct application for the efficacy of endothelin‐1 antagonists for treating PAH.
Collapse
Affiliation(s)
- James A Angus
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Vic., Australia
| | - Richard J A Hughes
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Vic., Australia
| | - Christine E Wright
- Cardiovascular Therapeutics Unit, Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Vic., Australia
| |
Collapse
|
7
|
Tagawa K, Ra SG, Kumagai H, Yoshikawa T, Yoshida Y, Takekoshi K, Sakai S, Miyauchi T, Maeda S. Effects of resistance training on arterial compliance and plasma endothelin-1 levels in healthy men. Physiol Res 2018; 67:S155-S166. [PMID: 29947536 DOI: 10.33549/physiolres.933818] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Arterial compliance (AC) is an index of the elasticity of large arteries. Endothelial dysfunction has been reported to result in reduced arterial compliance, which represents increased arterial stiffness. A reduction in AC is elicited by high-intensity resistance training, however the mechanisms are obscure. Because a single bout of resistance exercise causes a transient increase in circulating plasma endothelin-1 in humans, some vasoconstrictors may play a role in the mechanisms. The present study aimed to investigate whether resistance training-induced decrease in AC is associated with changes in circulating vasoconstrictors levels in young men. Young sedentary men were assigned to control (n=5) or training (n=9) groups. The training group performed four-week high-intensity resistance training (weight training exercise; three sessions/week). We measured AC and plasma levels of endothelin-1, angiotensin II, and norepinephrine before and after intervention. Resistance training significantly decreased AC, whereas the changes in plasma levels of neither endothelin-1, nor angiotensin II, nor norepinephrine were significantly different between the control and the training groups. Moreover, we found no significant correlations between changes in circulating plasma levels (endothelin-1, angiotensin II, and norepinephrine) and in the AC. Despite of no alteration of the resting circulating plasma levels (endothelin-1, etc.), we cannot exclude a possibility that the tissue/local concentrations of vasoconstrictors (endothelin-1, etc.) around the vessels might be increased and also involved in a reduction of AC in the training group. Taken together, the present results suggest that circulating vasoconstrictors (endothelin-1, etc.) in plasma are not involved in a reduction in AC by the resistance training.
Collapse
Affiliation(s)
- K Tagawa
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, Japan, Division of Sports Medicine, Faculty of Health and Sport Science, University of Tsukuba, Japan.
| | | | | | | | | | | | | | | | | |
Collapse
|