Activation of PI3K/Akt signaling in rostral ventrolateral medulla impairs brain stem cardiovascular regulation that underpins circulatory depression during mevinphos intoxication.

Abstract

As the most widely used pesticides in the globe, the organophosphate compounds are understandably linked with the highest incidence of suicidal poisoning. Whereas the elicited toxicity is often associated with circulatory depression, the underlying mechanisms require further delineation. Employing the pesticide mevinphos as our experimental tool, we evaluated the hypothesis that transcriptional upregulation of nitric oxide synthase II (NOS II) by NF-κB on activation of the PI3K/Akt cascade in the rostral ventrolateral medulla (RVLM), the brain stem site that maintains blood pressure and sympathetic vasomotor tone, underpins the circulatory depressive effects of organophosphate poisons. Microinjection of mevinphos (10 nmol) bilaterally into the RVLM of anesthetized Sprague-Dawley rats induced a progressive hypotension that was accompanied sequentially by an increase (Phase I) and a decrease (Phase II) of an experimental index for the baroreflex-mediated sympathetic vasomotor tone. There were also progressive augmentations in PI3K or Akt enzyme activity and phosphorylation of p85 or Akt(Thr308) subunit in the RVLM that were causally related to an increase in NF-κB transcription activity and elevation in NOS II or peroxynitrite expression. Loss-of-function manipulations of PI3K or Akt in the RVLM significantly antagonized the reduced baroreflex-mediated sympathetic vasomotor tone and hypotension during Phase II mevinphos intoxication, and blunted the increase in NF-κB/NOS II/peroxynitrite signaling. We conclude that activation of the PI3K/Akt cascade, leading to upregulation of NF-κB/NOS II/peroxynitrite signaling in the RVLM, elicits impairment of brain stem cardiovascular regulation that underpins circulatory depression during mevinphos intoxication.

• Authors: Ching-Yi Tsai, Alice Y W Chang, Julie Y H Chan, Samuel H H Chan
• Journal: Biochemical pharmacology (Biochem Pharmacol) Vol. 88 Issue 1 Pg. 75-85 (Mar 01 2014) ISSN: 1873-2968 [Electronic] England
• PMID: 24462917 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier Inc. All rights reserved.

Chemical References

• Insecticides
• NF-kappa B
• Mevinphos
• Nitric Oxide Synthase Type II
• Nos2 protein, rat
• Phosphatidylinositol 3-Kinases
• Oncogene Protein v-akt

Topics

• Animals
• Blood Circulation (drug effects)
• Brain Stem (drug effects, enzymology)
• Cardiovascular Physiological Phenomena (drug effects)
• Hypotension (chemically induced, enzymology, physiopathology)
• Insecticides (toxicity)
• Male
• Medulla Oblongata (drug effects, enzymology)
• Mevinphos (toxicity)
• Microinjections
• NF-kappa B (biosynthesis)
• Nitric Oxide Synthase Type II (biosynthesis)
• Oncogene Protein v-akt (metabolism)
• Phosphatidylinositol 3-Kinases (metabolism)
• Rats
• Rats, Sprague-Dawley
• Signal Transduction (drug effects)
• Sympathetic Nervous System (drug effects)