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Endothelin-A receptor antagonism attenuates carcinoma-induced pain through opioids in mice

Phuong N Quang1, Brian L Schmidt

  • 1UCSF School of Dentistry, Oral and Craniofacial Sciences Graduate Program, University of California, San Francisco, San Francisco, CA 94143-0440, USA.

The Journal of Pain
|January 15, 2010
PubMed
Abstract

Insights

Endothelin A (ET-A) receptor antagonism reduces cancer pain by increasing natural opioid release. This mechanism offers a new approach for managing carcinoma-induced pain, potentially serving as an alternative to morphine.

Area of Science:

  • Pharmacology
  • Oncology
  • Neuroscience

Background:

  • Endothelin A (ET-A) receptor antagonism has shown promise in alleviating cancer pain.
  • The precise mechanism underlying ET-A receptor-mediated antinociception, particularly its interaction with endogenous opioid systems, requires further elucidation.

Purpose of the Study:

  • To investigate the mechanism of ET-A receptor-mediated antinociception in a cancer pain model.
  • To evaluate the role of endogenous opioid analgesia in ET-A receptor antagonist efficacy.

Main Methods:

  • Squamous cell carcinoma (SCC) cells were cultured and treated with an ET-A receptor antagonist (BQ-123) to assess beta-endorphin and leu-enkephalin production.
  • Tumors were induced in mice via SCC cell inoculation, and pain was quantified by measuring withdrawal thresholds.
  • Antinociceptive effects of ET-A receptor antagonism were assessed following administration of opioid receptor antagonists (naloxone methiodide, CTOP, naltrindole, nor-BNI).

Main Results:

  • ET-A receptor antagonist treatment significantly increased beta-endorphin and leu-enkephalin secretion in SCC cells.
  • SCC inoculation induced significant pain in mice, characterized by reduced withdrawal thresholds.
  • Selective blockade of mu- and delta-opioid receptors, but not kappa-opioid receptors, reversed the antinociceptive effects of ET-A receptor antagonism.

Conclusions:

  • Peripheral ET-A receptor antagonism attenuates carcinoma pain by modulating the release of endogenous opioids.
  • This interaction with opioid receptors within the cancer microenvironment presents a novel therapeutic mechanism.
  • Understanding innate opioid analgesia in ET-A receptor-mediated antinociception may lead to alternative cancer pain management strategies beyond morphine.

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