Intravenous beta-endorphin administration fails to alter hypothalamic blood flow in rats expressing normal or reduced nitric oxide synthase activity

Matrix metalloproteinase 2 secretion in WEHI 164 fibrosarcoma cells is nitric oxide-related and modified by morphine

Matrix metalloproteinases (MMP) are ubiquitous enzymes involved in extracellular matrix remodeling, and as a consequence in a number of physiological and pathological states, including development, wound healing and cancer. A crucial feature of cancer progression and metastasis is the disruption of extracellular matrix, and spreading of proliferating cancer cells. Modulation of MMP is a main target of cancer research. Using the mouse fibrosarcoma cell line WEHI 164, producing high amounts of MMP-2, we investigated whether we could modulate its production. We report that MMP-2 is under the control of nitric oxide (NO)/nitric oxide synthase (NOS) system. In addition, we show that NOS activity is controlled by opioids in a non-opioid receptor-related manner. Finally, we provide evidence that morphine, when administrated at low, non-toxic concentrations (<10(-9) M) attenuates MMP-2 activity. We conclude that, as morphine is able to decrease metalloproteinase activity via the NO/NOS system, it may have a place in the treatment of several sarcomas including fibrosarcoma.

The role of CRF1 receptors for sympathetic nervous response to laparotomy in anesthetized rats

Corticotropin-releasing factor (CRF) is released in response to various types of stressors and mediates endocrine, autonomic, immune, and behavioral responses to stress through interaction with CRF1 and CRF2 receptors. To investigate the role of CRF1 receptors in physiological responses to surgical stress, we analyzed the effects of two different non-peptide selective CRF1 receptor antagonists (JTC-017 and CP-154,526) and a peptide non-selective CRF receptor antagonist (astressin) on laparotomy-induced sympathetic nervous responses in isoflurane-anesthetized rats. JTC-017, CP-154,526, and astressin similarly suppressed plasma ACTH elevation induced by laparotomy. JTC-017 and CP-154,526 significantly augmented plasma noradrenaline and adrenaline responses to laparotomy, while astressin showed no effect on these responses. Laparotomy-induced maximum increases in mean blood pressure and heart rate were augmented by JTC-017, but were not affected by astressin. The results suggested for the first time that there was a pathway to attenuate sympathetic nervous response to surgical stress through CRF1 receptors in the central nervous system.

Opioids are non-competitive inhibitors of nitric oxide synthase in T47D human breast cancer cells

Opioids and nitric oxide (NO) interact functionally in different systems. NO-generating agents decrease the activity of opioid agonists, prevent opioid tolerance, and are used in opioid withdrawal syndromes. There exist, however, few reports indicating a direct interaction of the two systems. T47D human breast cancer cells in culture express opioid receptors, and opioid agonists inhibit their growth, while they release high amounts of the NO-related molecules NO(2-)/NO(3-)to the culture medium. We have used this system to assay a possible direct interaction of opiergic and nitric oxide systems. Our results show that delta- or mu-acting opioid agonists do not modify the release of NO(2-)/NO(3-). In contrast, kappa-acting opioid agonists (ethylketocyclazocine, and alpha(S1)-casomorphine) decrease the release of NO(2-)/NO(3-), in a time- and dose-dependent manner. The general opioid antagonist diprenorphine (10(-6) M) produce a similar NO(2-)/NO(3-)release inhibition, indicating a possible non-opioid-receptor mediated phenomenon. In addition, ethylketocyclazocine, alpha(S1)-casomorphin and diprenorphine directly inhibit NOS activity: agonists, interact with both calcium-dependent and independent NOS-isoforms, while the antagonist diprenorphine modifies only the activity of the calcium-dependent fraction of the enzyme. Analysis of this interaction revealed that opioids modify the dimeric active form of NOS, through binding to the reductase part of the molecule, acting as non-competitive inhibitors of the enzyme. This interaction opens interesting new possibilities for tumor biology and breast cancer therapy.

Endogenous opiates: 1996

This paper is the nineteenth installment of our annual review of research concerning the opiate system. It summarizes papers published during 1996 reporting the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress, tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.