Subchronic in vivo treatments of morphine inhibit T-cell proliferation by acting on macrophages

Analysis of T-cell proliferation and cytokine secretion in the individuals exposed to arsenic

Over six million people in nine districts of West Bengal, India are exposed to very high levels of arsenic primarily through their drinking water. More than 300,000 people showed arsenic-induced skin lesions in these districts. This is regarded as the greatest arsenic calamity in the world. Chronic arsenicosis causes varied dermatological signs ranging from pigmentation changes, hyperkeratosis to non-melanocytic cancer of skin, and also malignancies in different internal organs. Higher incidences of opportunistic infections are found in the arsenic-exposed individuals, indicating that their immune systems may be impaired somehow. We have thus investigated the effect of arsenic on T-cell proliferation and cytokine secretion in 20 individuals with arsenic-induced skin lesions and compared the results with 18 arsenic-unexposed individuals. A marked dose-dependent suppression of Concanavalin A (Con A) induced T-cell proliferation was observed in the arsenic-exposed individuals compared with the unexposed ( P < 0.001) individuals. This correlated with a significant decrease in the levels of secreted cytokines by the T cells (TNF-α, IFN-γ, IL2, IL10, IL5, and IL4) in the exposed individuals ( P < 0.001). Thus it can be inferred that arsenic exposure can cause immunosuppression in humans.

Opioids as modulators of cell death and survival--unraveling mechanisms and revealing new indications

Opioids are powerful analgesics but also drugs of abuse. Because opioid addicts are susceptible to certain infections, opioids have been suspected to suppress the immune response. This was supported by the finding that various immune-competent cells express opioid receptors and undergo apoptosis when treated with opioid alkaloids. Recent evidence suggests that opioids may also effect neuronal survival and proliferation or migrating properties of tumor cells. A multitude of signaling pathways has been suggested to be involved in these extra-analgesic effects of opioids. Growth-promoting effects were found to be mediated through Akt and Erk signaling cascades. Death-promoting effects have been ascribed to inhibition of nuclear factor-kappaB, increase of Fas expression, p53 stabilization, cytokine and chemokine release, and activation of nitric oxide synthase, p38, and c-Jun-N-terminal kinase. Some of the observed effects were inhibited with opioid receptor antagonists or pertussis toxin; others were unaffected. It is still unclear whether these properties are mediated through typical opioid receptor activation and inhibitory G-protein-signaling. The present review tries to unravel controversial findings and provides a hypothesis that may help to integrate diverse results.

Systemic Morphine Administration Suppresses Genes Involved in Antigen Presentation

Administration of opioids in both humans and animal models results in significant alterations in immune system responsiveness. Although the majority of studies have focused on phenotypic changes in immune cells after short- and long-term morphine administration, few studies have determined whether alterations in gene expression profiles accompany these effects. To address this question, rats were treated with either morphine (20 mg/kg) or saline, and changes in gene expression and function in blood leukocytes were examined. Within 2 h, morphine administration resulted in a decrease in blood leukocyte expression of the major histocompatibility complex class II (MHC II RT1.B beta) (-3.27-fold) and related molecules, including the MHC II invariant chain (-2.73-fold). Furthermore, these changes in gene expression were accompanied by a significant decrease in surface MHC II RT1.B beta protein expression, specifically on B lymphocytes. Morphine administration was also found to inhibit IL-4 induced up-regulation of MHC II RT1.B beta cell surface expression on B lymphocytes. This is the first demonstration that receptors involved in antigen presentation are modified after systemic morphine administration. We propose that the inability of B lymphocytes to up-regulate key immune proteins, such as the MHC II molecule, after exposure to antigen-induced cytokine production may account for the increase in the susceptibility to bacterial and viral infections such as HIV in both drug abusers and patients receiving morphine.

The effects of morphine on cell proliferation

There is increasing evidence that endogenous opioid peptides ("enkephalins") and other neurotransmitters have widespread, receptor-mediated roles as growth regulators in non-neuronal cells and tissues. For example, it is now believed that enkephalins produced in placental trophoblast giant cells have multiple roles in supporting embryo growth, and in maternal adaptation to pregnancy. Since plant and synthetic narcotics (e.g., morphine) bind to the same receptors, the questions immediately arise: Do narcotics also have actions as growth regulators? If so, do these actions have physiological significance in addicts? Recent work on the first of these questions is covered in this review. While the greatest volume of research has been focused on the proliferative effects of narcotics for cells of the immune system, the roles of opioid peptides and narcotics on the growth of a variety of other cells has come under study recently.

High levels of endorphin and related pathologies of veterinary concern. A review

The authors report information about endogenous opioid peptides (EOP), receptors, antagonists and their interference with pain, stress, endocrine and immune system. A relationship between EOP and calcium homeostasis, both at extracellular and intracellular level, has been observed. In vitro, beta-endorphin exerts different actions through calcium channel functionality in epithelial cells. In rat aorta and cerebral cortex: beta-endorphin or Naloxone alternatively influence oocyte maturation through the mu-receptor gene expression and intracellular calcium concentration in granulosa and cumulus cells. Calcium channel block is removed by administrating Naloxone and calcium. In vivo, Naloxone and calcium removes EOP induced apoptosis in granulosa cells; is the most safe therapy in cow's milk fever; allow to remove ovarian follicular cysts. A negative influence of opioids on immune response after vaccination was established; EOP-related metabolic problems in post-partum cows. Abnormal intestinal motility, in which a Ca++ influence is well known, can be removed by Naloxone and calcium administration. Calcium-related function and neuromodulation must be re-evaluated since high level of EOP are involved in many pathologies through their influence on calcium activity. The use of calcium salts and Naloxone offers a safe and supplementary therapeutical possibility, active in any condition of altered endogenous opioids.