Kappa-opioid receptor agonist inhibition of HIV-1 envelope glycoprotein-mediated membrane fusion and CXCR4 expression on CD4(+) lymphocytes

Kappa-opioid receptor agonist U50448H protects against renal ischemia-reperfusion injury in rats via activating the PI3K/Akt signaling pathway

Renal ischemia-reperfusion injury (IRI) is regarded as a leading cause of acute kidney failure and renal dysfunction. Previous studies show that kappa opioid receptor (KOR) agonists can attenuate IRI in cardiomycytes and neuronal cells. In this study we explored the effects of a KOR agonist on renal IRI and the underlying mechanisms in vivo and in vitro. An IRI model was established in SD rats, which were intravenously pretreated with a KOR agonist U50448H (1 mg/kg), a KOR antagonist Nor-BNI (2 mg/kg) followed by U50448H (1 mg/kg), or the PI3K inhibitor wortmannin (1.4 mg/kg) followed by U50448H (1 mg/kg). U50448H pretreatment significantly decreased the serum levels of creatinine (Cr) and BUN, the renal tubular injury scores and the apoptotic index (AI) in IRI model rats. Furthermore, U50448H significantly increased SOD activity and NO levels, and reduced the MDA levels in the kidney tissues of IRI model rats. Moreover, U50448H significantly increased the phosphorylation of Akt, eNOS and PI3K in the kidney tissues of IRI model rats. All the beneficial effects of U50448H were blocked by Nor-BNI or wortmannin pre-administered. Similar results were observed in vitro in renal tubular epithelial NRK-52E cells subjected to a hypoxia-reoxygenation (HR) procedure. Our results demonstrate that the KOR agonist U50448H protects against renal IRI via activating the PI3K/Akt signaling pathway.

Opioids and Viral Infections: A Double-Edged Sword

Opioids and their receptors have received remarkable attention because they have the ability to alter immune function, which affects disease progression. In vitro and in vivo findings as well as observations in humans indicate that opioids and their receptors positively or negatively affect viral replication and virus-mediated pathology. The present study reviews recent insights in the role of opioids and their receptors in viral infections and discusses possible therapeutic opportunities. This review supports the emerging concept that opioids and their receptors have both favorable and unfavorable effects on viral disease, depending on the type of virus. Targeting of the opioid system is a potential option for developing effective therapies; however caution is required in relation to the beneficial functions of opioid systems.

Polymorphisms of the kappa opioid receptor and prodynorphin genes: HIV risk and HIV natural history

OBJECTIVE

Studies indicate cross-desensitization between opioid receptors (eg, kappa opioid receptor, OPRK1) and chemokine receptors (eg, CXCR4) involved in HIV infection. Whether gene variants of OPRK1 and its ligand, prodynorphin (PDYN), influence the outcome of HIV therapy was tested.

METHODS

Three study points, admission to the Women's Interagency HIV Study, initiation of highly active antiretroviral therapy (HAART), and the most recent visit, were chosen for analysis as crucial events in the clinical history of the HIV patients. Regression analyses of 17 variants of OPRK1 and 11 variants of PDYN with change of viral load (VL) and CD4 count between admission and initiation of HAART and initiation of HAART to the most recent visit to Women's Interagency HIV Study were performed in 598 HIV+ subjects, including African Americans, Hispanics, and Whites. Association with HIV status was done in 1009 subjects.

RESULTS

Before HAART, greater VL decline (improvement) in carriers of PDYN IVS3+189C>T and greater increase of CD4 count (improvement) in carriers of OPRK -72C>T were found in African Americans. Also, greater increase of CD4 count in carriers of OPRK1 IVS2+7886A>G and greater decline of CD4 count (deterioration) in carriers of OPRK1 -1205G>A were found in Whites. After HAART, greater decline of VL in carriers of OPRK1 IVS2+2225G>A and greater increase of VL in carriers of OPRK1 IVS2+10658G>T and IVS2+10963A>G were found in Whites. Also, a lesser increase of CD4 count was found in Hispanic carriers of OPRK1 IVS2+2225G>A.

CONCLUSIONS

OPRK1 and PDYN polymorphisms may alter severity of HIV infection and response to treatment.

Interactive Effects of Morphine on HIV Infection: Role in HIV-Associated Neurocognitive Disorder

HIV epidemic continues to be a severe public health problem and concern within USA and across the globe with about 33 million people infected with HIV. The frequency of drug abuse among HIV infected patients is rapidly increasing and is another major issue since injection drug users are at a greater risk of developing HIV associated neurocognitive dysfunctions compared to non-drug users infected with HIV. Brain is a major target for many of the recreational drugs and HIV. Evidences suggest that opiate drug abuse is a risk factor in HIV infection, neural dysfunction and progression to AIDS. The information available on the role of morphine as a cofactor in the neuropathogenesis of HIV is scanty. This review summarizes the results that help in understanding the role of morphine use in HIV infection and neural dysfunction. Studies show that morphine enhances HIV-1 infection by suppressing IL-8, downregulating chemokines with reciprocal upregulation of HIV coreceptors. Morphine also activates MAPK signaling and downregulates cAMP response element-binding protein (CREB). Better understanding on the role of morphine in HIV infection and mechanisms through which morphine mediates its effects may help in devising novel therapeutic strategies against HIV-1 infection in opiate using HIV-infected population.

Immunomodulatory properties of kappa opioids and synthetic cannabinoids in HIV-1 neuropathogenesis

Anti-retroviral therapy (ART) has had a tremendous impact on the clinical outcomes of HIV-1 infected individuals. While ART has produced many tangible benefits, chronic, long-term consequences of HIV infection have grown in importance. HIV-1-associated neurocognitive disorder (HAND) represents a collection of neurological syndromes that have a wide range of functional cognitive impairments. HAND remains a serious threat to AIDS patients, and there currently remains no specific therapy for the neurological manifestations of HIV-1. Based upon work in other models of neuroinflammation, kappa opioid receptors (KOR) and synthetic cannabinoids have emerged as having neuroprotective properties and the ability to dampen pro-inflammatory responses of glial cells; properties that may have a positive influence in HIV-1 neuropathogenesis. The ability of KOR ligands to inhibit HIV-1 production in human microglial cells and CD4 T lymphocytes, demonstrate neuroprotection, and dampen chemokine production in astrocytes provides encouraging data to suggest that KOR ligands may emerge as potential therapeutic agents in HIV neuropathogenesis. Based upon findings that synthetic cannabinoids inhibit HIV-1 expression in human microglia and suppress production of inflammatory mediators such as nitric oxide (NO) in human astrocytes, as well as a substantial literature demonstrating neuroprotective properties of cannabinoids in other systems, synthetic cannabinoids have also emerged as potential therapeutic agents in HIV neuropathogenesis. This review focuses on these two classes of compounds and describes the immunomodulatory and neuroprotective properties attributed to each in the context of HIV neuropathogenesis.

Salvinorin A inhibits colonic transit and neurogenic ion transport in mice by activating kappa-opioid and cannabinoid receptors

The major active ingredient of the plant Salvia divinorum, salvinorin A (SA) has been used to treat gastrointestinal (GI) symptoms. As the action of SA on the regulation of colonic function is unknown, our aim was to examine the effects of SA on mouse colonic motility and secretion in vitro and in vivo. The effects of SA on GI motility were studied using isolated preparations of colon, which were compared with preparations from stomach and ileum. Colonic epithelial ion transport was evaluated using Ussing chambers. Additionally, we studied GI motility in vivo by measuring colonic propulsion, gastric emptying, and upper GI transit. Salvinorin A inhibited contractions of the mouse colon, stomach, and ileum in vitro, prolonged colonic propulsion and slowed upper GI transit in vivo. Salvinorin A had no effect on gastric emptying in vivo. Salvinorin A reduced veratridine-, but not forskolin-induced epithelial ion transport. The effects of SA on colonic motility in vitro were mediated by kappa-opioid receptors (KORs) and cannabinoid (CB) receptors, as they were inhibited by the antagonists nor-binaltorphimine (KOR), AM 251 (CB(1) receptor) and AM 630 (CB(2) receptor). However, in the colon in vivo, the effects were largely mediated by KORs. The effects of SA on veratridine-mediated epithelial ion transport were inhibited by nor-binaltorphimine and AM 630. Salvinorin A slows colonic motility in vitro and in vivo and influences neurogenic ion transport. Due to its specific regional action, SA or its derivatives may be useful drugs in the treatment of lower GI disorders associated with increased GI transit and diarrhoea.

The chemokine CX3CL1/fractalkine interferes with the antinociceptive effect induced by opioid agonists in the periaqueductal grey of rats

We have reported that there is heterologous interaction between the mu, delta or kappa opioid receptors and the receptors for the chemokines CCL5/RANTES or CXCL12/SDF-1 in the regulation of antinociception in rats. CX3CL1/fractalkine, a chemokine that exclusively binds to CX3CR1, has been found to affect morphine analgesia and tolerance in the spinal cord. The purpose of the present study was to see if the interaction between the chemokine CX3CL1/fractalkine receptor and mu, delta or kappa opioid receptors occurs in the periaqueductal grey (PAG) of adult male S-D rats. The cold-water tail-flick (CWT) test was used to measure antinociception. The results showed that intra-PAG injection of 100 ng CX3CL1/fractalkine 30 min before administration of 400 ng DAMGO, 100 ng DPDPE or 20 microg dynorphin significantly reduced the antinociception induced by each of these peptides. These results demonstrate that activation of the CX3CL1 receptor diminishes the effect of mu, delta and kappa opioid agonists on their receptors in the PAG of rats.

Antinociceptive profile of salvinorin A, a structurally unique kappa opioid receptor agonist

Salvinorin A, is a structurally unique, non-nitrogenous, kappa opioid receptor (KOP) agonist. Given the role of KOPs in analgesic processes, we set out to determine whether salvinorin A has antinociceptive activity in thermal and chemo-nociceptive assays. The tail-flick assay was employed to investigate 1) salvinorin A's (0.5, 1.0, 2.0, and 4.0 mg/kg) dose-response and time-course (10, 20, and 30 min) effects in a thermal nociceptive assay, and 2) the ability for the KOP antagonist norBNI (10.0 mg/kg) to prevent salvinorin A antinociception. The hotplate assay was utilized as a second thermal nociceptive measure to test salvinorin A's dose-response effects. The acetic acid abdominal constriction assay was used to study salvinorin A's dose-response and time-course (over 30 min) effects in a chemo-nociceptive assay. Together, these studies revealed that salvinorin A produces a dose-dependent antinociception that peaked at 10 min post-injection but rapidly returned to baseline. Additionally, pretreatment with the KOP antagonist norbinaltorphimine (norBNI) reversed salvinorin A-induced antinociception. These findings demonstrate that salvinorin A produces a KOP mediated antinociceptive effect with a short duration of action.

Bremazocine: a kappa-opioid agonist with potent analgesic and other pharmacologic properties

Bremazocine is a kappa-opioid receptor agonist with potent analgesic and diuretic activities. As an analgesic it is three- to four-times more potent than morphine, as determined in both hot plate and tail flick tests. Bremazocine and other benzomorphan analogs were synthesized in an effort to produce opiates with greater kappa-opioid receptor selectivity and with minimal morphine-like side effects. Unlike morphine bremazocine is devoid of physical and psychological dependence liability in animal models and produces little or no respiratory depression. While bremazocine does not produce the characteristic euphoria associated with morphine and its abuse, it has been shown to induce dysphoria, a property that limits its clinical usefulness. Similarly to morphine, repeated administration of bremazocine leads to tolerance to its analgesic effect. It has been demonstrated that the marked diuretic effect of bremazocine is mediated primarily by the central nervous system. Because of its psychotomimetic side effects (disturbance in the perception of space and time, abnormal visual experience, disturbance in body image perception, de-personalization, de-realization and loss of self control) bremazocine has limited potential as a clinical analgesic. However, its possible utility for the therapy of alcohol and drug addiction warrants further consideration because of its ability to decrease ethanol and cocaine self-administration in non-human primates. In addition, the ability of bremazocine-like drugs to lower intraocular pressure and to minimize ischemic damage in animal models suggests their possible use in the therapy of glaucoma and cardiovascular disease.

Anti-HIV-1 activity of propolis in CD4(+) lymphocyte and microglial cell cultures

An urgent need for additional agents to treat human immunodeficiency virus type 1 (HIV-1) infection led us to assess the anti-HIV-1 activity of the natural product propolis in CD4(+) lymphocytes and microglial cell cultures. Propolis inhibited viral expression in a concentration-dependent manner (maximal suppression of 85 and 98% was observed at 66.6 microg/ml propolis in CD4(+) and microglial cell cultures, respectively). Similar anti-HIV-1 activity was observed with propolis samples from several geographic regions. The mechanism of propolis antiviral property in CD4(+) lymphocytes appeared to involve, in part, inhibition of viral entry. While propolis had an additive antiviral effect on the reverse transcriptase inhibitor zidovudine, it had no noticeable effect on the protease inhibitor indinavir. The results of this in vitro study support the need for clinical trials of propolis or one or more of its components in the treatment of HIV-1 infection.

[Nα-BenzylTyr,cyclo(d-Asp5,Dap8)]- dynorphin A-(1−11)NH2 Cyclized in the “Address” Domain Is a Novel κ-Opioid Receptor Antagonist

The cyclic dynorphin A analogue [N(alpha)-benzylTyr(1),cyclo(D-Asp(5),Dap(8))]dynorphin A-(1-11)NH(2) (Dap = 2,3-diaminopropionic acid) exhibits nanomolar affinity (30 nM) and high selectivity (K(i) ratio (kappa/mu/delta) = 1/194/330) for kappa-opioid receptors. This analogue antagonizes dynorphin A-(1-13)NH(2) at kappa-opioid receptors in the adenylyl cyclase assay (K(B) = 84 nM). This is the first dynorphin A-based antagonist with modifications in the C-terminal "address" domain that alter efficacy and thus represents a novel selective kappa-opioid receptor antagonist.

Studies toward the pharmacophore of salvinorin A, a potent kappa opioid receptor agonist

Salvinorin A (1), from the sage Salvia divinorum, is a potent and selective kappa opioid receptor (KOR) agonist. We screened other salvinorins and derivatives for binding affinity and functional activity at opioid receptors. Our results suggest that the methyl ester and furan ring are required for activity but that the lactone and ketone functionalities are not. Other salvinorins showed negligible binding affinity at the KOR. None of the compounds bound to mu or delta opioid receptors.

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.

Opioid therapy and immunosuppression: a review

The idea that opioids modulate the immune system is not new. By the late 19th century, Cantacuzene, used morphine to suppress cellular immunity and lower the resistance of guinea pigs to bacterial infection. While exogenous opioids mediate immunosuppression, endogenous opiates exert opposite actions. Acute and chronic opioid administration is known to have inhibitory effects on humoral and cellular immune responses including antibody production, natural killer cell activity, cytokine expression, and phagocytic activity. Opiates behave like cytokines, modulating the immune response by interaction with their receptors in the central nervous system and in the periphery. Potential mechanisms by which central opiates modulate peripheral immune functions may involve both the hypothalamic-pituitary-adrenal axis and the autonomic nervous system. The presence of opioid receptors outside the central nervous system is increasingly recognized. Those receptors have been identified not only in peripheral nerves but also in immune inflammatory cells. The immunosuppression mediated by opiates may explain the increased incidence of infection in heroin addicts. Opiates may also promote immunodeficiency virus infection by decreasing the secretion of alpha and beta chemokines (important inhibitory cytokines for the expression of HIV) and at the same time increasing the expression of chemoreceptors CCR5 and CCR3, coreceptors for the virus. The fact that peripheral immunosupression is mediated at least in part by opioid receptors located in the central nervous system and that intrathecally administered opioids do not exert the same immunosuppressive effects may have important clinical implications for those patients receiving long-term opioid therapy for malignant and nonmalignant pain.

κ-Opioid Receptor Ligands Inhibit Cocaine-Induced HIV-1 Expression in Microglial Cells

Cocaine abuse has been implicated as a cofactor in human immunodeficiency virus (HIV)-1-associated dementia (HAD). In this study, we tested the hypothesis that exposure of microglial cells, the resident macrophages of the brain, to cocaine would potentiate HIV-1 expression. Because kappa-opioid receptor (KOR) agonists have been shown to suppress neurochemical and neurobehavioral responses to cocaine and to inhibit HIV-1 expression in microglial cell cultures, we also postulated that KOR ligands would inhibit cocaine-induced potentiation of HIV-1 expression. Human microglial cells were infected with HIV-1(SF162), an R5 isolate, and viral expression was quantified by measurement of p24 antigen in culture supernatants. Treatment of microglia with the KOR agonists trans-(+/-)-3,4-dichlor-N-methyl-N-(2[1-pyrrolidnyl])benzeneacetamide methanesulfonate and 8-carboxamidocyclazocine inhibited viral expression (maximal suppression of 42 and 48%, respectively). Consistent with the hypotheses, treatment of microglia with cocaine promoted HIV-1 expression (maximal enhancement of 54%), and pretreatment of microglia with these KOR agonists as well as with the KOR-selective antagonist nor-binaltorphimine abrogated cocaine-induced potentiation of viral expression. Results of flow cytometry studies suggested that the mechanism whereby KOR ligands inhibit cocaine's stimulatory effect on viral expression involves the suppression of cocaine-induced activation of extracellular signal-regulated kinase1/2, thereby blunting cocaine-enhanced up-regulation of the HIV-1 entry chemokine coreceptor CCR5. The findings of this study suggest that in addition to its neurotoxic effects, cocaine could foster development of HAD by potentiating viral expression in the brain and that this phenomenon is inhibited by KOR ligands.

A novel and facile preparation of bremazocine enantiomers through optically pure N-norbremazocines

In order to provide ready access to multigram quantities of the optically pure bremazocines [(-)- and (+)-9,9-dimethyl-5-ethyl-2-hydroxy-2-(1-hydroxy-cyclopropylmethyl)-6,7-benzomorphan)], we have developed an improved non-chromatographic synthesis, and determined the optical purity of their N-nor precursors using a rapid and relatively simple 1H NMR method based on diastereomeric derivatization with optically pure 1-phenylethylisocyanate. This method of determining optical purity should be readily amenable to similar systems containing phenolic amino functionalities. Finally, a greatly simplified methodology for introduction of the N-(1-hydroxycyclopropylmethyl) substituent in bremazocine is described. The improved synthetic method-the overall yield was increased about 3-fold-combined with the practical methodology to determine optical purity will considerably facilitate the employment of these enantiomers as pharmacological tools for examination of the kappa-opioid receptor system, as well as their evaluation as drug abuse treatment agents. This synthesis will also enable the study of these enantiomers for other, non-classical applications (e.g., treatment agents for HIV).

Selective inactivation of CCR5 and decreased infectivity of R5 HIV-1 strains mediated by opioid-induced heterologous desensitization

The opiates are well-established immunomodulatory factors, and recent evidence suggests that mu- and delta-opioid receptor ligands alter chemokine-driven chemotactic responses through the process of heterologous desensitization. In the present report, we sought to examine the capacity of mu- and delta-opioids to modulate the function of chemokine receptors CCR5 and CXCR4, the two major human immunodeficiency virus (HIV) coreceptors. We found that the chemotactic responses to the CCR1/5 ligand CCL5/regulated on activation, normal T expressed and secreted, but not the CXCR4 ligand stromal cell-derived factor-1alpha/CXCL12 were inhibited following opioid pretreatment. Studies were performed with primary monocytes and Chinese hamster ovary cells transfected with CCR5 and the micro-opioid receptor to determine whether cross-desensitization of CCR5 was a result of receptor internalization. Using radiolabeled-binding analysis, flow cytometry, and confocal microscopy, we found that the heterologous desensitization of CCR5 was not associated with a significant degree of receptor internalization. Despite this, we found that the cross-desensitization of CCR5 by opioids was associated with a decrease in susceptibility to R5 but not X4 strains of HIV-1. Our findings are consistent with the notion that impairment of the normal signaling activity of CCR5 inhibits HIV-1 coreceptor function. These results have significant implications for our understanding of the effect of opioids on the regulation of leukocyte trafficking in inflammatory disease states and the process of coreceptor-dependent HIV-1 infection. The interference with HIV-1 uptake by heterologous desensitization of CCR5 suggests that HIV-1 interaction with this receptor is not passive but involves a signal transduction process.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Opioid-induced immunosuppression: is it centrally mediated or peripherally mediated?

Opioid compounds are commonly used pain medications. However, their administration is associated with a number of side-effects. Among them, opioid-induced immunosuppression is a significant medical problem, which is evidenced by a strong association between the use of opioids and exacerbated infections, including AIDS. Research data have demonstrated the effects of opioids to be suppressive on phagocytic, natural killer (NK), B and T cells. However, these immunosuppressive effects may be mediated by mechanisms different from those for antinociceptive actions. This article reviews possible central and peripheral mechanisms of opioid-induced immunosuppression. To the extent that peripherally mediated immunosuppressive effects play a significant role in opioid-induced immunosuppression, novel peripheral opioid antagonists may have a therapeutic role in attenuating opioid-induced immunosuppression without affecting analgesia.