Heroin-induced alterations in leukocyte numbers and apoptosis in the rat spleen

Female rats express heroin-induced and -conditioned suppression of peripheral nitric oxide production in response to endotoxin challenge

Opioids and opioid-conditioned stimuli (CS) negatively alter host immunity, impairing the response to pathogens during opioid use and following drug cessation. Using male rats, our laboratory has determined that heroin or heroin-CS exposure preceding a lipopolysaccharide (LPS) challenge markedly suppresses normal induction of peripheral pro-inflammatory biomarkers. Presently, it is unknown if these heroin-induced and -conditioned effects extend to the female immune response. To begin this venture, the current study tested the direct effects of heroin and heroin-CS on LPS-induced peripheral nitric oxide (NO) production in female rats. We focused investigations on peripheral NO as it is a critical pro-inflammatory molecule necessary for pathogen resistance. In Experiment 1, male and female Lewis rats were administered 0 (Saline), 1, or 3 mg/kg heroin subcutaneously (s.c). Sixty minutes later, animals were injected with LPS (1 mg/kg, s.c.). Spleen and plasma samples were collected 6 h later to examine NO production through inducible NO synthase (iNOS) expression and nitrate/nitrite concentration, respectively. In Experiment 2, female Lewis rats underwent five, 60-minute context conditioning sessions with heroin (1 mg/kg, s.c.) or saline. On test day, CS-exposed and control (home cage) animals were injected with LPS (1 mg/kg, s.c.). Tissue was collected 6 h later to examine splenic iNOS expression and plasma nitrate/nitrite concentration. Both heroin administration alone and exposure to heroin-CS suppressed LPS-induced indices of NO production in spleen and plasma. Our results are the first to indicate that, similar to males, female rats express heroin-induced and -conditioned immunomodulation to a LPS challenge.

Expression of a heroin contextually conditioned immune effect in male rats requires CaMKIIα-expressing neurons in dorsal, but not ventral, subiculum and hippocampal CA1

The physiological and motivational effects of heroin and other abused drugs become associated with environmental (contextual) stimuli during repeated drug use. As a result, these contextual stimuli gain the ability to elicit drug-like conditioned effects. For example, after context-heroin pairings, exposure to the heroin-paired context alone produces similar effects on peripheral immune function as heroin itself. Conditioned immune effects can significantly exacerbate the adverse health consequences of heroin use. Our laboratory has shown that exposure to a heroin-paired context suppresses lipopolysaccharide (LPS)-induced splenic nitric oxide (NO) production in male rats, and this effect is mediated in part by the dorsal hippocampus (dHpc). However, specific dHpc output regions, whose efferents might mediate conditioned immune effects, have not been identified, nor has the contribution of ventral hippocampus (vHpc) been investigated. Here, we evaluated the role of CaMKIIα-expressing neurons in the dHpc and vHpc main output regions by expressing G_i-coupled designer receptors exclusively activated by designer drugs (DREADDs) under a CaMKIIα promoter in the dorsal subiculum and CA1 (dSub, dCA1) or ventral subiculum and CA1 (vSub, vCA1). After context-heroin conditioning, clozapine-N-oxide (CNO, DREADD agonist) or vehicle was administered systemically prior to heroin-paired context (or home-cage control) exposure and LPS immune challenge. Chemogenetic inhibition of CaMKIIα-expressing neurons in dHpc, but not vHpc, output regions attenuated the expression of conditioned splenic NO suppression. These results establish that the main dHpc output regions, the dSub and dCA1, are critical for this context-heroin conditioned immune effect.

Beneficial effects of Bacopa monnieri extract on opioid induced toxicity

The present study examined the hepatotoxicity and nephrotoxicity of morphine and illicit street heroin and their amelioration by a standardized methanolic extract of Bacopa monnieri (L.) (mBME) in rats. Morphine or street heroin was administered at a dose of 20 mg/kg for 14 and 21 days. mBME (40 mg/kg) or ascorbic acid (50 mg/kg) was administered two hours before morphine or street heroin. High performance liquid chromatography (HPLC) was used for the standardization of bacoside-A major components in mBME. The antioxidant potential of mBME was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Administration of morphine and street heroin resulted in marked elevation of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatinine. Histopathological changes induced by morphine and street heroin after 14 days were of reversible nature while treatment for 21 days was associated with irreversible changes. Pretreatment with mBME or ascorbic acid restored the elevation of serum ALT, AST and creatinine and protected liver and kidneys from the toxicological influence of morphine and street heroin. HPLC analysis showed that mBME contained bacoside-A major components i.e. bacoside-A₃ (37.5 μg/mg), bacopaside-II (4.62 μg/mg) and bacopasaponin-C (1.91 μg/mg). The EC₅₀ for the DPPH free radical scavenging assay revealed that mBME possessed strong antioxidant potential. These results concluded that as compared to morphine, street heroin was associated with severe biochemical and histopathological changes in the liver and kidneys. Bacopa monnieri having strong antioxidant potential may provide a beneficial herbal remedy for the efficient management of opioid related hepatotoxicity and nephrotoxicity.

Region-specific contribution of the ventral tegmental area to heroin-induced conditioned immunomodulation

Dopamine receptor stimulation is critical for heroin-conditioned immunomodulation; however, it is unclear whether the ventral tegmental area (VTA) contributes to this phenomenon. Hence, rats received repeated pairings of heroin with placement into a distinct environmental context. At test, they were re-exposed to the previously heroin-paired environment followed by systemic lipopolysaccharide treatment to induce an immune response. Bilateral GABA agonist-induced neural inactivation of the anterior, but not the posterior VTA, prior to context re-exposure inhibited the ability of the heroin-paired environment to suppress peripheral nitric oxide and tumor necrosis factor-α expression, suggesting a role for the anterior VTA in heroin-conditioned immunomodulation.

Hematological changes in opium addicted diabetic rats

Background

Chronic opioid treatment in animal models has shown to alter hematological parameters.

Objectives

The aim of this study was to evaluate the biological effects of opium on the number of peripheral blood cells and red blood cells (RBCs) indices in diabetic rats.

Materials and Methods

Peripheral blood samples were collected from diabetic, opium-addicted, diabetic opium-addicted and normal male and female rats and hematological parameters were measured.

Results

The mean number of white blood cells (WBCs) was significantly higher in diabetic opium-addict females compared to diabetic non-addict female group. In both male and female, the mean number of neutrophils was significantly higher and the mean number of lymphocytes was lower in diabetic opium-addicted rats than those observed in diabetic non-addicted group. In diabetic opium-addicted male group the mean counts of RBC significantly increased as compared with diabetic male group. However, in diabetic addicted female, the mean number of RBCs was significantly lower than diabetic non-addicted female group. In both males and females, the mean number of platelets was significantly lower in diabetic addict rats compared to diabetic non-addict group.

Conclusions

Generally, the results indicated that opium addiction has different effects on male and female rats according to the number of WBC, RBC and RBC indices. It could also be concluded that in the opium-addicts the risk of infection is enhanced due to the weakness of immune system as a result of the imbalance effect of opium on the immune cells.

Heroin activates Bim via c-Jun N-terminal kinase/c-Jun pathway to mediate neuronal apoptosis

Heroin is reported to cause spongiform leukoencephalopathy (SLE) in heroin addicts and the exact mechanism has not yet been identified. In the present study, we found that heroin could induce apoptosis of primary cultured cerebellar granule cells (CGCs) and Bim was upregulated both transcriptionally and post transcriptionally during CGCs apoptosis. Upregulated Bim translocated to mitochondria and Bax was activated under heroin treatment. Genetic knockdown of Bim using lentiviruses significantly prevented neuronal apoptosis induced by heroin. Meanwhile, c-Jun N-terminal kinase (JNK)/c-Jun pathway was activated in heroin-induced apoptosis. Bim was demonstrated as a downstream target of JNK/c-Jun pathway in this process because pharmacological inhibition of JNK reduced the levels of Bim mRNA and protein. These results indicate that Bim plays a critical role in the neurotoxic process by heroin and JNK/c-Jun pathway acts upstream of Bim in regulating heroin-induced neuronal death. This represents a detailed mechanism of heroin-induced neuronal apoptosis and may provide a new and effective strategy to treat heroin-induced addiction and SLE.

Activation of caspase-3 and c-Jun NH2-terminal kinase signaling pathways involving heroin-induced neuronal apoptosis

Heroin has been shown to cause spongiform leukoencephalopathy (SLE) in heroin addicts. In this study, we found that heroin could induce apoptosis of primary cultured cerebellar granule cells (CGC) and c-Jun N-terminal kinase (JNK) pathway is activated during CGCs apoptosis. Inhibiting JNK with a specific inhibitor, SP600125, reduced the levels of c-Jun phosphorylation and caspase-3 activation. We also showed that use the JNK inhibitor SP600125, caspase inhibitor z-VAD, or use SP600125 and z-VAD together significantly suppressed cell death induced by heroin. These results indicate that JNK pathway is an important mediator of the neurotoxic effects of heroin and inhibiting JNK activity may represent a new and effective strategy to treat heroin-induced SLE.

Cellular and molecular mechanisms involved in the neurotoxicity of opioid and psychostimulant drugs

Substance abuse and addiction are the most costly of all the neuropsychiatric disorders. In the last decades, much progress has been achieved in understanding the effects of the drugs of abuse in the brain. However, efficient treatments that prevent relapse have not been developed. Drug addiction is now considered a brain disease, because the abuse of drugs affects several brain functions. Neurological impairments observed in drug addicts may reflect drug-induced neuronal dysfunction and neurotoxicity. The drugs of abuse directly or indirectly affect neurotransmitter systems, particularly dopaminergic and glutamatergic neurons. This review explores the literature reporting cellular and molecular alterations reflecting the cytotoxicity induced by amphetamines, cocaine and opiates in neuronal systems. The neurotoxic effects of drugs of abuse are often associated with oxidative stress, mitochondrial dysfunction, apoptosis and inhibition of neurogenesis, among other mechanisms. Understanding the mechanisms that underlie brain dysfunction observed in drug-addicted individuals may contribute to improve the treatment of drug addiction, which may have social and economic consequences.

Street heroin induces mitochondrial dysfunction and apoptosis in rat cortical neurons

Cortical function has been suggested to be highly compromised by repeated heroin self-administration. We have previously shown that street heroin induces apoptosis in neuronal-like PC12 cells. Thus, we analysed the apoptotic pathways involved in street heroin neurotoxicity using primary cultures of rat cortical neurons. Our street heroin sample was shown to be mainly composed by heroin, 6-monoacetylmorphine and morphine. Exposure of cortical neurons to street heroin induced a slight decrease in metabolic viability, without loss of neuronal integrity. Early activation of caspases involved in the mitochondrial apoptotic pathway was observed, culminating in caspase 3 activation, Poly-ADP Ribose Polymerase (PARP) cleavage and DNA fragmentation. Apoptotic morphology was completely prevented by the non-selective caspase inhibitor z-VAD-fmk, indicating an important role for caspases in neurodegeneration induced by street heroin. Ionotropic glutamate receptors, opioid receptors and oxidative stress were not involved in caspase 3 activation. Interestingly, street heroin cytotoxicity was shown to be independent of a functional mitochondrial respiratory chain, as determined using NT-2 rho(0) cells. Nonetheless, in street heroin-treated cortical neurons, cytochrome c was released, accompanied by a decrease in mitochondrial potential and Bcl-2/Bax. Pure heroin hydrochloride similarly decreased metabolic viability but only slightly activated caspase 3. Altogether, our data suggest an important role for mitochondria in mediating street heroin neurotoxic effects.

Modulation of apoptosis in the mouse brain after morphine treatments and morphine withdrawal

We have examined the effects of acute or chronic morphine and naltrexone-precipitated withdrawal on mouse brain apoptotic cell death. The associated changes in the expression of apoptosis regulatory proteins were also analyzed. After a single dose of morphine, no apoptotic cells were detected by TUNEL or active caspase-3 immunocytochemistry. Concurrently, a down-regulation of the proapoptotic proteins FasL and Bad was detected in cortical lysates. On the other hand, the brains of chronic-morphine-treated mice and abstinent mice exhibited scattered apoptotic neurons and astrocytes throughout the brain. This neurotoxic effect was accompanied by up-regulation of the proapoptotic proteins FasL, Fas, and Bad and the active fragments of caspases-8 and -3 in cortical and hippocampal lysates. Abstinent mice also displayed a reduced expression of the antiapoptotic protein Bcl-2. No changes on t-Bid expression were detected under any experimental condition. These results suggest a neurotoxic effect exerted by chronic, but not acute, morphine and its withdrawal by activating both the intrinsic and the extrinsic apoptotic pathways. The possible clinical implications of our findings are discussed.

Drugs of Abuse Induce Apoptotic Features in PC12 Cells

Drugs of abuse induce the release of dopamine in the central nervous system, particularly in the mesolimbic-mesocortical pathway. As dopamine may act as a neurotoxin, in this study, we analyzed the effects of the drugs of abuse, cocaine, heroin, and amphetamine, on the neurodegeneration of PC12 cells, a dopaminergic cell line, by evaluating the activity of caspase-3 and mitochondrial cytochrome c release. All the drugs were shown to induce caspase-3 activation, similarly to staurosporine, a classical inducer of apoptotic cell death. Furthermore, like staurosporine, the drugs of abuse induced a decrease in mitochondrial cytochrome c content, suggesting the involvement of the mitochondrial apoptotic pathway.

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.

Buprenorphine produces naltrexone reversible alterations of immune status

Substantial evidence demonstrates that administration of high efficacy mu opioid agonists such as morphine modulate the immune response in a dose-dependent and pharmacologically specific manner, indicating functional interactions between the opioid and immune systems. In contrast to the well-characterized immunomodulatory effects of high efficacy mu opioids, little is known about how these effects generalize to other clinically employed opioids and agonists of varying degrees of mu opioid receptor stimulation. Buprenorphine is a mu opioid agonist of intermediate efficacy that is used clinically for pain management and has recently been approved for the treatment of opioid dependence. Recent evidence indicates pharmacological and mechanistic differences between buprenorphine and morphine. Therefore, the aim of the present study was to investigate whether buprenorphine also possesses immunomodulatory properties. The results demonstrate that buprenorphine dose-dependently suppresses splenic natural killer cell activity, lymphocyte proliferation and IFN-gamma production in rats in a naltrexone reversible manner, demonstrating pharmacological specificity of buprenorphine-induced immune alterations.

Cocaine increases inducible nitric oxide synthase expression in rats: effects of acute and binge administration

The present studies assessed the effects of acute and binge cocaine administration on the in vivo production of inducible nitric oxide synthase in a rat model of endotoxemia. Inducible nitric oxide synthase is a key enzyme involved in host defense and inflammatory responses consequent to infection through its production of nitric oxide. Male Lewis rats received subcutaneous injections of saline or selected doses of cocaine (7.5-30 mg/kg) at the same time as a 50 microg/kg dose of lipopolysaccharide (LPS). Animals in the binge cocaine experiments received two additional injections of cocaine or saline at 2 and 4 h after the initial injections. All animals were sacrificed 6 h after initial drug administration and tissues harvested for determination of iNOS protein levels. Plasma nitrite/nitrate levels were also assayed to assess any treatment-related differences in the degradative by-products of nitric oxide metabolism. Western blot analyses of iNOS expression indicated that both acute and binge cocaine treatment resulted in significant increases in iNOS expression in all tissues assayed. Furthermore, acute and binge cocaine treatment also dose-dependently increased plasma nitrite levels. These data suggest that cocaine may impact resistance to gram-negative infections and severity of these infections via modulation of nitric oxide parameters.

Opioids and the apoptotic pathway in human cancer cells

This study was designed to examine the role of opioids in cell survival, with an emphasis on the mechanism of opioid growth factor (OGF, [Met(5)]-enkephalin)-dependent growth inhibition. Using three human cancer cell lines: MIA PaCa-2 pancreatic adenocarcinoma, HT-29 colon adenocarcinoma, and CAL-27 squamous cell carcinoma of the head and neck, and OGF and the opioid antagonist naltrexone (NTX) at a dosage (10(-6)M) selected because it is known to repress or increase, respectively, cell replication, the effects on apoptosis (TUNEL, Annexin V) and necrosis (trypan blue) were investigated on days 2, 5, and 7 of exposure. In addition, the influence of a variety of other natural and synthetic opioids on apoptosis and necrosis was examined at a dosage of 10(-6)M. OGF, NTX, naloxone, [D-Pen(2,5)]-enkephalin, [Leu(5)]-enkephalin, dynorphin A1-8, beta-endorphin, endomorphin-1 and -2, and methadone at concentrations of 10(-6)M did not alter cell viability of any cancer cell line. Exposure of cultures to [D-Ala(2),MePhe(4),Glycol(5)]-enkephalin (DAMGO), morphine, or etorphine at 10(-6)M significantly increased the number of adherent cells positively stained for TUNEL and Annexin V, as well as the number of necrotic cells in the supernatant, from control levels at all time points studied. The effects of DAMGO, morphine, and etorphine on apoptosis/necrosis were not fully blocked by concomitant administration of naloxone. Despite the increase in cell death in some opioid-treated groups, the number of apoptotic and necrotic adherent cells, and the number of necrotic cells in the supernatant, was no more than 1-2% of the total cell population. These results indicate that the inhibitory (OGF) or stimulatory (NTX) action on cell growth in tissue culture is not due to alterations in apoptotic or necrotic pathways. Moreover, although some opioids increased cell death, and dose-effect relationships need to be established, this activity was not of great magnitude and supports the previously reported lack of growth inhibition of many of these compounds.

Opioid peptides endomorphin-1 and endomorphin-2 in the immune system in humans and in a rodent model of inflammation

Endomorphin (EM)-1 and EM-2 are tetrapeptides with high affinity and selectivity for the micro-opioid receptor. We have utilized specific radioimmunoassays to characterize EM-1 and EM-2 in immune tissues from normal human subjects and from rats with adjuvant arthritis (AA). PBLs from three normal human subjects contained 248, 13, and 303 pg EM-1 per 100 million cells, whereas EM-2 was measured in two subjects at 69 and 588 pg per 100 million cells. In AA rats, EM-1 (but not EM-2) contents in the spleen and thymus were elevated compared with levels in tissues from non-AA controls. EM-1 was detectable in five of eight samples of synovial tissue from inflamed hind paws, whereas EM-2 was detectable in two of eight synovial extracts. Neither EM-1 nor EM-2 were detectable in synovial tissue from non-AA rats. To our knowledge, this is the first report of endomorphins in normal human immune cells. Increased endomorphin expression or uptake in peripheral tissues in a rodent model of chronic inflammation provides potential for endomorphins to selectively modulate chronic inflammation in mammals.

Toxic effects of opioid and stimulant drugs on undifferentiated PC12 cells

Cell death and reactive oxygen species production have been suggested to be involved in neurodegeneration induced by the drugs of abuse. In this study we analyze the toxicity of the following drugs of abuse: heroin, morphine, d-amphetamine, and cocaine in undifferentiated PC12 cells, used as dopaminergic neuronal models. Our data show that opioid drugs (heroin and morphine) are more toxic than stimulant drugs (d-amphetamine and cocaine). Toxic effects induced by heroin are associated with a decrease in intracellular dopamine, an increase in DOPAC levels, and the formation of ROS, whereas toxic effects induced by amphetamine are associated with a decrease in intracellular dopamine and in ATP/ADP levels. In contrast with cocaine, both amphetamine and heroin induced features of apoptosis. The data suggest that the death of cultured PC12 cells induced by the drugs of abuse is correlated with a decrease in intracellular dopamine levels, which can be associated with an increased dopamine turnover and oxidative cell injury.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied 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; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Morphine-6beta-glucuronide modulates the expression of inducible nitric oxide synthase

The immunomodulatory effects of morphine are well established; however, suprisingly little is known about the immunomodulatory properties of the major metabolites of morphine. The present study tests the hypothesis that expression of inducible nitric oxide synthase (iNOS) is modulated by the administration of the morphine metabolite, morphine-6beta-glucuronide. The initial study using rats shows that morphine-6beta-glucuronide administration (0, 1.0, 3.163, 10 mg/kg s.c.) results in a pronounced reduction in lipopolysaccharide (LPS)-induced expression of iNOS (inducible nitricoxide synthease) in spleen, lung, and liver tissue as measured by western blotting. Morphine-6beta-glucuronide also produces a reduction in the level of plasma nitrite/nitrate, the more stable end-product of nitric oxide degradation. In a subsequent study, administration of the opioid receptor antagonist, naltrexone (0.1 mg/kg) prior to the injection of morphine-6beta-glucuronide (10 mg/kg) blocks the morphine-6beta-glucuronide induced reduction of iNOS expression and plasma nitrite/nitrite levels indicating that the effect is mediated via the opioid-receptor. This study provides the first evidence that morphine-6beta-glucuronide alters the expression of iNOS.