Neurotoxicity of heroin-cocaine combinations in rat cortical neurons

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.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 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 (Section 16); and immunological responses (Section 17).

Dextromethorphan attenuated inflammation and combined opioid use in humans undergoing methadone maintenance treatment

Recent studies show that proinflammatory cytokines might be related to the development of opioid dependence (physiological, psychological, or both). In a double-blind, randomly stratified clinical trial investigating whether add-on dextromethorphan (60-120 mg/day) attenuated inflammation and the combined use of opioids in heroin-dependent patients undergoing methadone maintenance treatment, we evaluated whether inflammation is related to the progression of opioid dependence. All participants (107 heroin-dependent patients and 84 nondependent healthy controls) were recruited from National Cheng Kung University Hospital. Their plasma cytokine levels were measured to evaluate the effect of add-on dextromethorphan. Plasma TNF-α and IL-8 levels were significantly higher in long-term heroin-dependent patients than in healthy controls (p < 0.001). Chronic heroin-use-induced TNF-α and IL-8 levels were significantly (p < 0.05) attenuated in patients treated for 12 weeks with add-on dextromethorphan. Moreover, both tolerance to methadone and the combined use of opioids were significantly (p < 0.05) attenuated in patients taking dextromethorphan. We conclude that dextromethorphan might be a feasible adjuvant therapeutic for attenuating inflammation and inhibiting methadone tolerance and combined opioid use in heroin-dependent patients.

Low-dose memantine attenuated morphine addictive behavior through its anti-inflammation and neurotrophic effects in rats

Opioid abuse and dependency are international problems. Studies have shown that neuronal inflammation and degeneration might be related to the development of opioid addiction. Thus, using neuroprotective agents might be beneficial for treating opioid addiction. Memantine, an Alzheimer's disease medication, has neuroprotective effects in vitro and in vivo. In this study, we evaluated whether a low dose of memantine prevents opioid-induced drug-seeking behavior in rats and analyzed its mechanism. A conditioned-place-preference test was used to investigate the morphine-induced drug-seeking behaviors in rats. We found that a low-dose (0.2-1 mg/kg) of subcutaneous memantine significantly attenuated the chronic morphine-induced place-preference in rats. To clarify the effects of chronic morphine and low-dose memantine, serum and brain levels of cytokines and brain-derived neurotrophic factor (BDNF) were measured. After 6 days of morphine treatment, cytokine (IL-1β, IL-6) levels had significantly increased in serum; IL-1β and IL-6 mRNA levels had significantly increased in the nucleus accumbens and medial prefrontal cortex, both addiction-related brain areas; and BDNF levels had significantly decreased, both in serum and in addiction-related brain areas. Pretreatment with low-dose memantine significantly attenuated chronic morphine-induced increases in serum and brain cytokines. Low-dose memantine also significantly potentiated serum and brain BDNF levels. We hypothesize that neuronal inflammation and BDNF downregulation are related to the progression of opioid addiction. We hypothesize that the mechanism low-dose memantine uses to attenuate morphine-induced addiction behavior is its anti-inflammatory and neurotrophic effects.

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.