Differential effects of acute morphine administrations on polymorphonuclear cell metabolism in various mouse strains

CF3-substituted diselenide modulatory effects on oxidative stress, induced by single and repeated morphine administrations, in susceptible tissues of mice

Studies reveal that oxidative stress is associated with adverse effects of long-term morphine treatment. The m-trifluoromethyl-diphenyl diselenide (CF3) is a multi-target organoselenium compound that has antioxidant properties in different experimental models. This study aimed to investigate the CF3 effects against redox imbalance in peripheral and central tissues of mice, after single or multiple morphine doses. Swiss male mice received a single dose of morphine (5 mg/kg, s.c.) and CF3 (10 mg/kg, i.g.), or morphine was repeatedly injected (5 mg/kg, s.c.) and CF3 (10 mg/kg, i.g.) administered twice daily for 7 days. Oxidative stress was determined in the hippocampus, liver, and kidney. CF3 reversed the increase in reactive species caused by single and multiple morphine doses in the peripheral tissues. CF3 increased hepatic non-protein thiol levels and the superoxide dismutase (SOD) activity decreased by a single morphine dose. CF3 reversed the reduction in SOD activity in the kidney of mice repeatedly exposed to morphine. The study demonstrates that peripheral tissues were more susceptible than the hippocampus to oxidative stress induced by morphine in mice. The results show that CF3 modulated parameters of oxidative stress modified by single and multiple morphine administrations in peripheral and central tissues of mice.

Naloxone pretreatment prevents kidney injury after liver ischemia reperfusion injury

PURPOSE

The aim of this study was to assess the effects of naloxone, an opioid receptor antagonist, on the renal injury as a remote organ after hepatic ischemia reperfusion (IR) in rats.

MATERIALS AND METHODS

Forty male Wistar rats were randomly allocated into four groups as follows: sham, sham + naloxone, IR and IR + naloxone. In anesthetized rats, hepatic ischemia was applied for 30 min in IR and IR + naloxone groups. Sham + naloxone and IR + naloxone groups were given naloxone (3.0 mg/kg, iv) 30 min before ischemia. After 24 h, blood and tissue samples were obtained for histopathological, tissue malondialdehyde (MDA) and biochemical analyses.

RESULTS

Histopathological study of liver in IR group showed enlarged sinusoids, sinusoidal congestion, cellular degenerative changes and necrosis. The kidney of the rats with hepatic IR showed pathological changes in tubular cell swelling, tubular dilatation, moderate to severe necrosis, glomerular fibrosis and hemorrhage. Histological examination confirmed the extent of hepatic and renal changes in IR group was higher (P < 0.05) than in other groups. Rats that underwent hepatic IR exhibited significant increase in serum concentrations of urea and creatinine levels (P < 0.05). The serum alanine aminotransferase and aminotransferase values were significantly higher in IR group compared to the other groups (P < 0.05). Liver IR produced a significant increase in hepatic and renal tissue MDA levels, while pretreatment with naloxone was associated with a significantly lower MDA levels (P < 0.05).

CONCLUSION

The results of this study showed that naloxone pretreatment protected the renal injury from hepatic IR.

Heroin affects purine nucleotides metabolism in rat brain

OBJECTIVE

To explore the effects of heroin on purine nucleotides metabolism in rat brain.

METHODS

Biochemical changes in association with heroin administration were compared between heroin-administered rats and non-heroin rats. HPLC method was used to detect the absolute content of purine nucleotides in brain tissues. Concentrations of uric acid (UA), blood urea nitrogen (BUN) and creatinine (Cre) in plasma were measured. Enzymatic activities of adenosine deaminase (ADA) and xanthine oxidase (XO) in brain tissue were analyzed. Real-time PCR was used to determine the relative level of transcripts of ADA, XO, adenine phosphoribosyl transferase (APRT), hypoxanthine-guaninephosphoribosyl transferase (HGPRT) and adenosine kinase (AK) in brain tissue.

RESULTS

Compared with those in the saline group, the content of AMP and GTP of heroin group decreased significantly; the UA concentration in plasma, ADA and XO activities and the mRNA level of ADA and XO in brain tissues in heroin group increased significantly; the mRNA level of AK, APRT and HGPRT in brain tissues in heroin group decreased significantly (P<0.01).

CONCLUSION

Heroin administration may enhance the catabolism and inhibit the anabolism of purine nucleotides in brain. There may be a deficiency of purine nucleotides, especially GTP and AMP in rat brain exposed to heroin. Our findings may provide a new potential approach to study the mechanism of heroin addiction.

In vivo morphine treatment synergistically increases LPS-induced caspase activity in immune organs

Caspases are a family of proteins important for the elimination of infected cells through the induction of apoptosis as well as the initiation of inflammatory cytokines including IL-1β and IL-18. Morphine exposure to animals and/or cells has been associated with the induction of apoptosis. The most common practices of apoptosis detection have involved removing tissues from animal or humans and the analysis of apoptosis on cells or tissues. These methods can potentially induce spontaneous apoptosis that is unrelated to the actual treatment. The objective of this study was to develop an in vivo detection method for assessing caspase activity induced both by morphine directly and by morphine combined with lipopolysaccharide (LPS)-immune activation. Mice were administered saline, morphine, LPS, or a combination of morphine and LPS. Prior to sacrifice, mice were injected with a polycaspase-specific apoptosis detection probe to detect internal caspase activity in vivo. Results revealed that morphine alone did not directly induce caspase activity. However, morphine significantly enhanced the LPS-induced caspase activity in spleen, thymus, and bone marrow-derived immune cells. The use of a poly-caspase detection probe methodology to label caspase activity in vivo provides a powerful quantitative tool for the in vivo analysis of caspase activity.

Deciphering the mechanism(s) of action of natural products: analgesic peroxide oil as example

BACKGROUND

There are multiple reports of natural products having therapeutic effect. In an era of evidence-based medicine, clinical trials inform clinical decisions regarding use of the product, but prevailing preference is to identify and use a single 'active ingredient'. Yet, the clinical benefit of a natural product might derive from the fortuitous combination of its multiple components. Therefore, the elucidation of the mechanism(s) of action of natural products is important, but presents significant challenges. This article examines this issue using peroxide oil (essential oxygen oil) as an illustrative example.

OBJECTIVE

To review the published literature of a natural product in an effort to elucidate postulated mechanism(s) of action of a complex mixture.

METHODS

The clinical and preclinical literature was reviewed from the perspective of its contribution to elucidating a mechanism of analgesic action of a natural product.

RESULTS

Peroxide oil contains ingredients that are associated with analgesic mechanisms, such inhibition of lipid peroxidation and arachidonic acid metabolism and non-opioid, glibenclamide-sensitive receptor-mediated and K(ATP) -NO-cGMP channel pathways.

CONCLUSION

Although its exact mechanism remains unknown, peroxide oil provides an example of how a natural product can be evaluated for plausible mechanistic explanation of its purported therapeutic efficacy. Such an approach seems valuable, since, as in this case, the constituents appear to contribute in an additive or synergistic manner, something not possible with a single substance.

Morphine or its withdrawal affects plasma malondialdehyde, vitamin E levels and absence or presence of abstinence signs in rats

Objectives

Various experimental observations show that morphine treatment generates reactive oxygen species, and that its discontinuation leads to signs of withdrawal. We therefore investigated plasma malondialdehyde and vitamin E levels under both conditions to verify the occurrence of any alterations in oxidative metabolism, and whether these are associated with behavioural changes.

Methods

We investigated the effects of morphine or morphine plus naloxone on plasma malondialdehyde, vitamin E levels and withdrawal signs such as jumping, wet dog shakes and faecal excretion in rats. Furthermore, isopropylnoradrenaline was injected in rabbits to verify its effects on plasma malondialdehyde levels.

Key findings

Morphine treatment increased free malondialdehyde and decreased vitamin E levels. The elevation in malondialdehyde levels were exacerbated by the abrupt removal of morphine by naloxone, which also led to the appearance of withdrawal signs. The increased malondialdehyde values can be attributed to the interactions of reactive oxygen species with unsaturated fatty acids, and the lowered levels of vitamin E to its interactions with reactive oxygen species.

Conclusions

A connection seems to exist between altered peroxide status and withdrawal signs in abstinent animals.

Opioid use affects antioxidant activity and purine metabolism: preliminary results

OBJECTIVE

More must be learned about metabolic and biochemical alterations that contribute to the development and expression of drug dependence. Experimental opioid administration influences mechanisms and indices of oxidative stress, such as antioxidant compounds and purine metabolism. We examined perturbations of neurotransmitter-related pathways in opioid dependence (OD).

METHODS

In this preliminary study, we used a targeted metabolomics platform to explore whether biochemical changes were associated with OD by comparing OD individuals (n = 14) and non-drug users (n = 10).

RESULTS

OD patients undergoing short-term methadone detoxification showed altered oxidation-reduction activity, as confirmed by higher plasma levels of alpha- and gamma-tocopherol and increased GSH/GSSG ratio. OD individuals had also altered purine metabolism, showing increased concentration of guanine and xanthosine, with decreased guanosine, hypoxanthine and hypoxanthine/xanthine and xanthine/xanthosine ratios. Other drug use in addition to opioids was associated with partly different biochemical changes.

CONCLUSIONS

This is a preliminary investigation using metabolomics and showing multiple peripheral alterations of metabolic pathways in OD. Further studies should explore the metabolic profile of conditions of opioid abuse, withdrawal and long-term abstinence in relation to agonist and antagonist treatment and investigate biochemical signatures of opioid substances and medications.

Chronic morphine treatment induces oxidant and apoptotic damage in the mice liver

Recently many researchers have proposed a protective role for morphine against tumor growth and metastasis, especially through induction of apoptosis in tumoral cells. These findings may lead to underestimation of cytotoxic effects of opioid drugs which are usually expected only at high doses. The present study was conducted to clarify whether repeated morphine administration, which is commonly used for relief from chronic pain, would interfere with liver antioxidant defence and hepatocytes vitality. Morphine was injected repeatedly at doses that have been reported to relieve cancer pain and reduce tumor spread in mice (5 and 10 mg/kg/day for nine consecutive days). The changes in hepatic glutathione concentration, its synthesis pathway and enzymatic antioxidant defense revealed the pro-oxidant effects of chronic morphine treatment on the liver. None of these changes were observed in those mice that were co-treated with naltrexone (opioid antagonist) and same doses of morphine. However induction of liver conjugating enzymes following morphine treatment was not receptor mediated. Moreover, chronic morphine treatment induced hepatocytes apoptosis. Interestingly, the apoptotic changes were antagonized by co-administration of either naltrexone or thiol antioxidant. In conclusion, although hepatotoxic effects of morphine at high doses have been reported previously, our findings propose that repeated morphine administration even at lower doses would induce oxidative stress in the liver, which may contribute to induction of apoptosis in hepatocytes. Since many of the observed adverse effects were mediated by opioid receptors, our results suggest that other opioid analgesics should also be used more cautiously.

Opioid receptor blockade reduces Fas-induced hepatitis in mice

Fas (CD95)-induced hepatocyte apoptosis and cytotoxic activity of neutrophils infiltrating the injured liver are two major events leading to hepatitis. Because it has been reported that opioids, via a direct interaction, sensitize splenocytes to Fas-mediated apoptosis by upregulating Fas messenger RNA (mRNA) and modulated neutrophil activity, we assumed that opioids may participate in the pathophysiology of hepatitis. Using the hepatitis model induced by agonistic anti-Fas antibody in mice, we showed that opioid receptor blockade reduced liver damage and consequently increased the survival rate of animals when the antagonist naltrexone was injected simultaneously or prior to antibody administration. Treatment of mice with morphine enhanced mortality. Naloxone methiodide-a selective peripheral opioid antagonist-had a protective effect, but the absence of opioid receptors in the liver, together with lack of morphine effect in Fas-induced apoptosis of primary cultured hepatocytes, ruled out a direct effect of opioids on hepatocytes. In addition, the neutralization of opioid activity by naltrexone did not modify Fas mRNA expression in the liver as assessed with real-time quantitative polymerase chain reaction. Injured livers were infiltrated by neutrophils, but granulocyte-depleted mice were not protected against the enhancing apoptotic effect of morphine. In conclusion, opioid receptor blockade improves the resistance of mice to Fas-induced hepatitis via a peripheral mechanism that does not involve a down-modulation of Fas mRNA in hepatocytes nor a decrease in proinflammatory activity of neutrophils.

Morphine-induced enhancement in the granulocyte response to thioglycollate administration in the rat

The present study determined the pharmacological effects of acute morphine treatment on the granulocyte phase of the peritoneal inflammatory response to thioglycollate (TG) in rats. Dual-color flow cytometry using anti-CD11b/c-PE mAb in combination with HIS48-FITC mAb allowed for the determination of morphine's effects on 4 inflammatory cell subsets: CD11b/c(+)HIS48med granulocytes; CD11b/c(hi)HIS48neg/lo activated macrophages; CD11b/c(-)HIS48(-) lymphocytes; and CD11b/c(+)HIS48hi cells (a monocyte/macrophage and granulocyte subset). Morphine produced a dose-dependent increase in a select subset of inflammatory peritoneal cells, the CD11b/c(+)HIS48med granulocytes. The effect of morphine was time-dependent, with significant effects first apparent at 4 hr after TG, but the administration of morphine 1 hr before or simultaneously with TG produced a similar increase in CD11b/c(+)HIS48med granulocytes. Naltrexone completely antagonized the morphine-induced increase in CD11b/c(+)HIS48med granulocytes. Collectively, these studies show that a single administration of morphine produces a time-dependent, dose-dependent, opioid receptor-mediated enhancement in the peritoneal granulocyte response to TG.

Pain management in the critically ill child

Children frequently received no treatment, or inadequate treatment, for pain and for painful procedures. The newborn and critically ill children are especially vulnerable to no treatment or under-treatment. Nerve pathways essential for the transmission and perception of pain are present and functioning by 24 weeks of gestation. The failure to provide analgesia for pain results in rewiring the nerve pathways responsible for pain transmission in the dorsal horn of the spinal cord and results in increased pain perception for future painful results. Many children would withdraw or deny their pain in an attempt to avoid yet another terrifying and painful experiences, such as the intramuscular injections. Societal fears of opioid addiction and lack of advocacy are also causal factors in the under-treatment of pediatric pain. False beliefs about addictions and proper use of acetaminophen and other analgesics resulted in the failure to provide analgesia to children. All children even the newborn and critically ill require analgesia for pain and painful procedures. Unbelieved pain interferes with sleep, leads to fatigue and a sense of helplessness, and may result in increased morbidity or mortality.