morphinans and nalmefene

Hepatic fibrosis is characterized by excess type I collagen deposition and exacerbated inflammatory response. Naltrexone, an opioid receptor antagonist used for treating alcohol abuse, attenuates hepatocellular injury in fibrotic animal models, which can be accompanied by deleterious side effects. Additionally, opioid neurotransmission is upregulated in patients with inflammatory liver disease. Several derivatives of Naltrexone, Nalmefene (Nal) and JKB-119, exert immunomodulatory activity; however, unlike Nal, JKB-119 does not show significant opioid receptor antagonism. To delineate the potential hepatoprotective effects of these compounds, we investigated if JKB-119 and Nal could modulate activation of hepatic stellate cells (HSCs), primary effector cells that secrete type I collagen and inflammatory mediators during liver injury. Our results demonstrated that Nal or JKB-119 treatment decreased smooth muscle α-actin, a marker of HSC activation, mRNA and protein expression. Despite decreased collagen mRNA expression, both compounds increased intracellular collagen protein expression; however, inhibition of collagen secretion was observed. To address a possible mechanism for suppressed collagen secretion or retention of intracellular collagen, endoplasmic (ER) protein expression and matrix metalloproteinase (MMP) activity were examined. While no change in ER protein expression (Grp78, PDI, Hsp47) was observed, MMP13 mRNA expression was dramatically increased. In an acute LPS inflammatory injury animal model, JKB-119 treatment decreased liver injury (ALT), plasma TNFα and PMN liver infiltration. Overall, these results suggest that JKB-119 can directly inhibit HSC activation attributed to anti-inflammatory activity and may, therefore, attenuate inflammation associated with HSC activation and liver disease.

Topics: Actins; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cell Proliferation; Cell Survival; Cells, Cultured; Chemical and Drug Induced Liver Injury; Collagen; Disease Models, Animal; Hepatic Stellate Cells; Immunoblotting; Liver Cirrhosis; Male; Matrix Metalloproteinase 13; Matrix Metalloproteinase 2; Morphinans; Naltrexone; Narcotic Antagonists; Rats; Rats, Inbred WKY; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction

We have previously shown that the duration of opioid receptor blockade is critical in determining the degree of opioid antagonist effect following peripheral injection of naloxone and naltrexone. In the present work, we have used this ex vivo technique to compare receptor occupancy of a new opiate antagonist, SDZ 210-096 (SDZ), to that of nalmefene (NLM) in maturing female rats. Two doses (SDZ, 5.6 and 50 mg/kg; NLM, 2.5 and 50 mg/kg) were injected subcutaneously into 3 groups of rats (infantile, juvenile and peripubertal). Micropunches from hypothalamic coronal slices (300 microns) were removed at various times post-injection for quantification of mu-opioid receptors with [3H]-DAGO. Acute administration of the lower dose of SDZ inhibited ligand binding almost completely by 3 h but 50% recovery was observed in all age groups by 12 h. In contrast, SDZ 50 mg/kg provided 80-100% antagonism for at least 24 h. Age-related differences in the ability of SDZ to inhibit [3H]-DAGO binding were observed in that hypothalamic mu-opioid receptors were blocked for longer periods in younger rats. Determination of receptor occupation following NLM injection confirmed that it too has prolonged duration of action but a 24 h blockade is not achieved with either dose of this antagonist. Age-related and dose-related changes in receptor occupancy were minimal compared to SDZ. These studies clarify the interaction of these antagonists at hypothalamic mu-opioid receptors and provide information which allows a clearer interpretation of results in experiments involving opioid blockade.

Topics: Age Factors; Animals; Animals, Newborn; Binding, Competitive; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Female; Hypothalamus; Morphinans; Naltrexone; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, mu; Sexual Maturation; Vagina

White-tailed deer (Odocoileus virginianus) were immobilized with either 4.0 mg etorphine hydrochloride (ETOR) or 3.5 mg ETOR and 50.0 mg xylazine (XYL). Deer immobilized with ETOR only were given 4.0 mg nalmefene hydrochloride (NAL), a new opioid antagonist, 20 min after induction. Deer immobilized with ETOR and XYL received 3.5 mg NAL and 0.125 mg/kg yohimbine hydrochloride (YOH). The dose of 4.0 mg ETOR did not provide acceptable immobilization and was discontinued. A NAL:ETOR ratio of 1:1 was insufficient for complete and sustained antagonism of ETOR. Subsequently, deer were immobilized with ETOR and XYL as before which was then antagonized with 35.0 mg NAL and 0.125 mg/kg YOH. The 10:1 ratio of NAL:ETOR appeared to provide complete antagonism with no evidence of renarcotization. Although more study is required, NAL could become a useful antagonist for opioid-induced immobilizations.

Topics: Anesthesia, General; Anesthesia, Intravenous; Animals; Deer; Etorphine; Female; Immobilization; Injections, Intramuscular; Male; Morphinans; Naltrexone; Thiazines; Xylazine; Yohimbine

A high performance-liquid chromatographic procedure employing electrochemical detection (LCEC) has been developed for the quantitation of a new narcotic antagonist, nalmefene, in human plasma. Following extraction of the plasma at pH9, the extract was chromatographed on a reverse-phase C18 column using naltrexone as an internal standard. An electrochemical detector equipped with a glassy carbon electrode monitored the elution of nalmefene and the internal standard. The method had a limit of sensitivity of 3 ng/ml of nalmefene using a 1 ml sample of plasma and the calibration curve was linear over a range of 3-200 ng/ml. The intra- and inter-assay coefficients of variation did not exceed 6 and 12% respectively over the entire range of the calibration curve. The LCEC method has been used to quantitate the plasma concentrations of nalmefene in man following oral administration of 64 mg of the drug. In one subject, a peak plasma concentration of 58 ng/ml occurred 2 hr after drug administration and declined to 5 ng/ml after 24 hr.

Topics: Chromatography, High Pressure Liquid; Electrochemistry; Humans; Kinetics; Morphinans; Naloxone; Naltrexone; Narcotic Antagonists; Time Factors