Indirect evidence indicates that morphine-3-glucuronide (M3G) may contribute significantly to the... more Indirect evidence indicates that morphine-3-glucuronide (M3G) may contribute significantly to the neuro-excitatory side effects (myoclonus and allodynia) of large-dose systemic morphine. To gain insight into the mechanism underlying M3G's excitatory behaviors, we used fluo-3 fluorescence digital imaging techniques to assess the acute effects of M3G (5-500 microM) on the cytosolic calcium concentration ([Ca(2+)](CYT)) in cultured embryonic hippocampal neurones. Acute (3 min) exposure of neurones to M3G evoked [Ca(2+)](CYT) transients that were typically either (a) transient oscillatory responses characterized by a rapid increase in [Ca(2+)](CYT) oscillation amplitude that was sustained for at least approximately 30 s or (b) a sustained increase in [Ca(2+)](CYT) that slowly recovered to baseline. Naloxone-pretreatment decreased the proportion of M3G-responsive neurones by 10%-25%, implicating a predominantly non-opioidergic mechanism. Although the naloxone-insensitive M3G-induced increases in [Ca(2+)](CYT) were completely blocked by N-methyl-D-aspartic acid (NMDA) antagonists and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate antagonist), CNQX did not block the large increase in [Ca(2+)](CYT) evoked by NMDA (as expected), confirming that M3G indirectly activates the NMDA receptor. Additionally, tetrodotoxin (Na(+) channel blocker), baclofen (gamma-aminobutyric acid(B) agonist), MVIIC (P/Q-type calcium channel blocker), and nifedipine (L-type calcium channel blocker) all abolished M3G-induced increases in [Ca(2+)](CYT), suggesting that M3G may produce its neuro-excitatory effects by modulating neurotransmitter release. However, additional characterization is required. Large systemic doses of morphine administered to some patients for cancer pain management have been reported to produce myoclonus and allodynia. Indirect evidence implicates the major morphine metabolite, morphine-3-glucuronide (M3G), in these neuro-excitatory side effects. Hence, this study was designed to gain insight into the cellular mechanism responsible for M3G's neuro-excitatory actions.
Abstract The role of mitochondria in Ca 2+ homeostasis is controversial. We employed the Ca 2+-se... more Abstract The role of mitochondria in Ca 2+ homeostasis is controversial. We employed the Ca 2+-sensitive dye rhod 2 with novel, high temporal and spatial resolution imaging to evaluate changes in the matrix free Ca 2+ concentration of individual mitochondria ([Ca 2 ...
... Faddy, HM, Aung, CS, Lee, WJ, Roberts-Thomson, SJ and Monteith, GR (2006). ... Using real tim... more ... Faddy, HM, Aung, CS, Lee, WJ, Roberts-Thomson, SJ and Monteith, GR (2006). ... Using real time RT-PCR we have confirmed gene knockdown for specific isoforms and have studied the time course of knockdown over 96 hours. ...
Gopisetty Venkata, Nagaraj, Cabot, Peter, Monteith, Greg and Roberts-Thomson, Sarah (2007). Modul... more Gopisetty Venkata, Nagaraj, Cabot, Peter, Monteith, Greg and Roberts-Thomson, Sarah (2007). Modulation of PPARα and PPARβ by ethanol in human breast cancer cell lines. In: , AACR Meeting Abstracts: Proceedings of the American Association for Cancer Research Annual ...
The phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP) are environmental ... more The phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP) are environmental contaminants with significant human exposures. Both compounds are known reproductive toxins in rodents and DEHP also induces rodent hepatocarcinogenesis in a process believed to be mediated via the peroxisome proliferator-activated receptor α (PPARα). DEHP and DBP are metabolised to their respective monoesters, mono-(2-ethylhexyl)phthalate (MEHP) and mono-n-butyl phthalate (MBP), which are the active metabolites. MEHP also activates another member of the PPAR subfamily, PPARγ. The effects of PPARα and PPARγ activation in human breast cells appears to be opposing; PPARα activators in breast cells cause an increase in proliferation, while PPARγ activation in breast cells is associated with differentiation and an inhibition of cell proliferation. Further to this the activation of the PPARs is cell and ligand specific, suggesting the importance of examining the effect of MEHP and MBP on the activation of PPARα, PPARβ and PPARγ in human breast. We used the common model of human breast cancer MCF-7 and examined the ability of MEHP and MBP to activate human PPARs in this system. The ability of MBP and MEHP to block PPAR responses was also assessed. We found that both human PPARα and PPARγ were activated by MEHP whereas MEHP could not activate PPARβ. MBP was unable to activate any PPAR isoforms in this breast model, despite being a weak peroxisome proliferator in liver, although MBP was an antagonist for both PPARγ and PPARβ. Our results suggest that the toxicological consequences of MEHP in the breast could be complex given the opposing effects of PPARα and PPARγ in human breast cells.
Indirect evidence indicates that morphine-3-glucuronide (M3G) may contribute significantly to the... more Indirect evidence indicates that morphine-3-glucuronide (M3G) may contribute significantly to the neuro-excitatory side effects (myoclonus and allodynia) of large-dose systemic morphine. To gain insight into the mechanism underlying M3G's excitatory behaviors, we used fluo-3 fluorescence digital imaging techniques to assess the acute effects of M3G (5-500 microM) on the cytosolic calcium concentration ([Ca(2+)](CYT)) in cultured embryonic hippocampal neurones. Acute (3 min) exposure of neurones to M3G evoked [Ca(2+)](CYT) transients that were typically either (a) transient oscillatory responses characterized by a rapid increase in [Ca(2+)](CYT) oscillation amplitude that was sustained for at least approximately 30 s or (b) a sustained increase in [Ca(2+)](CYT) that slowly recovered to baseline. Naloxone-pretreatment decreased the proportion of M3G-responsive neurones by 10%-25%, implicating a predominantly non-opioidergic mechanism. Although the naloxone-insensitive M3G-induced increases in [Ca(2+)](CYT) were completely blocked by N-methyl-D-aspartic acid (NMDA) antagonists and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate antagonist), CNQX did not block the large increase in [Ca(2+)](CYT) evoked by NMDA (as expected), confirming that M3G indirectly activates the NMDA receptor. Additionally, tetrodotoxin (Na(+) channel blocker), baclofen (gamma-aminobutyric acid(B) agonist), MVIIC (P/Q-type calcium channel blocker), and nifedipine (L-type calcium channel blocker) all abolished M3G-induced increases in [Ca(2+)](CYT), suggesting that M3G may produce its neuro-excitatory effects by modulating neurotransmitter release. However, additional characterization is required. Large systemic doses of morphine administered to some patients for cancer pain management have been reported to produce myoclonus and allodynia. Indirect evidence implicates the major morphine metabolite, morphine-3-glucuronide (M3G), in these neuro-excitatory side effects. Hence, this study was designed to gain insight into the cellular mechanism responsible for M3G's neuro-excitatory actions.
Abstract The role of mitochondria in Ca 2+ homeostasis is controversial. We employed the Ca 2+-se... more Abstract The role of mitochondria in Ca 2+ homeostasis is controversial. We employed the Ca 2+-sensitive dye rhod 2 with novel, high temporal and spatial resolution imaging to evaluate changes in the matrix free Ca 2+ concentration of individual mitochondria ([Ca 2 ...
... Faddy, HM, Aung, CS, Lee, WJ, Roberts-Thomson, SJ and Monteith, GR (2006). ... Using real tim... more ... Faddy, HM, Aung, CS, Lee, WJ, Roberts-Thomson, SJ and Monteith, GR (2006). ... Using real time RT-PCR we have confirmed gene knockdown for specific isoforms and have studied the time course of knockdown over 96 hours. ...
Gopisetty Venkata, Nagaraj, Cabot, Peter, Monteith, Greg and Roberts-Thomson, Sarah (2007). Modul... more Gopisetty Venkata, Nagaraj, Cabot, Peter, Monteith, Greg and Roberts-Thomson, Sarah (2007). Modulation of PPARα and PPARβ by ethanol in human breast cancer cell lines. In: , AACR Meeting Abstracts: Proceedings of the American Association for Cancer Research Annual ...
The phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP) are environmental ... more The phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP) are environmental contaminants with significant human exposures. Both compounds are known reproductive toxins in rodents and DEHP also induces rodent hepatocarcinogenesis in a process believed to be mediated via the peroxisome proliferator-activated receptor α (PPARα). DEHP and DBP are metabolised to their respective monoesters, mono-(2-ethylhexyl)phthalate (MEHP) and mono-n-butyl phthalate (MBP), which are the active metabolites. MEHP also activates another member of the PPAR subfamily, PPARγ. The effects of PPARα and PPARγ activation in human breast cells appears to be opposing; PPARα activators in breast cells cause an increase in proliferation, while PPARγ activation in breast cells is associated with differentiation and an inhibition of cell proliferation. Further to this the activation of the PPARs is cell and ligand specific, suggesting the importance of examining the effect of MEHP and MBP on the activation of PPARα, PPARβ and PPARγ in human breast. We used the common model of human breast cancer MCF-7 and examined the ability of MEHP and MBP to activate human PPARs in this system. The ability of MBP and MEHP to block PPAR responses was also assessed. We found that both human PPARα and PPARγ were activated by MEHP whereas MEHP could not activate PPARβ. MBP was unable to activate any PPAR isoforms in this breast model, despite being a weak peroxisome proliferator in liver, although MBP was an antagonist for both PPARγ and PPARβ. Our results suggest that the toxicological consequences of MEHP in the breast could be complex given the opposing effects of PPARα and PPARγ in human breast cells.
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