Erythroxylum cuneatum prevented cellular adaptation in morphine-induced neuroblastoma cells.

Abstract

BACKGROUND Chronic morphine stimulates prolonged stimulation of opioid receptors, especially µ-opioid subtype (MOR), which in turn signals cellular adaptation. However, the sudden termination of morphine after chronic intake causes withdrawal syndrome. OBJECTIVES Hence, this study was designed to find an alternative treatment for the morphine withdrawal using the alkaloid leaf extract of Erythroxylum cuneatum (E. cuneatum), done on morphine-exposed neuroblastoma cell lines. METHODS SK-N-SH, a commercialised neuroblastoma cell line, was used in two separate study designs; the antagonistic and pre-treatment of morphine. The antagonistic treatment was conducted through concurrent exposure of the cells to morphine and E. cuneatum or morphine and methadone for 24 h. The pre-treatment design was carried out by exposing the cells to morphine for 24 h, followed by 24 h exposures to E. cuneatum or methadone. The cytosolic fraction was collected and run for protein expression involved in cellular adaptation; mitogen-activated protein (MAP)/extracellular signal-regulated (ERK) kinase 1/2 (MEK 1/2), extracellular signal-regulated kinase 2 (ERK 2), cAMP-dependent protein kinase (PKA) and protein kinases C (PKC). RESULTS The antagonistic treatment showed the normal level of MEK 1/2, ERK 2, PKA and PKC by the combination treatment of morphine and E. cuneatum, comparable to the combination of morphine and methadone. Neuroblastoma cells exposed to morphine pre-treatment expressed a high level of MEK 1/2, ERK 2, PKA and PKC, while the treatments with E. cuneatum and methadone normalised the expression of the cellular adaptation proteins. CONCLUSION E. cuneatum exerted anti-addiction properties by lowering the levels of cellular adaptation proteins, and its effects are comparable to that of methadone (an established anti-addiction drug).