Analysis of long-term treatment of Mu opioid receptors agonists effect on Dnm1L and Rab22a expression in HEK293 Flp-In MOP YFP

Morphine and its derivatives are well-known for their strong analgesic effects in medicine. However, their medical long-term administration is severely restricted because of tolerance and dependence. Morphine fails to induce endocytosis of Mu opioid receptors whereas other encephalin analogues such as DAMGO induce rapid endocytosis of these receptors. Repeated use of opioid drugs alters gene expressions. In current study, we analyze the effects of long-term opioid treatment on Dnm1L and Rab22a genes.
HEK293 cell lines that expressed MOP receptors were treated separately with morphine, methadone, and DAMGO. mRNAs were extracted from the cell suspension and we amplified the cDNA. Next, we analyzed Dnm1L and Rab22a gene expressions compared to control samples by qRT-PCR. Results were statistically validated by Graph Pad software.
Amplification graphs from qRT-PCR showed that Dnm1L gene expression was induced by 2.37-fold, whereas Rab22a gene expression decreased by 0.39-fold in response to long-term treatment of cells with morphine compared to control samples. Dnm1L gene expression was not significantly affected by treatment with methadone and DAMGO. Rab22a gene expression decreased by 0.41-fold with methadone treatment and by 0.45-fold in response to DAMGO treatment.
The Dnm1L gene could be involved in cellular pathways of morphine-induced tolerance which would indicate the difference between morphine and other similar Mu opioid receptor agonists.