Enhancement of Endothelial Barrier Permeability by Mitragynine

Abstract

Persistent inhalation of mitragynine (MG), a major alkaloid in the leaves of Mitragyna speciosa, causes various systemic adverse effects such as seizure, diarrhea and arthralgias, but its toxicity to endothelial cells and effects on barrier function of the cells are poorly understood. In this study, we compared toxicities of MG and mitraphylline, another constituent of the leaves, against human aortic endothelial (HAE), bronchial BEAS-2B, neuronal SK-N-SH, hepatic HepG2, kidney HEK293, gastric MKN45, colon DLD1, lung A549, breast MCF7 and prostate LNCaP cells, and found that MG, but not mitraphylline, shows higher toxicity to HAE cells compared to the other cells. Forty-eight-hours incubation of HAE cells with a high concentration of MG (60 µM) provoked apoptotic cell death, which was probably due to signaling through enhanced reactive oxygen species (ROS) generation and resultant caspase activation. Treatment of the cells with MG at sublethal concentrations less than 20 µM significantly lowered transendothelial electrical resistance and elevated paracellular permeability, without affecting the cell viability. In addition, the MG-elicited lowering of the resistance was abolished by a ROS inhibitor N-acetyl-L-cysteine and augmented by H 2 O 2 and 9,10-phenanthrenequinone, which generates ROS through its redox cycle. These results suggest the contribution of ROS generation to the increase in endothelial barrier permeability.

Kratom Alkaloids: Interactions With Enzymes, Receptors, and Cellular Barriers

“…The decrease in tightness of the tight junction was not observed in cells pre-treated with ROS inhibitor, while ROS generators made it worse. This indicates the involvement of ROS in the disruption of tight junction integrity of the human aortic endothelial cells upon exposure to mitragynine ( Matsunaga et al, 2017 ).…”

“…In vitro cell-based models of physiological barriers not only are great tools to investigate mechanisms of permeability but can also be used to determine the effects of exposure to compounds on the structure and function of the barriers. Exposure to mitragynine at 40 and 60 μM for 48 h reduced the viability of human aortic endothelial cells, which was linked to an increase in intracellular reactive oxygen species (ROS) production, leading to caspase-3 activation, DNA fragmentation, and apoptosis ( Matsunaga et al, 2017 ). The LC 50 determined was 43.1 μM.…”

“…Findings from the study showed that the long-term exposure to mitragynine caused a decrease in tight junction tightness of the human aortic endothelial cells at all concentrations tested i.e. 5, 10, and 20 μM, which might contribute to leakage of the FITC-dextran at 20 μM ( Matsunaga et al, 2017 ). The decrease in tightness of the tight junction was not observed in cells pre-treated with ROS inhibitor, while ROS generators made it worse.…”

Kratom-induced acute respiratory distress syndrome (ARDS)

“…Further in-depth review revealed that mitragynine causes apoptotic cell death by releasing oxygen free radicals and also enhances endothelial barrier permeability. These mechanisms are thought to play a major role in the pathogenesis of ARDS [ 16 ] .…”

Microglia enhanced the angiogenesis, migration and proliferation of co-cultured RMECs

“…Hyperpermeability is an important change associated with vascular dysfunction in neovascular diseases [ 42 ]. The paracellular permeability of the endothelium depends on the integrity of protein complexes involved in the inter-endothelial junctions [ 43 ]. ZO-1 and occludin are indispensable components of tight junctions regulated by pro-inflammatory cytokines and growth factors [ 44 – 49 ].…”