Abstract

Oxaliplatin (OXAL) is regarded as a platinum-based anti-neoplastic agent. However, its perturbations on membrane ionic currents in neurons and neuroendocrine or endocrine cells are largely unclear, though peripheral neuropathy has been noted during its long-term administration. In this study, we investigated how the presence of OXAL and other related compounds can interact with two types of inward currents; namely, hyperpolarization-activated cation current (Ih) and membrane electroporation-induced current (IMEP). OXAL increased the amplitude or activation rate constant of Ih in a concentration-dependent manner with effective EC50 or KD values of 3.2 or 6.4 μM, respectively, in pituitary GH3 cells. The stimulation by this agent of Ih could be attenuated by subsequent addition of ivabradine, protopine, or dexmedetomidine. Cell exposure to OXAL (3 μM) resulted in an approximately 11 mV rightward shift in Ih activation along the voltage axis with minimal changes in the gating charge of the curve. The exposure to OXAL also effected an elevation in area of the voltage-dependent hysteresis elicited by long-lasting triangular ramp. Additionally, its application resulted in an increase in the amplitude of IMEP elicited by large hyperpolarization in GH3 cells with an EC50 value of 1.3 μM. However, in the continued presence of OXAL, further addition of ivabradine, protopine, or dexmedetomidine always resulted in failure to attenuate the OXAL-induced increase of IMEP amplitude effectively. Averaged current-voltage relation of membrane electroporation-induced current (IMEP) was altered in the presence of OXAL. In pituitary R1220 cells, OXAL-stimulated Ih remained effective. In Rolf B1.T olfactory sensory neurons, this agent was also observed to increase IMEP in a concentration-dependent manner. In light of the findings from this study, OXAL-mediated increases of Ih and IMEP may coincide and then synergistically act to increase the amplitude of inward currents, raising the membrane excitability of electrically excitable cells, if similar in vivo findings occur.

Highlights

  • Oxaliplatin (OXAL, Eloxatin®) belongs to a family of platinum-based chemotherapeutic compounds

  • In agreement with previous studies described in different types of neurons, and neuroendocrine or endocrine cells, it was identified as an Ih [24,27,38,39]

  • The present study provides us with evidence showing that the presence of OXAL is able to exertTdhueaplrsetsiemnut lsatutodryy parcotivoindsesounstwwiothtyepveidseonfcieosnhicowcuinrrgenthtsa—t thIhe apnredseIMncEeP.ofItOisXAimLpiosratbalnetttooenxoetret dthuaatl tshtiemOuXlaAtoLrycoancctieonntsraotinontwuosetydpienstohfisiosntuicdcyuirsrecnlotsse—lyIhsaimndilaIMr EtPo

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Summary

Introduction

Oxaliplatin (OXAL, Eloxatin®) belongs to a family of platinum-based chemotherapeutic compounds. OXAL has been demonstrated to suppress different types of voltage-gated K+ or Na+ currents in various preparations, such as myelinated axons, sciatic-nerve preparations, and motoneuron-like cells [11,13,14,15,16]. Of interest, this agent was recently reported to activate Ih in isolated dorsal root ganglion neurons, and this action is thought to be implicated in its modifications of pain sensation [17,18,19,20]

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