Modifications of expression of genes and proteins involved in DNA repair and nitric oxide metabolism by carbatonides [disodium-2,6-dimethyl-1,4-dihydropyridine- 3,5-bis(carbonyloxyacetate) derivatives] in intact and diabetic rats

Studies on the pathogenesis of diabetes mellitus complications indicate that the compounds reducing free radicals and enhancing DNA repair could be prospective as possible remedies. Carbatonides, the disodium-2,6-dimethyl-1,4- dihydropyridine-3,5-bis(carbonyloxyacetate) derivatives, were tested for these properties. EPR spectroscopy showed that metcarbatone was an effective scavenger of hydroxyl radicals produced in the Fenton reaction, etcarbatone, and propcarbatone were less effective, styrylcarbatone was ineffective. UV/VIS spectroscopy revealed that styrylcarbatone manifested a hyperchromic effect when interacting with DNA, while all other carbatonides showeda hypochromic effect. Rats with streptozotocin induced type 1 DM were treated with metcarbatone, etcarbatone or styrylcarbatone (all compounds at doses 0.05 mg kg-1 or 0.5 mg kg-1) nine days after the DM approval. Gene expression levels in kidneys and blood were evaluated by quantitative RT-PCR; protein expression - immunohistochemically in kidneys, heart, sciatic nerve, and eyes; DNA breakage - by comet assay in nucleated blood cells. Induction of DM induced DNA breaks; metcarbatone and styrylcarbatone (low dose) alleviated this effect. Metcarbatone and etcarbatone up-regulated mRNA and protein of eNOS in kidneys of diabetic animals; etcarbatone also in myocardium. Etcarbatone reduced the expression of increased iNOS protein in myocardium, nerve, and kidneys. iNos gene expression was up-regulated in kidneys by etcarbatone and metcarbatone in diabetic animals. In blood, development of DM increased iNos gene expression; etcarbatone and metcarbatone normalised it. Etcarbatone up-regulated the expression of H2AX in kidneys of diabetic animals but decreased the production of c-PARP1. Taken together, our data indicate that carbatonides might have a potential as drugs intended to treat DM complications.

The dihydropyridine analogue cerebrocrast blocks both T-type and L-type calcium currents

Cerebrocrast is a novel lipophilic dihydropyridine derivative with potential neuroprotective and antidiabetic properties. We have analyzed its interaction with L-type (CaV1.2b) and T-type (CaV3.1) calcium channels using a whole-cell patch clamp in HEK 293 cells. Cerebrocrast inhibited current flux through both CaV1.2b and CaV3.1 channels. In both cases, the drug was about 10-fold less effective than neutral dihydropyridines, but more efficient than the charged dihydropyridine amlodipine. IC50 values for the CaV1.2b channel were 586 ± 96 nmol/L and 178 ± 78 nmol/L at holding potentials of –80 mV and –50 mV, respectively. Approximately 50 µmol/L of cerebrocrast was needed to block 50% of the current amplitude in the CaV3.1 channel, but this inhibition was not facilitated by shifting the holding potential from –100 mV to –70 mV. Cerebrocrast did not alter current kinetics in either investigated channel, and the inhibition of calcium current was partly reversible or irreversible. In conclusion, the interaction of cerebrocrast with CaV3.1 lacked the typical characteristics of a state-dependent interaction, and voltage-dependent inhibition of CaV1.2b was consistent with partial interaction with the inactivated state of the channel.