5-(4-phenylbutoxy)psoralen and margatoxin

Knockout of Kv1.3 improves glucose homeostasis and confers resistance to obesity. Additionally, Kv1.3 inhibition enhances glucose uptake. This is thought to occur through calcium release. Kv1.3 inhibition in T-lymphocytes alters mitochondrial membrane potential, and, as many agents that induce Ca(2+) release or inhibit mitochondrial function activate AMPK, we hypothesised that Kv1.3 inhibition would activate AMPK and increase glucose uptake. We screened cultured muscle with a range of Kv1.3 inhibitors for their ability to alter glucose uptake. Only Psora4 increased glucose uptake in C2C12 myotubes. None of the inhibitors had any impact on L6 myotubes. Magratoxin activated AMPK in C2C12 myotubes and only Pap1 activated AMPK in the SOL. Kv1.3 inhibitors did not alter cellular respiration, indicating a lack of effect on mitochondrial function. In conclusion, AMPK does not mediate the effects of Kv1.3 inhibitors and they display differential effects in different skeletal muscle cell lines without impairing mitochondrial function.

Topics: AMP-Activated Protein Kinases; Animals; Biological Transport; Calcium; Cell Line; Ficusin; Glucose; In Vitro Techniques; Kv1.3 Potassium Channel; Mice; Mitochondria, Muscle; Models, Animal; Muscle Fibers, Skeletal; Muscle, Skeletal; Pancreatitis-Associated Proteins; Potassium Channel Blockers; Rats; Scorpion Venoms

The aim of the study was to determine the potential for K(V)1 potassium channel blockers as inhibitors of human neoinitimal hyperplasia.. Blood vessels were obtained from patients or mice and studied in culture. Reverse transcriptase-polymerase chain reaction and immunocytochemistry were used to detect gene expression. Whole-cell patch-clamp, intracellular calcium measurement, cell migration assays, and organ culture were used to assess channel function. K(V)1.3 was unique among the K(V)1 channels in showing preserved and up-regulated expression when the vascular smooth muscle cells switched to the proliferating phenotype. There was strong expression in neointimal formations. Voltage-dependent potassium current in proliferating cells was sensitive to three different blockers of K(V)1.3 channels. Calcium entry was also inhibited. All three blockers reduced vascular smooth muscle cell migration and the effects were non-additive. One of the blockers (margatoxin) was highly potent, suppressing cell migration with an IC(50) of 85 pM. Two of the blockers were tested in organ-cultured human vein samples and both inhibited neointimal hyperplasia.. K(V)1.3 potassium channels are functional in proliferating mouse and human vascular smooth muscle cells and have positive effects on cell migration. Blockers of the channels may be useful as inhibitors of neointimal hyperplasia and other unwanted vascular remodelling events.

Topics: Animals; Aorta, Thoracic; Calcium; Cell Movement; Cell Proliferation; Cells, Cultured; Dose-Response Relationship, Drug; Ficusin; Humans; Hyperplasia; Immunohistochemistry; Kv1.3 Potassium Channel; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Organ Culture Techniques; Patch-Clamp Techniques; Potassium Channel Blockers; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Saphenous Vein; Scorpion Venoms; Time Factors; Triterpenes; Tunica Intima

Genetic ablation of the voltage-gated potassium channel Kv1.3 improves insulin sensitivity and increases metabolic rate in mice. Inhibition of Kv1.3 in mouse adipose and skeletal muscle is reported to increase glucose uptake through increased GLUT4 translocation. Since Kv1.3 represents a novel target for the treatment of diabetes, the present study investigated whether Kv1.3 is functionally expressed in human adipose and skeletal muscle and whether specific pharmacological inhibition of the channel is capable of modulating insulin sensitivity in diabetic mouse models. Voltage-gated K(+) channel currents in human skeletal muscle cells (SkMC) were insensitive to block by the specific Kv1.3 blockers 5-(4-phenoxybutoxy)psoralen (PAP-1) and margatoxin (MgTX). Glucose uptake into SkMC and mouse 3T3-L1 adipocytes was also unaffected by treatment with PAP-1 or MgTX. Kv1.3 protein expression was not observed in human adipose or skeletal muscle from normal and type 2 diabetic donors. To investigate the effect of specific Kv1.3 inhibition on insulin sensitivity in vivo, PAP-1 was administered to hyperglycemic mice either acutely or for 5 days prior to an insulin tolerance test. No effect on insulin sensitivity was observed at free plasma PAP-1 concentrations that are specific for inhibition of Kv1.3. Insulin sensitivity was increased only when plasma concentrations of PAP-1 were sufficient to inhibit other Kv1 channels. Surprisingly, acute inhibition of Kv1.3 in the brain was found to decrease insulin sensitivity in ob/ob mice. Overall, these findings are not supportive of a role for Kv1.3 in the modulation of peripheral insulin sensitivity.

Topics: 3T3-L1 Cells; Adipose Tissue; Animals; CHO Cells; Cricetinae; Cricetulus; Diabetes Mellitus, Experimental; Ficusin; Glucose; Humans; Hyperglycemia; Insulin; Insulin Resistance; Kv1.3 Potassium Channel; Mice; Muscle, Skeletal; Obesity; Pancreatitis-Associated Proteins; Patch-Clamp Techniques; Potassium; Scorpion Venoms