Minoxidil inhibits proliferation and migration of cultured vascular smooth muscle cells and neointimal formation after balloon catheter injury

Anti-invasive effects of minoxidil on human breast cancer cells: combination with ranolazine

A plethora of ion channels have been shown to be involved systemically in the pathophysiology of cancer and ion channel blockers can produce anti-metastatic effects. However, although ion channels are known to frequently function in concerted action, little is known about possible combined effects of ion channel modulators on metastatic cell behaviour. Here, we investigated functional consequences of pharmacologically modulating ATP-gated potassium (K_ATP) channel and voltage-gated sodium channel (VGSC) activities individually and in combination. Two triple-negative human breast cancer cell lines were used: MDA-MB-231 and MDA-MB-468, the latter mainly for comparison. Most experiments were carried out on hypoxic cells. Electrophysiological effects were studied by whole-cell patch clamp recording. Minoxidil (a K_ATP channel opener) and ranolazine (a blocker of the VGSC persistent current) had no effect on cell viability and proliferation, alone or in combination. In contrast, invasion was significantly reduced in a dose-dependent manner by clinical concentrations of minoxidil and ranolazine. Combining the two drugs produced significant additive effects at concentrations as low as 0.625 μM ranolazine and 2.5 μM minoxidil. Electrophysiologically, acute application of minoxidil shifted VGSC steady-state inactivation to more hyperpolarised potentials and slowed recovery from inactivation, consistent with inhibition of VGSC activation. We concluded (i) that clinically relevant doses of minoxidil and ranolazine individually could inhibit cellular invasiveness dose dependently and (ii) that their combination was additionally effective. Accordingly, ranolazine, minoxidil and their combination may be repurposed as novel anti-metastatic agents.

Potassium channel openers increase aortic elastic fiber formation and reverse the genetically determined elastin deficit in the BN rat

Hypertension is a cardiovascular disorder that appears in more than half of the patients with Williams-Beuren syndrome, hemizygous for the elastin gene among 26 to 28 other genes. It was shown that the antihypertensive drug minoxidil, an ATP-dependent potassium channel opener, enhances elastic fiber formation; however, no wide clinical application was developed because of its adverse side effects. The Brown Norway rat was used here as an arterial elastin-deficient model. We tested 3 different potassium channel openers, minoxidil, diazoxide, and pinacidil, and 1 potassium channel blocker, glibenclamide, on cultured smooth muscle cells from Brown Norway rat aorta. All tested potassium channel openers increased mRNAs encoding proteins and enzymes involved in elastic fiber formation, whereas glibenclamide had the opposite effect. The higher steady-state level of tropoelastin mRNA in minoxidil-treated cells was attributable to an increase in both transcription and mRNA stability. Treatment of Brown Norway rats for 10 weeks with minoxidil or diazoxide increased elastic fiber content and decreased cell number in the aortic media, without changing collagen content. The minoxidil-induced cardiac hypertrophy was reduced when animals simultaneously received irbesartan, an angiotensin II-receptor antagonist. This side effect of minoxidil was not observed in diazoxide-treated animals. In conclusion, diazoxide, causing less undesirable side effects than minoxidil, or coadministration of minoxidil and irbesartan, increases elastic fiber content, decreases cell number in the aorta and, thus, could be suitable for treating vascular pathologies characterized by diminished arterial elastin content and simultaneous hypertension.

Limitations of human occipital scalp hair follicle organ culture for studying the effects of minoxidil as a hair growth enhancer

Minoxidil induces new hair growth in approximately one-third of patients with androgenetic alopecia after 1 year of treatment. With several conflicting reports in the literature based on small-scale studies, the current study aimed to clarify whether organ culture of human scalp anagen VI hair follicles is a suitable in vitro test system for reproducing, and experimentally dissecting, the recognized in vivo hair-growth-promoting capacity of minoxidil. Hair shaft elongation was studied in terminal anagen VI hair follicles microdissected from the occipital scalp of 36 healthy adults. A total of 2300 hair follicles, approximately 65 per individual, were tested using modifications of a basic organ culture protocol. It is shown here that minoxidil does not significantly increase hair shaft elongation or the duration of anagen VI in ex vivo culture despite several enhancements on the conventional methodology. This disparity to what is seen clinically in minoxidil responders may be explained by the following: (i) use of occipital (rather than frontotemporal or vertex) hair follicles; (ii) use of, already maximally growing, anagen VI hair follicles; (iii) a predominance of hair follicles from minoxidil unresponsive-donors; (iv) use of minoxidil rather than its sulfate metabolite; and/or (v) use of a suboptimal minoxidil dosage. This disparity questions the usefulness of standard human hair follicle organ culture in minoxidil research. Unexpectedly, minoxidil even inhibited hair shaft elongation in the absence of insulin, which may indicate that the actual hair-growth-modulatory effects of minoxidil depend on the concomitant local presence/absence of other growth modulators.