The effect of minoxidil analogues and metabolites on the contraction of collagen lattices by human skin fibroblasts

Cyclic Nitroxide 4-Methoxy-Tempo May Decrease Serum Amyloid A-Mediated Renal Fibrosis and Reorganise Collagen Networks in Aortic Plaque

Acute-phase serum amyloid A (SAA) can disrupt vascular homeostasis and is elevated in subjects with diabetes, cardiovascular disease, and rheumatoid arthritis. Cyclic nitroxides (e.g., Tempo) are a class of piperidines that inhibit oxidative stress and inflammation. This study examined whether 4-methoxy-Tempo (4-MetT) inhibits SAA-mediated vascular and renal dysfunction. Acetylcholine-mediated vascular relaxation and aortic guanosine-3',5'-cyclic monophosphate (cGMP) levels both diminished in the presence of SAA. 4-MetT dose-dependently restored vascular function with corresponding increases in cGMP. Next, male ApoE-deficient mice were administered a vehicle (control, 100 µL PBS) or recombinant SAA (100 µL, 120 µg/mL) ± 4-MetT (at 15 mg/kg body weight via i.p. injection) with the nitroxide administered before (prophylaxis) or after (therapeutic) SAA. Kidney and hearts were harvested at 4 or 16 weeks post SAA administration. Renal inflammation increased 4 weeks after SAA treatment, as judged by the upregulation of IFN-γ and concomitant increases in iNOS, p38MAPK, and matrix metalloproteinase (MMP) activities and increased renal fibrosis (Picrosirius red staining) in the same kidneys. Aortic root lesions assessed at 16 weeks revealed that SAA enhanced lesion size (vs. control; p < 0.05), with plaque presenting with a diffuse fibrous cap (compared to the corresponding aortic root from control and 4-MetT groups). The extent of renal dysfunction and aortic lesion size was largely unchanged in 4-MetT-supplemented mice, although renal fibrosis diminished at 16 weeks, and aortic lesions presented with redistributed collagen networks. These outcomes indicate that SAA stimulates renal dysfunction through promoting the IFN-γ-iNOS-p38MAPK axis, manifesting as renal damage and enhanced atherosclerotic lesions, while supplementation with 4-MetT only affected some of these pathological changes.

Evaluation of glucuronide metabolite stability in dried blood spots

Background: Stabilization of phase II metabolites is an important consideration during bioanalytical method development, method validation and sample analysis. Generic approaches to stabilize these metabolites during storage in liquid-based matrices include pH adjustment of samples prior to storage and/or temperature control; although a variety of other compound-specific stabilization techniques exist. Dried blood spot (DBS) technology is becoming a popular alternative to liquid matrix sampling in many preclinical and clinical applications. However, concerns remain regarding the stability of metabolites stored under ambient conditions using DBS. Results: Experimental data have shown that, under ambient storage conditions, the stability of the glucuronides investigated herein stored as DBS is equivalent to that of liquid samples stored at -80°C. Conclusion: The decision to employ DBS technology for a given study needs to be considered on a case-by-case basis with an understanding of compound-specific metabolism characteristics and clinical study design.

Clinical Pharmacology of Antihypertensive Therapy

Adequate control of blood pressure poses challenges for hypertensive patients and their physicians. Success rates of greater than 80% in reducing blood pressure to target values among high-risk hypertensive patients reported by several recent clinical trials argue that effective medications currently are available. Yet, only 34% of hypertensive patients in the United States are at their goal blood pressure according to the most recent national survey. Rational selection of antihypertensive drugs that target both the patient's blood pressure and comorbid conditions coupled with more frequent use of low-dose drug combinations that have additive efficacy and low adverse-effect profiles could improve significantly US blood pressure control rates and have a positive impact on hypertension-related cardiovascular and renal mortality and morbidity. This article reviews the pharmacokinetic and pharmacodynamic principles that underlie the actions of drugs in each of the classes of antihypertensive agents when used alone and in combination, provides practical pharmacologic information about the drugs most frequently prescribed for treatment of hypertension in the outpatient setting, and summarizes the current data influencing the selection of drugs that might be used most effectively in combination for the majority of hypertensive patients whose blood pressures are not controlled adequately by single-drug therapy.

Minoxidil and male-pattern alopecia: a potential role for a local regulator of sebum secretion with vasoconstrictive effects?

Regulation of the hair cycle takes place at the pilo-sebaceous unit with the sebaceous gland as a sex hormone-dependent part. Although minoxidil stimulates proliferation of follicular cells and activation of prostaglandin endoperoxide synthase-1, it was suggested that other mechanisms, such as an increase in the local blood flow, might mediate the drug effect on hair growth. If that is the case, it is possible that minoxidil counteracts some vasoconstrictive mediator of male-pattern alopecia. This hypothetical vasoconstrictive mediator X would have to meet some criteria: (I) vasoconstriction both in the general circulation and in the hair-growing skin; (II) local vasoconstrictive activity in the hair growing skin should be related to the circulating testosterone level; (III) only an increase in the local mediator X activity causes male-pattern alopecia, since hypertensive patients are not balder than expected. The sebaceous gland is a possible place of the mediator X secretion since it is a sex-hormone-dependent part of the pilo-sebaceous unit. ET-1 might be a suitable candidate for the mediator X, since male hormones raise ET-1 plasma levels and female hormones lower them. The speculation presented here is that ET-1, beside vasoconstriction in the general circulation, might also regulate the sebum secretion, by triggering contractions of the myoepithelial cells. This hypothetical mechanism would normally remain confined to the sebaceous gland. During puberty, sex hormones stimulate growth of sebaceous glands in both sexes. In women hypertrophied sebaceous glands under estrogen control would not increase its ET-1 content, while in men, testosterone would increase ET-1 secretion that might affect the neighboring arterioles. Induced vasoconstriction might reduce the hair growth and promote hair loss. If ET-1 plays the described role, then an ET-1 antagonist, i.e. bosentane, should also have some hair-growing properties.

Tetracycline-based MMP inhibitors can prevent fibroblast-mediated collagen gel contraction in vitro

Collagen gels in vitro can be contracted by fibroblasts. The role of matrix metalloproteinases (MMPs) in the contraction of collagen lattices by human neonatal foreskin fibroblasts (HuFFs) was investigated in tissue culture media supplemented by various doses of known gelatinase inhibitors. Fluorescent assays with model gelatinase substrates and media conditioned by fibroblasts apparently confirmed the ability of chemically modified tetracyclines (CMTs) to act as inhibitors of MMP2, and zymography demonstrated that this was the major cell-derived MMP activity. There were no observable effects on the rate of contraction of attached FPCLs containing 6 x 10(4) HuFFs (passages 18-25) with either CMT-5 or CMT-2 at all concentrations tested (0-100 micrograms/mL). However, at greater than 20 micrograms/mL doxycycline and greater than 5 micrograms/mL CMT-3, FPCL contraction was completely abolished. Quantitative assessment of cell viability by means of the MTT assay in monolayer and qualitatively within the FPCLs with CalceinAM suggested that differences were not due to cytotoxic effects. Seeding FPCLs with lower-passage fibroblasts produced identical trends. These results may implicate the involvement of MMPs in the process of gel contraction, although tetracyclines have effects additional to their ability to inhibit MMPs directly.

Topical tamoxifen--a potential therapeutic regime in treating excessive dermal scarring?

Abnormal dermal scarring which affects a large number of people is aesthetically disfiguring and can be functionally disabling. Existing medical and surgical strategies to prevent or to treat scars are frequently disappointing and more effective therapies are needed. Tamoxifen, which has been used extensively in the treatment of breast cancer over the last 20 years has recently been shown to inhibit the proliferation of fibroblasts cultured from keloid biopsies. Successful treatment of retroperitoneal fibrosis and desmoid tumours with tamoxifen has also been reported. We have investigated the potential of tamoxifen as an inhibitor of wound contraction, using fibroblast-populated collagen lattices as an in vitro model. From these studies we postulate that tamoxifen may have potential clinical significance in the treatment of abnormal scarring. Normal adult human skin fibroblasts were embedded within type I collagen, then medium either with or without addition of tamoxifen was added to the collagen lattices. Lattice diameters were measured at intervals to assess the influence of tamoxifen on the lattice contraction. The reversibility of the inhibitory effect of tamoxifen on lattice contraction was investigated by 'washing out the tamoxifen' at different time-points. To visualise changes in the morphology of fibroblasts MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] was added to the lattices. Tamoxifen at 1 and 5 microM had no significant influence on lattice contraction but higher concentrations of 50 and 100 microM completely inhibited contraction. At intermediate concentrations from 10 to 20 microM the degree of lattice contraction was dose-dependent. The reversibility of the inhibition was both dose- and time-dependent. Both the inhibition of contraction and the reversibility of inhibition appeared to correlate with changes in fibroblast morphology. The dose- and time-dependent inhibition of contraction by fibroblasts suggests that tamoxifen could be investigated as a novel potential therapeutic agent in treating abnormal dermal scarring.

An aqueous extract of the leaves of Chromolaena odorata (formerly Eupatorium odoratum) (Eupolin) inhibits hydrated collagen lattice contraction by normal human dermal fibroblasts

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.