The Effect of Angiotensin (1–7) on Survival of Random Pattern Skin Flaps With Nicotine-Induced Ischemia in Rats

Could angiotensin-(1-7) be connected with improvement of microvascular function in diabetic patients? Angiotensin-(1-7) iontophoresis may provide the answer

Diabetes mellitus, a metabolic disorder with significant global health care burden, causes chronic microvascular and macrovascular complications that still comprise a therapeutic challenge. Angiotensin-(1-7), a heptapeptide with vasodilatory properties, has been found to restore vascular reactivity and endothelial cell function, mostly in experiments on larger isolated animal vessels and in cell cultures. The presented hypothesis suggests that angiotensin-(1-7) might have beneficial effects on microvascular function that is damaged in diabetic patients, alleviating endothelial dysfunction and increasing microvascular reactivity to various vasoactive agents in diabetes. It is further proposed that iontophoresis with angiotensin-(1-7) might be used to explore this potential beneficial effect, as well as provide a possible future therapeutic delivery method for angiotensin-(1-7). Since other peptides and proteins have been previously tested and used in iontophoretic transdermal delivery, it is plausible that angiotensin-(1-7) would be a suitable candidate for transdermal iontophoretic application for research (and potentially therapeutic) purposes. If confirmed, the delineated hypothesis would have immense implications for more effective care of diabetic patients, as well as for better understanding of microcirculatory pathophysiological mechanisms in diabetes.

The effect of TENS on random pattern flap survival in nicotinized rats

The adverse effects of cigarettes, due to their nicotine content, may cause important ischemic complications in flaps. Electrical stimulation increases blood flow in ischemic tissues, the level of vascular endothelial growth factor, capillary density, and angiogenesis while decreasing oxygen tension in tissues. Electrical stimulation is also known to increase survival rate in flaps. In this study, which tests the hypothesis that TENS (a type of electrical stimulation) contributes to enhancement of flap viability by eliminating the adverse effects of nicotine, 40 rats were divided into 4 groups of 10 rats. Nicotinization was achieved by subcutaneous administration of 2 mg/kg per day to the rats, other than those in the Control group, for 4 weeks. The rats in one of the nicotinized groups received 20 mA, 80 Hz TENS (TENS1 group) for 1 hour daily throughout the last week before McFarlane flaps of random pattern were made in the backs of all the rats. Another nicotinized group was subjected to TENS in a similar dose after flap elevation (TENS2 group). Flap blood flow was measured before and 48 hours after their construction, and their fluorescein perfusion was measured immediately after the flap elevation. The comparison of the survival rates of the flaps revealed that, although the blood flow in the Nicotine group was significantly lower than in the Control group, it was significantly higher in the TENS1 group than in both the Control and Nicotine groups. The proportion of the area stained with fluorescein, immediately after the elevation of flaps, was significantly reduced in the Nicotine group compared to the Control group. In the TENS1 group, however, it was greater than in the nicotine and TENS2 groups. Flap viability rates decreased significantly in the Nicotine group compared with the Control group. In the TENS2 group, however, an increase was observed compared with the Nicotine group.These findings suggest that although TENS performed before flap elevation does not contribute to flap survival, despite causing a rise in blood flow, it enhances flap survival when applied postoperatively. Given the practicality and low cost of TENS, it can be concluded that it may be possible to use it in the management of ischemic complications in flap operations in smokers.

Effect of hyperbaric oxygen therapy on healing in an experimental model of degloving injury in tails of nicotine-treated rats

The aim of this study was to investigate the effect of hyperbaric oxygen (HBO) therapy on healing in an experimental model of a degloving injury of the tails of nicotine-treated rats. Thirty-two male Sprague-Dawley rats were randomized to four groups (n = 8): nicotine (group 1); HBO (group 2); nicotine + HBO (group 3); and control (group 4). The mean length of the necrotic parts of the tails at the degloving injury site was significantly higher in group 1 compared with groups 2, 3, and 4, and was significantly lower in group 2 compared with groups 1, 3, and 4. The mean histopathological stage of ulcers at the degloving injury site was statistically significantly higher (more severe) in group 1 compared with groups 2, 3, and 4, and was statistically significantly lower in group 2 compared with groups 1, 3, and 4. It appears that the negative effects of nicotine on wound healing in degloving injuries are negated by the positive effects of immediate HBO therapy.

Angiotensin-(1-7): beyond the cardio-renal actions

It is well known that the RAS (renin-angiotensin system) plays a key role in the modulation of many functions in the body. AngII (angiotensin II) acting on AT1R (type 1 AngII receptor) has a central role in mediating most of the actions of the RAS. However, over the past 10 years, several studies have presented evidence for the existence of a new arm of the RAS, namely the ACE (angiotensin-converting enzyme) 2/Ang-(1-7) [angiotensin-(1-7)]/Mas axis. Ang-(1-7) can be produced from AngI or AngII via endo- or carboxy-peptidases respectively. ACE2 appears to play a central role in Ang-(1-7) formation. As described for AngII, Ang-(1-7) also has a broad range of effects in different organs and tissues which goes beyond its initially described cardiovascular and renal actions. Those effects are mediated by Mas and can counter-regulate most of the deleterious effects of AngII. The interaction Ang-(1-7)/Mas regulates different signalling pathways, such as PI3K (phosphoinositide 3-kinase)/AKT and ERK (extracellularsignal-regulated kinase) pathways and involves downstream effectors such as NO, FOXO1 (forkhead box O1) and COX-2 (cyclo-oxygenase-2). Through these mechanisms, Ang-(1-7) is able to improve pathological conditions including fibrosis and inflammation in organs such as lungs, liver and kidney. In addition, this heptapeptide has positive effects on metabolism, increasing the glucose uptake and lipolysis while decreasing insulin resistance and dyslipidaemia. Ang-(1-7) is also able to improve cerebroprotection against ischaemic stroke, besides its effects on learning and memory. The reproductive system can also be affected by Ang-(1-7) treatment, with enhanced ovulation, spermatogenesis and sexual steroids synthesis. Finally, Ang-(1-7) is considered a potential anti-cancer treatment since it is able to inhibit cell proliferation and angiogenesis. Thus the ACE2/Ang-(1-7)/Mas pathway seems to be involved in many physiological and pathophysiological processes in several systems and organs especially by opposing the detrimental effects of inappropriate overactivation of the ACE/AngII/AT1R axis.

NorLeu3-A(1-7) stimulation of diabetic foot ulcer healing: results of a randomized, parallel-group, double-blind, placebo-controlled phase 2 clinical trial

This randomized, double-blind, placebo-controlled Phase 2 clinical trial explored NorLeu(3)-A(1-7) (DSC127) safety and healing efficacy in diabetic foot ulcers. Patients with chronic, noninfected, neuropathic, or neuroischemic plantar Wagner Grade 1 or 2 foot ulcers (n = 172) were screened for nonhealing. Subjects were randomized to receive 4 weeks' once-daily topical treatment with 0.03% DSC127 (n = 26), 0.01% DSC127 (n = 27), or Placebo (n = 24), followed by 20 weeks' standard of care. DSC127 was assessed for safety (including laboratory values and adverse events), primary efficacy (% ulcers completely epithelialized at Week 12), and durability of effect. Baseline, demography, and safety parameters were compared between intent-to-treat groups and were comparable. Dose-response curves for DSC127 effect on % area reduction from baseline at Week 12 (40% placebo; 67% 0.01% DSC127; 80% 0.03% DSC127) and 24 (23% placebo; 53% 0.01% DSC127; 95% 0.03% DSC127) followed a log-linear pattern for both intent-to-treat and per-protocol populations. Covariate analysis compared reduction in ulcer area, depth, and volume from baseline; reductions in the 0.03% DSC127 group were greater at Weeks 12 and 24. Placebo-treated ulcers healed in a median 22 weeks vs. 8.5 weeks for 0.03%DSC127 (p = 0.04). This study provides preliminary evidence that DSC127 is safe and effective in accelerating the healing of diabetic foot ulcers.