Wound Repair Regen. 2017 Apr;25(2):217-223.

Topical application of nitrosonifedipine, a novel radical scavenger, ameliorates ischemic skin flap necrosis in a mouse model.

Fukunaga Y1, Izawa-Ishizawa Y2, Horinouchi Y2, Sairyo E2, Ikeda Y2, Ishizawa K3,4, Tsuchiya K5, Abe Y1, Hashimoto I1, Tamaki T2.

1 Department of Plastic and Reconstructive Surgery, Institute of Biomedical Sciences, Tokushima University Graduate School.
2 Department of Pharmacology, Institute of Biomedical Sciences, Tokushima University Graduate School.
3 Department of Pharmacy, Tokushima University Hospital.
4 Department of Clinical Pharmacy, Institute of Biomedical Sciences, Tokushima University Graduate School.
5 Department of Medical Pharmacology, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan.

Abstract

Ischemic skin flap necrosis can occur in random pattern flaps. An excess amount of reactive oxygen species is generated and causes necrosis in the ischemic tissue. Nitrosonifedipine (NO-NIF) has been demonstrated to possess potent radical scavenging ability. However, there has been no study on the effects of NO-NIF on ischemic skin flap necrosis. Therefore, they evaluated the potential of NO-NIF in ameliorating ischemic skin flap necrosis in a mouse model. A random pattern skin flap (1.0 × 3.0 cm) was elevated on the dorsum of C57BL/6 mice. NO-NIF was administered by topical injection immediately after surgery and every 24 hours thereafter. Flap survival was evaluated on postoperative day 7. Tissue samples from the skin flaps were harvested on postoperative days 1 and 3 to analyze oxidative stress, apoptosis and endothelial dysfunction. The viable area of the flap in the NO-NIF group was significantly increased (78.30 ± 7.041%) compared with that of the control group (47.77 ± 6.549%, p < 0.01). NO-NIF reduced oxidative stress, apoptosis and endothelial dysfunction, which were evidenced by the decrease of malondialdehyde, p22phox protein expression, number of apoptotic cells, phosphorylated p38 MAPK protein expression, and vascular cell adhesion molecule-1 protein expression while endothelial nitric oxide synthase protein expression was increased. In conclusion, they demonstrated that NO-NIF ameliorated ischemic skin flap necrosis by reducing oxidative stress, apoptosis, and endothelial dysfunction. NO-NIF is considered to be a candidate for the treatment of ischemic flap necrosis.

PMID: 28090711

 

Summary

The insufficient blood supply of random pattern flaps sometimes causes ischemic flap necrosis that prolongs the treatment period and occasionally requires additional surgery. An excess amount of Reactive oxygen species (ROS) is generated in the ischemic flap as a result of ischemia–reperfusion injury, leukocyte adhesion and hematoma. ROS in the ischemic skin flap leads to cell membrane damage, apoptosis, and endothelial dysfunction, which contributes to flap necrosis. Therefore, ROS is considered as a therapeutic target in ischemic flap necrosis. Nitrosonifedipine [2,6-dimethyl-4-(2-nitrosophenyl)-3,5-pyridinedicarboxylic acid dimethyl ester] (NO-NIF) is a nitroso analog of nifedipine which is an L-type Ca2+-channel blocker. NO-NIF is highly reactive to lipid-derived radicals in vitro, and participates in ROS radical scavenging activity at the cell membrane1, 2. We have already demonstrated by conducting in vivo studies that NO-NIF ameliorates diabetic nephropathy and vascular remodeling, in which oxidative stress plays a role in the pathogenesis. NO-NIF suppressed superoxide generation and the expression of p22phox, which is a component of NADPH oxidase. Moreover, NO-NIF prevented cultured cells such as HK2, an immortalized proximal tubule epithelial cell line, and human umbilical vein endothelial cells from oxidative stress-induced cytotoxicity3, 4.

From the abovementioned results, we considered NO-NIF as a possible candidate in the treatment of ischemic flap necrosis. However, there has been no study on the effects of NO-NIF on ischemic skin flap necrosis. Therefore, we evaluated the potential of NO-NIF in ameliorating ischemic necrosis of the random pattern flap in a mouse model.

In present study, we demonstrated that the novel anti-oxidant, NO-NIF, ameliorated ischemic skin flap necrosis by reducing apoptosis and endothelial dysfunction for the first time (Figure1, 2). NO-NIF could be a candidate for treatment of ischemic flap necrosis. Although further research of the mechanisms of NO-NIF is required for clinical application, this study highlights its potential for overcoming flap necrosis.

 

 

Figure 1. NO-NIF ameliorated ischemic skin flap necrosis by reducing apoptosis and endothelial dysfunction.

 

 

Figure 2. The appearance of the flaps on postoperative day 7. The viable area of the flaps in the NO-NIF group was significantly increased compared with that of flaps in the control group.