A continuous mode of action of nitric oxide in hard-to-heal wound healing

Nitric oxide: a gas transmitter in healthy and diseased skin

Numerous physiological processes in the human skin are mediated by nitric oxide, a gaseous signalling molecule. Almost every type of skin cell may produce nitric oxide, it is possible to generate nitric oxide without the need of enzymes. Nitric oxide plays a crucial role in regulating apoptosis, keratinocyte differentiation and proliferation, the protective properties of the epidermal barrier, and the structure and functions of the microcirculatory bed. Nitric oxide is involved in immunological and inflammatory responses, hair growth regulation, and wound healing processes. It mediates ultraviolet-induced processes such as erythema and edema development and participates in melanogenesis. Furthermore, the ability of nitric oxide to bind reactive oxygen species and prevent lipid peroxidation gives it antioxidant qualities. This coordinated action of nitric oxide on gene expression and membrane integrity effectively protects cells from ultraviolet A-induced apoptosis and necrosis. Furthermore, nitric oxide can be considered as a molecule that inhibits the development of cancer and photoaging. It directly harms microorganisms and indirectly activates the immune system, exhibiting antibacterial, antiviral, and antifungal qualities. Notably, nitric oxide is effective against antibiotics-resistant bacteria. All of the aforementioned findings suggest that nitric oxide is a gaseous mediator that can protect skin function.

Development of an Asymmetric Alginate Hydrogel Loaded with S-Nitrosoglutathione and Its Application in Chronic Wound Healing

Nitric oxide (NO) is an endogenous signaling molecule that plays a critical role in wound healing. However, the gaseous nature, short half-life, and low stability of NO present challenges for its clinical application. To address these issues, this study introduces an innovative S-nitrosoglutathione (GSNO)-loaded asymmetric alginate (SA) hydrogel (GSNO-SA) as a novel solution for treating infected chronic wounds. The hydrogel is designed with a layer-by-layer melting-permeation crosslinking approach, forming a dense upper layer and a sparse lower layer structure, effectively promoting exudate management while delaying NO release. The results demonstrate that the GSNO-SA hydrogel extends NO release for up to 48 h, exhibits rapid exudate absorption (72.3 ± 1.5% equilibrium swelling after 5 min), significant antibacterial activity (over 90% antibacterial rate against E. coli and S. aureus), and anti-inflammatory effects (marked reduction in TNF-α expression), and promotes angiogenesis (90.00 ± 5.92% migration rate at 48 h). Additionally, animal studies show that the GSNO-SA hydrogel accelerates wound healing, achieving a 99.2 ± 0.1% closure rate at 14 days. Histological and immunohistochemical evaluations further confirm its ability to regulate inflammation (13.34-fold upregulation of CD163) and promote angiogenesis (3.02-fold upregulation of α-SMA). Theoretically, this asymmetric design provides a novel strategy for developing exudate-managing dressings by integrating controlled NO release with hierarchical pore structures.

Modulation of Macrophage ferroptosis under the guide of infrared thermography promotes the healing of pressure injuries

BACKGROUND

Accurately recognizing and regulating the transition time of macrophages to a pro- (M1-like) or anti-inflammatory (M2-like) state is essential for improving chronic inflammation in pressure injuries (PIs).

OBJECTIVE

This study aimed to evaluate the effectiveness of infrared thermography (IRT) in measuring wound temperature of PIs for the purpose of guiding treatment in regulating chronic inflammation.

METHODS

The healing process of 21 patients with PIs was monitored using IRT prospectively followed for 30 days. The wound temperature changing pattern of different healing outcomes were analyzed and calculated the optimal wound temperature range to guide the treatment time of anti-inflammation for 100 patients with PIs accurately. Additionally, the molecular mechanisms underlying the observed temperature changes in a mouse model of PI were investigated, and the effect of IRT-guided chronic inflammation targeting ferroptosis modulation on PIs was validated.

RESULTS

The application of IRT to monitor PIs temperatures outside the 36.23 °C to 37.37 °C range is indicative of a potential risk indicator, which allows for the timely guidance of treatment to markedly enhance the efficacy of PIs healing outcomes. This wound temperature change was also observed during the process of PIs healing in mice, as a result of the imbalance of M1-like/M2-like macrophages and the subsequent chronic inflammation. Mechanically, evidence indicates that ferroptosis is hyperactivated in PIs, and the enrichment of M1-like macrophages with iNOS/NO• can enhance their resistance to ferroptosis compared with M2-like macrophages, resulting in the imbalance of M1-like/M2-like macrophages and subsequent alteration of wound temperature.

CONCLUSIONS

The modulation of M2-like macrophage resistance to ferroptosis in PIs by NO• donors, suggesting by IRT-monitored temperature changes, has been demonstrated to significantly improve chronic inflammation. This establishes a foundation for the application of IRT to direct a therapeutic strategy for the precise promotion of PIs healing.