Signaling mechanism underlying the promotion of keratinocyte migration by angiotensin II

AT2R Activation Improves Wound Healing in a Preclinical Mouse Model

Abnormal skin healing resulting in chronic wounds or hypertrophic scarring remains a major healthcare burden. Here, the antifibrotic angiotensin II type 2 receptor (AT2R) signaling pathway was modulated to determine its impact on cutaneous wound healing. Balb/c mice received two splinted full-thickness wounds. Topical treatments with the selective AT2R agonist compound 21 (C21) and/or selective antagonist PD123319 or saline vehicle were administered until sacrifice on post-wounding days 7 or 10. The rate of wound re-epithelialization was accelerated by PD123319 and combination treatments. In vitro, C21 significantly reduced human fibroblast migration. C21 increased both collagen and vascular densities at days 7 and 10 post-wounding and collagen I:III ratio at day 10, while PD123319 and combination treatments decreased them. Genes associated with regeneration and repair were upregulated by C21, while PD123319 treatment increased the expression of genes associated with inflammation and immune cell chemotaxis. C21 treatment reduced wound total leukocyte and neutrophil staining densities, while PD123319 increased these and macrophage densities. Overall, AT2R activation with C21 yields wounds that mature more quickly with structural, cellular, and gene expression profiles more closely approximating unwounded skin. These findings support AT2R signal modulation as a potential therapeutic target to improve skin quality during wound healing.

Unlocking the protective potential of the angiotensin type 2 receptor (AT2R) in acute lung injury and age-related pulmonary dysfunction

Despite its known importance in the cardiovascular system, the specific role and impact of the angiotensin type 2 receptor (AT2R) in lung physiology and pathophysiology remain largely elusive. In this study, we highlight the distinct and specialized lung-specific roles of AT2R, primarily localized to an alveolar fibroblast subpopulation, in contrast to the angiotensin type 1 receptor (AT1R), which is almost exclusively expressed in lung pericytes. Evidence from our research demonstrates that the disruption of AT2R (AT2R-/y), is associated with a surge in oxidative stress and impaired lung permeability, which were further intensified by Hyperoxic Acute Lung Injury (HALI). With aging, AT2R-/y mice show an increase in oxidative stress, premature enlargement of airspaces, as well as increased mortality when exposed to hyperoxia as compared to age-matched WT mice. Our investigation into Losartan, an AT1R blocker, suggests that its primary HALI lung-protective effects are channeled through AT2R, as its protective benefits are absent in AT2R-/y mice. Importantly, a non-peptide AT2R agonist, Compound 21 (C21), successfully reverses lung oxidative stress and TGFβ activation in wild-type (WT) mice exposed to HALI. These findings suggest a possible paradigm shift in the therapeutic approach for lung injury and age-associated pulmonary dysfunction, from targeting AT1R with angiotensin receptor blockers (ARBs) towards boosting the protective function of AT2R.

Differential effects of Losartan and Atorvastatin in partial and full thickness burn wounds

Healing of burn wounds is often associated with scar formation due to excessive inflammation and delayed wound closure. To date, no effective treatment is available to prevent the fibrotic process. The Renin Angiotensin System (RAS) was shown to be involved in fibrosis in various organs. Statins (e.g. Atorvastatin), Angiotensin receptor antagonists (e.g. Losartan) and the combination of these drugs are able to reduce the local RAS activation, and reduced fibrosis in other organs. We investigated whether inhibition of the RAS could improve healing of burn wounds by treatment with Atorvastatin, Losartan or the combination of both drugs. Therefore, full and partial thickness burn wounds were inflicted on both flanks of Yorkshire pigs. Oral administration of Atorvastatin, Losartan or the combination was started at post-burn day 1 and continued for 28 days. Full thickness wounds were excised and transplanted with an autologous meshed split-thickness skin graft at post-burn day 14. Partial thickness wounds received conservative treatment. Atorvastatin treatment resulted in enhanced graft take and wound closure of the full thickness wounds, faster resolution of neutrophils compared to all treatments and reduced alpha-smooth muscle actin positive cells compared to control treatment. Treatment with Losartan and to a lesser extent the combination therapy resulted in diminished graft take, increased wound contraction and poorer scar outcome. In contrast, Losartan treatment in partial thickness wounds decreased the alpha-smooth muscle actin+ fibroblasts and contraction. In conclusion, we showed differential effects of Losartan and Atorvastatin in full and partial thickness wounds. The extensive graft loss seen in Losartan treated wounds is most likely responsible for the poor clinical outcome of these full thickness burn wounds. Therefore, Losartan treatment should not be started before transplantation in order to prevent graft loss. Atorvastatin seems to accelerate the healing process in full thickness wounds possibly by dampening the pro-inflammatory response.

Multifunctional and biomimetic fish collagen/bioactive glass nanofibers: fabrication, antibacterial activity and inducing skin regeneration in vitro and in vivo

The development of skin wound dressings with excellent properties has always been an important challenge in the field of biomedicine. In this study, biomimetic electrospun fish collagen/bioactive glass (Col/BG) nanofibers were prepared. Their structure, tensile strength, antibacterial activity and biological effects on human keratinocytes, human dermal fibroblasts and human vascular endothelial cells were investigated. Furthermore, the Sprague Dawley rat skin defect model was used to validate their effect on wound healing. The results showed that compared with pure fish collagen nanofibers, the tensile strength of the Col/BG nanofibers increased to 21.87±0.21 Mpa, with a certain degree of antibacterial activity against Staphylococcus aureus. It was also found that the Col/BG nanofibers promoted the adhesion, proliferation and migration of human keratinocytes. Col/BG nanofibers induced the secretion of type one collagen and vascular endothelial growth factor by human dermal fibroblasts, which further stimulated the proliferation of human vascular endothelial cells. Animal experimentation indicated that the Col/BG nanofibers could accelerate rat skin wound healing. This study developed a type of multifunctional and biomimetic fish Col/BG nanofibers, which had the ability to induce skin regeneration with adequate tensile strength and antibacterial activity. The Col/BG nanofibers are also easily available and inexpensive, providing the possibility for using as a functional skin wound dressing.

Angiotensin II promotes endometrial cancer cell survival

Endometrial cancer (EC) is one of the most common female cancers. One of the key processes involved in EC development is uncontrolled proliferation stimulated by local factors such as angiotensin. The aim of the present study was to evaluate the influence of angiotensin II (Ang II) on human EC cells. Biological assays and gene expression analysis were performed on three cell lines: ISH, MFE-296 and MFE-280. Our results indicated that at the beginning of cancerogenesis Ang II induced abnormal proliferation at lower doses. We also showed that dose-dependent induction of proliferation was connected with changes in the expression of MKI67, CCND1 and CCNE1 genes in well- and poorly differentiated cancer cells. After Ang II treatment, poorly differentiated endometrial cancer cell line acquired a mesenchymal phenotype, which was characterized by induced expression of EMT-related genes (VIM, CD44, SNAI1, ZEB1 and ZEB2). Our study revealed that Ang II influences EC cells in terms of cancer-related processes, and is responsible for increased proliferation, reduction in apoptosis, increased mobility and modulation of adhesion potential. Its effect and effectiveness appear to be highly connected with the differentiation status of the cancerous cells, as Ang II appears to play a crucial role in the early and late stages of malignant transformation.

Silver nanoparticles/chitosan oligosaccharide/poly(vinyl alcohol) nanofiber promotes wound healing by activating TGFβ1/Smad signaling pathway

Wound healing occupies a remarkable place in everyday pathology and remains a challenging clinical problem. In our previous study, we prepared a silver nanoparticle/chitosan oligosaccharide/poly(vinyl alcohol) (PVA/COS-AgNPs) nanofiber via electrospinning and revealed that it could promote wound healing; however, the healing mechanism remained unknown. Therefore, we aimed to clarify the mechanism underlying the accelerated healing effect of the PVA/COS-AgNPs nanofiber. The TGFβ1/Smad signaling pathway is actively involved in wound healing. Considering the key role of this signaling pathway in wound healing, our preliminary study showed that the TGFβ1 level was significantly increased during the early stage of wound healing. Thus, in this study, hematoxylin-eosin, Masson's trichrome, immunofluorescent staining, hydroxyproline content, quantitative real-time polymerase chain reaction, and Western blot analyses were used to analyze the wound healing in a rat model treated with gauze, the PVA/COS-AgNPs nanofiber, and the nanofiber plus SB431542 (an inhibitor of TGFβ1 receptor kinase). The results showed that the PVA/COS-AgNPs nanofiber promoted wound healing and upregulated the expression levels of cytokines associated with the TGFβ1/Smad signaling pathway such as TGFβ1, TGFβRI, TGFβRII, collagen I, collagen III, pSmad2, and pSmad3. Inhibiting this pathway with SB431542 resulted in prevention of the PVA/COS-AgNPs nanofiber-associated salutary effects on the early stage of wound healing and relative cytokines expression. In conclusion, the wound healing effect of the PVA/COS-AgNPs nanofiber involves activation of the TGFβ1/Smad signaling pathway.