Balance and circumstance: The renin angiotensin system in wound healing and fibrosis

The current landscape of antifibrotic therapy across different organs: A systematic approach

Fibrosis is a common pathological process that can affect virtually all the organs, but there are hardly any effective therapeutic options. This has led to an intense search for antifibrotic therapies over the last decades, with a great number of clinical assays currently underway. We have systematically reviewed all current and recently finished clinical trials involved in the development of new antifibrotic drugs, and the preclinical studies analyzing the relevance of each of these pharmacological strategies in fibrotic processes affecting tissues beyond those being clinically studied. We analyze and discuss this information with the aim of determining the most promising options and the feasibility of extending their therapeutic value as antifibrotic agents to other fibrotic conditions.

Transcriptional Evaluation of Neuropeptides, Hormones, and Tissue Repair Modulators in the Skin of Gilthead Sea Bream (Sparus aurata L.) Subjected to Mechanical Damage

The skin of bony fish is the first physical barrier and is responsible for maintaining the integrity of the fish. Lesions make the skin vulnerable to potential infection by pathogens present in the aquatic environment. In this way, wound repair has barely been studied in gilthead sea bream. Thus, this study investigated the modulation of peripheral neuro-endocrine and tissue repair markers at the transcriptional level in the skin of teleost fish subjected to mechanical damage above or below the lateral line (dorsal and ventral lesions, respectively). Samples were evaluated using RT-qPCR at 2-, 4-, and 20-days post-injury. Fish with a ventral lesion presented a trend of progressive increase in the expressions of corticotropin-releasing hormone (crh), pro-opiomelanocortin-A (pomca), proenkephalin-B (penkb), cholecystokinin (cck), oxytocin (oxt), angiotensinogen (agt), and (less pronounced) somatostatin-1B (sst1b). By contrast, fish with a dorsal lesion registered no significant increase or biological trend for the genes evaluated at the different sampling times. Collectively, the results show a rapid and more robust response of neuro-endocrine and tissue repair markers in the injuries below than above the lateral line, which could be attributable to their proximity to vital organs.

Multifunctional polymeric nanofibrous scaffolds enriched with azilsartan medoxomil for enhanced wound healing

A prolonged and compromised wound healing process poses a significant clinical challenge, necessitating innovative solutions. This research investigates the potential application of nanotechnology-based formulations, specifically nanofiber (NF) scaffolds, in addressing this issue. The study focuses on the development and characterization of multifunctional nanofibrous scaffolds (AZL-CS/PVA-NF) composed of azilsartan medoxomil (AZL) enriched chitosan/polyvinyl alcohol (CS/PVA) through electrospinning. The scaffolds underwent comprehensive characterization both in vitro and in vivo. The mean diameter and tensile strength of AZL-CS/PVA-NF were determined to be 240.42 ± 3.55 nm and 18.05 ± 1.18 MPa, respectively. A notable drug release rate of 93.86 ± 2.04%, was observed from AZL-CS/PVA-NF over 48 h at pH 7.4. Moreover, AZL-CS/PVA-NF exhibited potent antimicrobial efficacy for Staphylococcus aureus and Pseudomonas aeruginosa. The expression levels of Akt and CD31 were significantly elevated, while Stat3 showed a decrease, indicating a heightened tissue regeneration rate with AZL-CS/PVA-NF compared to other treatment groups. In vivo ELISA findings revealed reduced inflammatory markers (IL-6, IL-1β, TNF-α) within treated skin tissue, implying a beneficial effect on injury repair. The comprehensive findings of the present endeavour underscore the superior wound healing activity of the developed AZL-CS/PVA-NF scaffolds in a Wistar rat full-thickness excision wound model. This indicates their potential as novel carriers for drugs and dressings in the field of wound care.

The AT1/AT2 Receptor Equilibrium Is a Cornerstone of the Regulation of the Renin Angiotensin System beyond the Cardiovascular System

The AT₁ receptor has mainly been associated with the pathological effects of the renin-angiotensin system (RAS) (e.g., hypertension, heart and kidney diseases), and constitutes a major therapeutic target. In contrast, the AT₂ receptor is presented as the protective arm of this RAS, and its targeting via specific agonists is mainly used to counteract the effects of the AT₁ receptor. The discovery of a local RAS has highlighted the importance of the balance between AT₁/AT₂ receptors at the tissue level. Disruption of this balance is suggested to be detrimental. The fine tuning of this balance is not limited to the regulation of the level of expression of these two receptors. Other mechanisms still largely unexplored, such as S-nitrosation of the AT₁ receptor, homo- and heterodimerization, and the use of AT₁ receptor-biased agonists, may significantly contribute to and/or interfere with the settings of this AT₁/AT₂ equilibrium. This review will detail, through several examples (the brain, wound healing, and the cellular cycle), the importance of the functional balance between AT₁ and AT₂ receptors, and how new molecular pharmacological approaches may act on its regulation to open up new therapeutic perspectives.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Polymorphism AGT2 (rs4762) is involved in the development of dermatologic events: Proof-of-concept in hepatocellular carcinoma patients treated with sorafenib

BACKGROUND

Dermatologic adverse events (DAEs) are associated with a better outcome in patients with hepatocellular carcinoma (HCC) irrespective of the therapeutic agent received. The exact mechanisms associated with the development of DAEs are unknown although several studies point to direct toxicity of tyrosine kinase inhibitors (TKIs) to the skin or an immune-mediated reaction triggered by the oncologic treatment. As is the case in other conditions, individual genetic variants may partially explain a higher risk of DAEs.

AIM

To evaluate the contribution of several gene variants to the risk of developing DAEs in HCC patients treated with TKIs.

METHODS

We first analyzed 27 single-nucleotide polymorphisms (SNPs) from 12 genes selected as potential predictors of adverse event (AE) development in HCC patients treated with sorafenib [Barcelona Clinic Liver Cancer 1 (BCLC1) cohort]. Three additional cohorts were analyzed for AGT1 (rs699) and AGT2 (rs4762) polymorphisms-initially identified as predictors of DAEs: BCLC2 (n = 79), Northern Italy (n = 221) and Naples (n = 69) cohorts, respectively. The relation between SNPs and DAEs and death were assessed by univariate and multivariate Cox regression models, and presented with hazard ratios and their 95% confidence intervals (95%CI).

RESULTS

The BCLC1 cohort showed that patients with arterial hypertension (AHT) (HR = 1.61; P value = 0.007) and/or AGT SNPs had an increased risk of DAEs. Thereafter, AGT2 (rs4762) AA genotype was found to be linked to a statistically significant increased probability of DAEs (HR = 5.97; P value = 0.0201, AA vs GG) in the Northern Italy cohort by multivariate analysis adjusted for BCLC stage, ECOG-PS, diabetes and AHT. The value of this genetic marker was externally validated in the cohort combining the BCLC1, BCLC2 and Naples cohorts [HR = 3.12 (95%CI: 1.2-8.14), P value = 0.0199, AGT2 (rs4762) AA vs AG genotype and HR = 2.73 (95%CI: 1.18-6.32) P value = 0.0188, AGT2 (rs4762) AA vs GG genotype]. None of the other gene variants tested were found to be associated with the risk of DAE development.

CONCLUSION

DAE development in HCC patients receiving TKIs could be explained by the AGT2 (rs4762) gene variant. If validated in other anti-oncogenic treatments, it might be considered a good prognosis marker.

Pleiotropic Effects of Simvastatin and Losartan in Preclinical Models of Post-Traumatic Elbow Contracture

Elbow trauma can lead to post-traumatic joint contracture (PTJC), which is characterized by loss of motion associated with capsule/ligament fibrosis and cartilage damage. Unfortunately, current therapies are often unsuccessful or cause complications. This study aimed to determine the effects of prophylactically administered simvastatin (SV) and losartan (LS) in two preclinical models of elbow PTJC: an in vivo elbow-specific rat injury model and an in vitro collagen gel contraction assay. The in vivo elbow rat (n = 3-10/group) injury model evaluated the effects of orally administered SV and LS at two dosing strategies [i.e., low dose/high frequency/short duration (D1) vs. high dose/low frequency/long duration (D2)] on post-mortem elbow range of motion (via biomechanical testing) as well as capsule fibrosis and cartilage damage (via histopathology). The in vitro gel contraction assay coupled with live/dead staining (n = 3-19/group) evaluated the effects of SV and LS at various concentrations (i.e., 1, 10, 100 µM) and durations (i.e., continuous, short, or delayed) on the contractibility and viability of fibroblasts/myofibroblasts [i.e., NIH3T3 fibroblasts with endogenous transforming growth factor-beta 1 (TGFβ1)]. In vivo, no drug strategy prevented elbow contracture biomechanically. Histologically, only SV-D2 modestly reduced capsule fibrosis but maintained elevated cellularity and tissue hypertrophy, and both SV strategies lessened cartilage damage. SV modest benefits were localized to the anterior region, not the posterior, of the joint. Neither LS strategy had meaningful benefits in capsule nor cartilage. In vitro, irrespective of the presence of TGFβ1, SV (≥10 μM) prevented gel contraction partly by decreasing cell viability (100 μM). In contrast, LS did not prevent gel contraction or affect cell viability. This study demonstrates that SV, but not LS, might be suitable prophylactic drug therapy in two preclinical models of elbow PTJC. Results provide initial insight to guide future preclinical studies aimed at preventing or mitigating elbow PTJC.

ACE2: a key modulator of the renin-angiotensin system and pregnancy

Angiotensin-converting enzyme 2 (ACE2) is a membrane-bound protein containing 805 amino acids. ACE2 shows approximately 42% sequence similarity to somatic ACE but has different biochemical activities. The key role of ACE2 is to catalyze the vasoconstrictor peptide angiotensin (ANG) II to Ang-(1–7), thus regulating the two major counterbalancing pathways of the renin-angiotensin system (RAS). In this way, ACE2 plays a protective role in end-organ damage by protecting tissues from the proinflammatory actions of ANG II. The circulating RAS is activated in normal pregnancy and is essential for maintaining fluid and electrolyte homeostasis and blood pressure. Renin-angiotensin systems are also found in the conceptus. In this review, we summarize the current knowledge on the regulation and function of circulating and uteroplacental ACE2 in uncomplicated and complicated pregnancies, including those affected by preeclampsia and fetal growth restriction. Since ACE2 is the receptor for SARS-CoV-2, and COVID-19 in pregnancy is associated with more severe disease and increased risk of abnormal pregnancy outcomes, we also discuss the role of ACE2 in mediating some of these adverse consequences. We propose that dysregulation of ACE2 plays a critical role in the development of preeclampsia, fetal growth restriction, and COVID-19-associated pregnancy pathologies and suggest that human recombinant soluble ACE2 could be a novel therapeutic to treat and/or prevent these pregnancy complications.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

Pro-inflammatory immunity supports fibrosis advancement in epidermolysis bullosa: intervention with Ang-(1-7)

Recessive dystrophic epidermolysis bullosa (RDEB), a genetic skin blistering disease, is a paradigmatic condition of tissue fragility-driven multi-organ fibrosis. Here, longitudinal analyses of the tissue proteome through the course of naturally developing disease in RDEB mice revealed that increased pro-inflammatory immunity associates with fibrosis evolution. Mechanistically, this fibrosis is a consequence of altered extracellular matrix organization rather than that of increased abundance of major structural proteins. In a humanized system of disease progression, we targeted inflammatory cell fibroblast communication with Ang-(1-7)-an anti-inflammatory heptapeptide of the renin-angiotensin system, which reduced the fibrosis-evoking aptitude of RDEB cells. In vivo, systemic administration of Ang-(1-7) efficiently attenuated progression of multi-organ fibrosis and increased survival of RDEB mice. Collectively, our study shows that selective down-modulation of pro-inflammatory immunity may mitigate injury-induced fibrosis. Furthermore, together with published data, our data highlight molecular diversity among fibrotic conditions. Both findings have direct implications for the design of therapies addressing skin fragility and fibrosis.

Emerging importance of ACE2 in external stratified epithelial tissues

Angiotensin converting enzyme 2 (ACE2), a component of the renin-angiotensin system (RAS), has been identified as the receptor for the SARS-CoV-2. Several RAS components including ACE2 and its substrate Ang II are present in both eye and skin, two stratified squamous epithelial tissues that isolate organisms from external environment. Our recent findings in cornea and others in both skin and eye suggest contribution of this system, and specifically of ACE2 in variety of physiological and pathological responses of these organ systems. This review will focus on the role RAS system plays in both skin and cornea, and will specifically discuss our recent findings on ACE2 in corneal epithelial inflammation, as well as potential implications of ACE2 in patients with COVID-19.

A cross-species analysis of systemic mediators of repair and complex tissue regeneration

Regeneration is an elegant and complex process informed by both local and long-range signals. Many current studies on regeneration are largely limited to investigations of local modulators within a canonical cohort of model organisms. Enhanced genetic tools increasingly enable precise temporal and spatial perturbations within these model regenerators, and these have primarily been applied to cells within the local injury site. Meanwhile, many aspects of broader spatial regulators of regeneration have not yet been examined with the same level of scrutiny. Recent studies have shed important insight into the significant effects of environmental cues and circulating factors on the regenerative process. These observations highlight that consideration of more systemic and possibly more broadly acting cues will also be critical to fully understand complex tissue regeneration. In this review, we explore the ways in which systemic cues and circulating factors affect the initiation of regeneration, the regenerative process, and its outcome. As this is a broad topic, we conceptually divide the factors based on their initial input as either external cues (for example, starvation and light/dark cycle) or internal cues (for example, hormones); however, all of these inputs ultimately lead to internal responses. We consider studies performed in a diverse set of organisms, including vertebrates and invertebrates. Through analysis of systemic mediators of regeneration, we argue that increased investigation of these "systemic factors" could reveal novel insights that may pave the way for a diverse set of therapeutic avenues.

Valsartan solid lipid nanoparticles integrated hydrogel: A challenging repurposed use in the treatment of diabetic foot ulcer, in-vitro/in-vivo experimental study

The article presents an experimental study on the possible repurposed use of valsartan (Val), in the local treatment of uncontrolled diabetic foot ulcer. Solid lipid nanoparticles (SLN), loaded with Val were prepared by applying 3² full factorial design using modified high shear homogenization method. The lipid phase composed of Precirol® ATO 5 (P ATO 5) and/or Gelucire 50/13 (G 50/13) in different ratios and a nonionic emulsifier, Pluronic 188 (P188), was used in different percentages. Optimized formulation was further integrated in hydroxyl propyl methyl cellulose (HPMC) gel for the ease of administration. In-vitro and in-vivo characterizations were investigated. The prepared nanoparticles showed small particle size, high entrapment efficiency and sustained drug release. Microbiologically, Val-SLN showed a prominent decrease in the biofilm mass formation for both gram-positive and gram-negative bacteria, as well as a comparable minimum inhibitory concentration level to levofloxacin alone. Diabetes was induced in 32 neonatal Sprague-Dawley rats. At 8 weeks of age, rats with blood sugar level >160 were subjected to surgically induced ulcer. Treatment with Val-SLN for 12 days revealed enhanced healing characteristics through cyclooxygenase-2 (COX-2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nitric oxide (NO), transforming growth factor-beta (TGF-β), matrix metalloproteinase (MMPs) and vascular endothelial growth factor (VEGF) pathways. Histological examination revealed re-epithelization in Val-SLN treated ulcer, as well as decrease in collagen using trichrome histomorphometric analysis.

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

Wound-Healing Markers Revealed by Proximity Extension Assay in Tears of Patients following Glaucoma Surgery

Tears are a constantly available and highly valuable body fluid collectable by non-invasive techniques. Although it can give information on ocular status and be used for follow-ups, tear analysis is challenging due to the low amount of sample that is available. Proximity extension assay (PEA) allows for a sensitive and scalable analysis of multiple proteins in a single run from a one-µL sample, so we applied this technique and examined the amount of 184 proteins in tears collected at different time points after trabeculectomy. The success rate of this surgical intervention highly depends on proper wound healing; therefore, information on the process is indispensable. We observed significantly higher levels of IL-6 and MMP1 at the early time points (day one, two, and four) following trabeculectomy, and the protein amounts went back to the level observed before the surgery three months after the intervention. Patients with or without complications were tested, and proteins that have roles in the immune response and wound healing could be observed with altered frequency and amounts in the cases of patients with complications. Our results highlight the importance of inflammation in wound-healing complications, and at the same time, indicate the utility of PEA in tear analysis.

Renin-angiotensin inhibitors reprogram tumor immune microenvironment: A comprehensive view of the influences on anti-tumor immunity

Renin-angiotensin system inhibitors (RASi) have shown potential anti-tumor effects that may have a significant impact in cancer therapy. The components of the renin-angiotensin system (RAS) including both, conventional and alternative axis, appear to have contradictory effects on tumor biology. The mechanisms by which RASi impair tumor growth extend beyond their function of modulating tumor vasculature. The major focus of this review is to analyze other mechanisms by which RASi reprogram the tumor immune microenvironment. These involve impairing hypoxia and acidosis within the tumor stroma, regulating inflammatory signaling pathways and oxidative stress, modulating the function of the non-cellular components and immune cells, and regulating the cross-talk between kalli krein kinin system and RAS.