P-glycoprotein Mediates Postoperative Peritoneal Adhesion Formation by Enhancing Phosphorylation of the Chloride Channel-3

Neutrophil Extracellular Traps: A Crucial Factor in Post-Surgical Abdominal Adhesion Formation

Post-surgical abdominal adhesions, although poorly understood, are highly prevalent. The molecular processes underlying their formation remain elusive. This review aims to assess the relationship between neutrophil extracellular traps (NETs) and the generation of postoperative peritoneal adhesions and to discuss methods for mitigating peritoneal adhesions. A keyword or medical subject heading (MeSH) search for all original articles and reviews was performed in PubMed and Google Scholar. It included studies assessing peritoneal adhesion reformation after abdominal surgery from 2003 to 2023. After assessing for eligibility, the selected articles were evaluated using the Critical Appraisal Skills Programme checklist for qualitative research. The search yielded 127 full-text articles for assessment of eligibility, of which 7 studies met our criteria and were subjected to a detailed quality review using the Critical Appraisal Skills Programme (CASP) checklist. The selected studies offer a comprehensive analysis of adhesion pathogenesis with a special focus on the role of neutrophil extracellular traps (NETs) in the development of peritoneal adhesions. Current interventional strategies are examined, including the use of mechanical barriers, advances in regenerative medicine, and targeted molecular therapies. In particular, this review emphasizes the potential of NET-targeted interventions as promising strategies to mitigate postoperative adhesion development. Evidence suggests that in addition to their role in innate defense against infections and autoimmune diseases, NETs also play a crucial role in the formation of peritoneal adhesions after surgery. Therefore, therapeutic strategies that target NETs are emerging as significant considerations for researchers. Continued research is vital to fully elucidate the relationship between NETs and post-surgical adhesion formation to develop effective treatments.

Nanofiber Hydrogel Drug Delivery System for Prevention of Postsurgical Intestinal Adhesion

Intestinal adhesion is one of the complications that occurs more frequently after abdominal surgery. Postsurgical intestinal adhesion (PIA) can lead to a series of health problems, including abdominal pain, intestinal obstruction, and female infertility. Currently, hydrogels and nanofibrous films as barriers are often used for preventing PIA formation; however, these kinds of materials have their intrinsic disadvantages. Herein, we developed a dual-structure drug delivery patch consisting of poly lactic-co-glycolic acid (PLGA) nanofibers and a chitosan hydrogel (NHP). PLGA nanofibers loaded with deferoxamine mesylate (DFO) were incorporated into the hydrogel; meanwhile, the hydrogel was loaded with anti-inflammatory drug dexamethasone (DXMS). The rapid degradation of the hydrogel facilitated the release of DXMS at the acute inflammatory stage of the early injury and provided effective anti-inflammatory effects for wound sites. Moreover, PLGA composite nanofibers could provide sustained and stable release of DFO for promoting the peritoneal repair by the angiogenesis effects of DFO. The in vivo results indicated that NHP can effectively prevent PIA formation by restraining inflammation and vascularization, promoting peritoneal repair. Therefore, we believe that our NHP has a great potential application in inhibition of PIA.

Injectable Multifunctional Composite Hydrogel as a Combination Therapy for Preventing Postsurgical Adhesion

Postsurgical adhesion (PA) is a common and serious postoperative complication that affects millions of patients worldwide. However, current commercial barrier materials are insufficient to inhibit diverse pathological factors during PA formation, and thus, highly bioactive materials are needed. Here, this work designs an injectable multifunctional composite hydrogel that can serve as a combination therapy for preventing PA. In brief, this work reveals that multiple pathological events, such as chronic inflammatory and fibrotic processes, contribute to adhesion formation in vivo, and such processes can not be attenuated by barrier material (e.g., hydrogel) alone treatments. To solve this limitation, this work designs a composite hydrogel made of the cationic self-assembling peptide KLD2R and TGF-β receptor inhibitor (TGF-βRi)-loaded mesenchymal stem cell-derived nanovesicles (MSC-NVs). The resulting composite hydrogel displays multiple functions, including physical separation of the injured tissue areas, antibacterial effects, and local delivery and sustained release of anti-inflammatory MSC-NVs and antifibrotic TGF-βRi. As a result, this composite hydrogel effectively inhibited local inflammation, fibrosis and adhesion formation in vivo. Moreover, the hydrogel also exhibits good biocompatibility and biodegradability in vivo. Together, the results highlight that this "all-in-one" composite hydrogel strategy may provide insights into designing advanced therapies for many types of tissue injury.

Homotypic targeted nanoplatform enable efficient chemoimmunotherapy and reduced DOX cardiotoxicity in chemoresistant cancer via TGF-β1 blockade

Doxorubicin (DOX) with broad-spectrum antitumor activity has been reported to induce effective immunogenic cell death (ICD) effect. However, the serious cardiotoxicity and chemoresistance severely restrict the widely clinical application of DOX. Herein, for the first time, a bio-inspired nanoplatform via co-assembly of DOX-conjugated polyethyleneimine (PEI-DOX), cancer cell membrane (CCM) and TGF-β1 siRNA (siTGF-β1) was rationally designed, which can not only overcome the drawbacks of DOX but also display high capability to modulate the tumor microenvironment and prevent the tumor progressing and metastasis. Experimental studies confirmed the pH-sensitivity of PEI-DOX and the homotypic-targeting and immuno-escapable ability of CCM, resulting an enhanced accumulation of DOX and siTGF-β1 in tumor sites. In addition to this, the bio-inspired nanoplatform could also improve the stability and facilitate the endosomal escape of siTGF-β1. All these effects ensured the silence efficiency of siTGF-β1 in tumor sites, which could further modulate the chemoresistant and immunosuppressive tumor microenvironment, resulting a synergistic effect with DOX to prevent tumor progressing and metastasis. Additionally, even trapped in cardiac tissues, siTGF-β1 could inhibit the production of TGF-β1 and ROS induced by DOX, resulting a reduced myocardial damage. Therefore, our newly designed bio-inspired nano-delivery system may be a promising nanoplatform with efficient chemoimmunotherapy to ameliorate DOX-induced cardiotoxicity and combat tumor growth and metastasis in chemoresistant cancer.

Prevention strategies of postoperative adhesion in soft tissues by applying biomaterials: Based on the mechanisms of occurrence and development of adhesions

Postoperative adhesion (POA) widely occurs in soft tissues and usually leads to chronic pain, dysfunction of adjacent organs and some acute complications, seriously reducing patients' quality of life and even being life-threatening. Except for adhesiolysis, there are few effective methods to release existing adhesion. However, it requires a second operation and inpatient care and usually triggers recurrent adhesion in a great incidence. Hence, preventing POA formation has been regarded as the most effective clinical strategy. Biomaterials have attracted great attention in preventing POA because they can act as both barriers and drug carriers. Nevertheless, even though much reported research has been demonstrated their efficacy on POA inhibition to a certain extent, thoroughly preventing POA formation is still challenging. Meanwhile, most biomaterials for POA prevention were designed based on limited experiences, not a solid theoretical basis, showing blindness. Hence, we aimed to provide guidance for designing anti-adhesion materials applied in different soft tissues based on the mechanisms of POA occurrence and development. We first classified the postoperative adhesions into four categories according to the different components of diverse adhesion tissues, and named them as "membranous adhesion", "vascular adhesion", "adhesive adhesion" and "scarred adhesion", respectively. Then, the process of the occurrence and development of POA were analyzed, and the main influencing factors in different stages were clarified. Further, we proposed seven strategies for POA prevention by using biomaterials according to these influencing factors. Meanwhile, the relevant practices were summarized according to the corresponding strategies and the future perspectives were analyzed.

Adaptation of the gut holobiont to malnutrition during mouse pregnancy depends on the type of nutritional adversity

Malnutrition can influence maternal physiology and programme offspring development. Yet, in pregnancy, little is known about how dietary challenges that influence maternal phenotype affect gut structure and function. Emerging evidence suggests that interactions between the environment, multidrug resistance (MDR) transporters and microbes may influence maternal adaptation to pregnancy and regulate fetoplacental development. We hypothesized that the gut holobiont (host and microbes) during pregnancy adapts differently to suboptimal maternal diets, evidenced by changes in the gut microenvironment, morphology, and expression of key protective MDR transporters during pregnancy. Mice were fed a control diet (CON) during pregnancy, or undernourished (UN) by 30% of control intake from gestational day (GD) 5.5-18.5, or fed 60% high fat diet (HF) for 8 weeks before and during pregnancy. At GD18.5, maternal small intestinal (SI) architecture (H&E), proliferation (Ki67), P-glycoprotein (P-gp - encoded by Abcb1a/b) and breast cancer resistance protein (BCRP/Abcg2) MDR transporter expression and levels of pro-inflammatory biomarkers were assessed. Circulating inflammatory biomarkers and maternal caecal microbiome composition (G3 PhyloChip^TM) were measured. MDR transporter expression was also assessed in fetal gut. HF diet increased maternal SI crypt depth and proinflammatory load, and decreased SI expression of Abcb1a mRNA, whilst UN increased SI villi proliferation and Abcb1a, but decreased Abcg2, mRNA expression. There were significant associations between Abcb1a and Abcg2 mRNA levels with relative abundance of specific microbial taxa. Using a systems physiology approach we report that common nutritional adversities provoke adaptations in the pregnancy holobiont in mice, and reveal new mechanisms that could influence reproductive outcomes and fetal development.

Progress in diagnosis and treatment of surgery-related adhesive small intestinal obstruction

Adhesive small bowel obstruction is a relatively common surgical acute abdomen, which is caused by various factors that result in the contents of the small bowel failing to pass smoothly. The clinical symptoms include abdominal pain, distension, nausea and vomiting, and defecation disorder. The chance of adhesive small bowel obstruction to develop in patients with a history of abdominal surgery is around 2.4%. This paper discusses the most recent developments in the conservative and surgical management of adhesive small bowel obstruction based on clinical manifestation, laboratory analysis, and imaging examination.

P-glycoprotein: new insights into structure, physiological function, regulation and alterations in disease

The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.

A review of physiological and cellular mechanisms underlying fibrotic postoperative adhesion

Postoperative adhesions (PA) are fibrotic tissues that are the most common driver of long-term morbidity after abdominal and pelvic surgery. The optimal drug or material to prevent adhesion formation has not yet been discovered. Comprehensive understanding of cellular and molecular mechanisms of adhesion process stimulates the design of future anti-adhesive strategies. Recently, disruption of peritoneal mesothelial cells were suggested as the 'motor' of PA formation, followed by a cascade of events (coagulation, inflammation, fibrinolysis) and influx of various immune cells, ultimately leading to a fibrous exudate. We showed that a variety of immune cells were recruited into adhesive peritoneal tissues in patients with small bowel obstruction caused by PA. The interactions among various types of immune cells contribute to PA development following peritoneal trauma. Our review focuses on the specific role of different immune cells in cellular and humoral mechanisms underpinning adhesion development.

The effect of Smad2- and Smad3-targeting RNA interference on extracellular matrix synthesis in rat fibroblasts of peritoneal adhesion tissues

Fibroblasts migrating to peritoneum injuries play an important role in the development of postoperative peritoneal adhesions due to the excessive synthesis and deposition of extracellular matrix (ECM). This effect is mainly induced by the transforming growth factor-β (TGF-β). Studies indicate that elevated TGF-β1 levels and TGF-β1/Smad signaling are both implicated in the formation of peritoneal adhesions. To confirm the effect of TGF-β1/Smad signaling interference in regulating excessive ECM synthesis, a total of four different R-Smad-targeting small interference RNA (siRNA) duplexes (Smad2-500, Smad2-956, Smad3-378, Smad3-1385) were tested in this study using a TGF-β1-stimulated adhesion tissue fibroblasts (ATFs) cell model. The in vitro assessments show that all proposed siRNAs are capable of significantly downregulating the mRNA and protein levels of Smad2 and Smad3 in ATFs. They also inhibit the phosphorylation of both Smads, which confirms their effect in blocking the TGF-β1/Smad signaling pathway. Moreover, the siRNA duplexes can appreciably lower the elevated levels of fibronectin and collagen 3 alpha 1 (COL3A1) in TGF-β1-stimulated ATFs, and the Smad3-378 siRNA can actually restore both molecules (fibronectin and COL3A1) to normal levels. Therefore, the Smad3-378 siRNA is suitable for both adhesion prevention and wound healing. Overall, our results indicate that postoperative adhesion prophylaxis may be achieved by temporarily blocking TGF-β1/Smad signaling transduction.

Postoperative peritoneal adhesion: an update on physiopathology and novel traditional herbal and modern medical therapeutics

Postoperative peritoneal adhesion (PPA) is a serious clinical condition that affects the high percentage of patients after abdominal surgery. In this review, we have tried to focus on pathophysiology and different underlying signal pathways of adhesion formation based on recent progress in the molecular and cellular mechanisms. Also, the strategies, developed based on traditional herbal and modern medicines, to prevent and treat the PPA via regulation of the molecular mechanisms were investigated. The search engines such as Google Scholar, PubMed, Scopus, and Science Direct have been used to evaluate the current literature related to the pathogenesis of adhesion formation and novel products. Recently, different mechanisms have been defined for adhesion formation, mainly categorized in fibrin formation and adhesion fibroblast function, inflammation, and angiogenesis. Therefore, the suppression of these mechanisms via traditional and modern medicine has been suggested in several studies. While different strategies with encouraging findings have been developed, most of the studies showed contradictory results and were performed on animals. The herbal products have been introduced as safe and effective agent which can be considered in future preclinical and clinical studies. Although a wide range of therapeutics based on traditional and modern medicines have been suggested, there is no agreement in the efficacy of these methods to prevent or treat adhesion formation after surgeries. Further basic and clinical researches are still needed to propose the efficiency of recommended strategies for prevention and treatment of PPA.

NPPB prevents postoperative peritoneal adhesion formation by blocking volume-activated Cl- current

5-Nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) is a non-specific chloride channel blocker. Peritoneal adhesion is an inevitable complication of abdominal surgery and remains an important clinical problem, leading to chronic pain, intestinal obstruction, and female infertility. The aim of this study is to observe the effects of NPPB on peritoneal adhesions and uncover the underlying mechanism. The formation of postoperative peritoneal adhesions was induced by mechanical injury to the peritoneum of rats. MTT assay and wound-healing assay were used to evaluate proliferation and migration of primary cultured adhesion fibroblasts (AFB) respectively. Whole-cell chloride currents were measured using a fully automated patch-clamp workstation. Cell volume changes were monitored by light microscopy and video imaging. Our results demonstrated that NPPB could significantly prevent the formation of peritoneal adhesion in rats and inhibit the proliferation of AFB in a concentration-dependent manner. NPPB also reduced the migration of AFB cells with an IC₅₀ of 53.09 μM. A 47% hypotonic solution successfully activated the I_Cl,vol in AFB cells. The current could be blocked by extracellular treatment with NPPB. Moreover, 100 μM NPPB almost completely eliminated the capacity of regulatory volume decrease (RVD) in these cells. These data indicate that NPPB could prevent the formation of postoperative peritoneal adhesions. The possible mechanism may be through the inhibition of the proliferation and migration of AFB cells by modulating I_Cl,vol and cell volume. These results suggest a potential clinical use of NPPB for preventing the formation of peritoneal adhesions.

Shape Effect of Nanoparticles on Tumor Penetration in Monolayers Versus Spheroids

The physical properties of nanoparticles (NPs), such as size, surface chemistry, elasticity, and shape, have exerted a profound influence on tumor penetration. However, the effect of shape on cellular uptake and tumor penetration is still unclear because of the different chemical compositions and shapes of tested particles and the use of inapposite cellular models. To discover the effect of NP shapes on cellular uptake and tumor penetration and bridge the gap between models in vivo and in vitro, elongated polystyrene (PS) NPs with a fixed volume, an identical chemical composition, and the same zeta potential, but with different aspect ratios (ARs), were generated. The physical properties, cellular uptake, tumor penetration, and corresponding mechanisms of these NPs were thoroughly investigated. We discovered that the elongated PS particles with higher ARs had lower uptake rates in the 2-dimensional cell monolayer culture model in vitro, but they showed optimal ARs in the evaluated three-dimensional spheroid model. Although the elongated PS particles had a similar tumor penetration mechanism (mainly through extracellular pathways), the percentage of penetration using these mechanisms was strongly dependent on the ARs. As an alternative model for studies in vivo, spheroids were used instead of the cell monolayer for the development of drug delivery systems. In addition, the physicochemical properties of NPs must be delicately balanced and adjusted to achieve the best therapeutic outcomes.

ClC-3 chloride channels are involved in estradiol regulation of bone formation by MC3T3-E1 osteoblasts

Evidence has been reported by us and others supporting the important roles of chloride channels in a number of osteoblast cell functions. The ClC-3 chloride channel is activated by estradiol binding to estrogen receptor alpha on the cell membranes of osteoblasts. However, the functions of these chloride channels in estrogen regulation of osteoblast metabolism remain unclear. In the present study, the roles of chloride channels in estrogen regulation of osteoblasts were investigated in the osteoblastic cell line MC3T3-E1. Estrogen 17β-estradiol enhanced collagen I protein expression, alkaline phosphatase activity, and mineralization were inhibited, by chloride channel blockers. Estradiol promoted ClC-3 chloride channel protein expression. Silencing of ClC-3 chloride channel expression prevented the elevation of osteodifferentiation in osteoblasts, which were regulated by estrogen. These data suggest that estrogen can regulate bone formation by activating ClC-3 chloride channels and the activation of ClC-3 chloride channels can enhance the osteodifferentiation in osteoblasts.

TEMPO oxidized nano-cellulose containing thermo-responsive injectable hydrogel for post-surgical peritoneal tissue adhesion prevention

The objective of this study was to present an effective injectable adhesion barrier comprised of TEMPO-oxidized cellulose nanofiber (TOCN), methyl cellulose, carboxymethyl cellulose, and polyethylene glycol. Hydrogels with different concentrations (0.2, 0.5, 0.8, 1% w/v) of bio compatible TOCN were investigated to determine their abilities to prevent post-surgical peritoneal adhesion using a rat cecal wall abrasion model. Sol-gel transition at body temperature (37 °C) was optimized by adjusting concentration of sodium ions (Na⁺), with a gelation time of 45 ± 7 s. These TOCN containing hydrogels showed non cytotoxicity to rat bone marrow mesenchymal stem cells (RBMSCs) and L929 fibroblast cells as cell models during in vitro assessment. Degradation studies revealed that, TOCN concentration in hydrogel was inversely proportional to hydrolytic degradation rate. From in vivo evaluations, TOCN 0.2 hydrogel significantly reduced peritoneal adhesion in rat (n = 8) compared to untreated controls based on gross observation, histological analysis, and expression analysis of marker proteins. By taking advantages of thermo gelling, high stability, non-invasive way of application and rapid recovery potential, TOCN containing bio compatible hydrogel could be used as a cost-effective barrier to efficiently inhibit post-surgical peritoneal adhesions.

Designing nanoparticles with improved tumor penetration: surface properties from the molecular architecture viewpoint

Cancer is the second most common cause of death, and nanomedicine is regarded as one of the strategies that may revolutionize cancer treatments. However, the tumor microenvironment (e.g., increased interstitial fluid pressure and dense extracellular matrix) hinders the penetration of nanomedicine into tumor cells, which leads to a short acting time and low drug concentration with tumors, eventually leading to a high recurrence rate and therapeutic failure in clinics. Developing a delivery system with deep penetration ability into the tumor has always been pursued and highly desirable for cancer treatments. Inspired by the high cellular uptake efficiency of enveloped viruses with rough and nanoscale surfaces, we constructed polystyrene nanoparticles (NPs) with similar sizes and charges, but with different surface topologies at the molecular level, by conjugating poly(propylene imine) (PPI) dendrimers with different generations onto the NPs. We found that subtle changes made to the surficial chemical properties led to changes in surface roughness and wettability, which considerably influenced the cellular internalization, endocytosis mechanism, and penetration into the tumor model both in vitro and in vivo. This will shed light on the future design of drug delivery vehicles and facilitate understanding the interactions between NP surfaces and cells, as well as tumor penetration.

Preventive Effects of the Intestine Function Recovery Decoction, a Traditional Chinese Medicine, on Postoperative Intra-Abdominal Adhesion Formation in a Rat Model

The intestine function recovery decoction (IFRD) is a traditional Chinese medicine that has been used for the treatment of adhesive intestinal obstruction. In this study, the preventative effects and probable mechanism of the IFRD were investigated in a rat model. We randomly assigned rats to five groups: normal, model, control, low dose IFRD, and high dose IFRD. In the animal model, the caecum wall and parietal peritoneum were abraded to induce intra-abdominal adhesion formation. Seven days after surgery, adhesion scores were assessed using a visual scoring system, and histopathological samples were examined. The levels of serum interleukin-6 (IL-6) and transforming growth factor beta-1 (TGF-β1) were analysed by an enzyme-linked immunosorbent assay (ELISA). The results showed that a high dose of IFRD reduced the grade of intra-abdominal adhesion in rats. Furthermore, the grades of inflammation, fibrosis, and neovascularization in the high dose IFRD group were significantly lower than those in the control group. The results indicate that the IFRD can prevent intra-abdominal adhesion formation in a rat model. These data suggest that the IFRD may be an effective antiadhesion agent.

Prevention and treatment of peritoneal adhesions in patients affected by vascular diseases following surgery: a review of the literature

Intra-abdominal adhesions are the most frequently occurring postoperative complication following abdomino-pelvic surgery. Abdominal and pelvic surgery can lead to peritoneal adhesion formation causing infertility, chronic pelvic pain, and intestinal obstruction. Laparoscopy today is considered the gold standard of care in the treatment of several abdominal pathologies as well as in a wide range of vascular diseases. Laparoscopy has several advantages in comparison to open surgery. These include rapid recovery times, shorter hospitalisation, reduced postoperative pain, as well as cosmetic benefits. The technological improvements in this particular surgical field along with the development of modern techniques and the acquisition of specific laparoscopic skills have allowed for its wider utilization in operations with fully intracorporeal anastomoses. Postoperative adhesions are caused by aberrant peritoneal healing and are the leading cause of postoperative bowel obstruction. The use of anti-adherence barriers is currently being advocated for their prevention. The outcome of the investigation showed adhesion formation inhibition without direct detrimental effects on anastomotic healing. Poor anasto-motic healing can provoke adhesions even in the presence of anti-adhesion barriers. This review gives a short overview on the current evidence on the pathophysiology and prevention of peritoneal adhesions.