Significance of cyclooxygenase-2 induced via p38 mitogen-activated protein kinase in mechanical stimulus-induced peritoneal adhesion in mice

Establishment and evaluation of an improved rat model of open abdomen

INTRODUCTION

This study aimed to establish an animal model of open abdomen (OA) through temporary abdominal closure via different techniques.

METHODS

Adult male Sprague-Dawley rats were randomly divided into three groups: group A (OA with polypropylene mesh alone); group B (OA with polypropylene mesh combined with a patch); and group C (OA with polypropylene mesh and a sutured patch). Vital signs, pathophysiological changes, and survival rates were closely monitored in the rats for 7 days after surgery. Abdominal X-rays and histopathological examinations were performed to assess abdominal organ changes and wound healing.

RESULTS

The results showed no significant difference in mortality rates among the three groups (p > 0.05). However, rats in group B exhibited superior overall condition, cleaner wounds, and a higher rate of wound healing compared to the other groups (p < 0.05). Abdominal X-rays indicated that varying degrees of distal intestinal obstruction in all groups. Histopathological examinations revealed fibrous hyperplasia, inflammatory cell infiltration, neovascularization, and collagen deposition in all groups. Group B demonstrated enhanced granulation tissue generation, neovascularization, and collagen deposition compared to the other groups (p < 0.05).

CONCLUSIONS

Polypropylene mesh combined with patches is the most suitable method for establishing an animal model of OA. This model successfully replicated the pathological and physiological changes in postoperative patients with OA, specifically the progress of abdominal skin wound healing. It provides a practical and reliable animal model for OA research.

Extracellular Vesicles Derived from Adipose Mesenchymal Stem Cells Promote Peritoneal Healing by Activating MAPK-ERK1/2 and PI3K-Akt to Alleviate Postoperative Abdominal Adhesion

Peritoneal regeneration and repair can alleviate postoperative intraperitoneal adhesions, and mesenchymal stem cells (MSCs) have demonstrated the potential for peritoneal repair and regeneration. However, extracellular vesicles (EVs) are the main carriers for the MSC activity. Thus far, the roles of MSC-derived EVs on peritoneal repair are not well understood. To investigate the therapeutic effect of adipose-derived mesenchymal stem cell-derived EVs (ADSC-EVs) in peritoneal injuries, ADSC-EVs were injected in vivo via the tail vein of rats. The antiadhesion effects were evaluated following abdominal surgery. In addition, the levels of the peritoneal fibrinolysis system were determined via enzyme-linked immunosorbent assay. Expression differences in inflammatory and apoptotic markers were detected using immunofluorescence. The expression of extracellular matrix-related indexes and peritoneal healing were observed using immunohistochemistry. In vitro, rat peritoneal mesothelial cell proliferation was assessed via a 5-ethynyl-2-deoxyuridine assay. Cell migration was determined using scratch wound and transwell assays. Related signaling networks were estimated based on sequencing and bioinformatics analyses. The roles of the MAPK–ERK1/2 and PI3K–Akt signaling networks were analyzed using immunoblotting. This is the first report of the effectiveness of ADSC-EVs in the treatment of postoperative adhesions. ADSC-EVs were incorporated in vitro and induced rat peritoneal mesothelial cell proliferation and migration. This was mediated by stimulation of the MAPK–ERK1/2 and PI3K–Akt axes. ADSC-EVs promote the healing of the injured peritoneum, suggesting a promising therapeutic approach for peritoneal adhesions.

Regulatory roles of PGE2 in LPS-induced tissue damage in bovine endometrial explants

Bovine endometritis is the most common uterine disease following parturition. The role of prostaglandin E₂ (PGE₂) in regulating normal physiological function in the bovine endometrium has been clearly established. Although PGE₂ accumulation is observed in multiple inflammatory diseases, such as endometritis, its association with pathogen-induced inflammatory damage in the endometrium is unclear. To clarify the role of PGE₂ in lipopolysaccharide (LPS)-induced endometritis in cultured bovine endometrial explants, the levels of PGE₂ secretion, prostaglandin synthetases, pro-inflammatory factors, and damage-associated molecular patterns (DAMPs) were evaluated in the present study. Significant PGE₂ accumulation in response to LPS stimulation, up-regulation of prostaglandin-endoperoxide synthase-2 (PTGS-2), microsomal prostaglandin E synthase-1 (mPGES-1), pro-inflammatory factors including interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and induced nitric oxide synthase (iNOS)/nitric oxide (NO) and DAMPs including hyaluronan binding protein 1 (HABP1) and high mobility group box-1 (HMGB1), were observed compared to the control group. LPS induced distinct damage in the bovine endometrium, characterized by morphological changes and increases in HABP1 and HMGB1 expression. PTGS-2 inhibitors CAY10404 and NS398 effectively decreased the secretion of PGE₂ and the expression of prostaglandin synthetases, pro-inflammatory factors and DAMPs, and alleviated LPS-induced tissue damage. These results indicate that PGE₂ accumulates via PTGS-2 and mPGES-1 and induces tissue damage by upregulating pro-inflammatory factors and DAMPs in LPS-treated bovine endometrial explants. These findings provide a basis for the effect of PGE₂ on LPS-treated bovine endometrium, and suggest a potential target for curing endometritis.

Lightweight, Highly Permeable, Biocompatible, and Antiadhesive Composite Meshes for Intraperitoneal Repairs

Ventral hernia is a public health issue and millions of meshes are used to repair abdominal wall defects every year. Polypropylene-based composite meshes represent an important class of materials for intraperitoneal repair, but the meshes generally give rise to infection, seroma, migration, and adhesion, leading to severe consequence or even reoperation. Here, a facile and versatile one-way fabrication of lightweight, highly permeable, and biocompatible composite meshes with superior antiadhesion properties is proposed by modifying polypropylene meshes with well-defined polydopamine nanocoating. The resulting composite meshes are found to significantly enhance the biocompatibility and antiadhesion effect in rat model. The scalable production and excellent biomedical properties of composite meshes make them a promising candidate for future-generation ventral hernia repair materials.

[Peritoneal adhesion formation]

Postoperative peritoneal adhesions are common sequelae of abdominal surgery. Acute as well as chronic complications, including bowel obstruction, abdominal pain and infertility can arise from adhesion formation. So far, the only reliable treatment is surgical adhesiolysis, which in turn is accompanied by an increased risk of adhesion recurrence. Despite significant progress in modern perioperative medicine, only limited prophylactic approaches are available and atraumatic surgery is still the most important factor.Current research concepts focus on two major antiadhesion strategies: firstly, the intraoperative placement of mechanical barriers and secondly novel immunomodulation concepts. Clinical data about the use of antiadhesive barriers show a heterogeneous outcome. Promising data have arisen from the immunomodulatory approaches and now require a step-up development from experimental to clinical trial level.The present review gives a short overview about the current research on the pathophysiology and prevention of peritoneal adhesions. The promising data are encouraging and require realization of carefully designed prospective clinical trials.

Inhibition of cyclooxygenase-2 prevents intra-abdominal adhesions by decreasing activity of peritoneal fibroblasts

BACKGROUND

Postoperative intra-abdominal adhesions are common complications after abdominal surgery. The exact molecular mechanisms that are responsible for these complications remain unclear, and there are no effective methods for preventing adhesion formation or reformation. The aim of the study reported here was to investigate the preventive effects and underlying potential molecular mechanisms of selective cyclooxygenase-2 (COX-2) inhibitors in a rodent model of postoperative intra-abdominal adhesions.

MATERIALS AND METHODS

The expression of COX-2 in postoperative intra-abdominal adhesions and normal peritoneal tissue was examined by immunohistochemistry and Western blot analysis. Assays were performed to elucidate the effect of COX-2 inhibition on hypoxia-induced fibroblast activity in vitro and on intra-abdominal adhesion formation in vivo.

RESULTS

Hypoxia-induced COX-2 expression in peritoneal fibroblasts was increased in postoperative intra-abdominal adhesions. Inhibition of COX-2 attenuated the activating effect of hypoxia on normal peritoneal fibroblasts in vitro. Data indicate that selective COX-2 inhibitor prevents in vivo intra-abdominal adhesion by inhibition of basic fibroblast growth factor and transforming growth factor-beta expression, but not through an antiangiogenic mechanism. Furthermore, using selective COX-2 inhibitors to prevent intra-abdominal adhesions did not adversely affect the weight, bowel motility, or healing of intestinal anastomoses in a rat model.

CONCLUSION

These results show that hypoxia-induced COX-2 expression in peritoneal fibroblasts is involved in the formation of intra-abdominal adhesions. Inhibition of COX-2 prevents postoperative intra-abdominal adhesions through suppression of inflammatory cytokines.

The role of cyclooxygenase-2 in mechanical ventilation-induced lung injury

Mechanical ventilation is necessary for patients with acute respiratory failure, but can cause or propagate lung injury. We previously identified cyclooxygenase-2 as a candidate gene in mechanical ventilation-induced lung injury. Our objective was to determine the role of cyclooxygenase-2 in mechanical ventilation-induced lung injury and the effects of cyclooxygenase-2 inhibition on lung inflammation and barrier disruption. Mice were mechanically ventilated at low and high tidal volumes, in the presence or absence of pharmacologic cyclooxygenase-2-specific inhibition with 3-(4-methylsulphonylphenyl)-4-phenyl-5-trifluoromethylisoxazole (CAY10404). Lung injury was assessed using markers of alveolar-capillary leakage and lung inflammation. Cyclooxygenase-2 expression and activity were measured by Western blotting, real-time PCR, and lung/plasma prostanoid analysis, and tissue sections were analyzed for cyclooxygenase-2 staining by immunohistochemistry. High tidal volume ventilation induced lung injury, significantly increasing both lung leakage and lung inflammation relative to control and low tidal volume ventilation. High tidal volume mechanical ventilation significantly induced cyclooxygenase-2 expression and activity, both in the lungs and systemically, compared with control mice and low tidal volume mice. The immunohistochemical analysis of lung sections localized cyclooxygenase-2 expression to monocytes and macrophages in the alveoli. The pharmacologic inhibition of cyclooxygenase-2 with CAY10404 significantly decreased cyclooxygenase activity and attenuated lung injury in mice ventilated at high tidal volume, attenuating barrier disruption, tissue inflammation, and inflammatory cell signaling. This study demonstrates the induction of cyclooxygenase-2 by mechanical ventilation, and suggests that the therapeutic inhibition of cyclooxygenase-2 may attenuate ventilator-induced acute lung injury.

Cyclooxygenase 2 pathway and its therapeutic inhibition in superantigen-induced toxic shock

Bacterial superantigens are a family of exotoxins that are the most potent T-cell activators known. Because of their ability to induce strong immune activation, superantigens have been implicated in a variety of diseases ranging from self-limiting food poisoning to more severe toxic shock syndrome (TSS) and have the potential to be used as agents of bioterrorism. Nonetheless, the precise molecular mechanisms by which T-cell activation by superantigens lead to acute systemic inflammatory response, multiple organ dysfunction, and ultimately death are unclear. Inadequate understanding of the pathogenesis has resulted in lack of development of effective therapy for superantigen-induced TSS. To fill these deficiencies, we systematically dissected the molecular pathogenesis of superantigen-induced TSS using the humanized human leukocyte antigen-DR3 transgenic mouse model by microarray-based gene expression profiling. Splenic expression of prostaglandin-endoperoxide synthase 2 (PTGS-2; also called cyclooxygenase 2 or COX-2) gene was increased by several hundred folds shortly after systemic superantigen (staphylococcal enterotoxin B [SEB]) exposure. In addition, expressions of several genes associated with eicosanoid pathway were significantly modulated by SEB, as analyzed by dedicated software. Given the importance of the COX-2 pathway in inflammation, we examined whether therapeutic inhibition of COX-2 by a highly selective inhibitor, CAY10404, could be beneficial. Our studies showed that i.p. administration of CAY10404 (50 mg/kg) immediately after challenge with 10 microg of SEB was unable to inhibit SEB-induced in vivo cytokine/chemokine production or T-cell activation/proliferation and did not prevent superantigen-associated thymocyte apoptosis.

The non-steroidal anti-inflammatory drugs protect mouse cochlea against acoustic injury

Acoustic injury is a common cause of hearing loss for people in industrial societies. Cyclooxygenase (COX) and lipoxygenase (LOX) are two important enzymes involved in arachidonic acid metabolism. Two COX isozymes are characterized, COX-1 and COX-2, that differ in terms of regulatory mechanisms of expression. Although COX-1, COX-2, and LOX are expressed in cochlea, their roles played in cochlear acoustic injury have not fully been evaluated. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit either COX or LOX, or both. This study evaluated the effects of NSAIDs on the functional recovery of the cochlea after acoustic injury. Mice were exposed to a 4-kHz pure tone of 128 dB SPL (sound pressure level) for 4 hours and received one of the following drugs for two weeks after acoustic overexposure: indomethacin (COX-1 inhibitor), meloxicam, SC58125, and CAY10404 (COX-2 inhibitors), and nordihydroguaiaretic acid (LOX inhibitor). The hearing ability was evaluated using an auditory brainstem response (ABR) before and after overexposure. The ABR threshold shifts, defined as subtraction between ABR thresholds before and after overexposure, were compared among the control and the medication groups at one and two weeks after acoustic overexposure. Treatment of mice with either indomethacin or nordihydroguaiaretic acid decreased the ABR threshold shifts after overexposure, indicating that COX-1 and LOX inhibitors exhibited protective effects against acoustic injury. In contrast, COX-2 inhibitors, meloxicam, SC58125, and CAY10404, showed no noticeable effects on the ABR threshold shifts. These findings suggest that COX-1 and LOX are involved in the pathogenesis of acoustic injury in cochlea.

An FDA approved neurokinin-1 receptor antagonist is effective in reducing intraabdominal adhesions when administered intraperitoneally, but not orally

INTRODUCTION

Postoperative adhesions pose a continued healthcare problem. We previously demonstrated that intraperitoneal (i.p.) administration of a neurokinin-1 receptor antagonist (NK-1RA) at surgery reduces intraabdominal adhesions in rats. The NK-1RA aprepitant (Emend, Merck) is clinically approved for preventing postoperative nausea and vomiting; however, its effects on adhesion formation are unknown. Thus, we determined the effects of i.p. and oral administration of aprepitant on adhesion formation in a rat model.

METHODS

Adhesions were surgically induced in rats that were randomized to receive either one or five oral preoperative doses or a single intraoperative i.p. dose of aprepitant (50 mg/kg). Adhesions were scored at 7 days. In similar experiments using i.p. dosing, animals were sacrificed at 24 h and peritoneal fluid, and tissue were collected to assess fibrinolytic activity and tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) mRNA levels, respectively.

RESULTS

I.p. aprepitant reduced adhesion formation by 33% (p < 0.05) compared with controls while oral aprepitant had no effect. Compared to controls i.p. aprepitant reduced tPA activity by 55% (p < 0.05), increased PAI-1 mRNA levels by 140% (p < 0.05), and had no affect on tPA mRNA levels.

CONCLUSION

These data suggest that aprepitant maybe a useful pharmacologic agent for reducing adhesion formation clinically.

Inhibition of CCL1-CCR8 interaction prevents aggregation of macrophages and development of peritoneal adhesions

Peritoneal adhesions are a significant complication of surgery and visceral inflammation; however, the mechanism has not been fully elucidated. The aim of this study was to clarify the mechanism of peritoneal adhesions by focusing on the cell trafficking and immune system in the peritoneal cavity. We investigated the specific recruitment of peritoneal macrophages (PMphi) and their expression of chemokine receptors in murine models of postoperative and postinflammatory peritoneal adhesions. PMphi aggregated at the site of injured peritoneum in these murine models of peritoneal adhesions. The chemokine receptor CCR8 was up-regulated in the aggregating PMphi when compared with naive PMphi. The up-regulation of CCR8 was also observed in PMphi, but not in bone marrow-derived Mphi, treated with inflammatory stimulants including bacterial components and cytokines. Importantly, CCL1, the ligand for CCR8, a product of both PMphi and peritoneal mesothelial cells (PMCs) following inflammatory stimulation, was a potent enhancer of CCR8 expression. Cell aggregation involving PMphi and PMCs was induced in vitro in the presence of CCL1. CCL1 also up-regulated mRNA levels of plasminogen activator inhibitor-1 in both PMphi and PMCs. CCR8 gene-deficient mice or mice treated with anti-CCL1-neutralizing Ab exhibited significantly reduced postoperational peritoneal adhesion. Our study now establishes a unique autocrine activation system in PMphi and the mechanism for recruitment of PMphi together with PMCs via CCL1/CCR8, as immune responses of peritoneal cavity, which triggers peritoneal adhesions.