Estradiol postconditioning relieves ischemia/reperfusion injury in axial skin flaps of rats, inhibits apoptosis and alters the MKP-1/ERK pathway

Agomelatine improves memory and learning impairments in a rat model of LPS-induced neurotoxicity by modulating the ERK/SorLA/BDNF/TrkB pathway

The mutual interplay between neuroinflammation, synaptic plasticity, and autophagy has piqued researchers' interest, particularly when it comes to linking their impact and relationship to cognitive deficits. Being able to reduce inflammation and apoptosis, melatonin has shown to have positive neuroprotective effects; that is why we thought to check the possible role of agomelatine (AGO) as a promising candidate that could have a positive impact on cognitive deficits. In the current study, AGO (40 mg/kg/day, p.o., 7 days) successfully ameliorated the cognitive and learning disabilities caused by lipopolysaccharide (LPS) in rats (250 μg/kg/day, i.p., 7 days). This positive impact was supported by improved histopathological findings and improved spatial memory as assessed using Morris water maze. AGO showed a strong ability to control BACE1 activity and to rein in the hippocampal amyloid beta (Aβ) deposition. Also, it improved neuronal survival, neuroplasticity, and neurogenesis by boosting BDNF levels and promoting its advantageous effects and by reinforcing the pTrkB expression. In addition, it upregulated the pre- and postsynaptic neuroplasticity biomarkers resembled in synapsin I, synaptophysin, and PSD-95. Furthermore, AGO showed a modulatory action on Sortilin-related receptor with A-type repeats (SorLA) pathway and adjusted autophagy. It is noteworthy that all of these actions were abolished by administering PD98059 a MEK/ERK pathway inhibitor (0.3 mg/kg/day, i.p., 7 days). In conclusion, AGO administration significantly improves memory and learning disabilities associated with LPS administration by modulating the ERK/SorLA/BDNF/TrkB signaling pathway parallel to its capacity to adjust the autophagic process.

Systematic review of pathologic markers in skin ischemia with and without reperfusion injury in microsurgical reconstruction: Biomarker alterations precede histological structure changes

BACKGROUND

Ischemia and ischemia-reperfusion injury contribute to partial or complete flap necrosis. Traditionally, skin histology has been used to evaluate morphological and structural changes, however histology does not detect early changes. We hypothesize that morphological and structural skin changes in response to ischemia and IRI occur late, and modification of gene and protein expression are the earliest changes in ischemia and IRI.

METHODS

A systematic review was performed in accordance with PRISMA guidelines. Studies reporting skin histology or gene/protein expression changes following ischemia with or without reperfusion injury published between 2002 and 2022 were included. The primary outcomes were descriptive and semi-quantitative histological structural changes, leukocyte infiltration, edema, vessel density; secondary outcomes were quantitative gene and protein expression intensity (PCR and western blot). Model type, experimental intervention, ischemia method and duration, reperfusion duration, biopsy location and time point were collected.

RESULTS

One hundred and one articles were included. Hematoxylin and eosin (H&E) showed inflammatory infiltration in early responses (12-24 h), with structural modifications (3-14 days) and neovascularization (5-14 days) as delayed responses. Immunohistochemistry (IHC) identified angiogenesis (CD31, CD34), apoptosis (TUNEL, caspase-3, Bax/Bcl-2), and protein localization (NF-κB). Gene (PCR) and protein expression (western blot) detected inflammation and apoptosis; endoplasmic reticulum stress/oxidative stress and hypoxia; and neovascularization. The most common markers were TNF-α, IL-6 and IL-1β (inflammation), caspase-3 (apoptosis), VEGF (neovascularization), and HIF-1α (hypoxia).

CONCLUSION

There is no consensus or standard for reporting skin injury during ischemia and IRI. H&E histology is most frequently performed but is primarily descriptive and lacks sensitivity for early skin injury. Immunohistochemistry and gene/protein expression reveal immediate and quantitative cellular responses to skin ischemia and IRI. Future research is needed towards a universally-accepted skin injury scoring system.

Exploration of the Protective Mechanism of Bax Removal against Ischemia Reperfusion Injury of Skin Flap through the p38 Mitogen-Activated Protein Kinase Pathway

This research is aimed at exploring the influences of the Bax gene in the p38 mitogen-activated protein kinase (MAPK) pathway and its protective mechanism against ischemia-reperfusion injury (IRI) of skin flap. Forty male Sprague-Dawley (SD) rats were equally divided into the experimental group (Bax gene knockout rats) and control group. The dorsal flap model was prepared, and the survival rate of flap was observed after surgery. The rat flap tissue was cut and stained with hematoxylin-eosin (HE) and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The distribution characteristics of p38MAPK and Bax were detected to evaluate the protective mechanism of Bax gene knockout on IRI of skin flap. After surgery, the survival rate of flaps in the experimental group (82.32%, 70.28%) was significantly higher than that in the control group (57.64%, 46.14%) (P < 0.05). The results of HE staining showed that on the 1^st day after surgery, compared with those in the control group, the skin flaps of the rats in the experimental group were arranged more neatly. The results of TUNEL staining showed that compared with that of the control group, the tissue structure of the skin flap of the experimental group was normal and only a few apoptotic cells appeared. In addition, compared with that in the control group (7.14, 4.25, 3.48, 2.18/6.46, 7.12, 4.86, and 2.44), the expression of Bax and p38 MAPK in the experimental group (0.96, 0.81, 0.76, 0.55/1.63, 1.33, 1.01, and 0.56) significantly decreased (P < 0.05). In short, after the Bax gene was knocked out, injury of the flap after ischemia-reperfusion was considerably improved, which may play a protective role on the IRI of the flap by affecting the p38MAPK pathway.

Cyclic helix B peptide promotes random-pattern skin flap survival via TFE3-mediated enhancement of autophagy and reduction of ROS levels

BACKGROUND AND PURPOSE

Necrosis of random-pattern skin flaps limits their clinical application. Helix B surface peptide (HBSP) protects tissues from ischemia-reperfusion injury; however, the short plasma half-life of HBSP limits its applications. Cyclic helix B peptide (CHBP) was synthesized in the present study, and the role of CHBP in flap survival and the underlying mechanism were investigated.

EXPERIMENTAL APPROACH

Flap viability was evaluated by survival area analysis, laser doppler blood flow, and histological analysis. RNA sequencing was used to identify the mechanisms relevant to the role of CHBP. Western blotting, real-time quantitative PCR, immunohistochemistry, and immunofluorescence were used to assay the levels of autophagy, oxidative stress, pyroptosis, necroptosis, and molecules related to the adenosine 5'-monophosphate-activated protein kinase (AMPK)-transient receptor potential mucolipin 1 (TRPML1)-calcineurin signaling pathway.

KEY RESULTS

The results indicated that CHBP promoted the survival of random-pattern skin flaps. The results of RNA sequencing analysis indicated that autophagy, oxidative stress, pyroptosis, and necroptosis were involved in the ability of CHBP to promote skin flap survival. Restoration of autophagy flux and enhanced resistance to oxidative stress contributed to inhibition of pyroptosis and necroptosis. Increased autophagy and inhibition of oxidative stress in the ischemic flaps are regulated by transcription factor E3 (TFE3). A decrease in the levels of TFE3 caused a reduction in autophagy flux and accumulation of ROS and eliminated the protective effect of CHBP. Moreover, CHBP regulated the activity of TFE3 via the AMPK-TRPML1-calcineurin signaling pathway.

CONCLUSION AND IMPLICATIONS

CHBP promotes skin flap survival by upregulating autophagy and inhibiting oxidative stress in the ischemic flap and may have potential clinical applications.

Ameliorating Effects of β-Glucan on Epigastric Artery Island Flap Ischemia-Reperfusion Injury

BACKGROUND

Ischemia-reperfusion injury has been one of the culprits of tissue injury and flap loss after island flap transpositions. Thus, significant research has been undertaken to study how to prevent or decrease the spread of ischemia-reperfusion injury. Preventive effects of β-glucan on ischemia-reperfusion injury in the kidney, lung, and small intestine have previously been reported. In this study, we present the ameliorating effects of β-glucan on ischemia-reperfusion injury using the epigastric artery island-flap in rats.

MATERIALS AND METHODS

Thirty Wistar-Albino rats were equally divided into three groups: sham, experimental model, and treatment groups. In the sham group, an island flap was elevated and sutured back to the original position without any ischemia. In the experimental model group, the same-sized flap was elevated and sutured back with 8 h of ischemia and consequent 12 h of reperfusion. In the treatment group, 50 mg per kilogram β-glucan was administered to the rats using an orogastric tube for 10 d before the experiment. The same-sized flap is elevated and sutured back to its original position with 8 h of ischemia and 12 h of consequent reperfusion in the treatment group. Tissue biopsies were taken on the first day of the experimental surgery. Tissue neutrophil aggregation and vascular responses were evaluated by histological examinations. Tissue oxidant and antioxidant enzyme levels are evaluated biochemically after tissue homogenization. Topographic follow-up and evaluation of the flaps were maintained, and photographs were taken on the first and seventh day of the experimental surgery.

RESULTS

Topographic flap survival was significantly better in the β-glucan administered group. The neutrophil number, malondialdehyde, and myeloperoxidase levels were significantly lower while glutathione peroxidase and superoxide dismutase levels were significantly higher in the β-glucan administered group respective to the experimental model group.

CONCLUSIONS

Based on the results of our study, we can conclude that β-glucan is protective against ischemia-reperfusion injury. Our study presents the first experimental evidence of such an effect on skin island flaps.

Dihydrolipoic acid protects against lipopolysaccharide-induced behavioral deficits and neuroinflammation via regulation of Nrf2/HO-1/NLRP3 signaling in rat

Background

Recently, depression has been identified as a prevalent and severe mental disorder. However, the mechanisms underlying the depression risk remain elusive. The neuroinflammation and NLRP3 inflammasome activation are known to be involved in the pathology of depression. Dihydrolipoic acid (DHLA) has been reported as a strong antioxidant and exhibits anti-inflammatory properties in various diseases, albeit the direct relevance between DHLA and depression is yet unknown. The present study aimed to investigate the preventive effect and potential mechanism of DHLA in the lipopolysaccharide (LPS)-induced sickness behavior in rats.

Methods

Adult male Sprague–Dawley rats were utilized. LPS and DHLA were injected intraperitoneally every 2 days and daily, respectively. Fluoxetine (Flu) was injected intraperitoneally daily. PD98059, an inhibitor of ERK, was injected intraperitoneally 1 h before DHLA injection daily. Small interfering ribonucleic acid (siRNA) for nuclear factor erythroid 2-like (Nrf2) was injected into the bilateral hippocampus 14 days before the DHLA injection. Depression-like behavior tests were performed. Western blot and immunofluorescence staining detected the ERK/Nrf2/HO-1/ROS/NLRP3 pathway-related proteins.

Results

The DHLA and fluoxetine treatment exerted preventive effects in LPS-induced sickness behavior rats. The DHLA treatment increased the expression of ERK, Nrf2, and HO-1 but decreased the ROS generation levels and reduced the expression of NLRP3, caspase-1, and IL-1β in LPS-induced sickness behavior rats. PD98059 abolished the effects of DHLA on preventive effect as well as the levels of Nrf2 and HO-1 proteins. Similarly, Nrf2 siRNA reversed the preventive effect of DHLA administration via the decreased expression of HO-1.

Conclusions

These findings suggested that DHLA exerted a preventive effect via ERK/Nrf2/HO-1/ROS/NLRP3 pathway in LPS-induced sickness behavior rats. Thus, DHLA may serve as a potential therapeutic strategy for depression.

D-allose alleviates ischemia/reperfusion (I/R) injury in skin flap via MKP-1

Background

D-allose was promising in the protection of ischemia/reperfusion (I/R) injury. We intended to investigate the function of D-allose in skin flap of rat followed by the injury of I/R and whether ERK signal pathway was involved in.

Methods

The back flap of Wistar rats was picked up with a vascular bundle of the lateral chest wall. I/R model was made by the venous clamp for 6 h. Rats received D-allose and PD-98059, the inhibitor of ERK1/2, 30 min before modeling. Morphology of tissue was observed by HE staining. Nitric oxide (NO), myeloperoxidase (MPO), malondialdehyde (MDA) and superoxide dismutase (SOD) levels in skin flap were determined by ELISA kits. mRNA and protein levels were determined by qPCR and Western blot respectively.

Results

D-allose alleviated the condition of pathological changes and raised the survival rate of skin flap injured by I/R. Moreover, D-allose suppressed NO, MPO and MDA while elevated SOD levels during I/R status. Furthermore, D-allose decreased MCP-1, TNF-α, IL-1β and IL-6 levels in skin flap injured by I/R. In addition, D-allose inhibited MKP-1 expression and activated ERK1/2 pathway in skin flap injured by I/R. PD-98059 partially counteracted D-allose effects on I/R injury.

Conclusions

D-allose exerted its protective function via inhibiting MKP-1expression and further activated ERK1/2 pathway to suppress the progress of oxidative stress, inflammation and necrosis, contributing to the survival of skin flap injured by I/R. Thus, D-allose was promising in the transplantation of skin flap.