Necrostatin-1 protects against ischemia/reperfusion injury by inhibiting receptor-interacting protein 1 in a rat flap model

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.

Necrostatin-1 Attenuates Delayed Paraplegia after Transient Spinal Cord Ischemia in Rabbits by Inhibiting the Upregulation of Receptor-Interacting Protein Kinase 1 and 3

BACKGROUND

Delayed-onset paraplegia is a disastrous complication after thoracoabdominal aortic open surgery and thoracic endovascular aortic repair. Studies have revealed that transient spinal cord ischemia caused by temporary occlusion of the aorta induces delayed motor neuron death owing to apoptosis and necroptosis. Recently, necrostatin-1 (Nec-1), a necroptosis inhibitor, has been reported to reduce cerebral and myocardial infarction in rats or pigs. In this study, we investigated the efficacy of Nec-1 in delayed paraplegia after transient spinal cord ischemia in rabbits and assessed the expression of necroptosis- and apoptosis-related proteins in motor neurons.

METHODS

This study used rabbit transient spinal cord ischemia models using a balloon catheter. They were divided into a vehicle-treated group (n = 24), Nec-1-treated group (n = 24), and sham-controls (n = 6). In the Nec-1-treated group, 1 mg/kg of Nec-1 was intravascularly administered immediately before ischemia induction. Neurological function was assessed using the modified Tarlov score, and the spinal cord was removed 8 hr and 1, 2, and 7 days after reperfusion. Morphological changes were examined using hematoxylin and eosin staining. The expression levels of necroptosis-related proteins (receptor-interacting protein kinase [RIP] 1 and 3) and apoptosis-related proteins (Bax and caspase-8) were assessed using western blotting and histochemical analysis. We also performed double-fluorescence immunohistochemical studies of RIP1, RIP3, Bax, and caspase-8.

RESULTS

Neurological function significantly improved in the Nec-1-treated group compared with that in the vehicle-treated group 7 days after reperfusion (median 3 and 0, P = 0.025). Motor neurons observed 7 days after reperfusion were significantly decreased in both groups compared with the sham group (vehicle-treated, P < 0.001; Nec-1-treated, P < 0.001). However, significantly more motor neurons survived in the Nec-1-treated group than in the vehicle-treated group (P < 0.001). Western blot analysis revealed RIP1, RIP3, Bax, and caspase-8 upregulation 8 hr after reperfusion in the vehicle-treated group (RIP1, P = 0.001; RIP3, P = 0.045; Bax, P = 0.042; caspase-8, P = 0.047). In the Nec-1-treated group, the upregulation of RIP1 and RIP3 was not observed at any time point, whereas that of Bax and caspase-8 was observed 8 hr after reperfusion (Bax, P = 0.029; caspase-8, P = 0.021). Immunohistochemical study revealed the immunoreactivity of these proteins in motor neurons. Double-fluorescence immunohistochemistry revealed the induction of RIP1 and RIP3, and that of Bax and caspase-8, in the same motor neurons.

CONCLUSIONS

These data suggest that Nec-1 reduces delayed motor neuron death and attenuates delayed paraplegia after transient spinal cord ischemia in rabbits by selectively inhibiting necroptosis of motor neurons with minimal effect on their apoptosis.

PTPMT1 protects cardiomyocytes from necroptosis induced by γ-ray irradiation through alleviating mitochondria injury

Radiation-induced heart disease (RIHD) progresses over time and may manifest decades after the initial radiation exposure, which is associated with significant morbidity and mortality. The clinical benefit of radiotherapy is always counterbalanced by an increased risk of cardiovascular events in survivors. There is an urgent need to explore the effect and the underlying mechanism of radiation-induced heart injury. Mitochondrial damage widely occurs in irradiation-induced injury, and mitochondrial dysfunction contributes to necroptosis development. Experiments were performed using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and rat H9C2 cells to investigate the effect of mitochondrial injury on necroptosis in irradiated cardiomyocytes and to further elucidate the mechanism underlying radiation-induced heart disease and discover possible preventive targets. After γ-ray irradiation, the expression levels of necroptosis markers were increased, along with higher oxidative stress and mitochondrial injury. These effects could be abated by overexpression of protein tyrosine phosphatase, mitochondrial 1 (PTPMT1). Inhibiting oxidative stress or increasing the expression of PTPMT1 could protect against radiation-induced mitochondrial injury and then decrease the necroptosis of cardiomyocytes. These results suggest that PTPMT1 may be a new target for the treatment of radiation-induced heart disease.NEW & NOTEWORTHY Effective strategies are still lacking for treating RIHD, with unclear pathological mechanisms. In cardiomyocytes model of radiation-induced injuries, we found γ-ray irradiation decreased the expression of PTPMT1, increased oxidative stress, and induced mitochondrial dysfunction and necroptosis in iPSC-CMs. ROS inhibition attenuated radiation-induced mitochondrial damage and necroptosis. PTPMT1 protected cardiomyocytes from necroptosis induced by γ-ray irradiation by alleviating mitochondrial injury. Therefore, PTPMT1 might be a potential strategy for treating RIHD.

Necroptosis in CNS diseases: Focus on astrocytes

In the last few years, necroptosis, a recently described type of cell death, has been reported to play an important role in the development of various brain pathologies. Necroptosis is a cell death mechanism that has morphological characteristics similar to necrosis but is mediated by fundamentally different molecular pathways. Necroptosis is initiated by signaling through the interaction of RIP1/RIP3/MLKL proteins (receptor-interacting protein kinase 1/receptor-interacting protein kinase 3/mixed lineage kinase domain-like protein). RIPK1 kinase is usually inactive under physiological conditions. It is activated by stimulation of death receptors (TNFR1, TNFR2, TLR3, and 4, Fas-ligand) by external signals. Phosphorylation of RIPK1 results in the formation of its complex with death receptors. Further, complexes with the second member of the RIP3 and MLKL cascade appear, and the necroptosome is formed. There is enough evidence that necroptosis plays an important role in the pathogenesis of brain ischemia and neurodegenerative diseases. In recent years, a point of view that both neurons and glial cells can play a key role in the development of the central nervous system (CNS) pathologies finds more and more confirmation. Astrocytes play complex roles during neurodegeneration and ischemic brain damage initiating both impair and protective processes. However, the cellular and molecular mechanisms that induce pathogenic activity of astrocytes remain veiled. In this review, we consider these processes in terms of the initiation of necroptosis. On the other hand, it is important to remember that like other types of programmed cell death, necroptosis plays an important role for the organism, as it induces a strong immune response and is involved in the control of cancerogenesis. In this review, we provide an overview of the complex role of necroptosis as an important pathogenetic component of neuronal and astrocyte death in neurodegenerative diseases, epileptogenesis, and ischemic brain damage.

Melatonin attenuates chronic stress-induced hippocampal inflammatory response and apoptosis by inhibiting ADAM17/TNF-α axis

Melatonin, as a dietary supplement, has a potent neuroprotective effect and exerts a certain antidepressant effect. This study explored the molecular mechanisms and targets of melatonin on chronic stress-induced hippocampal damage from the perspective of inhibiting inflammatory cytokines release. Our results indicated that melatonin alleviated chronic restraint stress (CRS)-induced inflammatory response and apoptosis, thus improving hippocampal structural damage and subsequent depression-like behaviors in rats. The radar map displayed that the change of TNF-α content was the most significant. Meanwhile, correlation analysis showed that TNF-α content was highly positively correlated with apoptosis. Molecular autodocking studies suggested that TNF-α converting enzyme ADAM17 as a potential target has a priority in docking with melatonin. Molecular mechanism studies indicated that melatonin inhibited CRS-induced activation of the ADAM17/TNF-α axis and its downstream proteins p38 and p53 phosphorylation in the hippocampus. Analogously, Both ADAM17 inhibitor TMI-1 and TNF-α inhibitor thalidomide relieved the effects of CRS on ADAM17/TNF-α axis and its downstream proteins phosphorylation, hippocampal apoptosis, hippocampal inflammatory response, and depression-like behaviors in rats. Altogether, these findings reveal that melatonin relieves CRS-induced inflammatory response and apoptosis, and subsequent depression-like behaviors by inhibiting ADAM17/TNF-α axis.

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.

The Effect of Ceruloplasmin Against Ischemia-Reperfusion Injury in Epigastric Island Flap in Rats

BACKGROUND

Flap surgery is frequently used in plastic surgery to close tissue defects. Ischemia-reperfusion (I/R) injury is a significant problem resulting in partial or total flap necrosis. This study aimed to investigate the effect of ceruloplasmin on I/R injury in epigastric island flaps in rats.

MATERIAL AND METHOD

A total of 32 male Sprague-Dawley rats were divided into four groups with eight rats in each group: The flap was not elevated in Group I; the flap was elevated without ischemia or any application in Group II, after the intraperitoneal saline and ceruloplasmin application the flaps were elevated and ischemia was created in group III-IV, respectively. Bilateral epigastric artery flap was elevated in all groups except Group I. After 6 h of ischemia, the flap was reperfused and inset. Samples were taken from the right and left side of the flap area in other groups at the postoperative 24th h for biochemical analysis (catalase and malondialdehyde-MDA) and the seventh postoperative day for histopathological analysis (Modified Verhofstad score and epidermal thicknesses), respectively. Image analysis for necrosis areas was performed on photos taken on the 7th d.

RESULTS

Catalase level was significantly higher in Group IV.(0.15 ± 0.04 U/mg protein) (P < 0.05) Necrosis area percentage(14.4% ± 3.3%),MDA(3.6 ± 0.9 nmol/mg protein), edema(3), necrosis(2.75), and polymorphonuclear leukocyte infiltration(2.87) scores were significantly higher in group III.(P < 0.05). Fibroblast proliferation, collagen density (0.25), vascular density (0.25) scores and epidermal thickness (15.68 µm,) was significantly lower in group III. (P < 0.05) CONCLUSIONS: Our study demonstrated that ceruloplasmin application before ischemia reduced I/R injury in epigastric island flaps in rats.

Targeting necroptosis as therapeutic potential in chronic myocardial infarction

Cardiovascular diseases (CVDs) are considered the predominant cause of morbidity and mortality globally. Of these, myocardial infarction (MI) is the most common cause of CVD mortality. MI is a life-threatening condition which occurs when coronary perfusion is interrupted leading to cardiomyocyte death. Subsequent to MI, consequences include adverse cardiac remodeling and cardiac dysfunction mainly contribute to the development of heart failure (HF). It has been shown that loss of functional cardiomyocytes in MI-induced HF are associated with several cell death pathways, in particular necroptosis. Although the entire mechanism underlying necroptosis in MI progression is still not widely recognized, some recent studies have reported beneficial effects of necroptosis inhibitors on cell viability and cardiac function in chronic MI models. Therefore, extensive investigation into the necroptosis signaling pathway is indicated for further study. This article comprehensively reviews the context of the underlying mechanisms of necroptosis in chronic MI-induced HF in in vitro, in vivo and clinical studies. These findings could inform ways of developing novel therapeutic strategies to improve the clinical outcomes in MI patients from this point forward.

Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial damage is a critical contributor to cardiac ischemia/reperfusion (I/R) injury. Mitochondrial quality control (MQC) mechanisms, a series of adaptive responses that preserve mitochondrial structure and function, ensure cardiomyocyte survival and cardiac function after I/R injury. MQC includes mitochondrial fission, mitochondrial fusion, mitophagy and mitochondria-dependent cell death. The interplay among these responses is linked to pathological changes such as redox imbalance, calcium overload, energy metabolism disorder, signal transduction arrest, the mitochondrial unfolded protein response and endoplasmic reticulum stress. Excessive mitochondrial fission is an early marker of mitochondrial damage and cardiomyocyte death. Reduced mitochondrial fusion has been observed in stressed cardiomyocytes and correlates with mitochondrial dysfunction and cardiac depression. Mitophagy allows autophagosomes to selectively degrade poorly structured mitochondria, thus maintaining mitochondrial network fitness. Nevertheless, abnormal mitophagy is maladaptive and has been linked to cell death. Although mitochondria serve as the fuel source of the heart by continuously producing adenosine triphosphate, they also stimulate cardiomyocyte death by inducing apoptosis or necroptosis in the reperfused myocardium. Therefore, defects in MQC may determine the fate of cardiomyocytes. In this review, we summarize the regulatory mechanisms and pathological effects of MQC in myocardial I/R injury, highlighting potential targets for the clinical management of reperfusion.

Lycopene ameliorates chronic stress-induced hippocampal injury and subsequent learning and memory dysfunction through inhibiting ROS/JNK signaling pathway in rats

The natural carotenoid lycopene (LYC) has strong antioxidant and neuroprotective capacities. This study investigated the effects and mechanisms of LYC on chronic stress-induced hippocampal lesions and learning and memory dysfunction. Rats were administered LYC and/or chronic restraint stress (CRS) for 21 days. Morris water maze results demonstrated that LYC prevented CRS-induced learning and memory dysfunction. Histopathological staining and transmission electron microscopy observation revealed that LYC ameliorated CRS-induced hippocampal microstructural and ultrastructural damage. Furthermore, LYC alleviated CRS-induced oxidative stress by reducing reactive oxygen species (ROS) production and enhancing antioxidant enzyme activities. LYC also improved CRS-induced hippocampal mitochondrial dysfunction by recovering mitochondrial membrane potential, and complex I (NADH dehydrogenase) and II (succinate dehydrogenase) activities. Moreover, LYC reduced CRS-induced apoptosis via the mitochondrial apoptotic pathway, and decreased the number of terminal deoxynucleotidyl transferase dUTP nick-end-labeled positive cells. Additionally, western blot analysis demonstrated that LYC inhibited CRS-induced activation of the c-Jun N-terminal kinase (JNK) signaling pathway. Correlation analysis indicated that ROS levels, JNK activation, and the mitochondrial apoptotic pathway were positively correlated. Further investigation of the underlying mechanisms revealed that the ROS scavenger N-acetyl-l-cysteine inhibited CRS-induced JNK activation. Furthermore, the JNK inhibitor SP600125 relieved CRS-induced hippocampal mitochondrial dysfunction, apoptosis via the mitochondrial apoptotic pathway, and learning and memory dysfunction. Together, these results suggest that LYC alleviates hippocampal oxidative stress, mitochondrial dysfunction, and apoptosis by inhibiting the ROS/JNK signaling pathway, thereby improving CRS-induced hippocampal injury and learning and memory dysfunction. This study provides a theoretical basis and new therapeutic strategies for the application of LYC to relieve chronic stress encephalopathy.

Evidence of necroptosis in osteoarthritic disease: investigation of blunt mechanical impact as possible trigger in regulated necrosis

Joint injuries are highly associated with cell death and development of posttraumatic osteoarthritis (PTOA). The present study focused on necroptosis as a possible modality of chondrocyte death after cartilage trauma and its relevance in OA disease in general. For this purpose, apoptosis- and necroptosis-associated markers were determined in highly degenerated (ICRS ≥ 3) as well as macroscopically intact cartilage tissue (ICRS ≤ 1) by means of real-time PCR and immunohistochemistry (IHC). Moreover, influence of blunt trauma and/or stimulation with cycloheximide (CHX), TNF-a, and caspase-inhibitor zVAD were investigated in cartilage explants (ICRS ≤ 1). Further characterization of necroptosis was performed in isolated chondrocytes. We found that gene expression levels of RIPK3 (4.2-fold, P < 0.0001) and MLKL (2.7-fold, P < 0.0001) were elevated in highly degenerated cartilage tissue, which was confirmed by IHC staining. After ex vivo trauma and/or CHX/TNF stimulation, addition of zVAD further enhanced expression of necroptosis-related markers as well as release of PGE2 and nitric oxide, which was in line with increased cell death and subsequent release of intracellular HMGB1 and dsDNA in CHX/TNF stimulated chondrocytes. However, trauma and/or chemically induced cell death and subsequent release of pro-inflammatory mediators could be largely attenuated by RIPK1-inhibitor necrostatin 1 or antioxidant N-acetylcysteine. Overall, the study provided clear evidence of necroptotic cell death in OA disease. Moreover, a possible link between cartilage injury and necroptotic processes was found, depending on oxidative stress and cytokine release. These results contribute to further understanding of cell death in PTOA and development of novel therapeutic approaches.