Elamipretide alleviates pyroptosis in traumatically injured spinal cord by inhibiting cPLA2-induced lysosomal membrane permeabilization

Hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect neurons from cardiac arrest-induced pyroptosis

JOURNAL/nrgr/04.03/01300535-202504000-00027/figure1/v/2024-07-06T104127Z/r/image-tiff Cardiac arrest can lead to severe neurological impairment as a result of inflammation, mitochondrial dysfunction, and post-cardiopulmonary resuscitation neurological damage. Hypoxic preconditioning has been shown to improve migration and survival of bone marrow-derived mesenchymal stem cells and reduce pyroptosis after cardiac arrest, but the specific mechanisms by which hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect against brain injury after cardiac arrest are unknown. To this end, we established an in vitro co-culture model of bone marrow-derived mesenchymal stem cells and oxygen-glucose deprived primary neurons and found that hypoxic preconditioning enhanced the protective effect of bone marrow stromal stem cells against neuronal pyroptosis, possibly through inhibition of the MAPK and nuclear factor κB pathways. Subsequently, we transplanted hypoxia-preconditioned bone marrow-derived mesenchymal stem cells into the lateral ventricle after the return of spontaneous circulation in an 8-minute cardiac arrest rat model induced by asphyxia. The results showed that hypoxia-preconditioned bone marrow-derived mesenchymal stem cells significantly reduced cardiac arrest-induced neuronal pyroptosis, oxidative stress, and mitochondrial damage, whereas knockdown of the liver isoform of phosphofructokinase in bone marrow-derived mesenchymal stem cells inhibited these effects. To conclude, hypoxia-preconditioned bone marrow-derived mesenchymal stem cells offer a promising therapeutic approach for neuronal injury following cardiac arrest, and their beneficial effects are potentially associated with increased expression of the liver isoform of phosphofructokinase following hypoxic preconditioning.

Astrocyte-derived lipocalin 2 promotes inflammation and scarring after spinal cord injury by activating SMAD in mice

BACKGROUND

The inflammatory response and scar formation after spinal cord injury (SCI) limit nerve regeneration and functional recovery. Our research group has previously shown that the expression of astrocyte-derived lipocalin 2 (Lcn2) is upregulated after SCI, which correlates with neuronal apoptosis and functional recovery. Therefore, we speculate that astrocyte-specific knockdown of Lcn2 after SCI may lead to a better prognosis.

METHODS

Tissue RNA sequencing, Western blotting, PCR, and immunofluorescence assays were conducted to assess the expression of Lcn2 following SCI in mice. Adeno-associated virus 9 (AAV9) transfection was employed to specifically reduce the expression of Lcn2 in astrocytes, and subsequent evaluations of scarring and inflammation were conducted. In vitro experiments involved treating primary astrocytes with TGF-β or an A1-induced mixture (C1q, TNF-α and IL-1α) following Lcn2 knockdown. Finally, the intrathecal injection of recombinant Lcn2 (ReLcn2) protein was conducted post-injury to further confirm the role of Lcn2 and its underlying mechanism in SCI.

RESULTS

Lcn2 expression was elevated in astrocytes after SCI at 7 dpi (days post injury). Lcn2 knockdown in astrocytes is beneficial for neuronal survival and functional recovery after SCI, and is accompanied by a reduced inflammatory response and inhibited scar formation. The inhibition of SMAD-associated signaling activation was identified as a possible mechanism, and in vitro experiments further confirmed this finding. ReLcn2 further activated SMAD-associated signaling and aggravated motor function after SCI.

CONCLUSION

The upregulation of Lcn2 expression in astrocytes is involved in neuroinflammation and scar formation after SCI, and the activation of SMAD-associated signaling is one of the underlying mechanisms.

Mitochondria-targeting peptide SS-31 attenuates ferroptosis via inhibition of the p38 MAPK signaling pathway in the hippocampus of epileptic rats

Ferroptosis is a newly identified form of non-apoptotic regulated cell death (RCD) andplaysanimportantrole in epileptogenesis. The p38 mitogen-activated protein kinase (p38 MAPK) pathway has been confirmed to be involved in ferroptosis. The mitochondria-targeting antioxidant Elamipretide (SS-31) can reduce the generation of lipid peroxidation and the buildup of reactive oxygen species (ROS). Collectively, our present study was to decipher whether SS-31 inhibits ferroptosis via the p38 MAPK signaling pathway in the rat epilepsy model induced by pilocarpine (PILO).Adult male Wistar rats were randomly divided into four groups: control group (CON group), epilepsy group (EP group), SS-31 treatment group (SS group), and p38 MAPK inhibitor (SB203580) treatment group (SB group). Our results demonstrated that the rat hippocampal neurons after epilepsy were followed by accumulated iron and malondialdehyde (MDA) content, upregulated phosphorylated p38 MAPK protein (P-p38) and nuclear factor erythroid 2-related factor 2 (Nrf2) levels, reduced glutathione peroxidase 4 (Gpx4) content, and depleted glutathione (GSH) activity. Morphologically, mitochondrial ultrastructural damage under electron microscopy was manifested by a partial increase in outer membrane density, disappearance of mitochondrial cristae, and mitochondrial shrinkage. SS-31 and SB203580 treatment blocked the initiation and progression of ferroptosis in the hippocampus of epileptic rats via reducing the severity of epileptic seizures, reversing the expression of Gpx4, P-p38 , decreasing the levels of iron and MDA, as well as increasing the activity of GSH and Nrf2. To summarize, our findings proved that ferroptosis was coupled with the pathology of epilepsy, and SS-31 can inhibit PILO-induced seizures by preventing ferroptosis, which may be connected to the inhibition of p38 MAPK phosphorylation, highlighting the potential therapeutic value for targeting ferroptosis process in individuals with seizure-related diseases.

Ginsenoside-Rh2 Promotes Functional Recovery after Spinal Cord Injury by Enhancing TFEB-Mediated Autophagy

Background: Following spinal cord injury (SCI), autophagy plays a positive role in neuronal protection, whereas pyroptosis triggers an inflammatory response. Ginsenoside-Rh2 (GRh2), known for its neuroprotective effects, is considered a promising drug. However, the exact molecular mechanisms underlying these protective effects remain unclear. Aim of the Study: Explore the therapeutic value of GRh2 in SCI and its potential mechanisms of action. Materials and Methods: An SCI mouse model was established, followed by random grouping and drug treatments under different conditions. Subsequently, the functional recovery of SCI mice after GRh2 treatment was assessed using hematoxylin and eosin, Masson's trichrome, and Nissl staining, footprint analysis, Basso Mouse Scale scoring, and inclined plane tests. The expression levels of relevant indicators in the mice were detected using Western blotting, immunofluorescence, and a quantitative polymerase chain reaction. Network pharmacology analysis was used to identify the relevant signaling pathways through which GRh2 exerts its therapeutic effects. Results: GRh2 promoted functional recovery after SCI. GRh2 significantly inhibits pyroptosis by enhancing autophagy in SCI mice. Simultaneously, the neuroprotective effect of GRh2, achieved through the inhibition of pyroptosis, is partially reversed by 3-methyladenine, an autophagy inhibitor. Additionally, the increase in autophagy induced by GRh2 is mediated by the promotion of transcription factor EB (TFEB) nuclear translocation and dephosphorylation. Partial attenuation of the protective effects of GRh2 was observed after TFEB knockdown. Additionally, GRh2 can modulate the activity of TFEB in mice post-SCI through the EGFR-MAPK signaling pathway, and NSC228155 (an EGFR activator) can partially reverse the effect of GRh2 on the EGFR-MAPK signaling pathway. Conclusions: GRh2 improves functional recovery after SCI by upregulating TFEB-mediated autophagic flux and inhibiting pyroptosis, indicating its potential clinical applicability.

Underlying Mechanism of Lysosomal Membrane Permeabilization in CNS Injury: A Literature Review

Lysosomes play a crucial role in various intracellular pathways as their final destination. Various stressors, whether mild or severe, can induce lysosomal membrane permeabilization (LMP), resulting in the release of lysosomal enzymes into the cytoplasm. LMP not only plays a pivotal role in various cellular events but also significantly contributes to programmed cell death (PCD). Previous research has demonstrated the participation of LMP in central nervous system (CNS) injuries, including traumatic brain injury (TBI), spinal cord injury (SCI), subarachnoid hemorrhage (SAH), and hypoxic-ischemic encephalopathy (HIE). However, the mechanisms underlying LMP in CNS injuries are poorly understood. The occurrence of LMP leads to the activation of inflammatory pathways, increased levels of oxidative stress, and PCD. Herein, we present a comprehensive overview of the latest findings regarding LMP and highlight its functions in cellular events and PCDs (lysosome-dependent cell death, apoptosis, pyroptosis, ferroptosis, and autophagy). In addition, we consolidate the most recent insights into LMP in CNS injury by summarizing and exploring the latest advances. We also review potential therapeutic strategies that aim to preserve LMP or inhibit the release of enzymes from lysosomes to alleviate the consequences of LMP in CNS injury. A better understanding of the role that LMP plays in CNS injury may facilitate the development of strategic treatment options for CNS injury.

SS-31 inhibits the inflammatory response by increasing ATG5 and promoting autophagy in lipopolysaccharide-stimulated HepG2 cells

SS-31 is a mitochondria-targeting short peptide. Recent studies have indicated its hepatoprotective effects. In our study, we investigated the impact of SS-31 on LPS-induced autophagy in HepG2 cells. The results obtained from a dual-fluorescence autophagy detection system revealed that SS-31 promotes the formation of autolysosomes and autophagosomes, thereby facilitating autophagic flux to a certain degree. Additionally, both ELISA and qPCR analyses provided further evidence that SS-31 safeguards HepG2 cells against inflammatory responses triggered by LPS through ATG5-dependent autophagy. In summary, our study demonstrates that SS-31 inhibits LPS-stimulated inflammation in HepG2 cells by upregulating ATG5-dependent autophagy.

SS-31 inhibits mtDNA-cGAS-STING signaling to improve POCD by activating mitophagy in aged mice

BACKGROUND

Neuroinflammation is crucial in the development of postoperative cognitive dysfunction (POCD), and microglial activation is an active participant in this process. SS-31, a mitochondrion-targeted antioxidant, is widely regarded as a potential drug for neurodegenerative diseases and inflammatory diseases. In this study, we sought to explore whether SS-31 plays a neuroprotective role and the underlying mechanism.

METHODS

Internal fixation of tibial fracture was performed in 18-month-old mice to induce surgery-associated neurocognitive dysfunction. LPS was administrated to BV2 cells to induce neuroinflammation. Neurobehavioral deficits, hippocampal injury, protein expression, mitophagy level and cell state were evaluated after treatment with SS-31, PHB2 siRNA and an STING agonist.

RESULTS

Our study revealed that SS-31 interacted with PHB2 to activate mitophagy and improve neural damage in surgically aged mice, which was attributed to the reduced cGAS-STING pathway and M1 microglial polarization by decreased release of mitochondrial DNA (mtDNA) but not nuclear DNA (nDNA). In vitro, knockdown of PHB2 and an STING agonist abolished the protective effect of SS-31.

CONCLUSIONS

SS-31 conferred neuroprotection against POCD by promoting PHB2-mediated mitophagy activation to inhibit mtDNA release, which in turn suppressed the cGAS-STING pathway and M1 microglial polarization.

BMSCs-derived exosomes inhibit macrophage/microglia pyroptosis by increasing autophagy through the miR-21a-5p/PELI1 axis in spinal cord injury

Spinal cord injury (SCI) results in a diverse range of disabilities and lacks effective treatment options. In recent years, exosomes derived from bone mesenchymal stem cells (BMSCs) have emerged as a promising cell-free therapeutic approach for treating ischemic brain injury and other inflammatory conditions. Macrophage/microglial pyroptosis has been identified as a contributing factor to neuroinflammation following SCI. The therapeutic potential of BMSC-derived exosomes in macrophage/microglia pyroptosis-induced neuroinflammation, however, has to be determined. Our findings demonstrate that exosomes derived from BMSCs can enhance motor function recovery and mitigate neuroinflammation subsequent to SCI by upregulating the expression of autophagy-related proteins and inhibiting the activation of NLRP3 inflammasomes in macrophage/microglia. Moreover, miR-21a-5p is markedly increased in BMSCs-derived exosomes, and knocking down miR-21a-5p in BMSCs-derived exosomes eliminates the beneficial effects of administration; upregulation of miR-21a-5p in BMSCs-derived exosomes enhances the beneficial effects of administration. Mechanistically, miR-21a-5p positively regulates the autophagy of macrophage/microglia by reducing PELI1 expression, which in turn inhibits their pyroptosis. This research provides novel evidence that exosomes derived from BMSCs can effectively suppress macrophage/microglia pyroptosis through the miR-21a-5p/PELI1 axis-mediated autophagy pathway, ultimately facilitating functional restoration following SCI. In particular, our constructed miR-21a-5p overexpression exosomes greatly improved the efficacy of BMSCs-derived exosomes in treating spinal cord injury. These results establish a foundation for the prospective utilization of exosomes derived from BMSCs as a novel biological intervention for spinal cord injury.

Ezrin inhibition alleviates oxidative stress and pyroptosis via regulating TRPML1-calcineurin axis mediated enhancement of autophagy in spinal cord injury

Spinal cord injury (SCI) presents profound ramifications for patients, leading to diminished motor and sensory capabilities distal to the lesion site. Once SCI occurs, it not only causes great physical and psychological problems for patients but also imposes a heavy economic burden. Ezrin is involved in various cellular processes, including signal transduction, cell death, inflammation, chemotherapy resistance and the stress response. However, whether Ezrin regulates functional repair after SCI and its underlying mechanism has not been elucidated. Here, our results showed that there is a marked augmentation of Ezrin levels within neurons and Ezrin inhibition markedly diminished glial scarring and bolstered functional recuperation after SCI. RNA sequencing indicated the potential involvement of pyroptosis, oxidative stress and autophagy in the enhancement of functional recovery upon reduced Ezrin expression. Moreover, the inhibition of Ezrin expression curtailed pyroptosis and oxidative stress by amplifying autophagy. Our studies further demonstrated that Ezrin inhibition promoted autophagy by increasing TFEB activity via the Akt-TRPML1-calcineurin pathway. Finally, we concluded that inhibiting Ezrin expression alleviates pyroptosis and oxidative stress by enhancing TFEB-driven autophagy, thereby promoting functional recovery after SCI, which may be a promising therapeutic target for SCI treatment.

Ferroptosis and mitochondrial dysfunction in acute central nervous system injury

Acute central nervous system injuries (ACNSI), encompassing traumatic brain injury (TBI), non-traumatic brain injury like stroke and encephalomeningitis, as well as spinal cord injuries, are linked to significant rates of disability and mortality globally. Nevertheless, effective and feasible treatment plans are still to be formulated. There are primary and secondary injuries occurred after ACNSI. Most ACNSIs exhibit comparable secondary injuries, which offer numerous potential therapeutic targets for enhancing clinical outcomes. Ferroptosis, a newly discovered form of cell death, is characterized as a lipid peroxidation process that is dependent on iron and oxidative conditions, which is also indispensable to mitochondria. Ferroptosis play a vital role in many neuropathological pathways, and ACNSIs may induce mitochondrial dysfunction, thereby indicating the essentiality of the mitochondrial connection to ferroptosis in ACNSIs. Nevertheless, there remains a lack of clarity regarding the involvement of mitochondria in the occurrence of ferroptosis as a secondary injuries of ACNSIs. In recent studies, anti-ferroptosis agents such as the ferroptosis inhibitor Ferrostain-1 and iron chelation therapy have shown potential in ameliorating the deleterious effects of ferroptosis in cases of traumatic ACNSI. The importance of this evidence is extremely significant in relation to the research and control of ACNSIs. Therefore, our review aims to provide researchers focusing on enhancing the therapeutic outcomes of ACNSIs with valuable insights by summarizing the physiopathological mechanisms of ACNSIs and exploring the correlation between ferroptosis, mitochondrial dysfunction, and ACNSIs.