Silencing of A20 Aggravates Neuronal Death and Inflammation After Traumatic Brain Injury: A Potential Trigger of Necroptosis

Necrostatin-1 and necroptosis inhibition: Pathophysiology and therapeutic implications

Necrostatin-1 (Nec-1) is a RIP1-targeted inhibitor of necroptosis, a form of programmed cell death discovered and investigated in recent years. There are already many studies demonstrating the essential role of necroptosis in various diseases, including inflammatory diseases, cardiovascular diseases and neurological diseases. However, the potential of Nec-1 in diseases has not received much attention. Nec-1 is able to inhibit necroptosis signaling pathway and thus ameliorate necroptotic cell death in disease development. Recent research findings indicate that Nec-1 could be applied in several types of diseases to alleviate disease development or improve prognosis. Moreover, we predict that Nec-1 has the potential to protect against the complications of coronavirus disease 2019 (COVID-19). This review summarized the effect of Nec-1 in disease models and the underlying molecular mechanism, providing research evidence for its future application.

Low Molecular Weight Dextran Sulfate (ILB®) Administration Restores Brain Energy Metabolism Following Severe Traumatic Brain Injury in the Rat

Traumatic brain injury (TBI) is the leading cause of death and disability in people less than 40 years of age in Western countries. Currently, there are no satisfying pharmacological treatments for TBI patients. In this study, we subjected rats to severe TBI (sTBI), testing the effects of a single subcutaneous administration, 30 min post-impact, of a new low molecular weight dextran sulfate, named ILB^®, at three different dose levels (1, 5, and 15 mg/kg body weight). A group of control sham-operated animals and one of untreated sTBI rats were used for comparison (each group n = 12). On day 2 or 7 post-sTBI animals were sacrificed and the simultaneous HPLC analysis of energy metabolites, N-acetylaspartate (NAA), oxidized and reduced nicotinic coenzymes, water-soluble antioxidants, and biomarkers of oxidative/nitrosative stress was carried out on deproteinized cerebral homogenates. Compared to untreated sTBI rats, ILB^® improved energy metabolism by increasing ATP, ATP/ adenosine diphosphate ratio (ATP/ADP ratio), and triphosphate nucleosides, dose-dependently increased NAA concentrations, protected nicotinic coenzyme levels and their oxidized over reduced ratios, prevented depletion of ascorbate and reduced glutathione (GSH), and decreased oxidative (malondialdehyde formation) and nitrosative stress (nitrite + nitrate production). Although needing further experiments, these data provide the first evidence that a single post-injury injection of a new low molecular weight dextran sulfate (ILB^®) has beneficial effects on sTBI metabolic damages. Due to the absence of adverse effects in humans, ILB^® represents a promising therapeutic agent for the treatment of sTBI patients.

Therapeutic Effect of Tetrapanax papyriferus and Hederagenin on Chronic Neuropathic Pain of Chronic Constriction Injury of Sciatic Nerve Rats Based on KEGG Pathway Prediction and Experimental Verification

Background

Hederagenin is one of the main components of Tetrapanax papyriferus, and Tetrapanax papyriferus is one of the ingredients of Danggui Sini decoction. To explore whether Tetrapanax papyriferus and hederagenin can alleviate mechanical pain, thermal hyperalgesia, and cold pain at the same time, we comprehensively investigated the effects of two drugs on the levels of p38 MAPK phosphorylation, TRP proteins, and IL1β, IL6, and TNF-α in serum.

Methods

Firstly, we obtained pain-related targets and performed KEGG pathway enrichment on these targets. Then, 42 SD rats were separated randomly into six groups: sham operation group, CCI group, pregabalin group, mecobalamin group, Tetrapanax papyriferus group, and hederagenin group. All drugs were given orally. Rats in the sham operation group and CCI group were gavaged with saline. Rats in the pregabalin group were given pregabalin, while rats in the mecobalamin group were given mecobalamin. Rats in the Tetrapanax papyriferus group were given Tetrapanax papyriferus, while rats in the hederagenin group were given hederagenin. Besides, we conducted behavioral tests including acetone test, hot plate experiment, and von Frey filaments, and then dorsal root ganglion neurons were taken out on the 21st day after operation. Then, western blot, ELISA, and hematoxylin-eosin staining were conducted.

Results

Rats in the CCI group were more sensitive to hyperalgesia and allodynia to mechanical and thermal stimuli, as well as cold pain. All four drugs could relieve these pains. Pregabalin, mecobalamin, and Tetrapanax papyriferus can reduce the levels of IL1β, IL6, and TNF-α in serum compared to those of the CCI group. The expression of TRPM8, TRPA1, TRPV1, TRPV4, and phosphorylated p38 MAPK in DRG increased evidently on the 21st day after the operation in the CCI group. All four drugs could reduce the expressions of TRPM8, TRPA1, TRPV1, TRPV4, and phosphorylated p38 MAPK in dorsal root ganglion compared to those of the CCI group.

Conclusion

Tetrapanax papyriferus and hederagenin relieved sciatica by reducing inflammation levels, inhibiting p38 MAPK phosphorylation, and decreasing the levels of dorsal root ganglion proteins.

Role of Pyroptosis in Traumatic Brain and Spinal Cord Injuries

Central nervous system (CNS) trauma, including traumatic brain injury (TBI) and spinal cord injury (SCI), remains a leading cause for morbidity and mortality worldwide. Past research has shown that cell death plays a critical role in the pathophysiology of CNS injuries. More recently, pyroptosis has been identified as a form of programmed inflammatory cell death, and it is a unique form of cell death in various aspects. Mechanistically, pyroptosis can be categorized into canonical (mediated by caspase-1) and non-canonical (mediated by caspase-4/5/11). In canonical pyroptosis, Nod-like receptors (NLRs) inflammasomes play a critical role, and their activation promotes the maturation and secretion of the inflammatory cytokines interleukin-1β/18 (IL-1β/18), cleavage of gasdermin D (GSDMD), and ultimately pyroptotic cell death. Despite a plethora of new knowledge regarding pyroptosis, detailed understanding of how pyroptosis is involved in CNS injuries and possible ways to improve clinical outcomes following CNS injuries remain elusive. This review discusses the current knowledge on how pyroptosis is involved in CNS injuries, focusing on new discoveries regarding how pyroptosis activation occurs, differences between CNS cell types following injury, time-course of inflammatory responses, and key regulatory steps of pyroptosis. In addition, we highlight various investigational agents that are capable of regulating key steps in pyroptotic cell death, and we discuss how these agents may be used as therapies to improve outcomes following CNS trauma.

Dual roles of astrocytes in plasticity and reconstruction after traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of fatality and disability worldwide. Despite its high prevalence, effective treatment strategies for TBI are limited. Traumatic brain injury induces structural and functional alterations of astrocytes, the most abundant cell type in the brain. As a way of coping with the trauma, astrocytes respond in diverse mechanisms that result in reactive astrogliosis. Astrocytes are involved in the physiopathologic mechanisms of TBI in an extensive and sophisticated manner. Notably, astrocytes have dual roles in TBI, and some astrocyte-derived factors have double and opposite properties. Thus, the suppression or promotion of reactive astrogliosis does not have a substantial curative effect. In contrast, selective stimulation of the beneficial astrocyte-derived molecules and simultaneous attenuation of the deleterious factors based on the spatiotemporal-environment can provide a promising astrocyte-targeting therapeutic strategy. In the current review, we describe for the first time the specific dual roles of astrocytes in neuronal plasticity and reconstruction, including neurogenesis, synaptogenesis, angiogenesis, repair of the blood-brain barrier, and glial scar formation after TBI. We have also classified astrocyte-derived factors depending on their neuroprotective and neurotoxic roles to design more appropriate targeted therapies.