Controlled decompression attenuates brain damage in a rat model of epidural extreme intracranial hypertension: Partially via inhibiting necroptosis and inflammatory response

The neuroprotection of controlled decompression after traumatic epidural intracranial hypertension through suppression of autophagy via PI3K/Akt signaling pathway

Acute intracranial hypertension (AIH) is a common and tricky symptom that inflicts upon patients after traumatic brain injury (TBI). A variety of clinical options have been applied for the management of AIH, such as physiotherapy, medication, surgery and combination therapy. Specifically, controlled decompression (CDC) alleviates the extent of brain injury and reduces the incidence of a series of post-TBI complications, thereby enhancing the prognosis of patients suffering from acute intracranial hypertension. The objective of the present project is to illuminate the potential molecular mechanism that underlies the neuroprotective effects of CDC in a rat model of traumatic epidural intracranial hypertension (TEIH). Herein, we observed the functional recovery, the degree of brain edema, the level of apoptosis, the expressions of neuronal cell autophagy-related signaling pathway proteins (including Akt, p-Akt, LC3 and Beclin-1) in rat TEIH model at 24 h post-surgery. The results showed in comparison with rapid decompression (RDC), CDC reduced the degree of brain edema, diminished the level of cellular apoptosis and enhanced neurological function, and whereas the neuroprotective effect of CDC could be reversed by rapamycin (Rap). The expressions of Beclin-1 and LC3 in CDC group were significantly lower than those of RDC group, and the expression levels of these two proteins were significantly elevated after the addition of Rap. The expression of p-Akt in CDC group was considerably enhanced than RDC group. After the addition of LY294002, a PI3K/Akt pathway inhibitor, p-Akt protein expression was reduced, and the neuroprotective effect of the rats was markedly inhibited. Taken together, our data demonstrate the superior neuroprotective effect of CDC with regard to alleviating early brain edema, improving the neurological status, suppressing apoptosis and inhibiting neuronal autophagy via triggering PI3K/Akt signaling pathway.

Comparison of the effects of stepwise intracranial decompression and decompressive craniectomy in the treatment of severe traumatic brain injury: A randomized controlled trial

BACKGROUND

To compare the effects of stepwise intracranial decompression (SID) and decompressive craniectomy (DC) on severe traumatic brain injury.

METHODS

This prospective randomized study was conducted at The Third Affiliated Hospital of Soochow University. Ninety two patients were divided into 2 groups according to the random number table method. The study group received SID, whereas the control group received DC. The surgical time and intraoperative bleeding of the 2 groups of patients were recorded, neurological function and glasgow coma score before and after treatment in both groups, incidence of complications, prognostic situation, and levels of brain oxygen metabolism indicators before and after treatment.

RESULTS

Among the 92 patients who agreed, 46 were assigned to the study and control groups, and 6 patients were excluded. Finally, 86 patients were analyzed, including 43 in the study group and 43 in the control group. After treatment, the glasgow coma score scores of the 2 groups increased compared to before treatment; the study group had a higher score, The National Institutes of Health Stroke Scale score decreased compared to before treatment, and the study group had a lower score (P < .05). The incidence of complications in the study group (4.65%) was significantly lower than that in the control group (18.60%) (P < .05). The good prognosis rate of the research group (41.86%) was significantly higher than that of the control group (16.28%) (P < .05).

CONCLUSION

Compared with DC, using SID to treat severe traumatic brain injury can shorten surgical time and reduce intraoperative bleeding, more effectively improve patients neurological function and consciousness state, reduce the incidence of complications, and regulate brain oxygen metabolism status, which is beneficial for improving prognosis and ensuring a good outcome of the disease.

Controlled Decompression Alleviates Motor Dysfunction by Regulating Microglial Polarization via the HIF-1α Signaling Pathway in Intracranial Hypertension

Decompressive craniectomy (DC) is a major form of surgery that is used to reduce intracranial hypertension (IH), the most frequent cause of death and disability following severe traumatic brain injury (sTBI) and stroke. Our previous research showed that controlled decompression (CDC) was more effective than rapid decompression (RDC) with regard to reducing the incidence of complications and improving outcomes after sTBI; however, the specific mechanisms involved have yet to be elucidated. In the present study, we investigated the effects of CDC in regulating inflammation after IH and attempted to identify the mechanisms involved. Analysis showed that CDC was more effective than RDC in alleviating motor dysfunction and neuronal death in a rat model of traumatic intracranial hypertension (TIH) created by epidural balloon pressurization. Moreover, RDC induced M1 microglia polarization and the release of pro-inflammatory cytokines. However, CDC treatment resulted in microglia primarily polarizing into the M2 phenotype and induced the significant release of anti-inflammatory cytokines. Mechanistically, the establishment of the TIH model led to the increased expression of hypoxia-inducible factor-1α (HIF-1α); CDC ameliorated cerebral hypoxia and reduced the expression of HIF-1α. In addition, 2-methoxyestradiol (2-ME2), a specific inhibitor of HIF-1α, significantly attenuated RDC-induced inflammation and improved motor function by promoting M1 to M2 phenotype transformation in microglial and enhancing the release of anti-inflammatory cytokines. However, dimethyloxaloylglycine (DMOG), an agonist of HIF-1α, abrogated the protective effects of CDC treatment by suppressing M2 microglia polarization and the release of anti-inflammatory cytokines. Collectively, our results indicated that CDC effectively alleviated IH-induced inflammation, neuronal death, and motor dysfunction by regulating HIF-1α-mediated microglial phenotype polarization. Our findings provide a better understanding of the mechanisms that underlie the protective effects of CDC and promote clinical translational research for HIF-1α in IH.

Effect of angiotensin II on irradiation exacerbated decompression sickness

In some complicated situations, decompression sickness (DCS) combined with other injuries, such as irradiation, will seriously endanger life safety. However, it is still unclear whether irradiation will increase the incidence of DCS. This study was designed to investigate the damage effects of irradiation on decompression injury and the underlying mechanism. Sprague-Dawley rats were exposed to irradiation followed by hyperbaric decompressing and the mortality and decompression symptoms were observed. Lung tissue and bronchoalveolar lavage fluid were collected to detect the lung lesion, inflammation response, activity of the angiotensin system, oxidative stress, and relative signal pathway by multiple methods, including Q-PCR, western blot, and ELISA. As a result, pre-exposure to radiation significantly exacerbated disease outcomes and lung lesions of DCS. Mechanically, the up-regulation of angiotensin-converting enzyme expression and angiotensin II levels was responsible for the exacerbated DCS and lung lesions caused by predisposing irradiation exposure. Oxidative stress and PI3K/AKT signal pathway activation in pulmonary tissue were enhanced after irradiation plus decompression treatment. In conclusion, our results suggested that irradiation could exacerbate lung injury and the outcomes of DCS by activating the angiotensin system, which included eliciting oxidative stress and activation of the PI3K/AKT signal pathway.

Mild hypothermia alleviates early brain injury after subarachnoid hemorrhage via suppressing pyroptosis through AMPK/NLRP3 inflammasome pathway in rats

As a subtype of stroke, subarachnoid hemorrhage (SAH) has a notoriously high rate of disability and mortality owing to the lack of effective intervention. Early brain injury (EBI) is the main factor responsible for the dismal prognosis of SAH patients. The current study intends to explore the molecular mechanism underlying the effect of MH on EBI after SAH from a novel perspective of pyroptosis, a highly specific inflammatory programmed cell death, in the SAH rat model. Sprague-Dawley (SD) rats were divided into different groups in accordance with various treatments. In the treatment group, the rats underwent mild hypothermia for 4 h after modeling; in the inhibitor group, Compound C (an inhibitor of AMPK) was administered intravenous injections (i.v.) 30 min before modeling. Neurological score, neuronal death, brain water content, inflammatory reaction, and expression levels of pyroptosis-related proteins were evaluated in the rats. Our results indicate that the MH therapy significantly increased the neurological score and assuaged brain edema, neuronal injury, and inflammatory reaction induced by SAH. Meanwhile, MH therapy upregulated the level of AMPK phosphorylation whereas downregulated the protein expressions of NLRP3, ASC, cleaved caspase-1, GSDMD, IL-1β, and IL-18. The reversed effect of MH therapy by Compound C concretely indicated that MH therapy inhibited pyroptosis through an AMPK-dependent pathway. Our study also found that MH therapy potently curbed the increasing trend of brain temperature (BT), rectal temperature (RT), and ICP after SAH. Taken together, our data indicate that the neuroprotective effects of MH therapy were manifested by inhibiting pyroptosis via the AMPK/NLRP3 inflammasome pathway, which may serve as a promising therapy for the intervention of SAH.

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.