Interleukin 4 Reduces Brain Hyperexcitability after Traumatic Injury by Downregulating TNF-α, Upregulating IL-10/TGF-β, and Potential Directing Macrophage/Microglia to the M2 Anti-inflammatory Phenotype

Interleukins in Epilepsy: Friend or Foe

Epilepsy is a chronic neurological disorder with recurrent unprovoked seizures, affecting ~ 65 million worldwide. Evidence in patients with epilepsy and animal models suggests a contribution of neuroinflammation to epileptogenesis and the development of epilepsy. Interleukins (ILs), as one of the major contributors to neuroinflammation, are intensively studied for their association and modulatory effects on ictogenesis and epileptogenesis. ILs are commonly divided into pro- and anti-inflammatory cytokines and therefore are expected to be pathogenic or neuroprotective in epilepsy. However, both protective and destructive effects have been reported for many ILs. This may be due to the complex nature of ILs, and also possibly due to the different disease courses that those ILs are involved in. In this review, we summarize the contributions of different ILs in those processes and provide a current overview of recent research advances, as well as preclinical and clinical studies targeting ILs in the treatment of epilepsy.

Progesterone induces neuroprotection associated with immune/inflammatory modulation in experimental traumatic brain injury

An imbalance of immune/inflammatory reactions aggravates secondary brain injury after traumatic brain injury (TBI) and can deteriorate clinical prognosis. So far, not enough therapeutic avenues have been found to prevent such an imbalance in the clinical setting. Progesterone has been shown to regulate immune/inflammatory reactions in many diseases and conveys a potential protective role in TBI. This study was designed to investigate the neuroprotective effects of progesterone associated with immune/inflammatory modulation in experimental TBI. A TBI model in adult male C57BL/6J mice was created using a controlled contusion instrument. After injury, the mice received consecutive progesterone therapy (8 mg/kg per day, i.p.) until euthanized. Neurological deficits were assessed via Morris water maze test. Brain edema was measured via the dry-wet weight method. Immunohistochemical staining and flow cytometry were used to examine the numbers of immune/inflammatory cells, including IBA-1 + microglia, myeloperoxidase + neutrophils, and regulatory T cells (Tregs). ELISA was used to detect the concentrations of IL-1β, TNF-α, IL-10, and TGF-β. Our data showed that progesterone therapy significantly improved neurological deficits and brain edema in experimental TBI, remarkably increased regulatory T cell numbers in the spleen, and dramatically reduced the activation and infiltration of inflammatory cells (microglia and neutrophils) in injured brain tissue. In addition, progesterone therapy decreased the expression of the pro-inflammatory cytokines IL-1β and TNF-α but increased the expression of the anti-inflammatory cytokine IL-10 after TBI. These findings suggest that progesterone administration could be used to regulate immune/inflammatory reactions and improve outcomes in TBI.

Crosstalk Among Glial Cells in the Blood-Brain Barrier Injury After Ischemic Stroke

Blood-brain barrier (BBB) is comprised of brain microvascular endothelial cells (ECs), astrocytes, perivascular microglia, pericytes, neuronal processes, and the basal lamina. As a complex and dynamic interface between the blood and the central nervous system (CNS), BBB is responsible for transporting nutrients essential for the normal metabolism of brain cells and hinders many toxic compounds entering into the CNS. The loss of BBB integrity following stroke induces tissue damage, inflammation, edema, and neural dysfunction. Thus, BBB disruption is an important pathophysiological process of acute ischemic stroke. Understanding the mechanism underlying BBB disruption can uncover more promising biological targets for developing treatments for ischemic stroke. Ischemic stroke-induced activation of microglia and astrocytes leads to increased production of inflammatory mediators, containing chemokines, cytokines, matrix metalloproteinases (MMPs), etc., which are important factors in the pathological process of BBB breakdown. In this review, we discussed the current knowledges about the vital and dual roles of astrocytes and microglia on the BBB breakdown during ischemic stroke. Specifically, we provided an updated overview of phenotypic transformation of microglia and astrocytes, as well as uncovered the crosstalk among astrocyte, microglia, and oligodendrocyte in the BBB disruption following ischemic stroke.

Inhibition of the proteoglycan receptor PTPσ promotes functional recovery on a rodent model of preterm hypoxic-ischemic brain injury

BACKGROUND

Preterm white matter injury (WMI) is the most common brain injury in preterm infants and is associated with long-term adverse neurodevelopmental outcomes. Protein tyrosine phosphatase sigma (PTPσ) was discovered as chondroitin sulfate proteoglycan (CSPG) receptor that played roles in inhibiting myelin regeneration in spinal injury, experimental autoimmune encephalomyelitis, and stroke models. However, the role of PTPσ in perinatal WMI is not well understood.

AIMS

This study examines the effect of PTPσ inhibition on neurodevelopmental outcomes, myelination, and neuroinflammation in a mouse model of preterm WMI.

MATERIALS AND METHODS

Modified Rice-Vannucci model was performed on postnatal day 3 (P3) C57BL/6 mice. Intracellular Sigma Peptide (ISP) or vehicle was administrated subcutaneously one hour after injury for an additional 14 consecutive days. A battery of behavioral tests was performed to evaluate the short- and long-term effects of ISP on neurobehavioral deficit. Real time qPCR, western blot, immunofluorescence, and transmission electron microscopy were performed to assess white matter development. qPCR and flow cytometry were performed to evaluate neuroinflammation and microglia/macrophage phenotype.

RESULTS

The expression of PTPσ was increased after preterm WMI. ISP improved short-term neurological outcomes and ameliorated long-term motor and cognitive function of mice after preterm WMI. ISP promoted oligodendrocyte differentiation, maturation, myelination, and improved microstructure of myelin after preterm WMI. Furthermore, ISP administration fostered a beneficial inflammatory response in the acute phase after preterm WMI, inhibited the infiltration of peripheral macrophages, and promoted anti-inflammatory phenotype of microglia/macrophages.

CONCLUSION

PTPσ inhibition can ameliorate neurofunctional deficit, promote white matter development, modulate neuroinflammation and microglia/macrophage phenotype after preterm WMI. Thus, ISP administration may be a potential therapeutic strategy to improve neurodevelopmental outcomes of perinatal WMI.

Intranasal Insulin Alleviates Traumatic Brain Injury by Inhibiting Autophagy and Endoplasmic Reticulum Stress-mediated Apoptosis Through the PI3K/Akt/mTOR Signaling Pathway

Intranasal insulin reduces lesion size and enhances memory capacity in traumatic brain injury (TBI) models, but the molecular mechanisms behind this neuroprotective action not yet understood. Here we used Feeney's free-falling method to construct TBI mouse models and administrated intranasal insulin, rapamycin, insulin and rapamycin, or normal saline to assess their effects on neurological functions, cerebral edema, and the expression of Iba1 in microglia through immunofluorescence assay. We also measured concentrations of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the brain using enzyme immunosorbent assay, investigated apoptosis with TUNEL staining and Western blotting, and evaluated autophagy, endoplasmic reticulum (ER) stress, and PI3K/Akt/mTOR signaling pathway with Western blotting. The autophagosome was assessed through transmission electron microscopy. Our findings demonstrated that intranasal insulin promoted neurological recovery, decreased brain swelling, and reduced injury lesions on days 1, 3, and 7 post TBI. Moreover, intranasal insulin reduced microglia activation and the concentration of IL-1β or TNF-α on the same days. Through Western blotting and transmission electron microscopy, we observed that intranasal insulin suppressed autophagy while activating the PI3K/AKT/mTOR signaling pathway on days 1 and 3 post TBI. TUNEL assay and Western blotting also indicated that intranasal insulin inhibited ER stress-mediated apoptosis. Interestingly, the mTOR inhibitor rapamycin partially blocked the pro-autophagy and anti-apoptosis effects of intranasal insulin both on days 1 and 3 post TBI. Our results suggest that intranasal insulin can ameliorate TBI by regulating autophagy and ER stress-mediated apoptosis through the PI3K/AKT/mTOR signaling pathway, providing a promising therapeutic strategy for TBI.