Expression of the NLRP3 inflammasome in cerebral cortex after traumatic brain injury in a rat model

Epigenetic regulation of ASC/TMS1 expression: potential role in apoptosis and inflammasome function

Cloning studies have revealed that the apoptosis-associated speck-like protein possessing a caspase-recruiting domain (ASC) and the target of methylation-induced silencing-1 (TMS) are identical proteins. ASC/TMS1 is a bipartite adaptor protein containing the N-terminal pyrin domain and the C-terminal caspase-recruitment domain. There is abundant literature on ASC/TMS1, mostly under the name TMS1, in the epigenetic regulation of apoptosis and carcinogenesis, whereas the abbreviation ASC has been adopted from studies on the assembly of inflammasomes and stimulation of inflammation. There is substantial literature emphasizing that there are common aspects in the regulation of apoptosis and inflammation, which may be related to the function of ASC/TMS1. The region of the transcription start site of ASC/TMS1 gene contains a 600-bp-long CpG island that is highly methylated and the transcription of ASC/TMS1 is repressed in several cancers. However, it is not known whether the ASC/TMS1-dependent epigenetic regulation controls the inflammasome functions and moreover whether this regulation has any role in the inflammation-mediated carcinogenesis or in the pathogenesis of age-related degenerative diseases. We will examine the mechanisms involved in the epigenetic regulation of ASC/TMS1 as well as their significance in the coordination of apoptosis and inflammasome functions. We will also review the role of aberrant methylation of ASC/TMS1 promoter in the function of inflammasomes, a major host defense system, in cellular housekeeping and carcinogenesis.

The role of the inflammasome in cardiovascular diseases

Inflammasome is a very important signaling platform sensing a variety of triggers of the innate immune system. Inflammasome promotes the production of important pro-inflammatory cytokines such as IL-1β and IL-18. Tight control of inflammasome activity is, therefore, essential and occurs at multiple levels. The activation of inflammasome pathways is linked to the pathogenesis of various prevalent disorders including cardiovascular disease such as atherosclerosis, ischemic injury, cardiomyopathy, and Kawasaki disease. The study of the inflammasome in the cardiovascular system has led to the identification of important triggers and endogenous modulators, and to the exploration of new treatment strategies based on the inhibition of inflammasome activation or its end products, i.e., IL-1β and IL-18. In summary, the discovery of the inflammasome has greatly advanced our understanding of how the innate immune system interferes with cardiovascular disease development and progression, and targeting inflammasome provides new avenues for the treatment and management of cardiovascular diseases.

Formononetin protects TBI rats against neurological lesions and the underlying mechanism

Traumatic brain injury (TBI) is a major cause of disability or death worldwide, especially in the young. Thus, effective medication with few side effects needs to be developed. This work aimed to explore the potential benefits of formononetin (FN) on TBI rodent model and to discuss the regarding mechanism. These findings showed that FN effectively increased the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in brain tissue of TBI rats (P<0.01), while it reduced intracephalic malonaldehyde (MDA), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) concentrations (P<0.01). Meanwhile, the hydrocephalus in the TBI rat was alleviated, and the injured nerve cell of the lesioned brain was reduced as showed in hematoxylin-eosin (HE) staining assay. In addition, the endogenous mRNA level of cyclooxygenase-2 (COX-2) in the brain of the TBI rat was significantly down-regulated (P<0.01). Furthermore, the protein expression of nuclear factor E2-related factor 2 (Nrf2) was effectively up-regulated (P<0.01). Taken together, we conclude that formononetin mediates the promising anti-TBI effects against neurocyte damage, which the underlying mechanisms are associated with inhibiting intracephalic inflammatory response and oxidative stress for neuroprotection.

Valproic acid: a new candidate of therapeutic application for the acute central nervous system injuries

Acute central nervous system (CNS) injuries, including stroke, traumatic brain injury (TBI), and spinal cord injury (SCI), are common causes of human disabilities and deaths, but the pathophysiology of these diseases is not fully elucidated and, thus, effective pharmacotherapies are still lacking. Valproic acid (VPA), an inhibitor of histone deacetylation, is mainly used to treat epilepsy and bipolar disorder with few complications. Recently, the neuroprotective effects of VPA have been demonstrated in several models of acute CNS injuries, such as stroke, TBI, and SCI. VPA protects the brain from injury progression via anti-inflammatory, anti-apoptotic, and neurotrophic effects. In this review, we focus on the emerging neuroprotective properties of VPA and explore the underlying mechanisms. In particular, we discuss several potential related factors in VPA research and present the opportunity to administer VPA as a novel neuropective agent.

Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury

Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.

Pathogenesis of acute stroke and the role of inflammasomes

Inflammation is an innate immune response to infection or tissue damage that is designed to limit harm to the host, but contributes significantly to ischemic brain injury following stroke. The inflammatory response is initiated by the detection of acute damage via extracellular and intracellular pattern recognition receptors, which respond to conserved microbial structures, termed pathogen-associated molecular patterns or host-derived danger signals termed damage-associated molecular patterns. Multi-protein complexes known as inflammasomes (e.g. containing NLRP1, NLRP2, NLRP3, NLRP6, NLRP7, NLRP12, NLRC4, AIM2 and/or Pyrin), then process these signals to trigger an effector response. Briefly, signaling through NLRP1 and NLRP3 inflammasomes produces cleaved caspase-1, which cleaves both pro-IL-1β and pro-IL-18 into their biologically active mature pro-inflammatory cytokines that are released into the extracellular environment. This review will describe the molecular structure, cellular signaling pathways and current evidence for inflammasome activation following cerebral ischemia, and the potential for future treatments for stroke that may involve targeting inflammasome formation or its products in the ischemic brain.