NLRC5 alleviated OGD/R-induced PC12-cell injury by inhibiting activation of the TLR4/MyD88/NF-κB pathway

Abstract

Objective To assess the role of NOD-like receptor C5 (NLRC5; a major NLRC family protein that regulates immunity, inflammation and tissue fibrosis), in cerebral ischemia-reperfusion injury, characterized by inflammation and oxidative damage. Methods Blood NLRC5 levels were assessed in neonates with cerebral ischemia and in healthy controls. A stable PC12 cell line was established that overexpressed or knocked down NLRC5. Inflammatory responses, apoptosis rate and oxidative damage in PC12 cells under oxygen-glucose deprivation/reperfusion (OGD/R) conditions were evaluated using enzyme-linked immunosorbent assay (ELISA), terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) and reactive oxygen species (ROS) assay. Results Blood NLRC5 levels were suppressed in neonates with cerebral ischemia. ELISAs showed that NLRC5 suppressed levels of tumour necrosis factor-α, interleukin (IL)-6, IL-1β, ROS and superoxide dismutase in OGD/R-treated PC12 cells. Furthermore, NLRC5 overexpression was associated with reduced apoptosis rate in PC12 cells treated by OGD/R. Overexpression of NLRC5 also inhibited levels of toll-like receptor (TLR)4, myeloid differentiation primary response protein MyD88 (MyD88) and phosphorylated nuclear factor kappa B-transcription factor p65 (NF-κB p-p65) in PC12 cells, and decreased nuclear levels of NF-κB p-p65. Conclusion NLRC5 alleviated inflammatory responses, oxidative damage and apoptosis in PC12 cells under OGD/R conditions by suppressing activation of the TLR4/MyD88/NF-κB pathway.

Roles of PRR-Mediated Signaling Pathways in the Regulation of Oxidative Stress and Inflammatory Diseases

“…In the NLRC5-knockout and -knockdown cardiac muscle cells challenged with LPS, no obvious effect was observed for ROS production [ 61 ]. However, overexpression of NLRC5 caused significant decrease in ROS levels [ 62 ], and NLRC5 silencing was associated with increased ROS levels under oxygen-glucose deprivation/reperfusion (OGD/R) [ 63 ]. The exact mechanism of NLRC5 on the regulation of ROS generation remains to be clarified.…”

NLRC5: A Potential Target for Central Nervous System Disorders

“…Activated caspase-1 promotes proteolysis and maturation of the pro-inflammatory cytokines IL-1b and IL-18, stimulating the occurrence of pyroptosis (38). It has been reported that inflammasome activation is associated with a variety of brain diseases, including ischemic and traumatic brain injury and neurodegenerative diseases (12,39,40). Co-immunoprecipitation experiments revealed that NLRC5 directly binds to the NLR family PYD containing 3 (NLRP3) and apoptosis-associated speck-like protein containing CARD (ASC), which is considered to be an activator and synergetic component of the inflammasome (41).…”

“…Thus, NLRC5 may serve as an effective target for the treatment of cerebral I/R injury. Furthermore, Zhang et al found that the expression of NLRC5 in neonates with cerebral ischemia and OGD/R-induced PC12 cells was significantly reduced (12). However, NLRC5 overexpression was found to suppress the levels of inflammatory cytokines such as TNF-a, IL-6, IL-1b, ROS, malondialdehyde (MDA), Bax, and caspase-3, as well as apoptosis.…”

“…However, NLRC5 overexpression was found to suppress the levels of inflammatory cytokines such as TNF-a, IL-6, IL-1b, ROS, malondialdehyde (MDA), Bax, and caspase-3, as well as apoptosis. Moreover, it inhibits the levels of TLR4, MyD88, and NF-kB p-p65 and upregulates the expression of superoxide dismutase (SOD) and bcl-2 (12). Therefore, NLRC5 alleviates inflammation, oxidative damage, and apoptosis in PC12 cells under OGD/R conditions by suppressing the activation of the TLR4/MyD88/NF-kB pathway.…”

“…It was previously reported that NLRC5 [NLR family caspase recruitment domain (CARD) containing 5, also known as NOD4, NOD27, and CLR16.1] accounts for a large proportion of the NLR family, which can modulate immune responses in the context of many human diseases, such as liver disease, renal disease, rheumatoid arthritis, and heart disease, by regulating nuclear factor-kB (NF-kB), type I interferon (IFN-1), inflammasome signaling pathways and the expression of the major histocompatibility complex (MHC) I genes (3)(4)(5). However, in recent years, studies have found that NLRC5 is also associated with CNS infection (CNSI) (6)(7)(8)(9), neuronal development (10), and neuropsychiatric disorders, such as cerebral ischemia/reperfusion (I/R) injury (11,12), glioma (13)(14)(15), multiple sclerosis (MS) (16), epilepsy (17), schizophrenia (SCZ), and bipolar disorder (BD) (18,19).…”