Paraquat-induced inflammatory response of microglia through HSP60/TLR4 signaling

Abstract

Previous studies showed that paraquat (PQ) caused the apoptosis of dopaminergic neurons by inducing the generation of oxygen radical. The purpose of this study is to explore PQ-induced microglial inflammatory response and its underlying molecular mechanisms. The murine microglia BV cell line was used. After stimulation with PQ and lipopolysaccharides (positive control), the concentrations of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6) in the culture supernatant and mRNA expression of TNF-α and IL-1β were determined by ELISA and quantitative real-time Polymerase Chain Reaction (PCR), respectively. The protein expression of heat shock protein 60 (HSP60) and toll-like receptor 4 (TLR4), along with the mRNA expression of transcription factors of nuclear factor κB-p65 (NF-κB-p65) and activated protein 1 (AP1, c-fos, and c-jun dimer) were evaluated with western blot and quantitative real-time PCR, respectively. The results showed that PQ activated microglia, which was characterized by increasing the generation and upregulated mRNA expression of pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6. In addition, PQ significantly enhanced the expressions of HSP60 and TLR4 proteins in BV cells, as well as NF-κB-p65, c-fos, and c-jun mRNA. These findings suggest that PQ can activate microglia and enhance the expression and secretion of pro-inflammatory cytokines in a HSP60/TLR4 signaling, leading to the inflammatory response.

Acupuncture Attenuates Inflammation in Microglia of Vascular Dementia Rats by Inhibiting miR-93-Mediated TLR4/MyD88/NF-κB Signaling Pathway

“…TLR4 is abundantly expressed in microglia and induces the activation of microglia [47]. Activated microglia gives rise to inflammatory cascade reaction, which results in brain injury and neurological dysfunction [48,49]. Qin et al demonstrated that TLR4 deficiency could suppress the proinflammatory state of microglia, alleviating cognitive dysfunction in CCH mice [50].…”

Heat Shock Proteins in Alzheimer’s Disease: Role and Targeting

“…On the other hand, Hsp60’s role in AD is still unclear. Many data demonstrated that it has a neuroprotective role but other authors have attributed a deleterious effect to the elevated expression of Hsp60 in AD [ 55 , 56 ]. It has been demonstrated that Hsp60 expression by activated microglia is high.…”

“…It has been demonstrated that Hsp60 expression by activated microglia is high. Moreover, the extracellular release of Hsp60 increases the production of other pro-inflammatory factors through binding to toll-like receptor 4 (TLR-4) and stimulating neuronal cell death [ 55 ]. Over-activation of microglia in response to certain harmful factors, contributes to the progression of several neurodegenerative diseases, including AD [ 57 ].…”

Environmental toxicant exposure and Parkinson’s disease: LRRK2 and inflammatory processes

“…Previous reports have found DSS increases LCN2 in both plasma and feces [312,314], while LCN2 mRNA was not induced in WT mice treated with paraquat [315]. Similarly we saw increased IL-6 following LPS and paraquat administration, as we and others have previously reported [298,316], however, no effect of DSS was observed on this measure contrary to previous reports in the gut [317]. In addition, we further found no alteration in IL-1B or IL-10 with either DSS or LPS and paraquat treatment.…”

“…Interestingly DSS pre-treatment significantly enhanced this activation while VSL#3 treatment trended to prevent this. Despite this, TH+ cell loss was not impacted by these microglial alterations which is surprising given the literature thus far examining the role of microglia in paraquat models of PD [150,153,247,316]. Given the increase we observed in GFAP expression following LPS and paraquat treatment, our TH+ cell loss may additionally be due to alteration in astrocyte function that may not be influenced by VSL#3 or DSS treatment.…”