Putative link between Polo-like kinases (PLKs) and Toll-like receptor (TLR) signaling in transformed and primary human immune cells

Identification of polo-like kinase 1 as a therapeutic target in murine lupus

Introduction

The signalling cascades that contribute to lupus pathogenesis are incompletely understood. We address this by using an unbiased activity‐based kinome screen of murine lupus.

Methods

An unbiased activity‐based kinome screen (ABKS) of 196 kinases was applied to two genetically different murine lupus strains. Systemic and renal lupus were evaluated following in vivo PLK1blockade. The upstream regulators and downstream targets of PLK1 were also interrogated.

Results

Multiple signalling cascades were noted to be more active in murine lupus spleens, including PLK1. In vivo administration of a PLK1‐specific inhibitor ameliorated splenomegaly, anti‐dsDNA antibody production, proteinuria, BUN and renal pathology in MRL.lpr mice (P < 0.05). Serum IL‐6, IL‐17 and kidney injury molecule 1 (KIM‐1) were significantly decreased after PLK1 inhibition. PLK1 inhibition reduced germinal centre and marginal zone B cells in the spleen, but changes in T cells were not significant. In vitro, splenocytes were treated with anti‐mouse CD40 Ab or F(ab’)2 fragment anti‐mouse IgM. After 24‐h stimulation, IL‐6 secretion was significantly reduced upon PLK1 blockade, whereas IL‐10 production was significantly increased. The phosphorylation of mTOR was assessed in splenocyte subsets, which revealed a significant change in myeloid cells. PLK1 blockade reduced phosphorylation associated with mTOR signalling, while Aurora‐A emerged as a potential upstream regulator of PLK1.

Conclusion

The Aurora‐A → PLK1 → mTOR signalling axis may be central in lupus pathogenesis, and emerges as a potential therapeutic target.

Trichlorocarban induces developmental and immune toxicity to zebrafish (Danio rerio) by targeting TLR4/MyD88/NF-κB signaling pathway

Trichlorocarban (TCC) is ubiquitously detected in environmental matrices, while there is a paucity of information regarding its systemic toxicity. In the present study, we observed that TCC exposure led to high embryo mortality, delayed hatching and yolk absorption, as well as increased malformations, such as closure of swim sac and yolk sac edema. Meanwhile, TCC affected the formation and branch of subintestinal veins (SIVs), intersegmental vessels and posterior cardinal veins. Especially, the SIVs were shrunk, and their branches were reduced or even broken along with reduced coverage area. TCC-induced oxidative stress and excessive apoptosis resulted from abnormal expression of the anti/pro-apoptotic genes. Significant reduction in the number and aggregation function of immune cells proved that TCC had prominent immunotoxicity to zebrafish. TCC-targeted TLR4 signaling pathway was demonstrated by abnormal expression of the marker genes (tlr4, MyD88 and nf-κb) and release of the downstream inflammatory factors (TNF-α, IL-6, etc.). Inhibition of TLR4/MyD88/NF-κB pathway by an inhibitor (CA-4948) rescued the decreasing trend of the immune cells induced by TCC. Molecular docking results demonstrated that TCC could stably bind to TLR4 receptor to form hydrogen bonds and hydrophobic interactions with amino acids. Overall, these findings reveal the underlying molecular mechanisms on TCC-induced developmental and immune toxicity to zebrafish.