Inhibition of viral infection-induced inflammatory responses by targeting the CLOCK regulator casein kinase 1 δ/&epsilon

Abstract

Background: The key CLOCK component casein kinase 1 δ/ε is implicated in TGF-β1 signalling and regulation of glucocorticoid activity. We have shown that inhibition of casein kinase 1 δ/ε with PF670462 reduces TGF-beta1-induced glucocorticoid insensitivity , and also ameliorates experimental fibrosis. We now demonstrate for the first time that casein kinase 1 δ/ε is a novel target with therapeutic potential to prevent viral infection-induced inflammatory responses.

Methods: casein kinase 1 δ/ε expression was assessed by IHC in human asthmatic cohort. In vitro poly (I C)-induced inflammatory cytokine production in BEAS-2B cells was assessed by RT-qPCR and ELISA. The potential involvement of casein kinase 1 δ/ε in above experimental settings was ascertained using pharmacological (PF670462) and genetic (short interference RNA) approaches. In vivo inflammatory responses were established in BALB/c mice infected with respiratory syncytial virus (RSV) through intranasal insufflation. Mice were treated 2 days later with either dexamethasone (1mg/kg/day, ip), PF670462 (30mg/kg/day, ip), or the combination for 3 days. Protein content and cell number in broncho alveolar lavage fluid (BALF) were determined. Inflammatory cytokine gene expression was determined in the whole lung extracts by RT-qPCR.

Results: Expression of casein kinase 1 δ/ε was elevated in the airway wall of severe asthmatics compared to well-controlled asthmatics and non-asthmatic controls. In BEAS-2B airway epithelial cells, poly (I:C)-induced pro-inflammatory cytokines (IL-6, IL-8 and GM-CSF) were significantly attenuated by inhibition of casein kinase 1 δ/ε using PF670462 or casein kinase 1 δ/ε knock down. RSV-induced increases in BALF protein content and IL-6 mRNA expression in the lung were significantly reduced by the combination of dexamethasone and PF670462. Increased inflammatory cell number in BALF was also reduced by the dexamethasone/PF670462 combination. Aerosolised PF670462 also protects from RSV induced lung damage in BALB/c mice.

Conclusions: Inhibition of casein kinase 1 δ/ε both in vitro and in vivo suppresses viral infection-induced inflammatory responses. Targeting casein kinase 1 δ/ε may thus be a novel therapeutic approach for sensitising glucocorticoid activity for the treatment of viral exacerbation of asthma.