Activation of glial cells by human coronavirus OC43 infection

Abstract

Multiple sclerosis (MS) is an immune-mediated demyelinating disease that could be triggered by a viral infection. Coronaviruses induce an MS-like disease in rodents, are neuroinvasive in humans and can infect primary cultures of human astrocytes and microglia. Infection of the human astrocytic cell line U-373MG by the OC43 strain of human coronavirus caused an upregulation of IL-6, TNF-alpha, and MCP-1 mRNA expression. This virus also modulated the activity of matrix metalloproteinases-2 and -9 and augmented nitric oxide production in both U-373MG cells and the human microglial cell line CHME-5. Thus, a coronaviral infection of glial cells could lead to the production of inflammatory molecules that have been associated with central nervous system pathologies such as MS.

Fig. 1

Upregulation of cytokine and chemokine mRNA expression in HCoV-OC43-infected and IFN-γ-treated U-373MG astrocytic cells. Stimulation indices were determined by semi-quantitative RT-PCR, using GAPDH as a housekeeping gene, and comparing to basal expression in non-stimulated cells. Data presented with error bar represent the mean±S.E. of three experiments. (A) IL-6; stimulation index for PMA-stimulated cells reached 15.7 at 6 h (data not shown). (B) TNF-α; stimulation index for PMA-stimulated cells reached 3.1 at 6 h (data not shown). (C) MCP-1; stimulation index for PMA-stimulated cells reached 2 at 6 h (data not shown). (■) HCoV-OC43; (▴) IFN-γ.

Fig. 2

Gelatinase secretion in supernatants of: (A) U-373MG astrocytic cells and (B) CHME-5 microglial cells. Cells were stimulated or not (NS) for 24 and 48 h with PMA (100 ng/ml) or infected with HCoV-OC43 (MOI 0.25). Supernatants were collected, concentrated and assayed for their gelatinase content by gelatin-based zymography. Results are representative of three independent experiments.

Fig. 3

NO secretion by: (A) U-373MG astrocytic cells and (B) CHME-5 microglial cells cultured with different stimuli, for 24, 48, and 72 h. Data shown in each panel represent mean±S.E. of four or three independent experiments, respectively.