Statins significantly repress rotavirus replication through downregulation of cholesterol synthesis

Abstract

Rotavirus is the most common cause of severe diarrhea among infants and young children and is responsible for more than 200,000 pediatric deaths per year. There is currently no pharmacological treatment for rotavirus infection in clinical activity. Although cholesterol synthesis has been proven to play a key role in the infections of multiple viruses, little is known about the relationship between cholesterol biosynthesis and rotavirus replication. The models of rotavirus infected two cell lines and a human small intestinal organoid were used. We investigated the effects of cholesterol biosynthesis, including inhibition, enhancement, and their combinations on rotavirus replication on these models. The knockdown of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) was built by small hairpin RNAs in Caco2 cells. In all these models, inhibition of cholesterol synthesis by statins or HMGCR knockdown had a significant inhibitory effect on rotavirus replication. The result was further confirmed by the other inhibitors: 6-fluoromevalonate, Zaragozic acid A and U18666A, in the cholesterol biosynthesis pathway. Conversely, enhancement of cholesterol production increased rotavirus replication, suggesting that cholesterol homeostasis is relevant for rotavirus replication. The effects of all these compounds toward rotavirus were further confirmed with a clinical rotavirus isolate. We concluded that rotavirus replication is dependent on cholesterol biosynthesis. To be specific, inhibition of cholesterol synthesis can downregulate rotavirus replication; on the contrary, rotavirus replication is upregulated. Statin treatment is potentially an effective novel clinical anti-rotavirus strategy.

Keywords: Rotavirus infection; antiviral therapy; cholesterol synthesis; statins.

Figure 1.

Statins impair rotavirus replication. (a) Caco2 cells were infected with rotavirus SA11 strain (MOI 0.7) and subsequently treated with different concentrations of atorvastatin (n = 7), lovastatin (n = 7), or simvastatin (n = 5) for 48 hours, then the intra- (left) and extracellular (right) rotavirus RNA levels were measured by qRT-PCR, and (b) rotavirus VP4 protein were measured with 50 µM atorvastatin, lovastatin, and simvastatin treatment for 48 hours respectively by western blot. In MA104 cells, (c) treated as described in a, the intra- (left) and extracellular (right) rotavirus RNA levels with the three statins treatments respectively (n = 5), and (d) the expressions of the rotavirus VP4 protein, treated as described in b. In HSI organoids, (e) treated as described in a, the inner rotavirus RNA level with the treatments of the three statins respectively (n = 3), and (f) the expression of rotavirus VP4 protein, treated as described in b. (g) The titers of infectious rotavirus particles were measured by TCID₅₀ assays with 50 µM three statins treatments respectively in MA104 cells (n = 6). (h) The 96-hour time course experiments of atorvastatin (left), lovastatin (middle), and simvastatin (right) treatments respectively (n = 3) on the intracellular rotavirus RNA replication. All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001

Figure 2.

Statins inhibit the expressions of rotavirus VP6 protein. (a) Schematic depiction of the inhibitors of cholesterol biosynthesis. Following the infection of rotavirus SA11 strain (MOI 0.7) with 50 µM atorvastatin, lovastatin, or simvastatin treatment for 48 hours respectively, the expression of rotavirus VP6 protein was observed by IF staining in Caco2 cells (b), MA104 cells (c) and HSI organoids (d). VP6 protein was green, and the nuclei of the cells were visualized by DAPI (blue). The results showed that statins significantly reduced the expression of rotavirus VP6 protein

Figure 3.

shRNA-mediated HMGCR knockdown in Caco2 cells represses rotavirus replication. (a) Lentiviral shRNA vectors, targeting HMGCR gene or non-targeted control lentivirus were produced in HEK 293 T cells. Subsequently, the transductions of the lentiviral shRNA vectors were performed in Caco2 cells. qRT-PCR analysis was conducted to detect the RNA levels of HMGCR among shRNA 10951–10955 HMGCR vectors. (b) Based on the qRT-PCR analysis, the HMGCR knockdown effects of sh10952 and sh10955 vectors were confirmed by western blot analysis (n = 3). (c) The HMGCR knockdown significantly inhibited the intracellular rotavirus RNA replications post-infection 48 hours (n = 6), and (d) the decreased expressions of rotavirus VP4 protein by western blot analysis (n = 3). (e) The decreased expressions of rotavirus VP6 protein by HMGCR knockdown. VP6 protein was stained as green, and nuclei were visualized by DAPI (blue). All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001

Figure 4.

The inhibitors of cholesterol biosynthesis impair rotavirus replication. With rotavirus SA11 strain (MOI 0.7) infection and subsequently treated with different concentrations of 6-fluoromevalonate for 48 hours. The intra- and extracellular rotavirus RNA levels were measured by qRT-PCR (n = 6) (left) and the expressions of rotavirus VP4 protein were tested by western blot (right) in Caco2 cells (a), and in MA104 cells (b). With ZA-A treatments, the intra- and extracellular rotavirus RNA levels (n = 9) (left) and the expressions of rotavirus VP4 protein (right) in Caco2 cells (c), and in MA104 cells (d). with 1.25 µM U18666A treatment, the intra- and extracellular rotavirus RNA levels (n = 6) (left) and the expressions of rotavirus VP4 protein (right) in Caco2 cells (e), and in MA104 cells (f). In HSI organoids, the inner rotavirus RNA level with 200 µM 6-fluoromevalonate (n = 5) (g), 50 µM ZA-A (n = 5) (h) and 1.25 µM U18666A (n = 4) (i); and the expressions of rotavirus VP4 protein with 200 µM 6-fluoromevalonate or 50 µM ZA-A treatment (left) (j), with 1.25 µM U18666A treatment (right) (k). All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001

Figure 5.

The rotavirus titers and VP6 protein expressions of 200 µM 6-Fluoromevalonate, 50 µM ZA-A or 1.25 µM U18666A treatment. The titers of infectious rotavirus particles were measured with 200 µM 6-Fluoromevalonate (a), 50 µM ZA-A (b) or 1.25 µM U18666A (c) treatment respectively (n = 6). Following the infection of rotavirus SA11 strain (MOI 0.7) with 200 µM 6-Fluoromevalonate or 50 µM ZA-A treatment respectively for 48 hours, the expression of rotavirus VP6 protein was observed in Caco2 cells (d), the expression of rotavirus VP6 protein was observed with 1.25 µM U18666A treatment in Caco2 cells (e), and the rotavirus VP6 expressions with the above treatments in MA104 cells (f) and HSI organoids (g). VP6 protein was green, and the nuclei of the cells were visualized by DAPI (blue). The results indicated that the inhibitors reduced the expressions of rotavirus VP6 protein

Figure 6.

Enhancement of cholesterol production provokes rotavirus replication. With rotavirus SA11 strain (MOI 0.7) infection and subsequently treated with different concentrations of R-MA for 48 hours and subsequently the intra- and extracellular rotavirus RNA levels were measured by qRT-PCR (n = 5) (left) and the expressions of rotavirus VP4 protein were tested by western blot (right) in Caco2 cells (a), and in MA104 cells (b). With different concentrations of cholesterol treatment, the intra- and extracellular rotavirus levels (n = 5) (left) and the expressions of rotavirus VP4 protein (right) in Caco2 cells (c), and in MA104 cells (d). In HSI organoids, the inner rotavirus RNA level (n = 3) (left) and the expressions of rotavirus VP4 protein (right) with R-MA treatment (e), with cholesterol treatment (f). (g) The titers of infectious rotavirus particles were measured by TCID₅₀ assay upon R-MA (n = 6) (left) or cholesterol (n = 6) (right) treatment respectively in MA104 cells. (h) The time-course experiment of 150 µM cholesterol treatment on the intracellular rotavirus replication. All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001

Figure 7.

Rotavirus VP6 expressions by R-MA or cholesterol treatment. Rotavirus SA11 strain (MOI 0.7) infected Caco2 cells with 1,000 µM R-MA or 150 µM cholesterol treatment for 48 hours respectively in Caco2 cells (a), MA104 cells (b) and HSI organoids (c). Rotavirus VP6 protein was green, and the nuclei of the cells were visualized by DAPI (blue). The results showed that both of R-MA and cholesterol markedly increased the expressions of rotavirus VP6 protein

Figure 8.

Cholesterol provokes rotavirus replication in the absence of HMGCR activity. With rotavirus SA11 strain (MOI 0.7) infection and subsequently treated with the combination of 50 µM atorvastatin and 150 µM cholesterol for 48 hours respectively. The intra- (left) and extracellular (right) rotavirus RNA levels were measured by qRT-PCR in Caco2 cells (n = 8) (a), and in MA104 cells (n = 6) (c). The expressions of rotavirus VP4 protein were measured by western blot in Caco2 cells (b), and in MA104 cells (d). With rotavirus SA11 infection (MOI 0.7), sh10952 and sh10955 HMGCR knockdown Caco2 cells were treated with 150 µM cholesterol for 48 hours. The intra- (left) and extracellular (right) rotavirus RNA levels (n = 4) (e) and the expression of rotavirus VP4 protein (f). All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001

Figure 9.

Rotavirus VP4 and VP6 proteins expressions of the combinations of atorvastatin or HMGCR knockdown and cholesterol treatment. Western blot analysis of the expressions of rotavirus VP4 protein with the combinations of 50 µM atorvastatin and 150 µM cholesterol in Caco2 cells (n = 3) (a), MA104 cells (n = 3) (b), and with the combinations of HMGCR knockdown and 150 µM cholesterol (n = 3) (c). The visual aspects of the combinations of 50 µM atorvastatin and 150 µM cholesterol in Caco2 cells (d), and MA104 cells (e), and with the combinations of HMGCR knockdown and 150 µM cholesterol treatment (f). The results showed that the combinations of atorvastatin or HMGCR knockdown and cholesterol treatment significantly increased the rotavirus replications

Figure 10.

Canonical cholesterol biosynthesis is the rate-limiting step for a rotavirus clinical isolate 026 K replication in Caco2 cells. With the rotavirus 026 K strain infection, subsequently the intracellular rotavirus RNA levels were measured by qRT-PCR, after 48 hours treated with 50 µM atorvastatin (n = 4), or lovastatin (n = 4), or simvastatin (n = 6) treatment respectively (a), in sh10952 and sh10955 HMGCR knockdown Caco2 cells (b), with 6-fluoromevalonate treatment (n = 4) (c), with ZA-A treatment (n = 5) (d), with U18666A treatment (n = 6) (e), with R-MA treatment (n = 8) (f), with cholesterol treatment (n = 8) (g). All data presented as mean ± SEM, *p < .05, **p < .01, ***p < .001