MiR-487b suppressed inflammation and neuronal apoptosis in spinal cord injury by targeted Ifitm3

Spinal cord injury (SCI) was a serious nerve injury, which involves complex genetic changes. This paper was intended to investigate the function and mechanism of differentially expressed genes in SCI. The three datasets GSE92657, GSE93561 and GSE189070 of SCI from GEO database were used to identify differentially expressed genes (DEGs). We identified the common DEGs in the three datasets GSE92657, GSE93561 and GSE189070 of SCI from GEO database. Next, a protein-protein interaction (PPI) network of DEGs was constructed. Subsequently, the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were significantly enriched in immune response, inflammatory response. The expression level of immune-related genes (Arg1, Ccl12, Ccl2, Ifitm2, Ifitm3, and et al.) at different time points of SCI were analyzed in GSE189070 dataset. Next, differentially expressed miRNAs (DE-miRNAs) were identified in SCI compared with normal based on GSE158194 database. DE-miRNA and targeted immune-related genes were predicted by miRwalk, including miR-487b-5p targeted Ifitm3, miR-3072-5p targeted Ccl3, and et al. What's more, the miR-487b was identified and verified to be down-regulated in Lipopolysaccharide (LPS)-induced BV-2 cell model. Further, the miR-487b inhibited cell inflammation and apoptosis in LPS-induced BV2 cell by targeted Ifitm3. For the first time, our results revealed that miR-487b may play an important regulatory role in SCI by targeted Ifitm3 and provide further evidence for SCI research.

Association between the interferon-induced transmembrane protein 3 gene (IFITM3) rs34481144 / rs12252 haplotypes and COVID-19

The interferon induced transmembrane-protein 3 (IFITM3) plays an important role in the defence against viral infection. IFITM3 gene variants have been linked to differences in expression and associated with the risk of severe influenza by some authors. More recently, these variants have been associated with the risk of COVID-19 after SARS-CoV-2 infection. We determined the effect of two common IFITM3 polymorphisms (rs34481144 ​C/T and rs12252 A/G) on the risk of hospitalization due to COVID-19 by comparing 484 patients (152 required support in thr intensive care unit, ICU) and 182 age and sex matched controls (no disease symptoms). We found significantly higher frequencies of rs34481144 ​T and rs12252 ​G carriers among the patients (OR ​= ​2.02 and OR ​= ​1.51, respectively). None of the two variants were associated with ICU-admission or death. We found a significantly higher frequency of rs34481144 CC ​+ ​rs12252 AA genotype carriers among the controls, suggesting a protective effect (p = 0.001, OR = 0.56, 95%CI = 0.40–0.80). Moreover, haplotype rs34481144 ​C - rs12252 A was significantly increased in the controls (p ​= ​0.008, OR ​= ​0.71, 95%CI ​= ​0.55–0.91).

Our results showed a significant effect of the IFITM3 variants in the risk for hospitalization after SARS-CoV-2 infection.

Innate immune activation of astrocytes impairs neurodevelopment via upregulation of follistatin-like 1 and interferon-induced transmembrane protein 3

BACKGROUND

Polyriboinosinic-polyribocytidylic acid (polyI:C) triggers a strong innate immune response that mimics immune activation by viral infections. Induction of interferon-induced transmembrane protein 3 (Ifitm3) in astrocytes has a crucial role in polyI:C-induced neurodevelopmental abnormalities. Through a quantitative proteomic screen, we previously identified candidate astroglial factors, such as matrix metalloproteinase-3 (Mmp3) and follistatin-like 1 (Fstl1), in polyl:C-induced neurodevelopmental impairment. Here, we characterized the Ifitm3-dependent inflammatory processes focusing on astrocyte-derived Fstl1 following polyI:C treatment to assess the neuropathologic role of Fstl1.

METHODS

Astrocytes were treated with PBS (control) or polyI:C (10 μg/mL). The conditioned medium was collected 24 h after the polyI:C treatment and used as astrocyte condition medium (ACM). The expression of Fstl1 mRNA and extracellular Fstl1 protein levels were analyzed by quantitative PCR and western blotting, respectively. For functional studies, neurons were treated with ACM and the effects of ACM on dendritic elongation were assayed. To examine the role of Fstl1, recombinant Fstl1 protein and siRNA for Fstl1 were used. To investigate the expression of Fstl1 in vivo, neonatal mice were treated with vehicle or polyI:C on postnatal day 2 to 6.

RESULTS

ACM prepared with polyI:C (polyI:C ACM) contained significantly higher Fstl1 protein than control ACM, but no increase in Fstl1 was observed in polyI:C ACM derived from Ifitm3-deficient astrocytes. We found that the production of Fstl1 involves the inflammatory responsive molecule Ifitm3 in astrocytes and influences neuronal differentiation. In agreement, the levels of Fstl1 increased in the hippocampus of polyI:C-treated neonatal mice. COS7 cells co-transfected with both Fstl1 and Ifitm3 had higher extracellular levels of Fstl1 than the cells transfected with Fstl1 alone. Treatment of primary cultured hippocampal neurons with recombinant Fstl1 impaired dendritic elongation, and the deleterious effect of polyI:C ACM on dendritic elongation was attenuated by knockdown of Fstl1 in astrocytes.

CONCLUSIONS

The extracellular level of Fstl1 is regulated by Ifitm3 in astrocytes, which could be involved in polyI:C-induced neurodevelopmental impairment.

Wif1 and Ifitm3 gene expression preferentially altered in the colon mucosa of benzo[a]pyrene pre-treated mice following exposure to dextran sulfate sodium

Benzo[a]pyrene (BP) is highly mutagenic and yet does not lead to tumor development in the murine colon. We recently reported the generation of colonic tumors one week after treatment with BP followed by dextran sulfate sodium (DSS), a colitis-inducer. In this BP/DSS model, male CD2F1 mice were treated orally with BP at 125 mg/kg/day for 5 days, followed by 4% DSS in drinking water for one week. There has been no report so far on the molecular mechanisms involved in tumor development in this model. In the present study, we performed global gene expression analysis on the colonic mucosae obtained from BP-exposed mice one week after treatment with DSS and those treated with the vehicle, BP, or DSS alone. Global gene expression analysis revealed that there were 563 genes preferentially altered (≥2-fold vs vehicle group) in the colonic mucosae exposed to both BP and DSS. Furthermore, comparative gene expression analysis combined with Ingenuity Pathway Analysis™ identified 2 genes associated with Wnt/β-catenin signaling pathway that were preferentially up-regulated (≥2-fold vs vehicle group) when BP and DSS were treated in combination in the distal part (site of predilection for tumor induction) of the colonic mucosae, especially in colonic tumors: WNT inhibitory factor 1 (Wif1; 14.6-fold increase) and interferon induced membrane protein 3 (Ifitm3; 5.7-fold increase). In colonic tumors, expression of Wif1 and Ifitm3 proteins were both confirmed by western blot analysis. These findings suggest that these genes are associated with rapid induction of colonic tumors in mice after exposure to BP/DSS, providing insights into the mechanisms of the BP/DSS short-term colon carcinogenesis.

Interferon-induced transmembrane protein 3 is a type II transmembrane protein

The interferon-induced transmembrane (IFITM) proteins are a family of small membrane proteins that inhibit the cellular entry of several genera of viruses. These proteins had been predicted to adopt a two-pass, type III transmembrane topology with an intracellular loop, two transmembrane helices (TM1 and TM2), and extracellular N and C termini. Recent work, however, supports an intramembrane topology for the helices with cytosolic orientation of both termini. Here we determined the topology of murine Ifitm3. We found that the N terminus of Ifitm3 could be stained by antibodies at the cell surface but that this conformation was cell type-dependent and represented a minority of the total plasma membrane pool. In contrast, the C terminus was readily accessible to antibodies at the cell surface and extracellular C termini comprised most or all of those present at the plasma membrane. The addition of a C-terminal KDEL endoplasmic reticulum retention motif to Ifitm3 resulted in sequestration of Ifitm3 in the ER, demonstrating an ER-luminal orientation of the C terminus. C-terminal, but not N-terminal, epitope tags were also degraded within lysosomes, consistent with their luminal orientation. Furthermore, epitope-tagged Ifitm3 TM2 functioned as a signal anchor sequence when expressed in isolation. Collectively, our results demonstrate a type II transmembrane topology for Ifitm3 and will provide insight into its interaction with potential targets and cofactors.