SARS-CoV-2 envelope protein triggers depression-like behaviors and dysosmia via TLR2-mediated neuroinflammation in mice.

BACKGROUND: Depression and dysosmia have been regarded as primary neurological symptoms in COVID-19 patients, the mechanism of which remains unclear. Current studies have demonstrated that the SARS-CoV-2 envelope (E) protein is a pro-inflammatory factor sensed by Toll-like receptor 2 (TLR2), suggesting the pathological feature of E protein is independent of viral infection. In this study, we aim to ascertain the role of E protein in depression, dysosmia and associated neuroinflammation in the central nervous system (CNS). METHODS: Depression-like behaviors and olfactory function were observed in both female and male mice receiving intracisternal injection of E protein. Immunohistochemistry was applied in conjunction with RT-PCR to evaluate glial activation, blood-brain barrier status and mediators synthesis in the cortex, hippocampus and olfactory bulb. TLR2 was pharmacologically blocked to determine its role in E protein-related depression-like behaviors and dysosmia in mice. RESULTS: Intracisternal injection of E protein evoked depression-like behaviors and dysosmia in both female and male mice. Immunohistochemistry suggested that the E protein upregulated IBA1 and GFAP in the cortex, hippocampus and olfactory bulb, while ZO-1 was downregulated. Moreover, IL-1ß, TNF-α, IL-6, CCL2, MMP2 and CSF1 were upregulated in both cortex and hippocampus, whereas IL-1ß, IL-6 and CCL2 were upregulated in the olfactory bulb. Furtherly, inhibiting microglia, rather than astrocytes, alleviated depression-like behaviors and dysosmia induced by E protein. Finally, RT-PCR and immunohistochemistry suggested that TLR2 was upregulated in the cortex, hippocampus and olfactory bulb, the blocking of which mitigated depression-like behaviors and dysosmia induced by E protein. CONCLUSIONS: Our study demonstrates that envelope protein could directly induce depression-like behaviors, dysosmia, and obvious neuroinflammation in CNS. TLR2 mediated depression-like behaviors and dysosmia induced by envelope protein, which could serve as a promising therapeutic target for neurological manifestation in COVID-19 patients.

Anti-SFT2D2 autoantibodies alter dendrite spine and cause psychotic behavior in mice.

BACKGROUND: Autoimmunity plays an important role in schizophrenia (SCZ). Autoantibodies against SFT2D2 have been reported in patients with SCZ; however, the specific mechanism remains unclear. This study aimed to describe an autoimmune model, namely, mice immunized against SFT2D2-peptides. METHODS: ApoE-/- and WT mice (C57BL/6) were immunized four times (day 0, day 14, day 21, day 35) with SFT2D2 peptide or KLH via subcutaneous injection. Behavioral tests were conducted after the third immunization, and immunochemistry of brain tissue were performed after the sacrifice of the mice. RESULTS: Active immunization with KLH-coupled SFT2D2-derived peptides in both WT and ApoE-/- (compromised blood-brain barrier) mice led to high circulating levels of anti-SFT2D2 IgG. While there was no detectable deficit in WT mice, impaired pre-pulse inhibition, motor impairments, and reduced cognition in ApoE-/- mice, without signs of anxiety and depression were observed. In addition, immunohistochemical assays demonstrated that activated microglia and astrocytes were increased but neuronal dendritic spine densities were decreased, accompanied by increased expression of complement molecule C4 across brain regions in ApoE-/- mice. CONCLUSIONS: In model mice with compromised blood-brain barrier, endogenous anti-SFT2D2 IgG can activate glial cells and modulate synaptic plasticity, and induce a series of psychosis-like changes. These antibodies may reveal valuable therapeutic targets, which may improve the treatment strategies for a subgroup of SCZ patients.

Genetic Screening of Targeted Region on the Chromosome 22q11.2 in Patients with Microtia and Congenital Heart Defect.

Microtia is a congenital malformation characterized by a small, abnormally shaped auricle (pinna) ranging in severity. Congenital heart defect (CHD) is one of the comorbid anomalies with microtia. However, the genetic basis of the co-existence of microtia and CHD remains unclear. Copy number variations (CNVs) of 22q11.2 contribute significantly to microtia and CHD, respectively, thus suggesting a possible shared genetic cause embedded in this genomic region. In this study, 19 sporadic patients with microtia and CHD, as well as a nuclear family, were enrolled for genetic screening of single nucleotide variations (SNVs) and CNVs in 22q11.2 by target capture sequencing. We detected a total of 105 potential deleterious variations, which were enriched in ear- or heart-development-related genes, including TBX1 and DGCR8. The gene burden analysis also suggested that these genes carry more deleterious mutations in the patients, as well as several other genes associated with cardiac development, such as CLTCL1. Additionally, a microduplication harboring SUSD2 was validated in an independent cohort. This study provides new insights into the underlying mechanisms for the comorbidity of microtia and CHD focusing on chromosome 22q11.2, and suggests that a combination of genetic variations, including SNVs and CNVs, may play a crucial role instead of single gene mutation.

The SARS-CoV-2 envelope protein disrupts barrier function in an in vitro human blood-brain barrier model.

Patients with coronavirus disease 2019 (COVID-19) have been frequently reported to exhibit neurological manifestations and disruption of the blood-brain barrier (BBB). Among the risk factors for BBB breakdown, the loss of endothelial cells and pericytes has caused widespread concern. Recent studies have revealed that severe acute respiratory syndrome coronavirus 2 envelope (S2E) protein caused cell death. We tested the hypothesis that the S2E protein alone could induce BBB dysfunction. The S2E protein bound to human BBB-related cells and inhibited cell viability in a dose- and time-dependent manner. Importantly, the S2E protein disrupted barrier function in an in vitro BBB model composed of HCMEC/D3 (brain endothelial cell line), HBVP (brain vascular pericyte), and U87MG (astrocyte cell line) cells and suppressed the expression of major genes involved in maintaining endothelial permeability and function. In addition, the S2E protein crossed the HCMEC/D3 monolayer. The S2E protein triggered inflammatory responses in HCMEC/D3 and U87MG cells. Taken together, these results show for the first time that the S2E protein has a negative impact on the BBB. Therapies targeting the S2E protein could protect against and treat central nervous system manifestations in COVID-19 patients.