The SARS-CoV-2 Virus and the Cholinergic System: Spike Protein Interaction with Human Nicotinic Acetylcholine Receptors and the Nicotinic Agonist Varenicline.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the worldwide coronavirus disease 2019 (COVID-19) pandemic. Although the pathophysiology of SARS-CoV-2 infection is still being elucidated, the nicotinic cholinergic system may play a role. To evaluate the interaction of the SARS-CoV-2 virus with human nicotinic acetylcholine receptors (nAChRs), we assessed the in vitro interaction of the spike protein of the SARS-CoV-2 virus with various subunits of nAChRs.

Lumican is required for neutrophil extravasation following corneal injury and wound healing.

An important aspect of wound healing is the recruitment of neutrophils to the site of infection or tissue injury. Lumican, an extracellular matrix component belonging to the small leucine rich proteoglycan (SLRP) family, is one of the major keratan sulfate proteoglycans (KSPGs) within the corneal stroma. Increasing evidence indicates that lumican can serve as a regulatory molecule for several cellular processes, including cell proliferation and migration.

Regulation of corneal inflammation by neutrophil-dependent cleavage of keratan sulfate proteoglycans as a model for breakdown of the chemokine gradient.

Keratocan and lumican are small, leucine-rich repeat KSPGs in the extracellular matrix (ECM) of the mammalian cornea, whose primary role is to maintain corneal transparency. In the current study, we examined the role of these proteoglycans in the breakdown of the chemokine gradient and resolution of corneal inflammation. LPS was injected into the corneal stroma of C57BL/6 mice, and corneal extracts were examined by immunoblot analysis.

Conditional deletion of Cited2 results in defective corneal epithelial morphogenesis and maintenance.

Cited2 is an important transcriptional cofactor involved in multiple organ development. Gene profile analysis has identified Cited2 as one of the transcription factors expressed at high levels in adult mouse cornea. To address the function of Cited2 in corneal morphogenesis, we deleted Cited2 in surface ectoderm derived ocular structures including cornea by crossing Cited2-floxed mice with Le-Cre transgenic mice.

Stem cell therapy restores transparency to defective murine corneas.

Corneal scarring from trauma and inflammation disrupts vision for millions worldwide, but corneal transplantation, the primary therapy for corneal blindness, is unavailable to many affected individuals. In this study, stem cells isolated from adult human corneal stroma were examined for the ability to correct stromal opacity in a murine model by direct injection of cells into the corneal stroma. In wild-type mice, injected human stem cells remained viable for months without fusing with host cells or eliciting an immune T-cell response.

Bone marrow chimeras and c-fms conditional ablation (Mafia) mice reveal an essential role for resident myeloid cells in lipopolysaccharide/TLR4-induced corneal inflammation.

The mammalian cornea contains an extensive network of resident macrophages and dendritic cells. To determine the role of these cells in LPS-induced corneal inflammation, TLR4(-/-) mice were sublethally irradiated and reconstituted with bone marrow cells from either enhanced GFP (eGFP)(+)/C57BL/6 or eGFP(+)/TLR4(-/-) mice. The corneal epithelium was abraded, LPS was added topically, and cellular infiltration to the corneal stroma and development of corneal haze were examined after 24 h.

CD40 mediates retinal inflammation and neurovascular degeneration.

Retinopathies are major causes of visual impairment. We used a model of ischemic retinopathy to examine the role of CD40 in the pathogenesis of retinal injury. Retinal inflammation, loss of ganglion cells, and capillary degeneration were markedly attenuated in ischemic retinas of CD40(-/-) mice.

Targeted expression of a lumican transgene rescues corneal deficiencies in lumican-null mice.

Purpose: To investigate whether targeted expression of lumican in the mouse cornea rescued the Lum(-/-) phenotype.

Methods: Lum(-/-)/Kera-Lum mice were generated by crossing Lum(-/-) mice with Kera-Lum transgenic mice that overexpressed lumican under the control of the keratocan promoter. Mouse eyes were analyzed in vivo by confocal microscopy through focusing (CMTF) to determine corneal sublayer thickness and haze.

Keratocan and lumican regulate neutrophil infiltration and corneal clarity in lipopolysaccharide-induced keratitis by direct interaction with CXCL1.

Keratocan and lumican are keratan-sulfate proteoglycans (KSPG), which have a critical role in maintaining corneal clarity. To determine whether these KSPGs have a role in corneal inflammation, we examined Kera(-/-) and Lum(-/-) mice in a model of lipopolysaccharide (LPS)-induced keratitis in which wild-type mice develop increased corneal thickness and haze due to neutrophil infiltration to the corneal stroma. Corneal thickness increases caused by LPS mice were significantly lower in Kera(-/-) and Lum(-/-) than wild-type mice.

Visualization and characterization of inflammatory cell recruitment and migration through the corneal stroma in endotoxin-induced keratitis.

Purpose: The infiltration of inflammatory cells into the cornea is a major determinant in the outcome of keratitis. The purpose of this study was to use enhanced green fluorescence protein (EGFP) bone marrow chimeric mice to visualize and characterize the inflammatory cells that migrate to the corneal stroma during endotoxin-induced keratitis and to explore the mechanisms underlying this process.

Methods: Keratitis was induced by injecting endotoxin into the corneas of EGFP chimeric mice.

Keratocan, a cornea-specific keratan sulfate proteoglycan, is regulated by lumican.

Lumican is an extracellular matrix glycoprotein widely distributed in mammalian connective tissues. Corneal lumican modified with keratan sulfate constitutes one of the major proteoglycans of the stroma. Lumican-null mice exhibit altered collagen fibril organization and loss of corneal transparency.

In vivo gene delivery and visualization of corneal stromal cells using an adenoviral vector and keratocyte-specific promoter.

Purpose: This study was conducted to determine whether intrastromal injection of adenoviral construct could be used to transfect corneal stroma cells effectively in vivo and to determine whether a tissue-specific promoter could be used to express exogenous genes in keratocytes.

Methods: An adenoviral construct with a cytomegalovirus (pCMV)-driven enhanced green fluorescent protein (EGFP) reporter gene was injected into the stroma of murine corneas. In vivo expression was quantitated and samples were analyzed by in vivo stereomicroscopy, and ex vivo expression was determined by confocal three dimensional (3-D) reconstruction.

Altered KSPG expression by keratocytes following corneal injury.

Purpose: Keratocytes synthesize keratan-sulfate proteoglycans (KSPG), lumican and keratocan, to develop and maintain proper collagen interfibrillar spacing and fibril diameter characteristics of the transparent cornea. The purposes of this study are to compare the expression patterns of KSPGs and keratin 12 (K12) respectively by corneal keratocytes and epithelial cells after three different types of injuries; partial and total epithelial debridement and alkali burn.

Methods: Corneas of 8-12 week old C57Bl/6J or FVBN mice were wounded by partial epithelial (2 mm in diameter) and total epithelial debridement, and alkali burn (0.

Role of Cys41 in the N-terminal domain of lumican in ex vivo collagen fibrillogenesis by cultured corneal stromal cells.

The keratan sulphate proteoglycan lumican regulates collagen fibrillogenesis to maintain the integrity and function of connective tissues such as cornea. We examined the role of a highly conserved cysteine-containing domain proximal to the N-terminus of lumican in collagen fibrillogenesis using site-specific mutagenesis to prepare plasmid DNA encoding wild-type murine lumican (Cys(37)-Xaa(3)-Cys(41)-Xaa-Cys-Xaa(9)-Cys) and a Cys-->Ser (C/S) mutant (Cys(37)-Xaa(3)-Ser(41)-Xaa-Cys-Xaa(9)-Cys). cDNAs were cloned into the pSecTag2A vector, and cultures of MK/T-1 cells (an immortalized cell line from mouse keratocytes) were transfected with the cDNAs.

Cis-regulatory elements of the mouse Krt1.12 gene.

Purpose: Keratin 12 is a cornea epithelial cell-specific intermediate filament component. To better understand the regulatory mechanism of its expression, the cis-regulatory elements located between the transcription start site and 600 bp upstream of the Krt1.12 gene were determined.