Severe acute respiratory syndrome coronavirus (SARS-CoV) is the pathogen of SARS, which caused a global panic in 2003. We describe here the screening of Chinese herbal medicine-based, novel small molecules that bind avidly with the surface spike protein of SARS-CoV and thus can interfere with the entry of the virus to its host cells. We achieved this by using a two-step screening method consisting of frontal affinity chromatography-mass spectrometry coupled with a viral infection assay based on a human immunodeficiency virus (HIV)-luc/SARS pseudotyped virus. Two small molecules, tetra-O-galloyl--D-glucose (TGG) and luteolin, were identified, whose anti-SARS-CoV activities were confirmed by using a wild-type SARS-CoV infection system. TGG exhibits prominent anti-SARS-CoV activity with a 50% effective concentration of 4.5 M and a selective index of 240.0. The two-step screening method described here yielded several small molecules that can be used for developing new classes of anti-SARS-CoV drugs and is potentially useful for the high-throughput screening of drugs inhibiting the entry of HIV, hepatitis C virus, and other insidious viruses into their host cells.
Heptad repeat regions (HR1 and HR2) are highly conserved sequences located in the glycoproteins of enveloped viruses. They form a six-helix bundle structure and are important in the process of virus fusion. Peptides derived from the HR regions of some viruses have been shown to inhibit the entry of these viruses. SARS-CoV was also predicted to have HR1 and HR2 regions in the S2 protein. Based on this prediction, we designed 25 peptides and screened them using a HIV-luc/SARS pseudotyped virus assay. Two peptides, HR1-1 and HR2-18, were identified as potential inhibitors, with EC(50) values of 0.14 and 1.19microM, respectively. The inhibitory effects of these peptides were validated by the wild-type SARS-CoV assay. HR1-1 and HR2-18 can serve as functional probes for dissecting the fusion mechanism of SARS-CoV and also provide the potential of further identifying potent inhibitors for SARS-CoV entry.
Intestinal barrier dysfunction and
inflammatory cytokine secretion
play crucial roles in inflammatory bowel disease (IBD). Herein, we
investigated the protective effects of Tricholoma matsutake-derived peptides SDIKHFPF and SDLKHFPF against dextran sulfate sodium-induced
colitis. Both peptides alleviated colitis signs, including diarrhea,
weight loss, bloody stools, colon shortening, and histopathological
changes, while reducing mucus destruction, goblet cell exhaustion,
and intestinal permeability. SDIKHFPF and SDLKHFPF protected the barrier
function by promoting the expression of tight junction (TJ) zonula
occludens-1 and occludin within the colon, as well as attenuating
colonic inflammation through myeloperoxidase and pro-inflammatory
cytokine suppression. Western blotting indicated that the peptides
suppressed myosin light chain kinase (MLCK) and nuclear factor kappa
B (NF-κB) levels, inhibiting MLC phosphorylation. SDLKHFPF was
more potent than SDIKHFPF. These findings suggest that peptide SDLKHFPF
mitigates colitis by regulating TJ protein expression and pro-inflammatory
cytokine production via NF-κB/MLCK/p-MLC signaling, improving
the barrier function.
In
this study, the binding mechanism, morphological, and conformational
analysis of the complex of a sea cucumber ovum derived octapeptide
(EDLAALEK) with Ca2+ as well as its calcium delivery behavior
via the gastrointestinal (GI) tract were investigated. The Ca2+ specifically bound to two carboxyl oxygen atoms of C-terminal
Glu and Asp on the EDLAALEK peptide at a stoichiometric ratio of 1:1.
Calcium coordination induced the self-assembly of the EDLAALEK peptide,
resulting in the formation of a nanocomposite with a crystal structure.
Furthermore, the formed nanocomposite went through dissociation and
self-assembly during in vitro GI digestion, accompanied by the release
and rechelation of Ca2+, which was related to changes in
their secondary structure. Nevertheless, the GI digests of the EDLAALEK–calcium
complex could significantly enhance Ca2+ absorption across
Caco-2 cell monolayers. The findings suggest that the sea cucumber
ovum derived peptide has the potential as an efficient nanocarrier
to transport calcium through the GI system.
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