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OBJECTIVE Our previous studies demonstrated that various ingredients from the traditional Chinese medicine (TCM) for promoting blood circulation and removing blood stasis, as exemplified by cryptotanshinone and salvi?anolic acid B, exerted striking effects on modulating angiogenesis and vascular permeability, which suggests that they may be effective in treating vascular leak-driven diseases (e.g. tumor, cerebral cavernous malformation and diabetic reti?nopathy). However, the lack of reliable and advanced technologies and models sets up difficult hurdles for better under?standing the role of TCM for promoting blood circulation and removing blood stasis. To this end, this study is to outline numerous cutting-edge platforms that can be utilized for exploring the function of TCM for promoting blood circulation and removing blood stasis in vascular leak-driven diseases. METHODS Two-photon laser scanning fluorescence micros?copy was used to observe the interactions between neutrophils and blood vessels in a real-time manner. Dynamic flow system was employed to mimic the in vivo behaviors of neutrophils. RIP1-Tag5 spontaneous pancreatic cancer model was used to study the function of tumor blood vessels. CCM2ECKO (deletion of CCM2 in endothelial cells) mice were employed to establish the cerebral cavernous malformation (CCM) animal model. Micro-computed tomography (micro-CT) was utilized to assess the CCM lesion. Müller cell-knockout mouse model was used to study the progression of dia?betic retinopathy. Vascular permeability in this model was assessed by fluorescein angiography. RESULTS The interac?tions between neutrophils and endothelial cells involve a series of complicated processes, including rolling, adhesion, intraluminal crawling and transmigration, which were all monitored in vivo by two-photon laser scanning fluorescence microscopy in a real-time manner. Dynamic flow system was capable of recapitulating the biological behaviors of neutro?phils in vitro. Tumor vascular function in particular vascular perfusion could be assessed in the RIP1-Tag5 spontaneous pancreatic cancer model. In terms of CCM studies, specific deletion of CCM2 in endothelial cells resulted in the initiation of CCM lesion. The size and number of CCM lesions could be visualized and quantified by micro-CT. Furthermore, the Müller cell-knockout mouse model was able to precisely reflect the clinical symptoms of diabetic retinopathy. Vascular leak could be monitored at different time points using fluorescein angiography. CONCLUSION An array of high technol?ogies and animal models can be used in investigating the occurrence and progression of multiple vascular leak-driven diseases. The pre-clinical and clinical studies of TCM for promoting blood circulation and removing blood stasis provide fundamental support for the application of the above-mentioned platforms, with the purpose of uncovering the scientific basis of TCM for promoting blood circulation and removing blood stasis.
RESUMO
Sphingosine kinase catalyzes the formation of sphingosine 1-phosphate, a lipid second messenger that has been implicated in a number of agonist-driven cellular responses including mitogenesis, anti-apoptosis, and expression of inflammatory molecules. Despite the importance of sphingosine kinase, very little is known regarding its structure or mechanism of catalysis. Moreover, sphingosine kinase does not contain recognizable catalytic or substrate-binding sites, based on sequence motifs found in other kinases. Here we have elucidated the nucleotide-binding site of human sphingosine kinase 1 (hSK1) through a combination of site-directed mutagenesis and affinity labeling with the ATP analogue, FSBA. We have shown that Gly(82) of hSK1 is involved in ATP binding since mutation of this residue to alanine resulted in an enzyme with an approximately 45-fold higher K(m)((ATP)). We have also shown that Lys(103) is important in catalysis since an alanine substitution of this residue ablates catalytic activity. Furthermore, we have shown that this residue is covalently modified by FSBA. Our data, combined with amino acid sequence comparison, suggest a motif of SGDGX(17-21)K is involved in nucleotide binding in the sphingosine kinases. This motif differs in primary sequence from all previously identified nucleotide-binding sites. It does, however, share some sequence and likely structural similarity with the highly conserved glycine-rich loop, which is known to be involved in anchoring and positioning the nucleotide in the catalytic site of many protein kinases.