No abstract

Polyhydroxybutyrate (PHB), co-polyesters of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx), and polylactic acid (PLA) were used to prepare nanoparticles with average sizes of 160, 250 and 150 nm, respectively. A lipid-soluble colorant, rhodamine B isothiocyanate (RBITC), was employed to study drug-release behaviors from these nanoparticles. A high RBITC drug-loading efficiency of over 75% was achieved with all PHA nanoparticles prepared. Macrophage endocytosis led to an intracellular RBITC drug sustained release over a period of at least 20 days for PHB and PHBHHx nanoparticles, while PLA nanoparticles and free drug lasted only 15 days and a week, respectively. Polymer properties and particle sizes showed little effect on drug-release behavior. This study showed for the first time that PHB and PHBHHx can be used effectively to achieve intracellular controlled drug releases.

AbstractSARS-CoV-2 caused a global pandemic in early 2020 and has resulted in more than 8,000,000 infections as well as 430,000 deaths in the world so far. Four structural proteins, envelope (E), membrane (M), nucleocapsid (N) and spike (S) glycoprotein, play a key role in controlling the entry into human cells and virion assembly of SARS-CoV-2. However, how these genes evolve during its human to human transmission is largely unknown. In this study, we screened and analyzed roughly 3090 SARS-CoV-2 isolates from GenBank database. The distribution of the four gene alleles is determined:16 for E, 40 for M, 131 for N and 173 for S genes. Phylogenetic analysis shows that global SARS-CoV-2 isolates can be clustered into three to four major clades based on the protein sequences of these genes. Intragenic recombination event isn’t detected among different alleles. However, purifying selection has conducted on the evolution of these genes. By analyzing full genomic sequences of these alleles using codon-substitution models (M8, M3 and M2a) and likelihood ratio tests (LRTs) of codeML package, it reveals that codon 614 of S glycoprotein has subjected to strong positive selection pressure and a persistent D614G mutation is identified. The definitive positive selection of D614G mutation is further confirmed by internal fixed effects likelihood (IFEL) and Evolutionary Fingerprinting methods implemented in Hyphy package. In addition, another potential positive selection site at codon 5 in the signal sequence of the S protein is also identified. The allele containing D614G mutation has undergone significant expansion during SARS-CoV-2 global pandemic, implying a better adaptability of isolates with the mutation. However, L5F allele expansion is relatively restricted. The D614G mutation is located at the subdomain 2 (SD2) of C-terminal portion (CTP) of the S1 subunit. Protein structural modeling shows that the D614G mutation may cause the disruption of salt bridge among S protein monomers increase their flexibility, and in turn promote receptor binding domain (RBD) opening, virus attachment and entry into host cells. Located at the signal sequence of S protein as it is, L5F mutation may facilitate the protein folding, assembly, and secretion of the virus. This is the first evidence of positive Darwinian selection in the spike gene of SARS-CoV-2, which contributes to a better understanding of the adaptive mechanism of this virus and help to provide insights for developing novel therapeutic approaches as well as effective vaccines by targeting on mutation sites.

Sorting nexin-1 (SNX1) is an important functional protein in cell endocytosis, efflux, protein sorting, cell signal transduction, etc; however, the expression, the role and clinical relevance of SNX1 have not been investigated in gastric cancer (GC). In this study, we first performed a bioinformatics investigation using the data obtained from The Cancer Genome Atlas (TCGA) database. The result showed that SNX1 mRNA levels were significantly lower in GC tissues than in paracancerous tissues. In a study of 150 cases of GC, including 60 cases with paired paracancerous and cancer tissues and 90 cases with detailed follow-up information, SNX1 expression was analyzed by immunohistochemistry. Our study on paired paracancerous and cancer tissues showed that SNX1 protein expression remarkably decreased in GC tissues (50/60, 83.33%). A study on 90 patients with detailed follow-up information showed that tumors with higher SNX1 protein level were correlated with better clinicopathologic stages (p = 0.0285), nodal status (p = 0.0286), smaller tumor sizes (p = 0.0294) and a better survival rate in patients with GC (p = 0.0245). Univariate analysis of the 90 patients with GC showed that low-level SNX1 was significantly correlated with decreased overall survival of GC patients (p = 0.008), and associated with a relatively higher cumulative hazard of death. Exogenous expression of SNX1 inhibited the growth, migration, invasion and promoted the apoptosis and enhanced the sensitivity of GC cells to the chemotherapeutic drug 5-Fluorouracil (5-Fu) in vitro, while knockdown of SNX1 by short hairpin RNA (shRNA) significantly promoted the growth, migration, invasion and reduced the apoptosis and the sensitivity of GC cells to 5-Fu. SNX1 also showed to influence the levels of epithelial-mesenchymal transition markers including Vimentin, Snail, and E-cadherin in GC cells in vitro. Taken together, we propose here that SNX1 serves as a tumor suppressor and prognostic marker that reduces tumor cell malignancy for GC.