Glutamine exerts a protective effect on osteoarthritis development by inhibiting the Jun N-terminal kinase and nuclear factor kappa-B signaling pathways.

Strategies for treating osteoarthritis (OA) have become a research focus because an effective treatment for OA is unavailable. The objective of this study was to explore the effects and underlying mechanisms of glutamine (Gln) in OA. First, the chondrocytes were identified and a standard IL-1ß-induced OA model was established. After treatment with Gln or saline, the viability and apoptosis of chondrocytes were evaluated using a CCK-8 assay and flow cytometry analysis, which revealed that Gln can improve the IL-1ß-induced OA cells. Meanwhile, Gln can enhance the expression of aggrecan and collagen II, which are protective proteins for articular cartilage. Instead, Gln inhibited the expression of matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13), which can degrade cartilage. To better understand the underlying mechanisms of Gln in IL-1ß-induced chondrocytes, the classical OA pathways of JNK and NF-κB were examined at the protein and mRNA levels using western blot and qRT-PCR analyses. We found that JNK and NF-κB were downregulated gradually depending on the Gln dose and protective and destructive factors changed based on changes of JNK and NF-κB. The effects of high-dose Gln were more effective than low-dose. Moreover, Gln was applied to the animal OA model to check the effects in vivo. The results showed that Gln attenuated cartilage degeneration and decreased OARSI scores, which demonstrated that Gln can improve OA. The experiments showed that Gln can benefit mice with OA by inhibiting the JNK and NF-κB signaling pathways.

A novel nacre matrix protein hic24 in Hyriopsis cumingii is essential for calcium carbonate nucleation and involved in pearl formation.

Matrix proteins play important roles in molluscan shell biomineralization, which helps in the understanding of mechanisms associated with pearl formation. In this study, we characterized the gene encoding a novel shell-matrix protein, hic24, in Hyriopsis cumingii and investigated its structure and function. The full cDNA sequence of hic24 is 756 bp, with an open reading frame of 654 bp encoding 217 amino acids, including a signal peptide of 18 amino acids. Sequence analysis revealed that the protein is ∼23.5 kDa, and that Gly accounted for 11.5% of the total amino acid content. Secondary structure prediction indicated a structure comprised predominantly by ß-folds. Quantitative real-time polymerase chain reaction and in situ hybridization indicated that hic24 is expressed in the dorsal epithelial cells of the mantle, indicating hic24 as a nacreous-layer matrix protein. Additionally, hic24 expression patterns during pearl biomineralization showed that hic24 regulates the growth of the later nacreous layer. After attenuating hic24 expression by RNA interference in the mantle, we observed that hic24 plays a role in biomineralization of the shell nacre by inhibiting calcium carbonate nucleation.

Characterization of MMP-9 gene from grass carp (Ctenopharyngodon idella): an Aeromonas hydrophila-inducible factor in grass carp immune system.

Matrix metalloproteinase-9 (MMP-9) belongs to a family of zinc-dependent endopeptidases and is associated with vital inflammatory processes. Here, we isolated and characterized MMP-9 cDNA from grass carp (Ctenopharyngodon idella) (designated as CiMMP-9). The cDNA was 2880 bp long and encoded a putative protein of 675 amino acids, with a predicted molecular mass of 75.816 kDa and an isoelectric point (pI) of 5.25. CiMMP-9 contained all three classical MMP-9 family signatures. The mRNA of CiMMP-9 was constitutively expressed in all tested tissues of untreated grass carp, with the highest expression levels in the blood, trunk kidney, head kidney and spleen. CiMMP9 transcript was present in unfertilized eggs, which suggests that CiMMP9 transcription is maternally inherited. Fluorescent real-time quantitative RT-PCR was used to examine the expression of the CiMMP-9 gene in C. idella after being challenged with Aeromonas hydrophila. A clear time-dependent expression pattern of CiMMP-9 was found after the bacterial challenge, and mRNA expression reached a maximum level at 7 days post challenge. This indicates that MMP-9 is inducible and is involved in immune responses, thus suggesting that CiMMP-9 plays an important role in A. hydrophila-related diseases and in early embryonic development stages in C. idella.

Molecular cloning and characterization of perlucin from the freshwater pearl mussel, Hyriopsis cumingii.

Perlucin is an important functional protein that regulates shell and pearl formation. In this study, we cloned the perlucin gene from the freshwater pearl mussel Hyriopsis cumingii, designated as Hcperlucin. The full-length cDNA transcribed from the Hcperlucin gene was 1460 bp long, encoding a putative signal peptide of 20 amino acids and a mature protein of 141 amino acids. The mature Hcperlucin peptide contained six conserved cysteine residues and a carbohydrate recognition domain, similar to other members of the C-type lectin families. In addition, a "QPS" and an invariant "WND" motif near the C-terminal region were also found, which are extremely important for polysaccharide recognition and calcium binding of lectins. The mRNA of Hcperlucin was constitutively expressed in all tested H. cumingii tissues, with the highest expression levels observed in the mantle, adductor, gill and hemocytes. In situ hybridization was used to detect the presence of Hcperlucin mRNA in the mantle, and the result showed that the mRNA was specifically expressed in the epithelial cells of the dorsal mantle pallial, an area known to express genes involved in the biosynthesis of the nacreous layer of the shell. The significant Hcperlucin mRNA expression was detected on day 14 post shell damage and implantation, suggesting that the Hcperlucin might be an important gene in shell nacreous layer and pearl formation. The change of perlucin expression in pearl sac also confirmed that the mantle transplantation results in a new expression pattern of perlucin genes in pearl sac cells that are required for pearl biomineralization. These findings could help better understanding the function of perlucin in the shell and pearl formation.