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Pearl is one of the well-known traditional Chinese medicine (TCM) prescribed for treating various skin and bone related disorders due to its abundant proteins and mineral contents. The present investigation focused on antioxidation and life span prolonging effects from different extracts of pearl powder. During in vitro studies, various oxidative indices were evaluated, along with lifespan-prolonging effect were checked using wild-type Caenorhabditis elegans. For the clinical trial, 20 healthy middle-aged subjects were recruited and separated into 2 groups as experimental and placebo group, who received 3 g of pearl powder/d (n = 10) and 3 g of placebo/d (n = 10) for 8 weeks, respectively. During the initial, 2nd, 4th, 6th, 8th and 10th weeks the blood samples were collected for biochemical analysis. The protein extract of pearl powder recorded maximum (p < 0.05) antioxidant activity (20–68%) as well as efficiently prolonged the life span of C. elegans by 18.87%. Pearl powder supplemented subjects showed a substantial increase (p < 0.05) in total antioxidant capacity from 0.45 to 0.69 mM, total thiols from 0.23 to 0.29 mM, Glutathione content from 5.89 to 9.19 μM, enzymic antioxidant activity (SOD-1248 to 1308; Gpx-30 to 32; GR-2.4 to 2.9) as well as considerably suppressed the lipid peroxidation products from 4.95 to 3.27 μM. The outcome of both in-vitro and in-vivo antioxidant activity inferred that protein extract of pearl powder was a potent antioxidant and thereby prolonged the lifespan of C. elegans. Hence, pearl powder could be recommended for treating various age-related degenerative disorders. [Display omitted] •The antioxidation and anti-aging efficacy of various extracts of pearl powder were assessed.•The protein extract of pearl powder exhibit highest antioxidant activity as well as effectively prolonged the life span of C. elegans to showcase its anti-aging property.•Pearl powder administration showed a substantial increase in total antioxidant capacity, total thiols, Glutathione content, enzymic antioxidant activity as well as considerably suppressed the lipid peroxidation products.•Pearl powder can be beneficial for treating various age-related degenerative disorders.

Mollusca evolutionary success can be attributed partly to their efficiency to sustain and protect their soft body with an external biomineralized structure, the shell. Current knowledge of the protein set responsible for the formation of the shell microstructural polymorphism and unique properties remains largely patchy. In Pinctada margaritifera and Pinctada maxima, we identified 80 shell matrix proteins, among which 66 are entirely unique. This is the only description of the whole \"biomineralization toolkit\" of the matrices that at least in part, is thought to regulate the formation of the prismatic and nacreous shell layers in the pearl oysters. We unambiguously demonstrate that prisms and nacre are assembled from very different protein repertoires. This suggests that these layers do not derive from each other.

The mollusk shell is a hard tissue consisting of calcium carbonate crystals and an organic matrix. The nacre of the shell is characterized by a stacked compartment structure with a uniformly oriented c axis of aragonite crystals in each compartment. Using a calcium carbonate-binding assay, we identified an acidic matrix protein, Pif, in the pearl oyster Pinctada fucata that specifically binds to aragonite crystals. The Pif complementary DNA (cDNA) encoded a precursor protein, which was posttranslationally cleaved to produce Pif 97 and Pif 80. The results from immunolocalization, a knockdown experiment that used RNA interference, and in vitro calcium carbonate crystallization studies strongly indicate that Pif regulates nacre formation.

Angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from natural products have shown a blood pressure lowering effect with no side effects. In this study, two novel ACE inhibitory peptides (His-Leu-His-Thr, HLHT and Gly-Trp-Ala, GWA) were purified from pearl oyster (Pinctada fucata martensii) meat protein hydrolysate with alkaline protease by ultrafiltration, polyethylene glycol methyl ether modified immobilized metal ion affinity medium, and reverse-phase high performance liquid chromatography. Both peptides exhibited high ACE inhibitory activity with IC50 values of 458.06 ± 3.24 μM and 109.25 ± 1.45 μM, respectively. Based on the results of a Lineweaver-Burk plot, HLHT and GWA were found to be non-competitive inhibitor and competitive inhibitor respectively, which were confirmed by molecular docking. Furthermore, the pearl oyster meat protein hydrolysate exhibited an effective antihypertensive effect on SD rats. These results conclude that pearl oyster meat protein is a potential resource of ACE inhibitory peptides and the purified peptides, HLHT and GWA, can be exploited as functional food ingredients against hypertension.

Long-term exposure to ultraviolet-B (UVB) can cause photoaging. Peptides from Pinctada martensii meat have been shown to have anti-photoaging activities, but their mechanism of action is rarely studied. In this study, Pinctada martensii meat hydrolysates (PME) were prepared by digestive enzymes and then separated by ultrafiltration and Sephadex G-25 gel filtration chromatography to obtain a purified fraction (G2). The fraction G2 was identified by ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS), and peptide sequences were synthesized by solid-phase synthesis. The mechanism of anti-photoaging activities was investigated using a human immortalised epidermal (HaCaT) cell model. Results showed that peptides from Pinctada martensii meat increased UVB-induced cell viability and reduced the contents of interstitial collagenase (MMP-1) and matrix lysing enzyme (MMP-3) in HaCaT cells. Furthermore, the fraction of G2 significantly downregulated the expression of p38, EKR, JNK, MMP-1, and MMP-3 in HaCaT cells. The peptide sequences Phe-His (FH), Ala-Leu (AL), Met-Tyr (MY), Ala-Gly-Phe (AGF), and Ile-Tyr-Pro (IYP) were identified and synthesized. Besides, FH reduced the contents of MMP-1 and MMP-3 in HaCaT cells, combining them effectively in molecular docking analysis. Thus, peptides from Pinctada martensii meat showed anti-photoaging activities and might have the potential to be used as an anti-photoaging agent in functional foods.

Previous studies found that both oral and topical administration of enzymatic digestion products < 3 K Da ultrafiltration fractions of Pinctada martensii mantle (PMPs) had pro-healing effects. Thus, we further purified them by Sephadex-G25 and screened them by cellular assays to obtain Pinctada martensii purified peptides (PMPPs). In this study, we explored the mechanism of PMPPs on wound healing by in vivo, in vitro, and in silico experiments. LC-MS/MS results showed that PMPPs consisted of 33 peptides with molecular weights ranging from 758.43 to 2014.04 Da, and the characteristic peptide was Leu-Asp. The results of cellular assays showed that PMPPs promoted the proliferation of human skin fibroblasts (HSF) (135%) and human immortalized keratinocyte (HaCaT) cells (125%) very significantly at 12.5 μg/mL. The in vivo results showed that PMPPs could achieve scarless healing by inhibiting the inflammatory response, accelerating the epithelialization process, and regulating collagen I/III ratio. The optimal peptide sequence FAFQAEIAQLMS of PMPPs was screened for key protein receptors in wound healing (EGFR1, FGFR1, and MMP-1) with the help of molecular docking technique, which also showed to be the key pro-healing active peptide sequence. Therefore, it may provide a therapeutic strategy with great potential for wound healing.

The molluscan shell is a biomineral that comprises calcium carbonate and organic matrices controlling the crystal growth of calcium carbonate. The main components of organic matrices are insoluble chitin and proteins. Various kinds of proteins have been identified by solubilizing them with reagents, such as acid or detergent. However, insoluble proteins remained due to the formation of a solid complex with chitin. Herein, we identified these proteins from the nacreous layer, prismatic layer, and hinge ligament of Pinctada fucata using mercaptoethanol and trypsin. Most identified proteins contained a methionine-rich region in common. We focused on one of these proteins, NU-5, to examine the function in shell formation. Gene expression analysis of NU-5 showed that NU-5 was highly expressed in the mantle, and a knockdown of NU-5 prevented the formation of aragonite tablets in the nacre, which suggested that NU-5 was required for nacre formation. Dynamic light scattering and circular dichroism revealed that recombinant NU-5 had aggregation activity and changed its secondary structure in the presence of calcium ions. These findings suggest that insoluble proteins containing methionine-rich regions may be important for scaffold formation, which is an initial stage of biomineral formation.

Skin wound healing, especially chronic wound healing, is a common challenging clinical problem. It is urgent to broaden the sources of bioactive substances that can safely and efficiently promote skin wound healing. This study aimed to observe the effects of active peptides (APs) of the mantle of Pinctada martensii on wound healing. After physicochemical analysis of amino acids and mass spectrometry of APs, the effect of APs on promoting healing was studied through a whole cortex wound model on the back of mice for 18 consecutive days. The results showed that APs consisted of polypeptides with molecular weights in the range 302.17–2936.43 Da. The content of polypeptides containing 2–15 amino acids accounted for 73.87%, and the hydrophobic amino acids accounted for 56.51%. Results of in vitro experimentation showed that mice in APs-L group which were fed a low dose of APs (0.5 g/kg bw) had a shortened epithelialization time due to a shortening inflammatory period (p < 0.05). Mechanistically, this relied on its specific ability to promote the proliferation of CD31, FGF and EGF which accelerated the percentage of wound closure. Moreover, the APs-L group mice had enhanced collagen synthesis and increased type III collagen content in their wounds through a TGF-β/Smad signaling pathway (p > 0.05). Consequently, scar formation was inhibited and wound healing efficiency was significantly improved. These results show that the APs of Pinctada martensii promote dermal wound healing in mice and have tremendous potential for development and utilization in skin wound healing.

The aim of this work was to produce bone scaffolds containing whey protein isolate and pearl powder and to conduct a preliminary assessment of the biomedical potential in vitro and in vivo. This included analysis of structural, physicochemical, mechanical, and biological properties, which revealed that biomaterials containing pearl powder exhibited an enhanced porous structure, increasing absorptive properties, and decreasing proteolytic capacity with increasing inorganic component content. Pearl powder content in the biomaterials did not clearly influence their mechanical properties or their ability to release calcium ions, as well as proteins. Extracts obtained from all tested biomaterials showed no cytotoxicity in vitro. The surfaces of all biomaterials promoted normal human osteoblast growth, proliferation, and osteogenic differentiation. Furthermore, all biomaterials did not display toxicity in vivo, but no changes in Danio rerio were observed after evaluation of the biomaterial containing the highest amount of pearl powder–10% v/w (marked as WPI/P10). Taking all the obtained results into account, it appears that this biomaterial can be promising for bone scaffolds and similar applications, thanks to its porous structure, high cytocompatibility in vitro, and lack of toxicity in vivo. However, advanced studies will be conducted in the future.

We determined the primary structures of jacalin-related lectins termed PPL3s (PPL3A, 3B, and 3C, which are dimers consisting of sequence variants α + α, α + β, β + β, respectively) and PPL4, which is heterodimer consisting of α + β subunits, isolated from mantle secretory fluid of Pteria penguin (Mabe) pearl shell. Their carbohydrate-binding properties were analyzed, in addition to that of PPL2A, which was previously reported as a matrix protein. PPL3s and PPL4 shared only 35–50% homology to PPL2A, respectively; they exhibited significantly different carbohydrate-binding specificities based on the multiple glycan binding profiling data sets from frontal affinity chromatography analysis. The carbohydrate-binding specificity of PPL3s was similar to that of PPL2A, except only for Man3Fuc1Xyl1GlcNAc2 oligosaccharide, while PPL4 showed different carbohydrate-binding specificity compared with PPL2A and PPL3s. PPL2A and PPL3s mainly recognize agalactosylated- and galactosylated-type glycans. On the other hand, PPL4 binds to high-mannose-and hybrid-type N-linked glycans but not agalactosylated- and galactosylated-type glycans.