Antibacterial activity of Bombyx mori and Samia cynthia ricini sericin proteins against Escherichia coli and Staphylococcus aureus

Aims@#This study was designed to investigate the antibacterial properties of the sericin protein Bombyx mori and Samia cynthia ricini against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus strains.@*Methodology and results@#Sericin protein was extracted from the cocoons of B. mori races A, B, C, D, F1-1, F1-2 and S. ricini from Indonesia using a degumming process. The extracted sericin protein was evaluated as anti-microbials using Kirby Breuer disc diffusion, spectrometer measurement in decreasing OD value and imaging scanning electron microscope (SEM). The tests revealed that sericin protein from B. mori was more capable of inhibiting bacteria S. aureus than E. coli. Sericin protein from S. ricini was also capable of strongly inhibiting both S. aureus and E. coli bacteria. The sericin proteins of B. mori and S. ricini were found to reduce the number of S. aureus and E. coli bacteria as the OD value decreased at a concentration of 9%. The SEM imaging suggests that sericin B. mori and S. ricini proteins caused changes in cell morphology in S. aureus and E. coli bacteria, resulting in bacterial cell function disruption and death.@*Conclusion, significance and impact of study@#Bombyx mori and S. ricini sericin proteins were found to act against S. aureus and E. coli bacteria. Therefore, sericin protein has a greater antibacterial activity against Gram-positive strain S. aureus.

Determinación de la estabilidad e irritabilidad del hidrolizado de sericina / Determination of the stability and irritability of the sericin hydrolyzate

RESUMEN La sericina es una proteína globular que se obtiene a partir de los capullos del gusano de seda Bombyx mori y tiene aplicaciones en la industria farmacéutica, alimentaria y cosmética. El objetivo de este trabajo fue determinar la estabilidad e irritabilidad dérmica y oftálmica del hidrolizado de sericina (líquido). 3 lotes producidos a escala piloto se almacenaron en frascos de polietileno de alta densidad en diferentes condiciones de temperatura: 40±2 °C por 6 meses y temperatura hasta los 30 °C durante 18 meses. Se hizo una evaluación fisicoquímica y microbiológica a tiempo inicial y 1, 2, 3, 6 meses (acelerada) y 3, 6, 9, 12, 18 meses (anaquel). Se llevaron a cabo los estudios toxicológicos correspondientes a productos con fines cosméticos. Se constató que las características organolépticas, densidad, el pH, la concentración de proteínas y la identidad de los lotes en las dos condiciones de temperaturas y no hubo variación significativa en el tiempo del estudio. Se definió el tiempo de vida útil del producto en 18 meses. Se concluyó que el hidrolizado de sericina en frascos de polietileno de alta densidad es estable a temperaturas hasta 30 °C durante 18 meses y no clasificó como irritante dérmico, ni oftálmico.

SUMMARY Sericin is a globular protein that is obtained from the cocoons of the Bombyx mori silkworm and has applications in the pharmaceutical, food and cosmetic industries. The objective of this work was to determine the stability and dermal and ophthalmic irritability of the sericine hydrolyzate (liquid). 3 batches produced on a pilot scale were stored in high density polyethylene bottles under different temperature conditions: 40 ± 2 °C for 6 months and temperature up to 30 °C for 18 months. A physical-chemical and microbiological evaluation was performed at initial time and 1, 2, 3, 6 months (accelerated) and 3, 6, 9, 12, 18 months (shelf). Toxicological studies corresponding to products for cosmetic purposes were performed. It was found that the organoleptic characteristics, density, pH, protein concentration and the identity of the lots in the two temperature conditions, there was no significant variation in the study time. The shelf life of the product was defined in 18 months. It was concluded that the sericin hydrolyzate in high density polyethylene bottles is stable at temperatures up to 30 °C for 18 months and this product did not classify as dermal or ophthalmic irritant.

Ameliorating effects of sericin on retinal oxidative stress and micro-inflammatory status in diabetic rats / 眼科新进展

Objective To investigate the improvement effects of sericin on the retinal oxidative stress and micro-inflammatory state in diabetic rats.Methods A diabetic rat model was established by using high-fat and high-sugar diet and intraperitoneal injection of streptozotocin.Then 24 diabetic rats were randomly divided into sericin treatment group and diabetic model group,with 12 rats for each group,and additional 12 normal rats with the same age were collected as a normal control group.Next,the rats in the sericin treatment group received sericin solution,while the other two groups was given the same amount of normal saline once a day for 35 days.After the agent intervention,the content of malondialdehyde (MDA) and glutathione (GSH) in the retina of all rats were detected by related kits.The expressions of nuclear factor erythroid 2-related factor 2 (Nrf2),heme oxygenase 1 (HO-1),nuclear factor-κB (NF-κB) and tumor necrosis factor-α (TNF-α) protein were detected by Western blot,and finally,the retinal morphology was examined by hematoxylin-eosin staining in the 3 groups.Results The content of MDA,NF-κB and TNF-α protein expression in the sericin treatment group was (4.145 ±0.282) mmol· gprot-1,0.232 ±0.027 and 0.761 ±0.058,respectively,which was significantly lower than that in the diabetic model group [(6.813 ± 0.446) mmol · gprot-1,0.334 ± 0.024 and 0.994 ± 0.084] (all P ＜ 0.05).The content of GSH,Nrf2 and HO-1 protein expression in rat retina in the sericin treatment group was (78.518 ± 4.317) mg · gprot 1,0.591 ± 0.054 and 0.954 ± 0.091,respectively,which was significantly higher than that in the diabetic model group [(59.890 ± 5.932) mg · gprot-1,0.351 ± 0.044 and 0.585 ± 0.054] (all P ＜ 0.05).The diabetic model group presented the disorder arrangement of the neurocyte in different levels in the retina,irregular and swollen inner limiting membrane,vacuoles in the ganglion cells,but in the sericin treatment group,the morphology of retinal layers was more regular and mildly disorderly arranged.The pathological damages in the retina were alleviated significantly.Conclusion Sericin can ameliorate oxidative stress and inflammation in diabetic retina,thereby delaying the development of diabetic retinopathy.

Effect of urea-extracted sericin on melanogenesis: potential applications in post-inflammatory hyperpigmentation

BACKGROUND: Hyperpigmentation disorders such as post-inflammatory hyperpigmentation are major concerns not only in light-skinned people but also in Asian populations with darker skin. The anti-tyrosinase and immunomodulatory effects of sericin have been known for decades. However, the therapeutic effects of sericin on hyperpigmentation disorders have not been well documented. METHODS: In this study, we used an in vitro model to study the anti-tyrosinase, tolerogenic, and anti-melanogenic effects of sericin on Staphylococcus aureus peptidoglycan (PEG)-stimulated melanocytes, dendritic cells (DCs), and artificial skin (MelanoDerm™). Enzyme-linked immunosorbent assay, conventional and immunolabeled electron microscopy, and histopathological studies were performed. RESULTS: The results revealed that urea-extracted sericin has strong anti-tyrosinase properties as shown by a reduction of tyrosinase activity in melanin pigments both 48 h and 10 days after allergic induction with PEG. Anti-inflammatory cytokines including interleukin (IL)-4, IL-10, and transforming growth factor-p were upregulated upon sericin treatment (10, 20, and 50 µg/mL), whereas production of allergic chemokines, CCL8 and CCL18, by DCs was diminished 48 h after allergic induction with PEG. Moreover, sericin lowered the expression of micropthalmia-associated transcription factor (MITF), a marker of melanogenesis regulation, in melanocytes and keratinocytes, which contributed to the reduction of melanin size and the magnitude of melanin deposition. However, sericin had no effect on melanin transport between melanocytes and keratinocytes, as demonstrated by a high retention of cytoskeletal components. CONCLUSION: In summary, sericin suppresses melanogenesis by inhibition of tyrosinase activity, reduction of inflammation and allergy, and modulation of MITF function.

The modification research of bionic silk fibroin nerve guidance conduits by silk sericin / 中华显微外科杂志

Objective To explore the modification of bionic silk fibroin nerve conduits (SF-NCs) by silk sencin.Methods The innovative SS/SF blended-NCs was fabricated by a vertical sequential cooling thermal induced phase separation (TIPS) processing with SF solution added sericin in proportion,its morphology was observed by Scanning electron microscopy (SEM),X-ray diffraction (XRD) and infrared spectroscopy (FTIR) were used to detect its internal molecular structure.MTT assay was used to quantitatively analyzed the PC12 cells viability co-cultured with the innovative SS/SF-NCs,SEM was used to observe the adhesion and morphology of PC12 cells seeded into the innovative SS/SF,PC12 cells were used to assess the NGF bioactivity released from the SS/SF.Results The SEM results showed that the new fabricated SS/SF-NCs had linearly oriented lamellar-like multiple-channel which distributed evenly,got great changes on the channel microstructure and their mechanical properties had been greatly improved,compared to SF-NCs.The XRD and FTIR results showed that the SS/SF-NCs had the similar internal molecular structure with natural silk.The spaces between parallel lamellar-like channels,porosities and compressive strengths of the SS/SF-NCs decreased with decreasing Sequential freezing temperature.MTT assay results showed that the viability of PC12 cell was better than the control group (P ＜ 0.05).The SEM observation indicated that PC12 cells showed good adhesion and differentiation with neuritis outgrowth during the period of co-culture with the SS/SF-NCs.NGF release from the innovative SS/SF-NCs was prolonged over 4 weeks,and remained bioactive.Conclusion The new fabricated SS/SF-NCs modified though silk sericin,which was highly bionic the structure of peripheral nerve fasciculus,had excellent mechanical properties and could be used as another alternative of artificial nerve conduits.

Effects of silk sericin on the proliferation and apoptosis of colon cancer cells

Sericin is a silk protein woven from silkworm cocoons (Bombyx mori). In animal model, sericin has been reported to have anti-tumoral action against colon cancer. The mechanisms underlying the activity of sericin against cancer cells are not fully understood. The present study investigated the effects of sericin on human colorectal cancer SW480 cells compared to normal colonic mucosal FHC cells. Since the size of the sericin protein may be important for its activity, two ranges of molecular weight were tested. Sericin was found to decrease SW480 and FHC cell viability. The small sericin had higher anti-proliferative effects than that of the large sericin in both cell types. Increased apoptosis of SW480 cells is associated with increased caspase-3 activity and decreased Bcl-2 expression. The anti-proliferative effect of sericin was accompanied by cell cycle arrest at the S phase. Thus, sericin reduced SW480 cell viability by inducing cell apoptosis via caspase-3 activation and down-regulation of Bcl-2 expression. The present study provides scientific data that support the protective effect of silk sericin against cancer cells of the colon and suggests that this protein may have significant health benefits and could potentially be developed as a dietary supplement for colon cancer prevention.

Effects of Sericin Pretreatment on the Expression of ECM Associated Protein in the Kidney of Diabetic Nephropathy Rats / 中国医科大学学报

Objective To investigate the effects of sericin pretreatment on the expression of extracellular matrix(ECM) associated protein in diabetic nephropathy(DN) rats' kidney.Methods Sixty six male SD rats were randomly divided into 3 groups(n=12):normal control group,DN model group and sericine pretreatment group.DN rats model in model group and sericine pretreatment group were established by intraperitoneally injection of streptozotocin(STZ).Blood glucose≥16.7 mmol/L was taken as the standard of successful modelization.The rats in sericine pretreatment group were lavaged with sericine(2.4 g·kg~(-1)·d~(-1)) for 35 days before injecting STZ.The enzymic method was used to measure the blood glucose.Type Ⅳ collagen(cⅣ)and laminin(LN)content in the serum were detected by ELBA.The expression of transforming growth factor-β_1,(TGF-β_1)and tissue inhibitors of maprix metalloproteinase-1(TMP-1) protein in the kidney was observed by immunohistochemical staining.The expression of Smad 3 protein in the kidney was detected by Western blot.Results Compared with normal control rats,the blood glucose,cⅣ and LN content in the serum,TGF-β_1,TIMP-1 and Smad 3 expression in the kidney of the model group rats increased obviously(P<0.01).The blood glucose,cⅣ and LN content in the serum,TGF-β_1,TMP-1 and Smad3 expression in the kidney of rats in sericine pretreatment group were significantly lower than those of the rats in model group(P<0.01).Conclusion Sericin pretreatment can inhibit the activation of TGF-β/Smad 3 signal pathway in the kidney of DN rats,and prevent the decrease of MMPs activity induced by up-regulation of TIMP-1.So sericin can prevent accumulation of ECM and glomerulosclerosis during DN,and has satisfactory apotropaic effects on the development of DN.

Dietary Effect of Silk Protein Sericin or Fibroin on Plasma and Epidermal Amino Acid Concentration of NC/Nga Mice

Free amino acids in epidermis function as a major component of Natural Moisturizing Factor (NMF), which maintains the optimal level of water in skin even at the low humidity. In fact, the depletion of free amino acids is reported in the epidermis of atopic dermatitis, the skin condition involving dryness. As an effort searching the dietary source for improving the level of water and free amino acid in epidermis, the dietary effects of silk protein, sericin (S) and fibroin (F) on trans epidermal water loss (TEWL), and plasma and epidermal levels of free amino acids were compared in this study. Thirty of male NC/Nga mice, an animal model of atopic dermatitis, were divided into three groups: group CA as an atopic control with control diet, group S: 1% sericin diet and group F: 1% fibroin diet. Ten of male BALB/c mice were served as group C (control group) with control diet. All mice were fed on diet and water ad libitum for 10weeks. Dry skin condition was established in group CA as TEWL was increased (148.7% of group C). In parallel, epidermal level of glutamate, one of major amino acids functioning as NMF, was dramatically decreased and epidermal levels of methionine and alanine were inversely elevated. Dietary supplementation of sericin (group S) reduced TEWL at the similar level with group C and increased epidermal levels of glutamate as well as serine and glycine, the other major amino acids as NMF. Despite a marked decrease of methionine and alanine, the reduction of TEWL and epidermal levels of glutamate, serine and glycine of group F were less than of group S. Furthermore, in contrast to similar levels of other free amino acids in plasma and epidermis of group S and group C, plasma and epidermal levels of other free amino acids, specifically phenylalanine, isoleucine, cysteine and tyrosine in epidermis of group F, were significantly higher than of group C. Together, our data demonstrate that dietary supplementation of sericin is more effective at improving dry skin condition that paralleled with the normalization of free amino acids in plasma and epidermis of NC/Nga mice.