Cholesterol and Sericin as First Aid for Damaged Cells

Cells are surrounded by a double-layered phospholipid cell membrane responsible for the isolation of intracellular contents, active regulation of uptake from the extracellular environment, and intercellular connection and communication. These cell membranes must be intact and functionally active for cell survival and biological functioning. Compromised damage repair mechanisms usually result in impaired cellular homeostasis, leading to early or late problems. Chronic myopathies, certain myocardial diseases, aging, and acute or chronic neurodegenerative diseases (like Parkinson and Alzheimer) are directly related to cell membrane damage. This study examined the effect of a cholesterol-loaded nanoparticle (methyl-beta cyclodextrin) or the silk protein sericin on cell membrane and DNA integrity and cell viability in an in vitro cell damage model (frozen-thawed rabbit sperm cells). The cells were stored in liquid nitrogen (-196°C), thawed in small batches, and treated with cholesterol-loaded cyclodextrin or sericin before incubation at 35°C for 4 hours. Cell membrane integrity, DNA damage, and viability rates were assessed immediately after thawing and after the incubation period. The administration of sericin and cholesterol in a cell damage model increased cell survival and reduced DNA damage over a 4-hour post-thaw incubation period, suggesting their potential use as a “first aid” intervention at the cellular level.

Sericin alleviates pentylenetetrazole kindling epilepsy and associated comorbidities via modulation of GABA-T enzyme and mitochondrial activity

Objective:To assess the effect of sericin against pentylenetetrazole(PTZ)kindling epilepsy and its associated comorbidities.Methods:Epilepsy was induced with PTZ at the dose of 30 mg/kg i.p.on alternative days for 25 days in rats.Sericin was administered orally at the doses of 250,500,and 1000 mg/kg for 35 days.The behavioral activities were performed using an elevated plus maze,forced swim test,and Morris water maze test.A PTZ challenge test was conducted on day 32.On day 35,rats were sacrificed to perform oxidative stress,mitochondrial dysfunction,neuroinflammation,neurotransmitters,GABA-T activity,and histopathological analyses.Results:Sericin at 500 and 1000 mg/kg significantly reduced behavioral changes and neuroinflammatory cytokines,as well as improved oxidative stress,mitochondrial enzyme complex activity,neurotransmitter level,and GABA-T enzymatic activity(P<0.05).Moreover,sericin improved the neuronal survival altered by PTZ kindling in rat hippocampus.Conclusions:Sericin mitigates epilepsy-associated secondary complications possibly by the modulation of mitochondrial enzyme complexes and GABA-T enzymatic activity.

A Novel Method for the Quantitative Detection of Sericin Content in Silk Fiber Based on the Ratio of Aspartate to Alanine

The development of a method for the quantitative determination of the sericin content ratio(SCR)is urgently needed for silk refining and the purification of silk fibroin for biomedical applications.In this work,a series of sericin/fibroin mixed samples with known SCRs were prepared by mixing initial samples of extracted sericin and fibroin from Bombyx mori silk.Significant differences were found in the contents of characteristic hydrophilic amino acids abundant in sericin and hydrophobic amino acids abundant in fibroin,and several linear relation-ships of SCR associated with the content ratios of Ser/Ala,Asp/Ala,Lys/Ala,Asp/Gly and Ser/Gly were estab-lished by amino acid analysis.Subsequently,the linear equation expressing SCR(%)as a function of the Asp to Ala content ratio X(%)was established as SCR=2.5634X−12.5587(R 2=0.9972).The results indicated that the SCR of degummed silks calculated by the equation is more objective and effective than the results obtained by the traditional weight loss method.Our study provides a novel approach for the sensitive and quantitative detection of the sericin content within the detection limit in unknown silks,which can contribute to quality control in the silk production process.

Therapeutic effects of sericin on diabetic keratopathy in Otsuka Long-Evans Tokushima Fatty rats

An Otsuka Long-Evans Tokushima Fatty(OLETF)rat provides a useful model for studies to develop corneal wound healing drugs for use in diabetic keratopathy resulting from type 2 diabetes mellitus.We investigated the effects of sericin on corneal wound healing in OLETF rats.Corneal wounds were prepared by removal of the corneal epithelium and documented using a TRC-50X.Sericin was instilled into the eyes of rats five times a day following corneal abrasion.The plasma levels of glucose,triglycerides,cholesterol and insulin in 38 wk old OLETF rats were significantly higher than in normal control rats(LETO rats),and the rate of corneal wound healing in OLETF rats was slower than in normal rat,probably due to the suppression of cell migration and proliferation caused by high plasma glucose levels.The corneal wounds of OLETF rats instilled with saline showed almost complete healing 72h after corneal epithelial abrasion.On the other hand,the instillation of sericin has a potent effect in promoting wound healing and wound size reduction in OLETF rats and the wounds showed almost complete healing at 48 h after abrasion.The sericin may be an effective and safe drug to promote corneal wound healing in diabetic keratopathy.

Sericin1上游调控序列多态性分析

在克隆家蚕sericin1基因上游调控序列时,出现多种扩增情况.为了调查其多态性,对野桑蚕、家蚕70个品系基因组进行了PCR扩增,扩增出660bp(DQ354392)、1000bp及660bp和1000bp同时出现的3种类型.序列分析表明:1000bp的条带与NCBI中登录的sericin1(AB00783)上游调控序列一样;多态性存在于顺式作用元件之前,而顺式作用元件区域是非常保守的.

Effects of sericin on heme oxygenase-1 expression in the hippocampus and cerebral cortex of type 2 diabetes mellitus rats

Previous studies have demonstrated that sericin effectively reduces blood glucose, and protects islet cells, as well as the gonads and kidneys. However, whether sericin improves diabetes mellitus-induced structural and functional problems in the central nervous system remains poorly understood. Rat models of type 2 diabetes mellitus were established by intraperitoneal injection of streptozotocin. The present study observed histological changes in the hippocampus and cerebral cortex, as well as heme oxygenase-1 expression, and explored sericin effects on the central nervous system in diabetic rats. Pathological damage to neural cells in the rat hippocampus and cerebral cortex was relieved following intragastric administration of sericin at a dose of 2.4 g/kg for 35 consecutive days. Heme oxygenase-1 protein and mRNA expressions were decreased in the hippocampus and cerebral cortex of diabetes mellitus rats after sericin treatment. The results suggest that sericin plays a protective effect on the nervous system by decreasing the high expression of heme oxygenase-1 following diabetes mellitus.

Sericin can reduce hippocampal neuronal apoptosis by activating the Akt signal transduction pathway in a rat model of diabetes mellitus

In the present study, a rat model of type 2 diabetes mellitus was established by continuous peritoneal injection of streptozotocin. Following intragastric perfusion of sericin for 35 days, blood glucose levels significantly reduced, neuronal apoptosis in the hippocampal CA1 region decreased, hippocampal phosphorylated Akt and nuclear factor kappa B expression were enhanced, but Bcl-xL/Bcl-2 associated death promoter expression decreased. Results demonstrated that sericin can reduce hippocampal neuronal apoptosis in a rat model of diabetes mellitus by regulating abnormal changes in the Akt signal transduction pathway.

Sericin protects against diabetes-induced injuries in sciatic nerve and related nerve cells

Sericin from discarded silkworm cocoons of silk reeling has been used in different fields, such as cosmetology, skin care, nutrition, and oncology. The present study established a rat model of type 2 diabetes by consecutive intraperitoneal injections of low-dose （25 mg/kg） streptozotocin. After intragastrical perfusion of sericin for 35 days, blood glucose levels significantly declined, and the expression of neurofilament protein in the sciatic nerve and nerve growth factor in L4-6 spinal ganglion and anterior horn cells significantly increased. However, the expression of neuropeptide Y in spinal ganglion and anterior horn cells significantly decreased in model rats. These findings indicate that sericin protected the sciatic nerve and related nerve cells against injury in a rat type 2 diabetic model by upregulating the expression of neurofilament protein in the sciatic nerve and nerve growth factor in spinal ganglion and anterior horn cells, and downregulating the expression of neuropeptide Y in spinal ganglion and anterior horn cells.

Effect of sericin on diabetic hippocampal growth hormone/insulin-like growth factor 1 axis

Previous studies have shown that sericin extracted from silk cocoon significantly reduces blood glucose levels and protects the nervous system against diabetes mellitus. In this study, a rat type 2 diabetes mellitus model was established by intraperitoneal injection of 25 mg/kg streptozotocin for 3 successive days, following which the rats were treated with sericin for 35 days. After treatment, the blood glucose levels of the diabetic rats decreased significantly, the growth hormone level in serum and its expression in the hippocampus decreased significantly, while the insulin-like growth factor-1 level in serum and insulin-like growth factor-1 and growth hormone receptor expression in the hippocampus increased significantly. The experimental findings indicate that sericin improves disorders of the growth hormone/insulin-like growth factor 1 axis to alleviate hippocampal damage in diabetic rats.

Constructing and Analyzing Fusion Promoter of Partial Sericin 1 and Bombyx A3 Cytoplasmic Actin

Previous report showed that the 209 bp DNA sequence upstream of the sericin 1 transcriptional start site （-586 to -378 bp） is involved in promoting transcription and responsible for the tissue specificity of sericin 1 promoter in silkworm Bombyx mori. In the present study, this 209 bp sequence exhibited enhancive effect by assembling in two different locations of ubiquitous Bombyx A3 cytoplasmic actin promoter. Sf-9 cells were transfected with recombinant plasmids using Cellfectin reagent. Firefly luciferase gene located downstream of fusion promoter was considered as a reporter, whereas the activity of the co-transfected Renilla luciferase gene （pGL2-SV40） provides an internal control. This 209 bp region up-regulates the strength of A3 promoter significantly （P〈0.01） when it enters into A3 promoter with respect to the position in sericin 1 gene promoter. This 209-bp fragment was almost functionless when being located upstream of A3 promoter.

Robust Waterborne Polyurethane/Wool Keratin/Silk Sericin Freeze-Drying Composite Membrane for Heavy Metal Ions Adsorption

Wool keratin(WK)and silk sericin(SS)have the ability to interact with metal ions.In order to take advantage of this potential,a novel environmentally friendly waterborne polyurethane(WPU)/WK/SS membrane named as WPU&WK&SS membrane with crosslinked structure was constructed by freeze-drying via self-assembly style.Surface morphology and chemical structure characterization were investigated by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).In addition,the adsorption experiments of Cu2+and Cr6+were performed to evaluate the adsorption of WPU&WK&SS membrane,including adsorption kinetics,adsorption isotherm models and various factors affecting adsorption.Further investigation indicates that the maximum adsorption capacity of Cu2+and Cr6+can reach 54.21 mg·g-1and 85.21 mg·g-1,respectively,which are higher than most of the reported adsorbents.Through adsorption kinetics and thermodynamic analysis,it is find that the pseudo-second-order kinetic equation and the Langmuir adsorption isotherm model are more suitable for the static adsorption of Cu2+and Cr6+by WPU&WK&SS membrane.

Cell Growth and Desorption on the Surface of Temperature-sensitive Semi-IPNs Hydrogels Based on Silk Sericin

Semi-interpenetrating （semi-IPNs） hydrogels containing biocompatible silk sericin （SS） and poly（N-isopropylacrylamide）（PNIPAM） were prepared as novel cellular matrices. Their maximum swelling degree and basic characteristics for biomedical applications such as mouse ？broblasts （L929） cell proliferation and desorption were investigated. The results showed that the incorporation of high hydrophilic SS into PNIPAM hydrogel increased the maximum swelling degree of the semi-IPNs hydrogels, and the adhesion and growth of the L929 on semi-IPNs hydrogels were at least comparable to, or even better than, that on conventional PNIPAM hydrogel. In addition, L929 cells were found to detach from the hydrogels surface naturally by controlling environmental temperature. These results suggest great potential of semi-IPNs hydrogels in tissue engineering.

Novel sericin-based hepatocyte serum-free medium and sericin's effect on hepatocyte transcriptome

AIM To develop a novel hepatocyte serum-free medium based on sericin,and to explore the effect of sericin on the hepatocyte transcriptome.METHODS A controlled trial comparing novel serum-free medium and other media: C3 A cells were cultured in our novel serum-free medium,Hepato ZYME,complete medium(DMEM/F12 with 100 m L/L FBS),and DMEM/F12,andthen cell attachment,proliferation,and function as well as the biocompatibility of the media were assessed.A comparative study of serum-free media with or without 2 mg/m L sericin: the effect of sericin on C3 A growth was assessed by cell viability and proliferation,the effect of sericin on C3 A cell cycle distribution was determined by flow cytometry,and the effect of sericin on the C3 A transcriptome was assessed by gene-chip array and RT-q PCR.RESULTS More C3 A cells attached to the plate containing our serum-free medium than to those containing Hepato ZYME and DMEM/F12 at 24 h post-seeding.Both the viability and proliferation rate of C3 A cells in sericin-based serum-free medium were superior to those of cells in Hepato ZYME and DMEM/F12(P < 0.001).The content of albumin and urea in our serum-free medium was significantly higher than that in Hepato ZYME and DMEM/F12 throughout the whole culture period(P < 0.001) and was similar to that in complete medium at day 3,4,and 5.In part 2,cell viability and proliferation were greater in the presence of 2 mg/m L sericin(P < 0.001),as was the proportion of cells in S phase(16.21% ± 0.98% vs 12.61% ± 0.90%,P < 0.01).Gene-chip array analysis indicated that the expression of CCR6,EGFR,and FOS were up-regulated by 2 mg/m L sericin,and RT-q PCR revealed that the expression of CCR6,EGFR,FOS,AKT1,JNK1,NFk B1,MMP-9,MEK2,ERK1/2 and MYC was upregulated by 2 mg/m L sericin(P < 0.05).CONCLUSION We developed a novel hepatocyte serum-free medium.Sericin probably enhances cell attachment through the CCR6-Akt-JNK-NF-κB pathway and promotes cell proliferation through CCR6-mediated activation of the ERK1/2-MAPK pathway.

Temperature-pH Sensitive IPN Hydrogels Composed of Silk Sericin and Poly(N-isopropylacrylamide)

Interpenetrating polymer network （IPN） composed of silk sericin （SS） and poly（N-isopropylacrylamide） （PNIPAAm） was prepared. The morphology of the IPNs, in which the SS phase was stained with ammonium cuprate, was examined with TEM and a relative homogeneous distribution of the two polymers was exhibited. The swelling behavior of the IPN hydrogels showed both temperature and pH dependences.

Characterization on Specific Characteristics of Sericin Silkworm, and Physiological Genetics Analysis

Sericin silkworm is a kind of gene mutant silkworm that can only synthesis and secrete sericin protein instead of fibroin protein. In this study, according to the knowledge of physiology and heredity, the reasons of this special phenomenon for the sericin silkworm were analyzed in order to explore the utilization clues in the production of natural sericin and product development.

Selective Adsorption of Ag(I) from Electronic Waste Leachate Using Modified Silk Sericin

A novel biosorbent was synthesized by grafting bisthiourea(BTU)on a silk sericin(SS)matrix.This biosorbent was denoted as BTU-SS and characterized by Fourier transform infrared spectroscopy(FTIR),zeta potential measurements,elemental analysis,and X-ray photoelectron spectroscopy(XPS).As revealed by the adsorption experiments,both BTU-SS and SS showed low affinity towards coexisting base metallic ions in Ag(I)-Cu(II)-Zn(II)-Ni(II)-Pb(II)electronic waste leachate mixtures,while their adsorption capacities towards Ag(I)reached 30.5 and 10.4 mg∙g-1 at a pH of 5.0,respectively.BTU-SS showed higher selectivity towards Ag(I)than SS,as revealed by the Ag(I)partition coefficients between the biosorbents and the leachate(16634.6 and 403.3,respectively).As further demonstrated by column experiments,BTU-SS allowed the separation of Ag(I)from an electronic waste leachate.Thermodynamic studies showed that the adsorption of Ag(I)was exothermic and spontaneous,while adsorption kinetic experiments revealed that chemisorption dominated the adsorption process with activation energies of 47.67 and 53.27 kJ∙mol-1 for BTU-SS and SS,respectively.FTIR and XPS analyses of fresh and Ag(I)-loaded BTU-SS further revealed an adsorption mechanism mainly involving electrostatic and coordination interactions.

ANALYSIS ON THE PRINCIPLE OF SERICIN MODIFICATION WITH DIRECT STEAMING FOR COOKING COCOON

Results of circular dichromatic spectrographic analysis of sericin revealcd a modification in the character of sericinafter direct steaming for cooking dry cocoon.That is,the molecular structure of cocoon shell sericin transforms fromthe frowned random structure to β- fold structure.The sericin modification reduces undulation of the gummingforce of cocoon shell sericin. Therefore,it is one of the key ways to improve the neatness of raw silk.

Equilibrium and Kinetic Study of Sericin Protein Absorption onto Anion-Exchangable Fibers

Silk is made of sericin and fibroin proteins. The sericin constitutes 20%- 30% of silk proteins and it covers the fibmin. Sericin is usually treated as impurity and removed during the process of degumming in dyeing and printing factories. However, sericin is a useful natural protein. In this paper, viscose auion-exchange fibers have been used to absorb seriein from waste water. The amount of adsorbed sericin into the viscose anion-exchange fibers at different temperatures and times has been studied. The study show that the anion-exchange fibers can adsorb sericin from the waste water. Furthermore, the equilibrium adsorption data show that the adsorption of sericin onto anion-exchange fiber fit the Freundlich isotherm at 25 1C and 50 ℃, and fit the Langmuir isotherm at 75 ℃.

Technical Methods for Recovering Sericin from Degumming Wastewater

Silk sericin is a natural polymer,which is often discarded as waste in silk reeling production.Sericin protein increases the COD value of degumming wastewater and increases the difficulty of sewage treatment.The recovery and utilization of sericin protein can minimize environmental problems,and has high scientific and commercial value.This paper introduced and analyzed current technical methods of recycling sericin from silk degumming wastewater,providing a reference for the utilization of recovered sericin.

Cell Proliferation Inhibition by Sericin from the Wild Silkworm, Cricula trifenestrata

Sericin is a major silk protein, and recent studies have shown that sericin has numerous physiological activities against cultured cells. For example, it accelerates mammalian cell proliferation and protects insect cells against cell death. In this study, we examined the activities of sericin prepared from the wild silkworm, Cricula trifenestrata. The results presented here indicated that C. trifenestrata sericin has anti-proliferative activity against feline kidney cells, while sericin from Bombyx mori promoted cell proliferation. The components of the sericin preparation that played a role in inhibition of proliferation were analyzed by fractionation through partition chromatography (Folch method) and reversed-phase chromatography. Our analysis showed that at least two components in the C. trifenestrata sericin preparation promoted the anti-proliferative activity in an additive or even synergistic manner. Therefore, differences in components between insect species may contribute to different activities against cultured cells.