Impact of elastin-derived VGVAPG peptide on bidirectional interaction between peroxisome proliferator-activated receptor gamma (Pparγ) and beta-galactosidase (β-Gal) expression in mouse cortical astrocytes in vitro

Interaction Between Aging-Related Elastin-Derived Peptide (VGVAPG) and Sirtuin 2 and its Impact on Functions of Human Neuron Cells in an In Vitro Model

Elastin is a stable protein present in many tissues, including brain tissues, and is one of the most long-life proteins with a half-life of approximately 70 years. The peptide with a Val-Gly-Val-Ala-Pro-Gly (VGVAPG) amino acid sequence is released during elastin decay, which correlates with aging-related neurodegeneration. A recent study has shown enhanced protein expression of Sirtuin 2 (SIRT2 - one of the redox homeostatic factors) in aged rodent brains, while the correlation between VGVAPG and SIRT2 has never been evaluated so far. Therefore, the study aimed to determine the impact of the VGVAPG hexapeptide on SIRT2 and neuronal functions in differentiated SH-SY5Y cells at the gene and protein expression levels. The present results showed that VGVAPG caused a 52.69% decrease in the level of reactive oxygen species (ROS), as in the case of neurons treated with AGK2 (Sirtuin 2 inhibitor) after 24h and 48h. Furthermore, a decrease in superoxide dismutase (SOD) activity was observed. The SIRT2 gene expression was found to fluctuate after 6h and 24h as a result of the exposure to the VGVAPG peptide. In turn, a decrease in the PPARγ, P53, SOD2, and CAT mRNA expression was shown in VGVAPG-treated cells. Additionally, an increase in the Sirtuin 2 protein expression was recorded after 24h and 48h in the VGVAPG peptide-treated neurons. Last but not least, the decrease in the level of acetylation of α-tubulin after the hexapeptide treatment was correlated with shortening of neurites, which may indicate the destabilization of the microtubule and ROS-independent induction of neurodegeneration.

The Involvement of Glial Cells in Blood-Brain Barrier Damage in Neuroimmune Diseases

The blood-brain barrier and glial cells, particularly astrocytes, interact with each other in neuroimmune diseases. In the inflammatory environment typical of these diseases, alterations in vascular endothelial cell surface molecules and weakened cell connections allow immune cells and autoantibodies to enter the central nervous system. Glial cells influence the adhesion of endothelial cells by changing their morphology and releasing various signaling molecules. Multiple sclerosis has been the most studied disease in relation to vascular endothelial and glial cell interactions, but these cells also significantly affect the onset and severity of other neuroimmune conditions, including demyelinating and inflammatory diseases. In this context, we present an overview of these interactions and highlight how they vary across different neuroimmune diseases.

Elastin-derived peptides (EDPs) affect gene and protein expression in human mesenchymal stem cells (hMSCs) - preliminary study

During the aging process, elastin is degraded and the level of elastin-derived peptides (EDPs) successively increases. The main peptide released from elastin during its degradation is a peptide with the VGVAPG sequence. To date, several papers have described that EDPs or elastin-like peptides (ELPs) affect human mesenchymal stem cells (hMSCs) derived from different tissues. Unfortunately, despite the described effect of EDPs or ELPs on the hMSC differentiation process, the mechanism of action of these peptides has not been elucidated. Therefore, the aim of the present study was to evaluate the impact of the VGVAPG and VVGPGA peptides on the hMSC stemness marker and elucidation of the mechanism of action of these peptides. Our data show that both studied peptides (VGVAPG and VVGPGA) act with the involvement of ERK1/2 and c-SRC kinases. However, their mechanism of activation is probably different in hMSCs derived from adipose tissue. Both studied peptides increase the KI67 protein level in hMSCs, but this is not accompanied with cell proliferation. Moreover, the changes in the NANOG and c-MYC protein expression and in the SOX2 and POU5F1 mRNA expression suggest that EDPs reduced the hMSC stemness properties and could initiate cell differentiation. The initiation of differentiation was evidenced by changes in the expression of AhR and PPARγ protein as well as specific genes (ACTB, TUBB3) and proteins (β-actin, RhoA) involved in cytoskeleton remodeling. Our data suggest that the presence of EDPs in tissue can initiate hMSC differentiation into more tissue-specific cells.

Elastin-derived peptides (EDPs) as a potential pro-malignancy factor in human leukemia cell lines

The extracellular matrix (ECM) is currently considered to be an important factor influencing the migration and progression of cancer cells. Therefore, the aim of our study was to investigate the mechanism of action of elastin-derived peptides in cancerous cells derived from the immunological system, i.e., HL-60, K562, and MEG-A2 cell lines. Moreover, an attempt to clarify the involvement of c-SRC kinase in EDP mechanism of action was also undertaken. Our data show that the VGVAPG and VVGPGA peptides are not toxic in the studied cell lines. Moreover, due to the involvement of KI67 and PCNA proteins in the cell cycle and proliferation, we can assume that neither peptide stimulates cell proliferation. Our data suggest that both peptides could initiate the differentiation process in all the studied cell lines. However, due to the different origins (HL-60 and K562-leukemic cell line vs. MEG-A2-megakaryoblastic origin) of the cell lines, the mechanism may differ. The increase in the ELANE mRNA expression noted in our experiments may also suggest enhancement of the migration of the tested cells. However, more research is needed to fully explain the mechanism of action of the VGVAPG and VVGPGA peptides in the HL-60, K562, and MEG-A2 cell lines. HIGHLIGHTS: • VGVAPG and VVGPGA peptides do not affect the metabolic activity of HL-60, K562, and MEG-A2 cells. • mTOR and PPARγ proteins are involved in the mechanism of action of VGVAPG and VVGPGA peptides. • Both peptides may initiate differentiation in HL-60, K562, and MEG-A2 cell lines.

The Role of PGC-1α in Aging Skin Barrier Function

Skin provides a physical and immune barrier to protect the body from foreign substances, microbial invasion, and desiccation. Aging reduces the barrier function of skin and its rate of repair. Aged skin exhibits decreased mitochondrial function and prolonged low-level inflammation that can be seen in other organs with aging. Peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α (PGC-1α), an important transcriptional coactivator, plays a central role in modulating mitochondrial function and antioxidant production. Mitochondrial function and inflammation have been linked to epidermal function, but the mechanisms are unclear. The aim of this review is to discuss the mechanisms by which PGC-1α might exert a positive effect on aged skin barrier function. Initially, we provide an overview of the function of skin under physiological and aging conditions, focusing on the epidermis. We then discuss mitochondrial function, oxidative stress, cellular senescence, and inflamm-aging, the chronic low-level inflammation observed in aging individuals. Finally, we discuss the effects of PGC-1α on mitochondrial function, as well as the regulation and role of PGC-1α in the aging epidermis.

Involvement of the aryl hydrocarbon receptor (AhR) in the mechanism of action of elastin-derived peptide (VGVAPG) and its impact on neurosteroidogenesis

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor from the family of basic helix-loop-helix transcription factors. Several studies have indicated an important role of AhR signaling pathways in senescence, aging, and neurodegenerative diseases. During aging, elastin is degraded and elastin-derived peptides (EDPs) are formed. EDPs have been detected in human blood, serum, and cerebrospinal fluid. Literature data suggest a role of EDPs in the development of neurodegenerative diseases. However, the impact of EDPs on the AhR signaling pathway has never been investigated. Therefore, the aim of our paper was to study the role of AhR in the mechanism of action of the VGVAPG peptide (one of the EDPs) in mouse primary astrocytes in vitro. Our experiments have shown that AhR plays an important role in the EDP mechanism of action in a model of mouse primary astrocytes. Moreover, due to the involvement of Sirt3, Pparγ, AhR, Glb1, Nf-κb1, Ece1, Ide, and Nepr genes and the production and release of neurosteroids, VGVAPG can accelerate the development of neurodegenerative diseases in which the proper metabolism of astrocytes is crucial. Furthermore, our studies have proved that AhR is likely involved in the co-control of the Sirt1, Glb1, Nf-κb1, Ece1, and Nepr expression in astrocytes.

The elastin-derived peptide (VGVAPG) activates autophagy in neuroblastoma (SH-SY5Y) cells via peroxisome proliferator-activated receptor gamma (PPARγ)

Autophagy is a self-degradative process important for balancing the sources of energy and involved in the development of Alzheimer's disease (AD). To date, a number of papers have shown that elastin-derived peptides (EDPs) affect the expression and activation of peroxisome proliferator-activated receptor gamma (PPARγ), which is crucial for the development of AD and autophagy initiation. Therefore, the aim of the present study was to determine whether EDPs with a Val-Gly-Val-Ala-Pro-Gly (VGVAPG) amino acid sequence activate the autophagic process in undifferentiated SH-SY5Y human neuroblastoma cells. Our study is the first to show that EDPs with the VGVAPG sequence initiate the autophagy process in the undifferentiated SH-SY5Y cell line exhibiting a number of features of normal neuroblasts. In particular, we observed in our study that VGAVPG peptide increased ULK1, AKT, PPARγ, and LC3B protein expression. Moreover, our experiments with the agonist (rosiglitazone) and antagonist (GW9662) of PPARγ confirm that the studied EDP acts through the PPARγ pathway affecting mTOR and finally autophagy. Some studies have shown that autophagy disturbances are involved in the development of AD. Therefore, we believe that our study will provide new evidence of the possible involvement of EDPs (especially VGVAPG) in the development of AD.

A multimodal imaging study to highlight elastin-derived peptide pro-tumoral effect in a pancreatic xenograft model

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is highly malignant with a very poor prognosis due to its silent development and metastatic profile with a 5-year survival rate below 10%. PDAC is characterised by an abundant desmoplastic stroma modulation that influences cancer development by extracellular matrix/cell interactions. Elastin is a key element of the extracellular matrix. Elastin degradation products (EDPs) regulate numerous biological processes such as cell proliferation, migration and invasion. The aim of the present study was to characterise for the first time the effect of two EDPs with consensus sequences "GxxPG" and "GxPGxGxG" (VG-6 and AG-9) on PDAC development. The ribosomal protein SA (RPSA) has been discovered recently, acting as a new receptor of EDPs on the surface of tumour cells, contributing to poor prognosis.

METHODS

Six week-old female Swiss nude nu/nu (Nu(Ico)-Foxn1nu) mice were subcutaneously injected with human PDAC MIA PaCa-2/eGFP-FLuc+ cells, transduced with a purpose-made lentiviral vector, encoding green fluorescent protein (GFP) and Photinus pyralis (firefly) luciferase (FLuc). Animals were treated three times per week with AG-9 (n = 4), VG-6 (n = 5) or PBS (n = 5). The influence of EDP on PDAC was examined by multimodal imaging (bioluminescence imaging (BLI), fluorescence imaging (FLI) and magnetic resonance imaging (MRI). Tumour volumes were also measured using a caliper. Finally, immunohistology was performed at the end of the in vivo study.

RESULTS

After in vitro validation of MIA PaCa-2 cells by optical imaging, we demonstrated that EDPs exacerbate tumour growth in the PDAC mouse model. While VG-6 stimulated tumour growth to some extent, AG-9 had greater impact on tumour growth. We showed that the expression of the RPSA correlates with a possible effect of EDPs in the PDAC model. Multimodal imaging allowed for longitudinal in vivo follow-up of tumour development. In all groups, we showed mature vessels ending in close vicinity of the tumour, except for the AG-9 group where mature vessels are penetrating the tumour reflecting an increase of vascularisation.

CONCLUSIONS

Our results suggest that AG-9 strongly increases PDAC progression through an increase in tumour vascularisation.

Understanding Acquired Brain Injury: A Review

Any type of brain injury that transpires post-birth is referred to as Acquired Brain Injury (ABI). In general, ABI does not result from congenital disorders, degenerative diseases, or by brain trauma at birth. Although the human brain is protected from the external world by layers of tissues and bone, floating in nutrient-rich cerebrospinal fluid (CSF); it remains susceptible to harm and impairment. Brain damage resulting from ABI leads to changes in the normal neuronal tissue activity and/or structure in one or multiple areas of the brain, which can often affect normal brain functions. Impairment sustained from an ABI can last anywhere from days to a lifetime depending on the severity of the injury; however, many patients face trouble integrating themselves back into the community due to possible psychological and physiological outcomes. In this review, we discuss ABI pathologies, their types, and cellular mechanisms and summarize the therapeutic approaches for a better understanding of the subject and to create awareness among the public.

Elastin-like Polypeptides in Development of Nanomaterials for Application in the Medical Field

Elastin-like polypeptides (ELPs) are biopolymers formed by amino acid sequences derived from tropoelastin. These biomolecules can be soluble below critical temperatures, forming aggregates at higher temperatures, which makes them an interesting source for the design of different nanobiomaterials. These nanobiomaterials can be obtained from heterologous expression in several organisms such as bacteria, fungi, and plants. Thanks to the many advantages of ELPs, they have been used in the biomedical field to develop nanoparticles, nanofibers, and nanocomposites. These nanostructures can be used in multiple applications such as drug delivery systems, treatments of type 2 diabetes, cardiovascular diseases, tissue repair, and cancer therapy. Thus, this review aims to shed some light on the main advances in elastin-like-based nanomaterials, their possible expression forms, and importance to the medical field.

Naturally Occurring Antioxidant Therapy in Alzheimer's Disease

It is estimated that the prevalence rate of Alzheimer's disease (AD) will double by the year 2040. Although currently available treatments help with symptom management, they do not prevent, delay the progression of, or cure the disease. Interestingly, a shared characteristic of AD and other neurodegenerative diseases and disorders is oxidative stress. Despite profound evidence supporting the role of oxidative stress in the pathogenesis and progression of AD, none of the currently available treatment options address oxidative stress. Recently, attention has been placed on the use of antioxidants to mitigate the effects of oxidative stress in the central nervous system. In preclinical studies utilizing cellular and animal models, natural antioxidants showed therapeutic promise when administered alone or in combination with other compounds. More recently, the concept of combination antioxidant therapy has been explored as a novel approach to preventing and treating neurodegenerative conditions that present with oxidative stress as a contributing factor. In this review, the relationship between oxidative stress and AD pathology and the neuroprotective role of natural antioxidants from natural sources are discussed. Additionally, the therapeutic potential of natural antioxidants as preventatives and/or treatment for AD is examined, with special attention paid to natural antioxidant combinations and conjugates that are currently being investigated in human clinical trials.

Elastin-Derived Peptides in the Central Nervous System: Friend or Foe

Elastin is one of the main structural matrix proteins of the arteries, lung, cartilage, elastic ligaments, brain vessels, and skin. These elastin fibers display incredible resilience and structural stability with long half-life. However, during some physiological and pathophysiological conditions, elastin is prone to proteolytic degradation and, due to the extremely low turnover rate, its degradation is practically an irreversible and irreparable phenomenon. As a result of elastin degradation, new peptides called elastin-derived peptides (EDPs) are formed. A growing body of evidence suggests that these peptides play an important role in the development of age-related vascular disease. They are also detected in the cerebrospinal fluid of healthy people, and their amount increases in patients after ischemic stroke. Recently, elastin-like polypeptides have been reported to induce overproduction of beta-amyloid in a model of Alzheimer's disease. Nevertheless, the role and mechanism of action of EDPs in the nervous system is largely unknown and limited to only a few studies. The article summarizes the current state of knowledge on the role of EDPs in the nervous system.

Elastin-derived peptide VGVAPG decreases differentiation of mouse embryo fibroblast (3T3-L1) cells into adipocytes

Elastin is a highly elastic protein present in connective tissue. As a result of protease activity, elastin hydrolysis occurs, and during this process, elastin-derived peptides (EDPs) are released. One of the constitutively repeating elastin and EDP building sequences is the hexapeptide VGVAPG. Therefore, the aim of our research was to define the effect of VGVAPG peptide on adipogenesis in a mouse 3T3-L1 cell line. 3T3-L1 cells were differentiated according to a previously described protocol and exposed to increasing concentrations of VGVAPG or VVGPGA peptide. The obtained results showed that VGVAPG peptide does not stimulate reactive oxygen species (ROS) production, caspase-1 activation, and 3T3-L1 cell proliferation. In the second part of the experiments, it was proved that VGVAPG peptide decreased lipid accumulation as measured by oil red O staining, which was confirmed by the profile of increased expression markers of undifferentiated preadipocytes. In our experiments, 10 nM VGVAPG added for differentiating to adipocytes increased the expression of Pref-1, serpin E1, and adiponectin as compared to rosiglitazone (PPARγ agonist)-treated group and simultaneously decreased the expression of VEGF and resistin as compared to the rosiglitazone-treated group. The obtained results show that VGVAPG peptide sustains 3T3 cells in undifferentiated state.

ABBREVIATIONS

DMSO: dimethyl sulphoxide; EBP: elastin-binding protein; EDPs: elastin-derived peptides; FBS: foetal bovine serum; Glb1: gene for beta-galactosidase; LDL: low-density-lipoprotein; PAI-1 (Serpin E1): plasminogen activator inhibitor-1; PBS: phosphate-buffered saline; PPARγ: peroxisome proliferator-activated receptor gamma; Pref-1: preadipocyte factor 1; ROS: reactive oxygen species; VEGF-A: vascular endothelial growth factor-A; VGVAPG: Val-Gly-Val-Ala-Pro-Gly; β-Gal: beta-galactosidase; ORO: oil red O; IBMX: 3-isobutyl-1-methylxanthine; H2DCFDA: 2',7'-dichlorodihydrofluorescein diacetate; DMEM: Dulbecco's Modified Eagle's Medium; VVGPGA: Val-Val-Gly-Pro-Gly-Ala.

Regulation of cellular senescence by extracellular matrix during chronic fibrotic diseases

The extracellular matrix (ECM) is a complex network of macromolecules surrounding cells providing structural support and stability to tissues. The understanding of the ECM and the diverse roles it plays in development, homoeostasis and injury have greatly advanced in the last three decades. The ECM is crucial for maintaining tissue homoeostasis but also many pathological conditions arise from aberrant matrix remodelling during ageing. Ageing is characterised as functional decline of tissue over time ultimately leading to tissue dysfunction, and is a risk factor in many diseases including cardiovascular disease, diabetes, cancer, dementia, glaucoma, chronic obstructive pulmonary disease (COPD) and fibrosis. ECM changes are recognised as a major driver of aberrant cell responses. Mesenchymal cells in aged tissue show signs of growth arrest and resistance to apoptosis, which are indicative of cellular senescence. It was recently postulated that cellular senescence contributes to the pathogenesis of chronic fibrotic diseases in the heart, kidney, liver and lung. Senescent cells negatively impact tissue regeneration while creating a pro-inflammatory environment as part of the senescence-associated secretory phenotype (SASP) favouring disease progression. In this review, we explore and summarise the current knowledge around how aberrant ECM potentially influences the senescent phenotype in chronic fibrotic diseases. Lastly, we will explore the possibility for interventions in the ECM-senescence regulatory pathways for therapeutic potential in chronic fibrotic diseases.

Lactosylceramide induced by elastin-derived peptides decreases adipocyte differentiation

Elastin, the major protein of the extracellular matrix, is specially found in cardiovascular tissues and contributing to 30-50% of the dry weight of blood vessels. Elastin regulates cell signalling pathways involved in morphogenesis, injury response and inflammation. The function of elastin is frequently compromised in damaged or aged elastic tissues. Indeed, elastin degradation, observed during ageing, and the resulting production of elastin-derived peptides (EDPs), have crucial impacts on cardiovascular disease (atherosclerosis, thrombosis) or on metabolism disease progressions (type 2 diabetes or non-alcoholic steatohepatitis). In the present study, we analysed the EDP effects on 3T3 preadipocyte cell differentiation. In a first part, we treated 3T3-L1 cells with EDP and visualized the lipid droplet accumulation by the oil red O staining and measured the expression of various transcription factors and adipocyte-specific mRNAs by real-time RT-PCR. We demonstrated that the elastin receptor complex, ERC, is activated by EDPs and decreased adipocyte differentiation by a modulation of crucial adipogenesis transcriptional factor particularly PPARγ. In a second part, we identified the signalling pathway implicated in EDP-reduced cell differentiation. The flow cytometry and immunocytochemistry approaches showed that ERC activated by EDP produced a second messenger, lactosylceramide (Lac-Cer). Moreover, this Lac-Cer production favoured the phosphorylation of ERK1-2 (p-ERK1-2), to decrease adipocyte differentiation by a modulation of adipogenesis transcriptional factor PPARγ. To conclude, the EDP/Lac-Cer/p-ERK1-2 signalling pathway may be studied further as a critical target for treating complications associated with adipocyte dedifferentiation such as obesity and diabetes insulin resistance.

The Elastin-Derived Peptide VGVAPG Does Not Activate the Inflammatory Process in Mouse Cortical Astrocytes In Vitro

During vascular aging or in pathological conditions in humans, elastin is degraded and its by-products, the elastin-derived peptides (EDPs), enter the blood circulation. EDPs may be detected in the serum of healthy subjects or people who suffered a stroke. Moreover, recent evidence suggests a potential role of inflammatory mechanisms in neurological conditions, which are usually not categorized as inflammatory. Therefore, the present in vitro study was conducted to investigate the impact of the VGVAPG peptide on the activation of inflammatory process in mouse primary astrocytes, which were maintained in phenol red-free DMEM/F12 supplemented with 10% fetal bovine serum. The cells were exposed to VGVAPG or VVGPGA peptides for 24 and 48 h; this was followed by the determination of the activity of caspase-1 and levels of SOD, CAT, PPARγ, NF-κB, IL-1β, and IL-1βR1. Furthermore, rosiglitazone-a PPARγ agonist-was applied. Our study pioneered the finding that the VGVAPG peptide increases caspase-1 activity in astrocytes in vitro. The VGVAPG peptide simultaneously decreases the release of IL-1β into the cell-culture medium from astrocytes. The ELISA method revealed that the VGVAPG peptide increases the protein expression of SOD1 whereas it decreases the expression of IL-1βR1, CAT, and NF-κB. Therefore, the available data suggest that the VGVAPG peptide (concentration 10 nM) synergistically acts with agonists of PPARγ in mouse astrocytes. However, given the lack of sufficient data to explain the molecular mechanism of action of the VGVAPG peptide in the nervous system, more studies in this area are necessary.

Specific role of N-methyl-D-aspartate (NMDA) receptor in elastin-derived VGVAPG peptide-dependent calcium homeostasis in mouse cortical astrocytes in vitro

Under physiological and pathological conditions, elastin is degraded to produce elastin-derived peptides (EDPs). EDPs are detected in the healthy human brain, and its concentration significantly increases after ischemic stroke. Both elastin and EDPs contains replications of the soluble VGVAPG hexapeptide, which has a broad range of biological activities. Effects of VGVAPG action are mainly mediated by elastin-binding protein (EBP), which is alternatively spliced, enzymatically inactive form of the GLB1 gene. This study was conducted to elucidate the activation and role of the N-methyl-D-aspartate receptor (NMDAR) in elastin-derived VGVAPG peptide-dependent calcium homeostasis in mouse cortical astrocytes in vitro. Cells were exposed to 10 nM VGVAPG peptide and co-treated with MK-801, nifedipine, verapamil, or Src kinase inhibitor I. After cell stimulation, we measured Ca²⁺ level, ROS production, and mRNA expression. Moreover, the Glb1 and NMDAR subunits (GluN1, GluN2A, and GluN2B) siRNA gene knockdown were applied. We found the VGVAPG peptide causes Ca²⁺ influx through the NMDA receptor in mouse astrocytes in vitro. Silencing of the Glb1, GluN1, GluN2A, and GluN2B gene prevented VGVAPG peptide-induced increase in Ca²⁺. Nifedipine does not completely reduce VGVAPG peptide-activated ROS production, whereas MK-801, verapamil, and Src inhibitor reduce VGVAPG peptide-activated Ca²⁺ influx and ROS production. These data suggest the role of Src kinase signal transduction from EBP to NMDAR. Moreover, the VGVAPG peptide affects the expression of NMDA receptor subunits.

Elastin-Derived Peptide VGVAPG Affects Production and Secretion of Testosterone in Mouse Astrocyte In Vitro

Astrocytes play many distinct roles in the nervous system providing structural support for neurons and maintaining blood-brain barrier integrity. Steroid hormones exhibit a broad spectrum of actions in the central and peripheral nervous system, acting as trophic factors affecting cell differentiation and synaptic plasticity. In steroidogenesis, astrocytes play a key role by producing cholesterol, progesterone (P₄), testosterone (T), and estradiol (E₂). Currently there are only few studies which show that the Gly-Val-Ala-Pro-Gly (VGVAPG) peptide may affect the metabolism of astrocytes. Therefore, due to the role of neurosteroids, it is necessary to determine whether VGVAPG affects the level of E₂, P₄, and T in astrocytes. Primary mouse astrocytes were maintained in DMEM/F12 without phenol red, and supplemented with 10% charcoal/dextran-treated fetal bovine serum. Cells were exposed to 10 nM and 1 µM VGVAPG peptide and co-treated with cSrc kinase inhibitor I. After cell stimulation, we measured the Ki67 protein level and the production and secretion of P₄, T, and E₂. Our report presents the novel finding that the VGVAPG peptide affects the production and secretion of neurosteroids in astrocytes in vitro. The VGVAPG peptide increases the production of P₄; however, at the same time, it decreases the secretion of P₄ by astrocytes. On the other hand, it stimulates the production and secretion of T. Interestingly, the production of E₂ did not change in any studied time interval. The expression of Ki67 protein increased after 48 h of exposition to the VGVAPG peptide. The cSrc kinase inhibitor I prevented most of the effects of VGVAPG peptide. Therefore, we postulate that T and cSrc kinase may be responsible for increasing astrocyte proliferation.

Elastin-derived peptide VGVAPG affects the proliferation of mouse cortical astrocytes with the involvement of aryl hydrocarbon receptor (Ahr), peroxisome proliferator-activated receptor gamma (Pparγ), and elastin-binding protein (EBP)

During aging and ischemic and hemorrhagic stroke, elastin molecules are degraded and elastin-derived peptides are released into the brain microenvironment. Val-Gly-Val-Ala-Pro-Gly (VGVAPG) is a repeating hexapeptide in the elastin molecule. It is well documented that the peptide sequence binds with high affinity to elastin-binding protein (EBP) located on the cell surface, thereby transducing a molecular signal into the cell. The aim of our study was to investigate whether EBP, aryl hydrocarbon receptor (Ahr), and peroxisome proliferator-activated receptor gamma (Pparγ) are involved in VGVAPG-stimulated proliferation. Primary astrocytes were maintained in DMEM/F12 medium without phenol red, supplemented with 10 or 1% charcoal/dextran-treated fetal bovine serum (FBS). The cells were exposed to increasing concentrations of VGVAPG peptide, and resazurin reduction was measured. In addition, Glb1, Pparγ, and Ahr genes were silenced. After 48 h of exposure to 10 nM and 1 µM of VGVAPG peptide, the level of estradiol (E₂) and the expression of Ki67 and S100B proteins were measured. The results showed that at a wide range of concentrations, VGVAPG peptide increased the metabolism of astrocytes depending on the concentration of FBS. After silencing of Glb1, Pparγ, and Ahr genes, VGVAPG peptide did not affect the cell metabolism which suggests the involvement of all the mentioned receptors in its mechanism of action. Interestingly, in the low-FBS medium, the silencing of Glb1 gene did not result in complete inhibition of VGVAPG-stimulated proliferation. On the other hand, in the medium with 10% FBS VGVAPG increased Ki67 expression after Pparγ silencing, whereas in the medium with 1% FBS VGVAPG decreased Ki67 expression. Following the application of Ahr siRNA, VGVAPG peptide decreased the production of E₂ and increased the expression of Ki67 and S100B proteins.

Aggravation of Cerebral Ischemia/Reperfusion Injury by Peroxisome Proliferator-Activated Receptor-Gamma Deficiency via Endoplasmic Reticulum Stress

BACKGROUND Ischemic stroke is a dominant contributor to disability and mortality worldwide and is recognized as an important health concern. As a transcription factor triggered via stress, peroxisome proliferator-activated receptor-gamma (PPAR-γ) has a crucial impact on differentiation, cell death, and cell growth. However, the role of PPAR-γ and its precise mechanism in cerebral ischemia injury (CII) remain unclear. MATERIAL AND METHODS The male C57Bl/6 mice (12 weeks old, n=52) were subjected to middle cerebral artery occlusion (MCAO). Infarct volume was evaluated by 2, 3, 5-Triphenyltetrazolium chloride staining. Cell apoptosis was measured by terminal dUTP nick-end labeling (TUNEL) staining. The expression of apoptotic-related protein was examined by Western blotting. Neuron2A cells were transfected with PPAR-γ-specific siRNA and then were subjected to oxygen-glucose exhaustion and reoxygenation. RESULTS It was observed that PPAR-γ-deficient mice displayed extended infarct trigon in the MCAO stroke model. Neuronal deficiency was more severe in PPAR-γ-deficient models. Additionally, expression of cell death-promoting Bcl-2 associated X and active caspase-3 was reinforced, while that of cell death-counteracting Bcl-2 was repressed in PPAR-γ-deficient mice. This was characterized by reinforced endoplasmic reticulum (ER) stress reactions in in vivo brain specimens as well as in vitro neurons in ischemia/reperfusion (I/R) injury. CONCLUSIONS This research proved that PPAR-γ protected the brain from cerebral I/R injury by repressing ER stress and indicated that PPAR-γ is a potential target in the treatment of ischemia.

The role of elastin-derived peptides in human physiology and diseases

Once considered as inert, the extracellular matrix recently revealed to be biologically active. Elastin is one of the most important components of the extracellular matrix. Many vital organs including arteries, lungs and skin contain high amounts of elastin to assure their correct function. Physiologically, the organism contains a determined quantity of elastin from the early development which may remain physiologically constant due to its very long half-life and very low turnover. Taking into consideration the continuously ongoing challenges during life, there is a physiological degradation of elastin into elastin-derived peptides which is accentuated in several disease states such as obstructive pulmonary diseases, atherosclerosis and aortic aneurysm. These elastin-derived peptides have been shown to have various biological effects mediated through their interaction with their cognate receptor called elastin receptor complex eliciting several signal transduction pathways. In this review, we will describe the production and the biological effects of elastin-derived peptides in physiology and pathology.

Antiproliferative Effect of Elastin-Derived Peptide VGVAPG on SH-SY5Y Neuroblastoma Cells

Throughout the lifetime of humans, the amount of stem cells and the rate of cell proliferation continue to decrease. Reactive oxygen species (ROS) are one among the many factors that promote stem cell aging. Both a decrease in the level of stem cells and increase in ROS production can lead to the development of different neurodegenerative diseases. This study was conducted to determine how the VGVAPG peptide, liberated from elastin during the aging process and under pathological conditions, affects ROS production and activities of antioxidant enzymes in undifferentiated, proliferating SH-SY5Y cells. SH-SY5Y cells were maintained in Dulbecco's modified Eagle's medium/nutrient mixture F-12 supplemented with 10% heat-inactivated fetal bovine serum (FBS). After treating the SH-SY5Y cells with VGVAPG peptide, we measured ROS production; cell metabolism, proliferation, and expression; and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). We demonstrated that the VGVAPG peptide increases GPx expression and activity, whereas it decreases CAT expression in SH-SY5Y cells. Silencing of the GLB1 gene prevents changes in GPx activity. Despite the fact that the VGVAPG peptide increases GPx expression, it increases the ROS level. Moreover, the VGVAPG peptide decreases SH-SY5Y proliferation, which is prevented by the ROS scavenger N-acetyl-L-cysteine. Our data suggest that ROS production and decreased proliferation of SH-SY5Y cells are the results of excitotoxicity meditated through close unrecognized molecular pathways. More research is needed to elucidate the unknown mechanism of action of VGVAPG peptide in the nervous system.

The VGVAPG Peptide Regulates the Production of Nitric Oxide Synthases and Reactive Oxygen Species in Mouse Astrocyte Cells In Vitro

The products of elastin degradation, namely elastin-derived peptides (EDPs), are detectable in the cerebrospinal fluid of healthy individuals and in patients after ischemic stroke, and their number increases with age. Depending on their concentrations, both nitric oxide (NO) and reactive oxygen species (ROS) take part either in myocardial ischemia reperfusion injury or in neurovascular protection after ischemic stroke. The aim of our study was to determine the impact of VGVAPG peptide on ROS and NO production and expression of endothelial nitric oxide synthase (eNos), inducible nitric oxide synthase (iNos) and neuronal nitric oxide synthase (nNos) in mouse cortical astrocytes in vitro. Primary astrocytes were maintained in DMEM/F12 without phenol red supplemented with 10% fetal bovine serum. The cells were exposed to rising VGVAPG peptide concentrations, and ROS and NO production was measured. After 6 h (for mRNA) and 24 (for the protein) of exposure to 10 nM and 1 µM of the peptide, expression of nNos, iNos and eNos was measured. Moreover, the Glb1 siRNA gene knockdown method and Pioglitazone, a peroxisome proliferator-activated receptor gamma (Pparγ) agonist, were applied. Our study shows that the VGVAPG peptide decreased eNos, iNos and nNos mRNA and protein expression in mouse astrocytes in vitro. The VGVAPG peptide also decreased NO production while increasing ROS production in the cells. Furthermore, silencing of the Glb1 gene reversed all effects caused by the VGVAPG peptide. However, due to the lack of sufficient data explaining the molecular mechanism of action of the VGVAPG peptide in the nervous system, more studies in this area are necessary.