Transforming growth factor-β/Smad - signalling pathway and conjunctival remodelling in vernal keratoconjunctivitis

Proteomic analysis reveals key differences in pro-stromal corneal tissue between highly myopic males and females

Background and purpose

Nowadays, myopia has become a highly prevalent disease globally, especially in East Asia. Epidemiological studies have found that there may be sex differences in the occurrence and progression of myopia, with females having a higher incidence of myopia and higher risk of myopia progression. The purpose of this study was to explore the sex differences in myopic cornea using corneal stroma removed by small incision lenticule extraction (SMILE) surgery.

Methods

The corneal stroma of females with high myopia (FH) and males with high myopia (MH) were subjected to proteomic assays. Proteomic-related data were statistically analyzed using software such as MaxQuan, KAAS, Proteome Discovery, etc. The total number of proteins in the cornea and the proteins specifically expressed in the two groups were counted, and the differentially expressed proteins in the two groups were identified by expression fold change >2 and p-value <0.05, and volcano plots were constructed, and functional enrichment analysis, subcellular organelle analysis, and molecular interaction were implemented.

Results

Ten samples from each group were analyzed. Twenty-seven proteins were down-regulated and 27 proteins were up-regulated in the FH group, of which 23 proteins were up-regulated in the range of 2-10-fold and 4 proteins were up-regulated in the range of >10-fold. Comparative proteomic analysis of the cornea of male and female patients with high myopia revealed that the expression of corneal extracellular matrix and collagen I, III, V, and VIII-associated proteins were increased in the cornea of female patients, and the transforming growth factor-β (TGF-β)/Smad pathway was an important pathway obtained by functional analysis.

Conclusion

Comparative proteomic analysis of cornea from male and female patients with high myopia revealed increased expression of proteins related to extracellular matrix and collagen I, III, V, and VIII in female patients, and the TGF-β/Smad pathway was an important pathway obtained from the functional analysis, suggesting that extracellular matrix remodeling and collagen fiber synthesis may be more active in the cornea of female patients.

Evaluation of Autophagy in Conjunctival Fibroblasts

Vernal keratoconjunctivitis (VKC) is a serious eye allergy characterized by poorly understood pathogenic mechanisms and a lack of effective treatments. Autophagy, a process involved in both triggering and suppressing immune and inflammatory responses, plays a role in VKC's pathophysiology. Understanding autophagy's involvement in VKC could lead to new treatment possibilities, such as utilizing specific topical substances to induce or inhibit autophagy and prevent severe complications of this eye condition. In our current protocol, we present a robust methodology established in our laboratory for studying autophagy in primary conjunctival fibroblasts. We assess autophagy through techniques like immunocytochemistry, immunoblotting, and qPCR.

Cellular senescence and ophthalmic diseases: narrative review

PURPOSE

Cellular senescence is a state of permanent growth arrest whereby a cell reaches its replicative limit. However, senescence can also be triggered prematurely in certain stressors including radiation, oxidative stress, and chemotherapy. This stress-induced senescence has been studied in the context of promoting inflammation, tumor development, and several chronic degenerative diseases of aging. Emerging research has elucidated the role of senescence in various ocular diseases.

METHODS

The literature search was performed using PubMed with using the query (senescence OR aging) AND (eye disease OR ocular disease OR ophthalmic disease OR cornea OR glaucoma OR cataract OR retina) on October 20th, 2022. No time restriction was proposed. Articles were excluded if they were not referenced in English.

RESULTS

Overall, 51 articles regarding senescence and ocular diseases were found and summarized in this study. Several signaling pathways have been implicated in the development of senescence. Currently, senescence has been linked to various corneal and retinal pathologies, as well as cataract and glaucoma. Given the number of pathologies, senolytics, which are small molecules with the ability to selective targeting of senescent cells, can be used as therapeutic or prophylactic agents.

CONCLUSIONS

Senescence has been shown to underlie the pathogenesis of numerous ocular diseases. The overall literature on senescence and ocular disease is growing rapidly. There is an ongoing debate whether or not cellular senescence detected in experiments contributes in a significant way to diseases. Research on understanding the mechanism of senescence from ocular cells and tissues is just beginning. Multiple animal models are required to test potential senolytics. Currently, no studies exist to date which have demonstrated the benefits of senolytic therapies in human studies.

Impact of Exposomes on Ocular Surface Diseases

Ocular surface diseases (OSDs) are significant causes of ocular morbidity, and are often associated with chronic inflammation, redness, irritation, discomfort, and pain. In severe OSDs, loss of vision can result from ocular surface failure, characterised by limbal stem cell deficiencies, corneal vascularisation, corneal opacification, and surface keratinisation. External and internal exposomes are measures of environmental factors that individuals are exposed to, and have been increasingly studied for their impact on ocular surface diseases. External exposomes consist of external environmental factors such as dust, pollution, and stress; internal exposomes consist of the surface microbiome, gut microflora, and oxidative stress. Concerning internal exposomes, alterations in the commensal ocular surface microbiome of patients with OSDs are increasingly reported due to advancements in metagenomics using next-generation sequencing. Changes in the microbiome may be a consequence of the underlying disease processes or may have a role in the pathogenesis of OSDs. Understanding the changes in the ocular surface microbiome and the impact of various other exposomes may also help to establish the causative factors underlying ocular surface inflammation and scarring, the hallmarks of OSDs. This review provides a summary of the current evidence on exposomes in various OSDs.

Tissue remodeling in adult vernal keratoconjunctivitis

Our aim is to describe local tissue remodeling in a cohort of adult VKC patients. Male patients diagnosed with active VKC were enrolled in an open pilot study into two groups according disease onset: childhood classic VKC and adult VKC. Visual acuity and ocular surface clinical examination focusing on chronic inflammatory sequelae and impression cytology were performed in all enrolled subjects. Conjunctival imprints were processed for molecular, biochemical and immunofluorescent analysis for tissue remodeling (TGFβ1,2,3 and αSMA) and epigenetic (DNMT3a, Keap1; Nrf2) markers as well as androgen receptors were investigated and compared between groups. Clinical assessment showed increased conjunctival scarring in adult VKC compared to classic VKC. Immunoreactivity for αSMA and expression of TGFβ were higher in adult VKC group. Significantly higher levels of TGFβ3 (3.44 ± 1.66; p < 0.05) were detected in adult VKC compared to childhood VKC, associated with an increasing trend of TGFβ1 (1.58 ± 0.25) and TGFβ2 (1.65 ± 0.20) isoforms levels. Molecular analysis showed a relative increase in tissue remodeling/fibrogenic transcripts (TGFβ isoforms and αSMA) associated to a significant increase of selective epigenetic targets (DNMT3, Nrf2 and keap1) in adult VKC phenotype. Increased local conjunctival androgen receptors was detected in patients with adult variants compared to classic childhood VKC and healthy subjects. Finally, a direct correlation between TGFβ and androgen receptor expression was also detected. A pro-fibrotic clinical and biomolecular trait was unveiled in adult variant of VKC, which causes ocular surface disease and visual impairment.

The multifaceted aspects of ocular allergies: Phenotypes and endotypes

Like the lung, skin, and nose, the external eye is a common target of allergic inflammation. Ocular allergy (OA) represents a collection of underestimated diseases of the eye observed in children and adults. The ocular manifestations are the expression of multifactorial immune mechanisms that generally have a good prognosis, but for a few patients, long term inflammation may remarkably reduce the visual function. Evidence suggests that other co-participant systems, including epigenetic, genetic, environmental, individual factors, sex hormones, and the central and autonomic nervous systems may influence the ocular response from distant sites. This is consistent with the concept that the eye is an organ fully integrated with the rest of the body and that the therapeutic approach should be holistic, dynamic, and personalized. For instance, androgens and estrogens binding to receptors on the ocular surface and the continuous cross-talking of neuromediators and growth factors with immune cells act to maintain the ocular surface homeostasis in response to environmental challenges. The immune system links and regulates the response of the ocular surface. Complex and incompletely understood mechanisms influence the innate and adaptive immune responses and generate different OA phenotypes and endotypes discussed in the present review.

Epithelial barrier dysfunction in ocular allergy

The epithelial barrier is the first line of defense that forms a protective barrier against pathogens, pollutants, and allergens. Epithelial barrier dysfunction has been recently implicated in the development of allergic diseases such as asthma, atopic dermatitis, food allergy, and rhinitis. However, there is limited knowledge on epithelial barrier dysfunction in ocular allergy (OA). Since the ocular surface is directly exposed to the environment, it is important to understand the role of ocular epithelia and their dysfunction in OA. Impaired epithelial barrier enhances allergen uptake, which lead to activation of immune responses and development of chronic inflammation as seen in allergies. Abnormal expression of tight junction proteins that helps to maintain epithelial integrity has been reported in OA but sufficient data not available in chronic atopic (AKC) and vernal keratoconjunctivitis (VKC), the pathophysiology of which is not just complex, but also the current treatments are not completely effective. This review provides an overview of studies, which indicates the role of barrier dysfunction in OA, and highlights how ocular barrier dysfunction possibly contributes to the disease pathogenesis. The review also explores the potential of ocular epithelial barrier repair strategies as preventive and therapeutic approach.

miR-200-3p suppresses cell proliferation and reduces apoptosis in diabetic retinopathy via blocking the TGF-β2/Smad pathway

Increasing evidence has shown that microRNAs (miRNAs) play an important role in the pathogenesis of diabetic retinopathy (DR). However, the role and mechanism of miRNA in regulating high glucose (HG)-induced ARPE-19 cell injury are still not well understood. The present study aimed to investigate the effects of miR-200a-3p on DR progression and reveal the underlying mechanisms of their effects. In the present study, we observed that miR-200a-3p was significantly decreased, while transforming growth factor-β2 (TGF-β2) expression was up-regulated in ARPE-19 cells treated with HG and retina tissues of DR rats. Subsequently, overexpression of miR-200a-3p significantly promoted cell proliferation, reduced apoptosis, as well as inhibited the levels of inflammatory cytokines secreted, matrix metalloprotease 2/9 (MMP2/9), and vascular endothelial growth factor (VEGF) in HG-injured ARPE-19 cells. Moreover, miR-200a-3p was proved to target TGF-β2 mRNA by binding to its 3′ untranslated region (3′UTR) using a luciferase reporter assay. Mechanistically, overexpression of miR-200a-3p reduced HG-induced ARPE-19 cell injury and reduced inflammatory cytokines secreted, as well as down-regulated the expression of VEGF via inactivation of the TGF-β2/Smad pathway in vitro. In vivo experiments, up-regulation of miR-200a-3p ameliorated retinal neovascularization and inflammation of DR rats. In conclusion, our findings demonstrated that miR-200a-3p-elevated prevented DR progression by blocking the TGF-β2/Smad pathway, providing a new therapeutic biomarker for DR treatment in the clinic.

Eye drop emulsion containing 0.1% cyclosporin (1 mg/mL) for the treatment of severe vernal keratoconjunctivitis: an evidence-based review and place in therapy

Vernal keratoconjunctivitis (VKC) is a rare, recurrent and multifactorial ocular disease, which typically flares up during spring and affects especially male children and adolescents. This condition does not usually respond to common treatments with antihistamines or mast cells stabilizers, whereas corticosteroids have effective results. Corticosteroids need to be carefully administered, to avoid adverse effects, mainly the secondary development of glaucoma, cataracts, or infections. Immunosuppressive agents, such as cyclosporin (CyA) or tacrolimus are, therefore, frequently employed in VKC patients. Only the 0.1% CyA (1 mg/mL) concentration has an approved and specific clinical indication for the treatment of VKC and this drug was given the denomination of orphan drug by the European Commission (EU/3/06/360) in 2006. So far, few studies have been conducted to evaluate the efficacy and the side effects of topical 0.1% CyA. Different topical CyA concentrations, ranging from 0.05% to 2%, and various types of formulation are available at the moment. In the future, 0.1% CyA will presumably take an important part in the management of VKC. The present review focuses on eye drops containing 0.1% CyA; however, more studies will be needed to define its long-term efficacy in the natural course of this severe ocular disease.

The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets

Histamine and its receptors (H1R–H4R) play a crucial and significant role in the development of various allergic diseases. Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body. H1R are expressed in many cells, including mast cells, and are involved in Type 1 hypersensitivity reactions. H2R are involved in Th1 lymphocyte cytokine production. H3R are mainly involved in blood–brain barrier function. H4R are highly expressed on mast cells where their stimulation exacerbates histamine and cytokine generation. Both H1R and H4R have important roles in the progression and modulation of histamine-mediated allergic diseases. Antihistamines that target H1R alone are not entirely effective in the treatment of acute pruritus, atopic dermatitis, allergic asthma, and other allergic diseases. However, antagonists that target H4R have shown promising effects in preclinical and clinical studies in the treatment of several allergic diseases. In the present review, we examine the accumulating evidence suggesting novel therapeutic approaches that explore both H1R and H4R as therapeutic targets for histamine-mediated allergic diseases.

Modulation of Fibroblasts in Conjunctival Wound Healing

Modulating conjunctival wound healing has the potential to improve outcomes after glaucoma filtration surgery and for several ocular disorders, including ocular cicatrial pemphigoid, vernal keratoconjunctivitis, and pterygium. Although anti-inflammatories and antimetabolites have been used with success, these nonspecific agents are not without their complications. The search for novel and more targeted means to control conjunctival fibrosis without such limitations has brought much attention to the regulation of fibroblast proliferation, differentiation, extracellular matrix production, and apoptosis. This review provides an update on where we stand with current antifibrotic agents and outlines the strategies that novel agents use, as they evolve from the bench to the bedside.

Chaperone patterns in vernal keratoconjunctivitis are distinctive of cell and Hsp type and are modified by inflammatory stimuli

BACKGROUND

Vernal keratoconjunctivitis (VKC) is a severe ocular allergy with pathogenic mechanism poorly understood and no efficacious treatment. The aims of the study were to determine quantities and distribution of Hsp chaperones in the conjunctiva of VKC patients and assess their levels in conjunctival epithelial and fibroblast cultures exposed to inflammatory stimuli.

METHODS

Hsp10, Hsp27, Hsp40, Hsp60, Hsp70, Hsp90, Hsp105, and Hsp110 were determined in conjunctiva biopsies from nine patients and nine healthy age-matched normal subjects, using immunomorphology and qPCR. Conjunctival epithelial cells and fibroblasts were cultured and stimulated with IL-1β, histamine, IL-4, TNF-α, or UV-B irradiation, and changes in Hsp levels were determined by Western blotting.

RESULTS

Hsp27, Hsp40, Hsp70, and Hsp90 levels increased in the patients' conjunctiva, whereas Hsp10, Hsp60, Hsp100, and Hsp105 did not. Double immunofluorescence demonstrated colocalization of Hsp27, Hsp40, Hsp70, and Hsp90 with CD68 and tryptase. Testing of cultured conjunctival cells revealed an increase in the levels of Hsp27 in fibroblasts stimulated with IL-4; Hsp40 in epithelial cells stimulated with IL-4 and TNF-α and in fibroblasts stimulated with IL-4, TNF-α, and IL-1β; Hsp70 in epithelial cells stimulated with histamine and IL-4; and Hsp90 in fibroblasts stimulated with IL-1β, TNF-α, and IL-4. UV-B did not induce changes.

CONCLUSIONS

VKC conjunctiva displays distinctive quantitative patterns of Hsps as compared with healthy controls. Cultured conjunctival cells respond to cytokines and inflammatory stimuli with changes in the Hsps quantitative patterns. The data suggest that interaction between the chaperoning and the immune systems drives disease progression.

Inflammatory Cytokine-Mediated Regulation of Thrombospondin-1 and CD36 in Conjunctival Cells

PURPOSE

Increased expression of transforming growth factor-β2 (TGF-β2) is reported in the conjunctiva of dry eye patients with no increase of anti-inflammatory activity of TGF-β2. Our aim was to compare the expression of molecules involved in TGF-β2 activation, thrombospondin-1 (TSP-1) and CD36, during murine and human conjunctival inflammation.

METHODS

Human conjunctival tissue from cadaveric donors, human conjunctival epithelial primary cells and fibroblasts, and murine conjunctivas were immunostained for TSP-1, CD36, or TGF-β2. Inflamed conjunctival tissues were obtained from C57BL/6 wild-type (WT) mice induced to develop experimental dry eye (EDE) with 10 days of desiccating conditions and scopolamine injections and TSP-1-deficient (TSP1(-/-)) mice, which spontaneously develop Sjögren's syndrome-associated conjunctival inflammation with age. Immunostaining intensities were compared using ImageJ software. Cultures of human conjunctival fibroblasts were stimulated with IL-1β and both secreted protein and message levels of TSP-1, CD36, and TGF-β2 were analyzed.

RESULTS

TSP-1 and CD36 were detectable in human and murine conjunctival tissues as well as primary conjunctival epithelial cells and fibroblasts. Increased conjunctival immunostaining of TGF-β2 and reduced CD36 were detected in EDE mice compared with WT mice. Interestingly, increased TGF-β2 and CD36 conjunctival immunostaining was detected in TSP1(-/-) mice. The expression of TSP-1 and CD36 was downregulated in IL-1β-stimulated conjunctival fibroblasts at both the protein and message level, while active TGF-β2 was undetected.

CONCLUSIONS

The absence or reduced expression of either of the molecules involved in TGF-β2 activation supports proinflammatory conditions in the conjunctiva. Changes in TSP-1 and CD36 may serve as potential biomarkers of conjunctival inflammation.

Immunomodulatory cross-talk between conjunctival goblet cells and dendritic cells

Goblet cells are secretory epithelial cells of mucosal tissues that confer protection from environmental agents or pathogens via expression and secretion of soluble mucins. Loss of these cells is associated with several chronic inflammatory disorders of the mucosa. Although demonstrated to transfer antigens from the luminal surface to stromal cells in the intestinal mucosa, it is not known if goblet cells contribute to the regulation of an immune response. In this study we report that similar to intestinal and respiratory mucosal epithelia, mouse ocular surface epithelia predominantly express the TGF-ß2 isoform. Specifically, we demonstrate the ability of goblet cells to express TGF-ß2 and increase it in response to Toll-Like Receptor 4 mediated stimulus in cultures. Goblet cells not only express TGF-ß2, but are also able to activate it in a thrombospondin-1 (TSP-1) dependent manner via their cell surface receptor CD36. Furthermore, goblet cell derived soluble factors that possibly include TGF-ß2, alter dendritic cell (DC) phenotype to a tolerogenic type by downregulating DC expression of MHC class II and co-stimulatory molecules CD80, CD86 and CD40. Thus our study demonstrates goblet cells as a cellular source of active TGF-ß2 in ocular mucosa and implicates their immunomodulatory function in maintaining mucosal immune homeostasis.

Prevention of bleomycin-induced lung inflammation and fibrosis in mice by naproxen and JNJ7777120 treatment

Pulmonary fibrosis, a progressive and lethal lung disease characterized by inflammation and accumulation of extracellular matrix components, is a major therapeutic challenge for which new therapeutic strategies are warranted. Cyclooxygenase (COX) inhibitors have been previously utilized to reduce inflammation. Histamine H4 receptor (H4R), largely expressed in hematopoietic cells, has been identified as a novel target for inflammatory and immune disorders. The aim of this study was to evaluate the effect of JNJ7777120 (1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine), a selective H4R antagonist, and naproxen, a well known nonsteroidal anti-inflammatory drug, and their combination in a murine model of bleomycin-induced fibrosis. Bleomycin (0.05 IU) was instilled intratracheally to C57BL/6 mice, which were then treated by micro-osmotic pump with vehicle, JNJ7777120 (40 mg/kg b.wt.), naproxen (21 mg/kg b.wt.), or a combination of both. Airway resistance to inflation, an index of lung stiffness, was assessed, and lung specimens were processed for inflammation, oxidative stress, and fibrosis markers. Both drugs alone were able to reduce the airway resistance to inflation induced by bleomycin and the inflammatory response by decreasing COX-2 and myeloperoxidase expression and activity and thiobarbituric acid-reactive substance and 8-hydroxy-2'-deoxyguanosine production. Lung fibrosis was inhibited, as demonstrated by the reduction of tissue levels of transforming growth factor-β, collagen deposition, relative goblet cell number, and smooth muscle layer thickness. Our results demonstrate that both JNJ7777120 and naproxen exert an anti-inflammatory and antifibrotic effect that is increased by their combination, which could be an effective therapeutic strategy in the treatment of pulmonary fibrosis.

High-mobility group box-1 (HMGB-1) and serum soluble receptor for advanced glycation end products (sRAGE) in children affected by vernal keratoconjunctivitis

BACKGROUND

Vernal keratoconjunctivitis (VKC) is a chronic disease affecting conjunctiva even though the immunopathogenetic mechanisms underlying this inflammation are unclear. The aim of our study is to investigate serum levels of HMGB1 and circulating sRAGE in children affected by VKC before and after treatment with cyclosporine A (CsA) eye drops and in a group of healthy children.

METHODS

Twenty-four children affected by VKC aged between 5 and 12 yrs of life were enrolled at the Department of Pediatrics, Division of Allergy and Immunology, 'Sapienza' University of Rome. Twenty-four healthy children without atopy, ocular, and systemic disease, cross-matched for sex and age to patients affected by VKC, represented the controls. All children affected by VKC were treated with CsA 1% eye drops for 4 wks, and blood samples were collected before and 2 wks after the end of treatment while the controls underwent to a single blood sample at the time of enrollment.

RESULTS

Serum basal levels of HMGB1 and sRAGE were higher in children with VKC when compared with controls while, in patients affected by VKC, no difference was detected between atopic and non-atopic, and between ANA-positive and ANA-negative children. A significant reduction in serum HMGB1 and sRAGE levels was detected after the therapy while CsA serum levels were negative.

CONCLUSIONS

Our study gives a support to the definition of VKC as a systemic inflammation in which HMGB1 and its soluble receptors could play a role.

Molecular immunology of allergic conjunctivitis

PURPOSE OF REVIEW

Successful treatment of allergic eye disease depends on understanding the pathophysiology of ocular allergy. Thus, in this review, recent experimental and clinical research that has provided significant information about the immunopathology of allergic eye disease will be discussed.

RECENT FINDINGS

Recently, role of various cells, cytokines and chemokines has been scrutinized in the immunopathogenesis of ocular allergy. In this respect, current research highlights contribution of special molecules and cells in the development and clinical features of immunoglobulin E (IgE) and T-cell-mediated eye allergies.

SUMMARY

Recent findings in molecular immunology of ocular allergy, which comprise complex inflammatory conditions of the conjunctiva, have enabled us to better understand the pathophysiology of these diseases and have aided in the potential development of new therapeutic agents.

Effect of TGF-β on ocular surface epithelial cells

A role for transforming growth factor (TGF)-β in the pathogenesis of some ocular surface diseases has been proposed. We determined if secretion of TGF-β and expression of TGF-β receptors RI, RII, and RIII by human ocular surface epithelial cells were modified under inflammatory conditions. We also determined how these cells responded to TGF-β. A human corneal epithelial (HCE) cell line and a conjunctival epithelial cell line (IOBA-NHC) were exposed to TGF-β1 and -β2 and to proinflammatory cytokines. TGF-β receptor mRNAs were analyzed by real time reverse transcription polymerase chain reaction (RT-PCR) in both cell lines, and in conjunctival, limbal, and corneal epithelial cells from post-mortem human specimens. Expression of TGF-β receptors and pSMAD2/SMAD2 were determined by Western blot and immunofluorescence assays. Secretion of TGF-β isoforms, cytokine/chemokine, and metalloproteinases (MMPs) were analyzed in cell supernatants by immunobead-based assays. Secretory leukocyte proteinase inhibitor (SLPI) secretion was analyzed by enzyme-linked immunosorbent assay. TGF-β isoform and receptor gene expression was determined by RT-PCR in conjunctival epithelium of dry eye (DE) patients and healthy subjects. Our results showed that TGF-β RI expression was down-regulated with IL-4 exposure, whereas TGF-β RII and TGF-β2 were upregulated by TNF-α in HCE cells. TGF-β RIII receptor expression was upregulated in IOBA-NHC cells by TNF-α and IFN-γ. SMAD2 phosphorylation occurred in HCE and IOBA-NHC cells after TGF-β treatment. TGF-β significantly up- and down-regulated secretion of several cytokines/chemokines by both cell lines and MMP by HCE cells. TGF-β2 and TGF-β3 were upregulated and TGF-β RIII mRNA was down-regulated in DE conjunctival epithelium. These results show that TGF-β plays an important role in directing local inflammatory responses in ocular surface epithelial cells.

Neuroprotective effects of exogenous activin A on oxygen-glucose deprivation in PC12 cells

Ischemic cerebrovascular disease is one of the most common causes of death in the World. Exogenous activin A (ActA) protects neurons against toxicity and plays a central role in regulating the brain's response to injury. In the present study, we investigated the mechanisms involved in the neuroprotective effects of ActA in a model of hypoxic-ischemic brain disease. We found that ActA could effectively increase the survival rate of PC12 cells and relieve oxygen-glucose deprivation (OGD) damage. To clarify the neuroprotective mechanisms of ActA, the effects of ActA on the ActA/Smad pathway and on the up-regulation of inducible nitric oxide synthase (NOS) and superoxide dismutase (SOD) were investigated using OGD in PC12 cells. The results showed that ActA could increase the expression of activin receptor IIA (ActRIIA), Smad3 and Smad4 and that 50 ng/mL and 100 ng/mL of ActA could reduce NO levels and increase SOD activity by 78.9% and 79.9%, respectively. These results suggested that the neuroprotective effects of ActA in ischemia could be related to the activation of the ActA/Smad signaling pathway and to its anti-oxidant activities.