Thymosin beta 4 attenuates PrP(106-126)-induced human brain endothelial cells dysfunction

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

A Novel Combination Therapy Tβ4/VIP Protects against Hyperglycemia-Induced Changes in Human Corneal Epithelial Cells

Despite the prevalence of diabetic retinopathy, the majority of adult diabetic patients develop visually debilitating corneal complications, including impaired wound healing. Unfortunately, there is limited treatment for diabetes-induced corneal damage. The current project investigates a novel, peptide-based combination therapy, thymosin beta-4 and vasoactive intestinal peptide (Tβ4/VIP), against high-glucose-induced damage to the corneal epithelium. Electric cell-substrate impedance sensing (ECIS) was used for real-time monitoring of barrier function and wound healing of human corneal epithelial cells maintained in either normal glucose (5 mM) or high glucose (25 mM) ± Tβ4 (0.1%) and VIP (5 nM). Barrier integrity was assessed by resistance, impedance, and capacitance measurements. For the wound healing assay, cell migration was also monitored. Corneal epithelial tight junction proteins (ZO-1, ZO-2, occludin, and claudin-1) were assessed to confirm our findings. Barrier integrity and wound healing were significantly impaired under high-glucose conditions. However, barrier function and cell migration significantly improved with Tβ4/VIP treatment. These findings were supported by high-glucose-induced downregulation of tight junction proteins that were effectively maintained similar to normal levels when treated with Tβ4/VIP. These results strongly support the premise that Tβ4 and VIP work synergistically to protect corneal epithelial cells against hyperglycemia-induced damage. In addition, this work highlights the potential for significant translational impact regarding the treatment of diabetic patients and associated complications of the cornea.

Antioxioxidant and antiapoptotic effects of Thymosin β4 in Aβ-induced SH-SY5Y cells via the 5-HTR1A/ERK axis

Alzheimer's disease (AD) is a common amnestic cognitive impairment characterised by β-amyloid (Aβ) plaques deposit in the brain of the elderly. AD is a yet incurable disease due to its unknown exact pathogenesis and unavailability of effective remedies in clinical application. Thymosin β4 (Tβ4) is a housekeeping protein that plays important role in cell proliferation, migration and differentiation. It has the ability to protect and repair neurons however it is still unclear involvement in AD. Therefore, the aim of this study is to elucidate the role and mechanism of Tβ4 in mediating the improvement of AD. AD-like cell model was constructed in neuroblastoma cell line SH-SY5Y treated with Aβ. Overexpression of Tβ4 were done using lentivirus infection and downregulation through siRNA transfection. We performed western blot and flow cytometry to study the apoptosis and standard kits to measure the oxidative stress-associated biomarkers. There is significant increased in viability and decreased apoptosis in Tβ4 overexpression group compared to control. Furthermore, overexpression of Tβ4 suppressed the expression of pro-apoptotic markers such as Caspase-3, Caspase-8, and Bax meanwhile upregulated the expression of anti-apoptotic gene Bcl-2. Tβ4 alleviated oxidative damage by reducing MDA, LDH and ROS and increasing SOD and GSH-PX in Aβ-treated SH-SY5Y cells. We found that Tβ4 inhibit ERK/p38 MAPK pathway and intensify the expression of 5-HTR1A. Additionally, we showed that upregulation of 5-HTR1A dampened the Tβ4 to activate ERK signalling. In conclusion, our study revealed the neuroprotective role of Tβ4 in AD which may open up new therapeutic applications in AD treatment.

Thymosin Beta 4 Protects Hippocampal Neuronal Cells against PrP (106-126) via Neurotrophic Factor Signaling

Prion protein peptide (PrP) has demonstrated neurotoxicity in brain cells, resulting in the progression of prion diseases with spongiform degenerative, amyloidogenic, and aggregative properties. Thymosin beta 4 (Tβ₄) plays a role in the nervous system and may be related to motility, axonal enlargement, differentiation, neurite outgrowth, and proliferation. However, no studies about the effects of Tβ₄ on prion disease have been performed yet. In the present study, we investigated the protective effect of Tβ₄ against synthetic PrP (106-126) and considered possible mechanisms. Hippocampal neuronal HT22 cells were treated with Tβ₄ and PrP (106-126) for 24 h. Tβ₄ significantly reversed cell viability and reactive oxidative species (ROS) affected by PrP (106-126). Apoptotic proteins induced by PrP (106-126) were reduced by Tβ₄. Interestingly, a balance of neurotrophic factors (nerve growth factor and brain-derived neurotrophic factor) and receptors (nerve growth factor receptor p75, tropomyosin related kinase A and B) were competitively maintained by Tβ₄ through receptors reacting to PrP (106-126). Our results demonstrate that Tβ₄ protects neuronal cells against PrP (106-126) neurotoxicity via the interaction of neurotrophic factors/receptors.

Cytoskeleton Elements Contribute to Prion Peptide-Induced Endothelial Barrier Breakdown in a Blood–Brain Barrier In Vitro System

The mechanisms involved in the interaction of PrP 106-126, a peptide corresponding to the prion protein amyloidogenic region, with the blood–brain barrier (BBB) were studied. PrP 106-126 treatment that was previously shown to impair BBB function, reduced cAMP levels in cultured brain endothelial cells, increased nitric oxide (NO) levels, and changed the activation mode of the small GTPases Rac1 (inactivation) and RhoA (activation). The latter are well established regulators of endothelial barrier properties that act via cytoskeletal elements. Indeed, liquid chromatography-mass spectrometry (LC-MS)-based proteomic profiling study revealed extensive changes in expression of cytoskeleton-related proteins. These results shed light on the nature of the interaction between the prion peptide PrP 106-126 and the BBB and emphasize the importance of the cytoskeleton in endothelium response to prion- induced stress.

Tβ4 ameliorates oxidative damage and apoptosis through ERK/MAPK and 5-HT1A signaling pathway in Aβ insulted SH-SY5Y cells

AIMS

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder seriously endangering the physical and mental health of the elderly, while no effective treatments and drugs in clinical practice are available. Thymosin β4 (Tβ4) is a multifunctional polypeptide involved in many physiological and pathological processes including AD. This study aims to understand the function and molecular mechanism of Tβ4 in the development of AD.

MAIN METHODS

Neuroblastoma cell line SH-SY5Y was treated with β-amyloid (Aβ) to induce AD-like pathological changes, which serves as Alzheimer's disease model. Tβ4 was overexpressed in SH-SY5Y cells by lentivirus infection, and downregulated by siRNA transfection. Apoptosis of transfected SH-SY5Y cells after Aβ-treatment was examined by western blot and flow cytometry. Apoptotic proteins and Tβ4-related signaling pathways were also investigated by western blot.

KEY FINDINGS

We found that Tβ4 overexpression increased viability and suppressed apoptosis of Aβ-treated SH-SY5Y cells. Tβ4 ameliorated oxidative damage and suppressed reactive oxygen species production in Aβ-treated SH-SY5Y cells. Consistently, Tβ4 overexpression down-regulated the expression levels of pro-apoptotic markers such as Caspase-3, Caspase-8, and Bax, while up-regulated the expression level of anti-apoptotic gene Bcl-2 in Aβ-stimulated SH-SY5Y cells. Mechanistically, we demonstrated that Tβ4 dampened ERK/p38 MAPK signaling and enhanced 5-HTR1A expression in Aβ-treated SH-SY5Y cells. Moreover, we revealed that Tβ4 inhibited the activation of ERK pathway through up-regulating 5-HTR1A in Aβ-treated SH-SY5Y cells.

SIGNIFICANCE

Taken together, our findings provide evidences to support the neuroprotective role of Tβ4 and might open up new therapeutic applications of Tβ4 in AD treatment.

Sulfasalazine maintains blood-brain barrier integrity and relieves lipopolysaccharide-induced inflammation in hCMEC/D3 cells

Sulfasalazine is a recognized therapy for inflammatory bowel disease and is of paramount importance for maintaining intestinal barrier homeostasis. However, its effects on blood-brain barrier (BBB) function and inflammation have not yet been explored. We sought to examine whether sulfasalazine has anti-inflammatory and antiapoptotic effects on the BBB. hCMEC/D3 cells are a well-established BBB in vitro model, were treated with 1 μg/mL Escherichia coli O111:B4 lipopolysaccharide for 12 h. The cell counting kit-8 assay was used to assess cell viability. The cells were also treated with gradient concentrations of sulfasalazine for 12 h. The levels of apoptosis-related proteins and inflammatory factors (IL-1χ and TNF-α IL-6) were measured by western blotting. ZO-1 and F-actin expression was measured by immunofluorescence staining. This study confirmed that 5 mM sulfasalazine improved the maintenance of BBB integrity and relieved lipopolysaccharide-induced inflammatory apoptosis and showed that sulfasalazine might be an effective treatment for BBB disruption.

Prion Protein at the Leading Edge: Its Role in Cell Motility

Cell motility is a central process involved in fundamental biological phenomena during embryonic development, wound healing, immune surveillance, and cancer spreading. Cell movement is complex and dynamic and requires the coordinated activity of cytoskeletal, membrane, adhesion and extracellular proteins. Cellular prion protein (PrPC) has been implicated in distinct aspects of cell motility, including axonal growth, transendothelial migration, epithelial-mesenchymal transition, formation of lamellipodia, and tumor migration and invasion. The preferential location of PrPC on cell membrane favors its function as a pivotal molecule in cell motile phenotype, being able to serve as a scaffold protein for extracellular matrix proteins, cell surface receptors, and cytoskeletal multiprotein complexes to modulate their activities in cellular movement. Evidence points to PrPC mediating interactions of multiple key elements of cell motility at the intra- and extracellular levels, such as integrins and matrix proteins, also regulating cell adhesion molecule stability and cell adhesion cytoskeleton dynamics. Understanding the molecular mechanisms that govern cell motility is critical for tissue homeostasis, since uncontrolled cell movement results in pathological conditions such as developmental diseases and tumor dissemination. In this review, we discuss the relevant contribution of PrPC in several aspects of cell motility, unveiling new insights into both PrPC function and mechanism in a multifaceted manner either in physiological or pathological contexts.