Biology subjects

Duncan, R. L.

Publications and source records attributed to Duncan, R. L..

3 recordsLinked to original sources

bioRxiv2021

Extracellular Matrix Stiffness Alters TRPV4 Regulation in Chondrocytes

During the progression of osteoarthritis (OA), degradation of the extracellular matrix alters the biomechanical properties of cartilage, especially the compressive modulus. The mechanosensitive ion channel transient receptor potential vanilloid 4 (TRPV4) is required for chondrocyte mechanotransduction However, how OA-mediated cartilage degradation influences TRPV4 signaling remains unknown. To determine if ATDC5 cells alter TRPV4-mediated calcium signaling and cell phenotype in response to softer substrates, we created PEGDA-RGDS hydrogels with Youngs moduli that simulated healthy (~350 kPa), OA (~175 kPa) and severe OA (~35 kPa) tissue. We found that softer substrates reduced the influx of calcium through TRPV4 when challenging chondrocytes with hypotonic swelling (HTS). Chondrocyte apoptosis also increased on the OA and severe OA gels due to elevated basal [Ca2+]i, which is attenuated with pharmacological agonism of TRPV4. Pharmacological agonism of TRPV4 rescued the expression of aggrecan and TRPV4 in chondrocytes cultured on OA gels and enhanced the type II collagen (col2) expression in cells on the normal and OA gels. These data suggest that the biomechanical properties of degraded cartilage alter TRPV4-mediated mechanotransduction in chondrocytes. Given that TRPV4 reduced apoptosis and improved the chondrogenic capacity of cells, TRPV4 stimulation could provide a potential therapeutic target in patients with early to moderate OA.

cell biology↗

bioRxiv2021

In Vitro Assessment of Efficacy and Cytotoxicity of Prunus africana Extracts on Prostate Cancer C4-2 Cells

Phenolic compounds are products of secondary plant metabolism known for their biological activity including their antimicrobial, antioxidant, analgesic, stimulant, anti- carcinogenic, and aphrodisiac properties. The main objective of this study was to assess the potency/cytotoxic effects of Prunus africana extracts on prostate cancer cells in vitro. Using different concentrations of P. africana extracts, prostate cancer C4-2 cells, a hormonally insensitive subline of LNCaP cells, were treated in a proliferation assay. A concentration dependent inhibition of cell growth in cells treated with P. africana bark and root extracts was present from days 1 through 3 of incubation, with the methanol extract of the bark showing the strongest effect. Compared to other plant parts, leaf extracts were significantly less cytotoxic at the same concentrations. As C4-2 cells are hormonally insensitive and designed to mimic advanced prostate cancer, crude extracts of P. africana are a possible treatment option, not only for hormone sensitive prostate cancer, but also advanced, hormonally insensitive prostate cancer.

cancer biology↗

bioRxiv2020

Insulin-like Growth Factor-1 Regulates the Mechanosensitivity of Chondrocytes by Modulating TRPV4

Both mechanical and IGF-1 stimulation are required for normal articular cartilage development and maintenance of the extracellular matrix. While much effort has been made to define the signaling pathways associated with these anabolic stimuli, we focused on how these pathways interact to regulate chondrocyte function. The Transient Receptor Potential Vanilloid 4 (TRPV4) channel is central to chondrocyte mechanotransduction and regulation of cartilage homeostasis. However, the mechanism by which TRPV4 is mechanically gated or regulated is not clear. In this study we propose that insulin-like growth factor 1 (IGF-1), which is important in regulating matrix production during mechanical load, modulates TRPV4 channel activity. Our studies indicate that IGF-1 reduces hypotonic-induced TRPV4 currents, and intracellular calcium flux by increasing stress fiber formation and apparent cell stiffness. Disruption of F-actin following IFG-1 treatment results in the return of the intracellular calcium response to hypotonic swelling. Furthermore, we highlight that IGF-1 suppresses TRPV4 mediated calcium flux through the MAP7 binding domain (aa. 798-809), where actin binds to the TRPV4 channel. IGF-1 treatment differentially influences the intracellular calcium flux of HEK 293 cells stably expressing either wild-type or mutant (P799L or G800D) TRPV4 during hypotonic challenge. A key down-stream response to mechanical stimulation of chondrocytes is ATP release. Data here indicate that activation of TRPV4 through hypotonic swelling induces ATP release, but this release is greatly reduced with IGF-1 treatment. Taken together this study indicates that IGF-1 modulates TRPV4 channel response to mechanical stimulation by increasing cell stiffness. As chondrocyte response to mechanical stimulation is greatly altered during OA progression, IGF-1 presents as a promising candidate for prevention and treatment of articular cartilage damage.

cell biology↗