Biology subjects

Farnsworth, N. L.

Publications and source records attributed to Farnsworth, N. L..

6 recordsLinked to original sources

bioRxiv2026

Laminin-511 protects pancreatic β-cells from cytokine-induced death through integrin-mediated pro-survival signaling and modulation of protein kinase C δ

During the progression of type 1 diabetes (T1D), the extracellular matrix (ECM) surrounding pancreatic islets is degraded concurrent with infiltration of autoreactive immune cells and {beta}-cell death. Among the lost ECM proteins, laminin-511 is known to be essential for islet survival under healthy and T1D associated conditions, including high levels of pro-inflammatory cytokines. However, the key {beta}-cell signaling pathways regulated by laminin and the contributions to T1D pathogenesis when these cues are lost are poorly understood. This study utilizes a biomimetic reverse thermal gel (RTG) with laminin-511 to determine if laminin protects {beta}-cells against cytokine-induced death and elucidate the signaling pathways involved. MIN6 cells, C57Bl/6 mouse islets and human islets were encapsulated in RTG scaffolds with laminin-511 and treated with a cytokine cocktail for 24 hours. Islet viability and the activities of several pro- and anti-apoptotic proteins were studied. Laminin-511 was shown to protect islets against cytokine-induced death by interacting with {beta}1 integrins and activating pro-survival Akt signaling. Pro-survival signaling was mediated by reduced activity of protein kinase C{delta} (PKC{delta}), a key mediator of cytokine-induced {beta}-cell death, at the cell membrane in the presence of laminin via reduced levels of diacylglycerol (DAG), a canonical activator of PKC{delta}. Taken together, these results demonstrate that laminin-511 is an essential factor in protecting {beta}-cells against cytokine-induced death by downregulation of membrane DAG, inhibiting activation of pro-apoptotic PKC{delta}. Our results suggest that loss of ECM in T1D may make {beta}-cells more susceptible to cytokine-induced death by increasing activation of PKC{delta}. HighlightsO_LILaminin-511 improves islet survival under cytokine treatment C_LIO_LIPro-survival Akt is upregulated by laminin-511 C_LIO_LIPro-apoptotic PKC{delta} activity is downregulated at the cell membrane by laminin-511 C_LIO_LILaminin-511 decreases membrane DAG levels leading to reduced PKC{delta} activation C_LIO_LILaminin-511 is an essential ECM component for islet survival during type 1 diabetes C_LI

cell biology↗

bioRxiv2025

Stressed β-cells contribute to loss of peri-islet extracellular matrix in type 1 diabetes

Type 1 diabetes (T1D) is characterized by the immune-mediated destruction of insulin-producing {beta}-cells in pancreatic islets. The peri-islet extracellular matrix (ECM) is a complex protein barrier that is lost in T1D, in part due to infiltrating immune cells. The contribution of stressed {beta}-cells to ECM degradation during T1D remains unclear. To bridge this gap, we used 12-15-week-old NOD mice and pancreas sections from healthy, [≥]2 autoantibody positive (Aab+), and recent onset T1D donors. We focused on MMP-3 due to its role in degrading type IV collagen (COL IV) in the peri-islet ECM. Treatment with proinflammatory cytokines or hyperglycemia increased MMP-3 gene expression and protein levels in mouse and human islets. In NOD pancreas sections, increased MMP-3 expression in {beta}-cells correlates with loss of COL IV during insulitis and hyperglycemia; however, this was independent of insulitis score. We observed similar increases in MMP-3 and loss of COL IV in islets and exocrine tissue from Aab+ and recent onset T1D donors. These results suggest that stressed {beta}-cells degrade the ECM during preclinical T1D, further weakening the peri-islet ECM barrier and facilitating islet infiltration and death. Inhibiting expression of MMP-3 may represent a novel treatment to prevent islet death in T1D.

cell biology↗

bioRxiv2024

Peptide Coated Polycaprolactone-Benzalkonium Chloride Nanocapsules for Targeted Drug Delivery to the Pancreatic β-Cell

Targeting of current therapies to treat or prevent loss of pancreatic islet {beta}-cells in Type 1 Diabetes (T1D) may provide improved efficacy and reduce off target effects. Current efforts to target the {beta}-cell are limited by a lack of {beta}-cell specific targets and the inability to test multiple targeting moieties with the same delivery vehicle. Here we fabricate a novel tailorable polycaprolactone nanocapsule (NC) where multiple different targeting peptides can be interchangeably attached for {beta}-cell specific delivery. Incorporation of a cationic surfactant in the NC shell allows for the attachment of Exendin-4 and an antibody for ectonucleoside triphosphate diphosphohydrolase 3 (ENTPD3) for {beta}-cell specific targeting. The average NC size ranges from 250-300nm with a polydispersity index under 0.2. The NCs are non-toxic, stable in media culture, and can be lyophilized and reconstituted. NCs coated with targeting peptide were taken up by human cadaveric islet {beta}-cells and human stem cell-derived {beta}-like cells (sBC) in vitro with a high level of specificity. Furthermore, NCs successfully delivered both hydrophobic and hydrophilic cargo to human {beta}-cells. Finally, Exendin-4 coated NCs were stable and targeted the mouse pancreatic islet {beta}-cell in vivo. Our unique NC design allows for the interchangeable coating of targeting peptides for future screening of targets with improved cell specificity. The ability to target and deliver thera-peutics to human pancreatic {beta}-cells opens avenues for improved therapies and treatments to help the delay onset, prevent, or reverse T1D.

bioengineering↗

bioRxiv2022

Cleavage of Protein Kinase C δ by Caspase-3 Mediates Pro-inflammatory Cytokine-Induced Apoptosis in the Pancreatic Islet

In type 1 diabetes (T1D), autoreactive immune cells infiltrate the pancreas and secrete pro-inflammatory cytokines that initiate cell death in insulin producing islet {beta}-cells. Protein kinase C {delta} (PKC{delta}) plays a role in mediating cytokine-induced {beta}-cell death; however, the exact mechanisms are not well understood. To address this, we utilized an inducible {beta}-cell specific PKC{delta} KO mouse as well as a small peptide specific inhibitor of PKC{delta}. We identified a role for PKC{delta} in mediating cytokine-induced {beta}-cell death and have shown that inhibiting PKC{delta} protects pancreatic {beta}-cells from cytokine-induced apoptosis in both mouse and human islets. We determined that cytokines induced nuclear translocation and activity of PKC{delta} and that caspase-3 cleavage of PKC{delta} may be required for cytokine-mediated islet apoptosis. Further, cytokine-activated PKC{delta} increases activity both of pro-apoptotic Bax with acute treatment and JNK with prolonged treatment. Overall, our results suggest that PKC{delta} mediates cytokine-induced apoptosis via nuclear translocation, cleavage by caspase-3, and upregulation of pro-apoptotic signaling in pancreatic {beta}-cells. Combined with the protective effects of PKC{delta} inhibition with {delta}V1-1, the results of this study will aid in the development of novel therapies to prevent or delay {beta}-cell death and preserve {beta}-cell function in T1D.

cell biology↗

bioRxiv2020

RESTORING CONNEXIN-36 FUNCTION IN DIABETOGENIC ENVIRONMENTS PRECLUDES MOUSE AND HUMAN ISLET DYSFUNCTION

The secretion of insulin from {beta}-cells in the islet of Langerhans is governed by a series of metabolic and electrical events, which can fail during the progression of type2 diabetes (T2D). {beta}-cells are electrically coupled via Cx36 gap junction channels, which coordinates the pulsatile dynamics of [Ca2+] and insulin release across the islet. Factors such as pro-inflammatory cytokines and free fatty acids disrupt gap junction coupling under invitro conditions. Here we test whether gap junction coupling and coordinated [Ca2+] dynamics are disrupted in T2D, and whether recovery of gap junction coupling can recover islet function. We examine islets from donors with T2D, from db/db mice, and islets treated with proinflammatory cytokines (TNF-, IL-1{beta}, IFN-{gamma}) or free fatty acids (palmitate). We modulate gap junction coupling using Cx36 over-expression or pharmacological activation via modafinil. We also develop a peptide mimetic (S293) of the c-terminal regulatory site of Cx36 designed to compete against its phosphorylation. Cx36 gap junction permeability and [Ca2+] dynamics were disrupted in islets from both human donors with T2D and db/db mice, and in islets treated with proinflammatory cytokines or palmitate. Cx36 over-expression, modafinil treatment and S293 peptide all enhanced Cx36 gap junction coupling and protected against declines in coordinated [Ca2+] dynamics. Cx36 over-expression and S293 peptide also reduced apoptosis induced by proinflammatory cytokines. Critically S293 peptide rescued gap junction coupling and [Ca2+] dynamics in islets from both db/db mice and a sub-set of T2D donors. Thus, recovering or enhancing Cx36 gap junction coupling can improve islet function in diabetes. KEY POINTS- Cx36 gap junction permeability and associated coordination of [Ca2+] dynamics is diminished in human type 2 diabetes (T2D) and mouse models of T2D. - Enhancing Cx36 gap junction permeability protects against disruptions to the coordination of [Ca2+] dynamics. - A novel peptide mimetic of the Cx36 c-terminal regulatory region protects against declines in Cx36 gap junction permeability. - Pharmacological elevation in Cx36 or Cx36 peptide mimetic recovers [Ca2+] dynamics and GSIS in human T2D and mouse models of T2D.

biophysics↗

bioRxiv2020

Caloric Restriction recovers impaired β-cell-β-cell coupling, calcium oscillation coordination and insulin secretion in prediabetic mice

Caloric restriction has been shown to decrease the incidence of metabolic diseases such as obesity and type 2 diabetes mellitus (T2DM). The mechanisms underlying the benefits of caloric restriction involved in insulin secretion and glucose homeostasis and are not fully understood. Intercellular communication within the islets of Langerhans, mediated by Connexin36 (Cx36) gap junctions, regulates insulin secretion dynamics and glucose homeostasis. The goal of this study was to determine if caloric restriction can protect against decreases in Cx36 gap junction coupling and altered islet function induced in models of obesity and prediabetes. C57BL6 mice were fed with a high fat diet (HFD), showing indications of prediabetes after 2 months, including weight gain, insulin resistance, and elevated fasting glucose and insulin levels. Subsequently, mice were submitted to one month of 40% caloric restriction (2g/day of HFD). Mice under 40% caloric restriction showed reversal in weight gain and recovered insulin sensitivity, fasting glucose and insulin levels. In islets of mice fed the HFD, caloric restriction protected against obesity-induced decreases in gap junction coupling and preserved glucose-stimulated calcium signaling, including Ca2+ oscillation coordination and oscillation amplitude. Caloric restriction also promoted a slight increase in glucose metabolism, as measured by increased NAD(P)H autofluorescence, as well as recovering glucose-stimulated insulin secretion. We conclude that declines in Cx36 gap junction coupling that occur in obesity can be completely recovered by caloric restriction and obesity reversal, improving Ca2+ dynamics and insulin secretion regulation. This suggests a critical role for caloric restriction in the context of obesity to prevent islet dysfunction.

physiology↗