Lyso-Gb3 activates Notch1 in human podocytes

Area of Science:

• Nephrology
• Molecular Biology
• Cell Biology

Background:

• Podocyte injury is a key early indicator in Fabry nephropathy.
• The precise molecular pathways driving podocyte injury remain unclear.
• Lyso-Gb3 accumulation in Fabry disease correlates with increased extracellular matrix synthesis in podocytes.

Purpose of the Study:

• To investigate the role of Notch1 signaling in lyso-Gb3-induced podocyte responses.
• To elucidate the molecular mechanisms linking lyso-Gb3 to podocyte injury in Fabry nephropathy.

Main Methods:

• Cultured human podocytes were treated with lyso-Gb3 at clinically relevant concentrations.
• Notch1 signaling activation was assessed via active Notch1 and HES1 expression.
• Inhibitors of γ-secretase and Notch1 small interfering RNA (siRNA) were used to block Notch1 activity.
• Expression of Notch1, Jagged1, chemokines (MCP1, RANTES), and fibronectin mRNA was measured.
• Nuclear factor kappa B (NFκB) activation and inhibition were also studied.
• Findings were validated in human Fabry kidney biopsies and mouse kidney models.

Main Results:

• Lyso-Gb3 activated Notch1 signaling, increasing active Notch1 and HES1 levels in podocytes.
• γ-secretase inhibition or Notch1 siRNA blocked HES1 upregulation and prevented lyso-Gb3-induced increases in Notch1, Jagged1, MCP1, and RANTES.
• Notch1 siRNA inhibited NFκB activation, which was found to mediate inflammatory responses.
• Notch1 inhibition also prevented lyso-Gb3-induced fibronectin mRNA upregulation, indicating a role in fibrogenesis.
• Active Notch1, Jagged1, and HES1 were detected in Fabry kidney biopsies, corroborating cell culture findings.

Conclusions:

• Lyso-Gb3 activates Notch1 signaling in podocytes.
• This activation promotes inflammatory and fibrogenic responses, potentially contributing to the pathogenesis of Fabry nephropathy.
• Targeting Notch1 signaling may represent a therapeutic strategy for Fabry nephropathy.