Loss of pleckstrin homology domain and leucine rich repeat protein phosphatase 2 has protective effects on high glucose-injured retinal ganglion cells via Akt-GSK-3β-Nrf2 pathway

Abstract

Purpose : Pleckstrin homology domain and leucine-rich repeat protein phosphatase 2 (PHLPP2) is linked to various pathological
states. However, whether PHLPP2 mediates diabetic retinopathy is unaddressed. This work explored the biological
function of PHLPP2 in modulating high glucose (HG)-elicited damage of retinal ganglion cells (RGCs), an in vitro model
for studying diabetic retinopathy.

Methods : Mouse RGCs were treated with HG to establish a cell model. PHLPP2 was silenced by transfecting specific shRNAs
targeting PHLPP2. RT-qPCR, immunoblotting, CCK-8 assay, flow cytometry, TUNEL assay, and ELISA were carried out.

Results : Significant increases in PHLPP2 levels were observed in cultured RGCs exposed to HG. The severe damages evoked
by HG to RGCs were remarkably weakened in PHLPP2-silenced RGCs, including improved cell survival, attenuated cell
apoptosis, repressed oxidative stress, and prohibited proinflammatory response. The silencing of PHLPP2 strengthened
the activation of Nrf2 in HG-treated RGCs via modulation of the Akt–GSK–3β axis. Interruption of the Akt–GSK–3β axis
reversed PHLPP2-silencing-elicited Nrf2 activation. The protective effects of PHLPP2 silencing on HG-induced injury of
RGCs were diminished by Nrf2 inhibition.

Conclusions : The loss of PHLPP2 was beneficial for HG-injured RGCs through the effect on the Akt–GSK–3β–Nrf2 pathway.
This work suggests a possible role of PHLPP2 in diabetic retinopathy.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Fig. 1 Expression of PHLPP2 in cultured RGCs.
Fig. 2 PHLPP2 knockdown weakened HG-elicited apoptosis in RGCs.
Fig. 3 PHLPP2 knockdown attenuated HG-evoked oxidative stress.
Fig. 4 PHLPP2 knockdown repressed HG-elicited proinflammatory response in RGCs.
Fig. 5 PHLPP2 knockdown enhanced Nrf2 activation in HG-exposed RGCs.
Fig. 6 Akt inhibition reversed PHLPP2-silencing-mediated Nrf2 activation.
Fig. 7 Akt inhibition reversed PHLPP2-silencing-mediated protective effects on HG-exposed RGCs.
Fig. 8 The inhibition of Nrf2 abolished the protective effects of PHLPP2 knockdown on HG-exposed RGCs.

 

Fig. 9 Schematic diagram depicts the mechanism of PHLPP2 in mediating HG injury of RGCs