3.3 Lysine inhibits PQ-induced EMT process in AT II cells
We and others both found that PQ-induced EMT is critical for pulmonary
fibrosis. Our previous work further suggested that PQ-promoted
STIM1-TRPC1 association and intracellular calcium burden are essential
for EMT. We therefore wondered whether PQ-induced EMT would be reversed
by lysine treatment. PQ treatment significantly reduced the expression
of E-Cadherin, the epithelial marker, while enhanced the expression of
Vimentin, the mesenchymal marker. Lysine treatment significantly
alleviated the reduction of E-Cadherin and normalized the upregulated
Vimentin in PQ- treated A549 cells (Fig. 2F). Similar results were
observed in MLE-12 cells (Fig. 2G). Intriguingly, we have also examined
the efficacy of lysine in STIM1-overexpressed A549 cells. Though lysine
still inhibited PQ-induced EMT process (Fig. 2H), such inhibition seemed
not to be as striking as those observed in normal A549 cells (Fig. 2F),
indicating that cells with STIM1 overexpression were much sensitive to
PQ stimulation and the efficacy of lysine could be ameliorated probably
due to additional STIM1 targeted by PQ. We further confirmed the
protective effect of lysine in PQ-induced EMT by analyzing the mRNA
expression of E-Cadherin and Vimentin (Fig. 2I&2J). Note, we have
repeatedly observed that lysine alone enhanced Vimentin expression in
the protein level but not the mRNA level, indicating that lysine might
affect Vimentin stability. Nevertheless, these results together suggest
that lysine is sufficient to suppress PQ-induced EMT, indicating that
lysine is a potential antidote for PQ poisoning and pulmonary fibrosis
by reducing STIM1-TRPC1 activation.