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According to published estimates, pyruvate kinase isoform M2 (PKM2) was expressed in low amounts in patients with Parkinson's disease (PD). However, the function and molecular mechanism of PKM2 in PD remain largely unknown. The main purpose of our study was to reveal the function and mechanism of PKM2 in the in vitro model of PD. Here, we show that PKM2 decreased in PC12 cells after 6-hydroxydopamine (6-OHDA) treatment, which inhibited PC12 cell survival and induced its apoptosis. PKM2 overexpression is required for 6-OHDA-induced PC12 cell survival. Moreover, up-regulated PKM2 expression suppressed PC12 cell apoptosis and caspase-3 activity compared with the 6-OHDA treatment alone group. Increased brahma-related gene 1 (Brg1) and p-STAT3 expression was observed in PKM2-overexpressed PC12 cells compared to those in 6-OHDA treated PC12 cells. Further studies suggested that Brg1 knockdown impeded the high expression of p-STAT3, which was induced by PKM2 overexpression. Finally, the STAT3 inhibitor reversed the effects of PKM2 on cell survival and apoptosis in 6-OHDA-induced PC12 cells. Our results suggest that PKM2 was involved in 6-OHDA-induced PC12 cell injury by mediating the Brg1/STAT3 pathway., Competing Interests: The authors declare that they have no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Optical bistability (OB) and optical multistability (OM) behaviors are investigated theoretically in a four-level N-type diamond germanium-vacancy (GeV) color center scheme immersed in a unidirectional ring cavity based on electromagnetically induced transparency (EIT). It is found that OB behavior is very sensitive to the system parameters, such as the detunings of probe and coupling fields and the intensities of coupling fields as well as the density of GeV centers, and the thresholds of OB can be controlled via changing these parameters. In addition, we can switch OB to OM by adjusting the intensity of control field and the density of GeV centers or vice versa. Our results may provide some guidance for an all-optical switching, optical communications, and optical logic devices in a solid-state system.