xCT blockade inhibits autophagy of zymogenic granules in downscaling chief cells. (A) Immunostained sections from untreated (n = 4), L635-treated (n = 4), and L635 + sulfasalazine–treated (n = 3) C57Bl/6J mice killed after 3 days of L635 treatment for zymogenic granule marker GIF (red) and chief cell transcription factor Mist1 (green). Scale bars: 50 μm. (B) Quantification of Mist1-positive cells per 20× field. (C) Immunostained sections from untreated (n = 5), L635-treated (n = 5), and L635 + sulfasalazine–treated (n = 4) C57Bl/6J mice killed after 24 hours of L635 treatment for GIF (red) and autophagosome marker LC3B (green). Scale bars: 50 μm. Magnified inset of GIF-positive cell with arrows indicating puncta (right). (D) Average number of LC3B puncta per GIF-positive cell (P = .003∗∗). (E) Immunostained sections from untreated (n = 5), L635-treated (n = 5), and L635 + sulfasalazine–treated (n = 4) C57Bl/6J mice killed after 24 hours of L635 treatment for GIF (red) and lysosome marker LAMP2 (green). Scale bars: 50 μm. Magnified inset of GIF-positive cell with arrows indicating puncta (right). (F) Average number of LAMP2 puncta per GIF-positive cell (P = .0003∗∗∗). Statistical significance determined by 1-way analysis of variance with the Bonferroni post hoc multiple comparisons test. (G) Transmission electron micrographs of zymogenic chief cells 12 hours after L635 treatment ± sulfasalazine. Scale bars: 2 μm. Magnified inset of double-membrane autophagic structures (right). (H) Relative mRNA expression of autophagy-related proteins in L635-treated and L635 + sulfasalazine–treated mice (Atg4, Atg5, Atg7, Atg12, Atg16L1, Beclin1, Lamp1, Lamp2, and Lc3) (P = .02∗, .005∗, .03∗, .01∗, and .02∗, respectively). Statistical significance was determined by an unpaired Student t test.