Search for author "Zhaohua Cai"

Induction of endoplasmic reticulum (ER) stress in aortic valve (AV) leaflets of patients with calcified AV stenosis (CAVS). Immunoblotting for osteoblast differentiation markers Runx2 and osteocalcin, and ER stress markers in AV leaflet samples from patients with CAVS as well as normal leaflets. Runx2 and osteocalcin expressions were strongly induced, and the expressions of phosphorylated-protein kinase-like ER kinase (p-PERK), phosphorylated-inositol-requiring transmembrane kinase and endonuclease-1α (p-IRE1α), and C/EBP homologous protein (CHOP) were markedly increased in calcified AV compared with normal AV (**P<0.01 vs normal).

Aortic valve (AV) calcification of animals with different intervention. A, Alizarin red staining for calcified nodules in AV leaflets of animals with indicated intervention. Scale bars, 200 μm in rabbits or 100 μm in ApoE^−/− mice. B and C, High-cholesterol (HC)+vitamin D₂ (vitD₂) diet led to significant AV calcification in rabbits, and HC diet caused marked calcification in AV leaflets of ApoE^−/− mice as well. Tauroursodeoxycholic acid (TUDCA) treatment markedly reduced these effects (in rabbits: control, n=6; HC+vitD₂, n=7; HC+vitD₂+TUDCA, n=7; in ApoE^−/− mice: control, n=15; HC, n=15; HC +TUDCA, n=15; **P<0.01 vs control; ##P<0.01 vs HC+vitD₂ in rabbits or HC in ApoE^−/− mice).

TUDCA administration reduces osteoblastic differentiation and macrophage infiltration in aortic valve (AV) leaflets induced by high-cholesterol (HC) diet in ApoE^−/− mice. A, Osteoblastic differentiation markers, osterix, Runx2, and osteocalcin, and macrophage marker F4/80 staining in AV leaflets of indicated groups. Scale bars, 100 μm. HC diet significantly induced AV osterix (B), Runx2 (C), and osteocalcin (D) staining, and increased AV macrophage infiltration (E) in ApoE^−/− mice. Tauroursodeoxycholic acid (TUDCA) effectively suppressed these effects (control, n=15; HC, n=15; HC +TUDCA, n=15; **P<0.01 vs control; ##P<0.01 vs HC).

Endoplasmic reticulum stress is involved in oxidized low-density lipoprotein (oxLDL)–mediated osteoblastic differentiation and inflammation in valvular interstitial cells. A, OxLDL induced abundant osteocalcin expression, whereas small interfering RNA (siRNA) silencing of protein kinase-like ER kinase (PERK) significantly inhibited its downstream activating transcription factor 4 (ATF4) induction as well as osteocalcin expression stimulated by oxLDL. B, Silencing of ATF4 markedly prevented oxLDL-induced osteocalcin expression. C, OxLDL incubation led to significant induction of Runx2, whereas siRNA silencing of inositol-requiring transmembrane kinase and endonuclease-1α (IRE1α) significantly prevented downstream X-box–binding protein 1 (XBP1) splicing and Runx2 expression induced by oxLDL. D, Silencing of XBP1 markedly reduced Runx2 expression stimulated by oxLDL incubation. E, IRE1α silencing markedly attenuated c-Jun N-terminal kinase (JNK) phosphorylation induced by oxLDL. F, OxLDL caused marked degradation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα), whereas IRE1α silencing blocked this effect. G, IRE1α silencing inhibited nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 nuclear translocation induced by oxLDL (n=3 for each experiment; *P<0.05 vs scrambled siRNA served as control [Scr siRNA]; **P<0.01 vs Scr siRNA; #P<0.05 vs oxLDL+Scr siRNA; ##P<0.01 vs oxLDL+Scr siRNA).