Activation of liver X receptor suppresses angiogenesis via induction of ApoD.

Liver X receptors (LXRs) are important sensors and regulators for cholesterol, fatty acid, and glucose. LXRs play essential roles in the development and progression of cardiovascular diseases. We examined the effects of T0901317, a potent LXR agonist, on angiogenesis of human umbilical vein endothelial cells (HUVECs). Treatment with T0901317 inhibited the tube formation and migration of HUVECs and reduced the in vivo angiogenesis, as determined by chorioallantoic membrane assay. T0901317 stimulated gene and protein expression of LXR target gene apolipoprotein D (ApoD). Overexpression of ApoD suppressed the tube formation of HUVECs. ApoD interacted with scavenger receptor class B member 1 (SR-B1), while knockdown of SR-B1 blocked suppressive effects of T0901317 on HUVEC migration. T0901317 treatment or overexpression of ApoD lessened expression of proteins regulating angiogenesis, including phospho-eNOS S1177, phospho-Akt T308, phospho-Akt S473, eNOS, mammalian target of rapamycin, VEGF-A, VEGF-C, IL-8, RhoB, matrix metalloproteinase (MMP)-8, -9, and monocyte chemoattractant protein 1. Our study suggested that activation of LXR interferes with angiogenesis through induction of LXR target gene ApoD, which in turn suppresses PI3K-Akt-eNOS signaling, an essential pathway regulating angiogenesis. ApoD may be a potential therapeutic target for tumor angiogenesis.-Lai, C.-J., Cheng, H.-C., Lin, C.-Y., Huang, S.-H., Chen, T.-H., Chung, C.-J., Chang, C.-H., Wang, H.-D., Chuu, C.-P. Activation of liver X receptor suppresses angiogenesis via induction of ApoD.

YAP promotes myogenic differentiation via the MEK5-ERK5 pathway.

Yes-associated protein (YAP) is a transcriptional coactivator in the Hippo pathway that regulates cell proliferation, differentiation, and apoptosis. The MEK5/ERK5 MAPK cascade is essential for the early step of myogenesis. In this study, we generated C2C12 stable cell lines that expressed YAP (C2C12-YAP cells) and found that ERK5 and MEK5 were activated in C2C12-YAP cells compared with control C2C12 (C2C12-vector) cells. C2C12-YAP stable cells also differentiated into myotubes better than C2C12-vector cells, and expressed elevated levels of myogenin, a transcription factor that regulates myogenesis, as well as elevated levels of myosin heavy chain, a skeletal muscle marker. Western blot analysis revealed that Src and c-Abl (Abelson murine leukemia viral oncogene homolog 1) activation were enhanced in C2C12-YAP cells. Conversely, treatment of inhibitors of c-Abl, Src, or MEK5 inhibited activation of MEK5 and ERK5 and myogenesis of C2C12 myoblasts. Specific interactions between YAP and proteins in the ERK5 pathway, such as MEK kinase 3 (MEKK3) and ERK5, were illustrated by coimmunoprecipitation experiments. MEKK3 contains the PPGY motif (aa 178-181), which may interact with YAP. Site-directed mutagenesis experiments revealed that expression of MEKK3 Y181F mutant inhibited MEK5/ERK5 activation and myogenic differentiation. These results suggest that YAP promotes muscle differentiation by activating the Abl/Src/MEKK3/MEK5/ERK5 kinase cascade.-Chen, T.-H., Chen, C.-Y., Wen, H.-C., Chang, C.-C., Wang, H.-D., Chuu, C.-P., Chang, C.-H. YAP promotes myogenic differentiation via the MEK5-ERK5 pathway.

Urinary glycated uromodulin in diabetic kidney disease.

Advanced glycation end-products (AGEs) form during oxidative stress, which is increased in diabetes mellitus (DM). Uromodulin is a protein with a renal protective effect, and may be subject to glycation. The implications of uromodulin glycation and AGEs in the urine are not understood. Here, immunoprecipitation and liquid chromatography-mass spectrometry identified glycated uromodulin (glcUMOD) in the urine of 62.5% of patients with diabetic kidney disease (DKD), 20.0% of patients with non-diabetic chronic kidney disease (CKD), and no DM patients with normal renal function or healthy control participants; a finding replicated in a larger cohort of 84 patients with CKD in a case-control study (35 with DM, 49 without). Uromodulin forms high molecular weight polymers that associate with microvesicles and exosomes. Differential centrifugation identified uromodulin in the supernatant, microvesicles, and exosomes of the urine of healthy participants, but only in the supernatant of samples from patients with DKD, suggesting that glycation influences uromodulin function. Finally, the diagnostic and prognostic utility of measuring urinary glcUMOD concentration was examined. Urinary glcUMOD concentration was substantially higher in DKD patients than non-diabetic CKD patients. Urinary glcUMOD concentration predicted DKD status, particularly in patients with CKD stages 1-3a aged <65 years and with urine glcUMOD concentration ≥9,000 arbitrary units (AU). Urinary uromodulin is apparently glycated in DKD and forms AGEs, and glcUMOD may serve as a biomarker for DKD.

Albumins represent highly cross-reactive animal allergens.

Albumins from animals are highly cross-reactive allergens for patients suffering from immunoglobulin E (IgE)-mediated allergy. Approximately 20-30% of cat and dog allergic patients show IgE reactivity and mount IgE-mediated allergic reactions to cat and dog albumin. It is astonishing that allergic patients can develop specific IgE responses against animal albumins because these proteins exhibit a more than 70% sequence identity to human serum albumin (HSA) which is the most abundant protein in the blood of the human body. The sequence identity of cat albumin (Fel d 2) and dog albumin (Can f 3) and HSA are 82% and 80%, respectively. Given the high degree of sequence identity between the latter two allergens and HSA one would expect that immunological tolerance would prohibit IgE sensitization to Fel d 2 and Can f 3. Here we discuss two possibilities for how IgE sensitization to Fel d 2 and Can f 3 may develop. One possibility is the failed development of immune tolerance in albumin-allergic patients whereas the other possibility is highly selective immune tolerance to HSA but not to Fel d 2 and Can f 3. If the first assumption is correct it should be possible to detect HSA-specific T cell responses and HSA-containing immune complexes in sensitized patients. In the latter scenario few differences in the sequences of Fel d 2 and Can f 3 as compared to HSA would be responsible for the development of selective T cell and B cell responses towards Fel d 2 as well as Can f 3. However, the immunological mechanisms of albumin sensitization have not yet been investigated in detail although this will be important for the development of allergen-specific prevention and allergen-specific immunotherapy (AIT) strategies for allergy to albumin.

Hyperglycemia and advanced glycation end products (AGEs) suppress the differentiation of 3T3-L1 preadipocytes.

Aging is characterized by mild hyperglycemia and accumulation of advanced glycation end products (AGEs). Effects of chronic exposure to hyperglycemia or AGEs on the adipogenic differentiation of 3T3-L1 preadipocytes remain unclear. We examined the chronic effect of AGEs and high glucose on the differentiation of 3T3-L1 cells by culturing 3T3-L1 cells in the presence of AGEs or 25 mM glucose for 1 month. Chronic incubation of 3T3-L1 cells with AGEs or high glucose blocked their differentiation into mature adipocytes as evidenced by reduced levels of adipocyte markers such as accumulated oil droplets, GPDH, aP2, adiponectin and of adipogenesis regulators PPARγ and C/EBPα. Levels or activities of Src, PDK1, Akt, and NF-κB were higher in AGEs- and high glucose-treated cells than those in 3T3-L1 cells. Levels of Bcl-2 were elevated in AGEs- and high glucose-treated cells, and were attenuated by inhibitors of PI3-kinase, Akt and NF-κB. Moreover, adipogenesis was attenuated in 3T3-L1 cells stably expressing Bcl-2 or YAP. These results suggest that chronic AGEs and high glucose treatments up-regulate Bcl-2 and YAP via the Akt-NF-κB pathway and impair adipogenesis.