Inhalation of titanium dioxide induces endoplasmic reticulum stress-mediated autophagy and inflammation in mice

Titanium dioxide (TiO₂) nanoparticles are widely used in cosmetics, sunscreen, electronics, drug delivery systems, and diverse bio-application fields. In the workplace, the primary exposure route for TiO₂ nanoparticles is inhalation through the respiratory system. Because TiO₂ nanoparticles have different physiological properties, in terms of size and bioactivity, their toxic effects in the respiratory system must be determined. In this study, to determine the toxic effect of inhaled TiO₂ nanoparticles in the lung and the underlying mechanism, we used a whole-body chamber inhalation system to expose A/J mice to TiO₂ nanoparticles for 28 days. During the experiments, the inhaled TiO₂ nanoparticles were characterized using a cascade impactor and transmission electron microscopy. After inhalation of the TiO₂ nanoparticles, hyperplasia and inflammation were observed in a TiO₂ dose-dependent manner. To determine the biological mechanism of the toxic response in the lung, we examined endoplasmic reticulum (ER) and mitochondria in lung. The ER and mitochondria were disrupted and dysfunctional in the TiO₂-exposed lung leading to abnormal autophagy. In summary, we assessed the potential risk of TiO₂ nanoparticles in the respiratory system, which contributed to our understanding of the mechanism underlining TiO₂ nanoparticle toxicity in the lung.     

ER Stress During the Pubertal Growth Spurt Results in Impaired Long‐Bone Growth in Chondrocyte‐Specific ERp57 Knockout Mice

Long‐bone growth by endochondral ossification is cooperatively accomplished by chondrocyte proliferation, hypertrophic differentiation, and appropriate secretion of collagens, glycoproteins, and proteoglycans into the extracellular matrix (ECM). Before folding and entering the secretory pathway, ECM macromolecules in general are subject to extensive posttranslational modification, orchestrated by chaperone complexes in the endoplasmic reticulum (ER). ERp57 is a member of the protein disulfide isomerase (PDI) family and facilitates correct folding of newly synthesized glycoproteins by rearrangement of native disulfide bonds. Here, we show that ERp57‐dependent PDI activity is essential for postnatal skeletal growth, especially during the pubertal growth spurt characterized by intensive matrix deposition. Loss of ERp57 in growth plates of cartilage‐specific ERp57 knockout mice (ERp57 KO) results in ER stress, unfolded protein response (UPR), reduced proliferation, and accelerated apoptotic cell death of chondrocytes. Together this results in a delay of long‐bone growth with the following characteristics: (1) enlarged growth plates; (2) expanded hypertrophic zones; (3) retarded osteoclast recruitment; (4) delayed remodeling of the proteoglycan‐rich matrix; and (5) reduced numbers of bone trabeculae. All the growth plate and bone abnormalities, however, become attenuated after the pubertal growth spurt, when protein synthesis is decelerated and, hence, ERp57 function is less essential. © 2015 American Society for Bone and Mineral Research.     

乳腺导管原位癌的发病危险因素及生物学指标ER、PR、C-erbB-2表达的研究

目的探讨年龄、初绝经年龄、生育史及哺乳情况等危险因素与乳腺癌发病之间的关系及生物学指标ER、PR、C-erb B-2在乳腺导管原位癌的表达。方法用Logistic回归分析年龄、初潮绝经年龄、生育史及哺乳情况等与乳腺癌发病风险的相关性;同时分析56例乳腺导管原位癌ER、PR、C-erb B-2的表达情况。结果 1在女性的月经、生育、哺乳等因素中,无生育史为乳腺癌发病的危险因素,而哺乳时间长、初潮年龄晚、生产数多则为乳腺癌的保护因素。2乳腺癌组织中ER、PR、C-erb B-2的表达水平明显高于乳腺良性病变。结论女性的月经、生育、哺乳情况与乳腺癌的患病风险有一定关系。通过ER、PR、C-erb B-2表达水平可以对癌组织的生物学行为和预后进行评估,并为内分泌治疗提供依据。     

The role of hypothalamic estrogen receptors in metabolic regulation

Estrogens regulate key features of metabolism, including food intake, body weight, energy expenditure, insulin sensitivity, leptin sensitivity, and body fat distribution. There are two ‘classical’ estrogen receptors (ERs): estrogen receptor alpha (ERS1) and estrogen receptor beta (ERS2). Human and murine data indicate ERS1 contributes to metabolic regulation more so than ESR2. For example, there are human inactivating mutations of ERS1 which recapitulate aspects of the metabolic syndrome in both men and women. Much of our understanding of the metabolic roles of ERS1 was initially uncovered in estrogen receptor α-null mice (ERS1^−/−); these mice display aspects of the metabolic syndrome, including increased body weight, increased visceral fat deposition and dysregulated glucose intolerance. Recent data further implicate ERS1 in specific tissues and neuronal populations as being critical for regulating food intake, energy expenditure, body fat distribution and adipose tissue function. This review will focus predominantly on the role of hypothalamic ERs and their critical role in regulating all aspects of energy homeostasis and metabolism.     

DangER: protein ovERload. Targeting protein degradation to treat myeloma

Myeloma is a malignancy of the antibody-producing plasma cells and, as such, these cells synthesize large quantities of unfolded or misfolded immunoglobulin. The build-up of excess protein triggers a number of downstream signal transduction cascades, including endoplasmic reticulum stress and autophagy. As a result, myeloma cells are uniquely reliant on these and other protein handling pathways for their survival. Strategies aimed at targeting this vulnerability have proved successful with the proteasome inhibitor, bortezomib, already licensed for clinical use. In addition to the proteasome, various other points within the protein handling pathways are also the subject of drug discovery projects, with some already progressing into clinical trials. These include compounds directed against heat shock proteins, the unfolded protein response and pathways both upstream and downstream of the proteasome. More recently, the role of autophagy has been recognized in myeloma. In this review, we discuss the various pathways used by myeloma cells for survival, with particular emphasis on the emerging role and conundrum of autophagy, as well as highlighting pre-clinical research on novel inhibitors targeting protein handling pathways.     

Membrane insertion and topology of the p7B movement protein of Melon Necrotic Spot Virus (MNSV)

Cell-to-cell movement of the Melon Necrotic Spot Virus (MNSV) is controlled by two small proteins working in trans, an RNA-binding protein (p7A) and an integral membrane protein (p7B) separated by an amber stop codon. p7B contains a single hydrophobic region. Membrane integration of this region was observed when inserted into model proteins in the presence of microsomal membranes. Furthermore, we explored the topology and targeting mechanisms of full-length p7B. Here we present evidence that p7B integrates in vitro into the ER membrane cotranslationally and with an Nt-cytoplasmic/Ct-luminal orientation. The observed topology was monitored in vivo by fusing GFP to the Ct of p7B, enabling the overexpression in Escherichia coli cultures. Finally, the topology of a putative p14 movement protein was established by replacing the amber stop codon located between p7A and p7B.     

Prediction of Human Brain Penetration of P-glycoprotein and Breast Cancer Resistance Protein Substrates Using In Vitro Transporter Studies and Animal Models

Four P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) substrates with human cerebrospinal fluid (CSF) concentrations and preclinical neuropharmacokinetics were used to assess in vitro–in vivo extrapolation of brain penetration in preclinical species and the ability to predict human brain penetration. Unbound brain (C_b,u), unbound plasma (C_p,u), and CSF compound concentrations (C_CSF) were measured in rats and nonhuman primates (NHPs), and the unbound partition coefficients (C_b,u/C_p,u and C_CSF/C_p,u) were used to assess brain penetration. The results indicated that for P-gp and BCRP dual substrates, brain penetration was severally impaired in all species. In comparison, for P-gp substrates that are weak or non-BCRP substrates, improved brain penetration was observed in NHPs and humans than in rats. Overall, NHP appears to be more predictive of human brain penetration for P-gp substrates with weak or no interaction with BCRP than rat. Although C_CSF does not quantitatively correspond to C_b,u for efflux transporter substrates, it is mostly within 3-fold higher of C_b,u in rat and NHP, suggesting that C_CSF can be used as a surrogate for C_b,u. Taken together, a holistic approach including both in vitro transporter and in vivo neuropharmacokinetics data enables a better estimation of human brain penetration of P-gp/BCRP substrates.