Effect of Calcium Supplementation and TMEM16A Inhibition on Endoplasmic Reticulum Stress Induced by Dental Fluorosis in Mice.

BACKGROUND: Dental fluorosis is a discoloration of the teeth caused by the excessive consumption of fluoride. It represents a distinct manifestation of chronic fluorosis in dental tissues, exerting adverse effects on the human body, particularly on teeth. The transmembrane protein 16a (TMEM16A) is expressed at the junction of the endoplasmic reticulum and the plasma membrane. Alterations in its channel activity can disrupt endoplasmic reticulum calcium homeostasis and intracellular calcium ion concentration, thereby inducing endoplasmic reticulum stress (ERS). This study aims to investigate the influence of calcium supplements and TMEM16A on ERS in dental fluorosis. METHODS: C57BL/6 mice exhibiting dental fluorosis were subjected to an eight-week treatment with varying calcium concentrations: low (0.071%), medium (0.79%), and high (6.61%). Various assays, including Hematoxylin and Eosin (HE) staining, immunohistochemistry, real-time fluorescence quantitative polymerase chain reaction (qPCR), and Western blot, were employed to assess the impact of calcium supplements on fluoride content, ameloblast morphology, TMEM16A expression, and endoplasmic reticulum stress-related proteins (calreticulin (CRT), glucose-regulated protein 78 (GRP78), inositol requiring kinase 1α (IRE1α), PKR-like ER kinase (PERK), activating transcription factor 6 (ATF6)) in the incisors of mice affected by dental fluorosis. Furthermore, mice with dental fluorosis were treated with the TMEM16A inhibitor T16Ainh-A01 along with a medium-dose calcium to investigate the influence of TMEM16A on fluoride content, ameloblast morphology, and endoplasmic reticulum stress-related proteins in the context of mouse incisor fluorosis. RESULTS: In comparison to the model mice, the fluoride content in incisors significantly decreased following calcium supplements (p < 0.01). Moreover, the expression of TMEM16A, CRT, GRP78, IRE1α, PERK, and ATF6 were also exhibited a substantial reduction (p < 0.01), with the most pronounced effect observed in the medium-dose calcium group. Additionally, the fluoride content (p < 0.05) and the expression of CRT, GRP78, IRE1α, PERK, and ATF6 (p < 0.01) were further diminished following concurrent treatment with the TMEM16A inhibitor T16Ainh-A01 and a medium dose of calcium. CONCLUSIONS: The supplementation of calcium or the inhibition of TMEM16A expression appears to mitigate the detrimental effects of fluorosis by suppressing endoplasmic reticulum stress. These findings hold implications for identifying potential therapeutic targets in addressing dental fluorosis.

Comprehensive Identification of Chemical Fingerprint and Screening of Potential Quality Markers of Aloe vera (L.) Burm. f. from Different Geographical Origins via Ultra-High-Performance Liquid Chromatography Hyphenated with Quadrupole-Orbitrap-High-Resolution Mass Spectrometry Combined with Chemometrics.

An integrated strategy was developed for the systematic chemical fingerprint and chemometrics analysis for the quality assessment of Aloe vera (L.) Burm. f. The ultra-performance liquid chromatography fingerprint was established, and all common peaks were tentatively identified by using ultra-high-performance liquid chromatography hyphenated with quadrupole-orbitrap-high-resolution mass spectrometry. Afterwards, the datasets of common peaks were subjected to hierarchical cluster analysis, principal component analysis and partial least squares discriminant analysis to holistically compare the differences. The results revealed that the samples were predicted to fall into four clusters, which were related to four different geographical locations. Using the proposed strategy, aloesin, aloin A, aloin B, aloeresin D and 7-O-methylaloeresin A were rapidly determined to be the potential characteristic quality markers. Finally, five screened compounds in 20 batches of samples were simultaneously quantified, and their total contents were ranked as follows: Sichuan province > Hainan province > Guangdong province > Guangxi province, which suggests that geographical origins may be an important factor affecting the quality of A. vera (L.) Burm. f. This new strategy can not only be used to explore possibly the latent active substance candidates for pharmacodynamic studies, but it is also an efficient analytical strategy for other complex traditional Chinese medicine systems.

Comprehensive chemical profile and quantitative analysis of the Shabyar tablet, a traditional ethnic medicine prescription, by ultra-high-performance liquid chromatography with quadrupole-orbitrap high-resolution mass spectrometry.

The Shabyar tablet is commonly used as a traditional ethnic medicine prescription for the treatment of night blindness, poor vision, and headaches. However, the chemical components of the Shabyar tablet have not been holistically explored, which seriously hinders the discovery of the activity. This study qualitatively and quantitatively investigated the overall chemical profile of the Shabyar tablet using ultra-high-performance liquid chromatography hyphenated with quadrupole-orbitrap high-resolution mass spectrometry. Altogether, 170 chemical components, including 59 flavonoids, 78 organic acids, 12 anthranones, three anthraquinones, one naphthalene, and 17 other compounds were tentatively identified and attributed, with 40 among these being unambiguously characterized in comparison with their corresponding authentic standards. To further determine the major representative constituents of the Shabyar tablet, a quantitative method was used for the simultaneous analysis of 33 characteristic components in Shabyar samples. The results were validated in terms of linearity, precision, repeatability, stability, and recovery. This newly developed approach could be successfully employed for evaluating the holistic quality of crude extracts and Chinese medicines in the Shabyar compound tablet and provide a solid chemical foundation for additional investigations on in vivo pharmacodynamics and therapeutic mechanisms to identify the potential effective components of traditional medicines.

Crystal structure of protein Z-dependent inhibitor complex shows how protein Z functions as a cofactor in the membrane inhibition of factor X.

Protein Z (PZ) binds to PZ-dependent inhibitor (ZPI) and accelerates the inhibition of the coagulation protease, activated factor X (FXa), in the presence of phospholipids and Ca2+. A 2.3A resolution crystal structure of PZ complexed with ZPI shows that ZPI is a typical serine protease inhibitor and that PZ has a serine protease fold with distorted oxyanion hole and S1 pocket. The 2 molecules bind with fully complementary surfaces spanning over 2400A(2) and involving extensive ionic and hydrophobic interactions. ZPI has an unusual shutter region with a negatively charged residue buried within the hydrophobic core of the molecule. This unique Asp(213) is critical in maintaining the balanced metastability required for optimal protease inhibition, especially when PZ is bound, with its replacement with Asn resulting in increased thermal stability, but decreased efficiency of protease inhibition. The structure of ZPI shows negatively and positively charged surfaces on top of the molecule, in keeping with mutagenesis studies in this work indicating exosite interactions with FXa when it docks on top of ZPI. As modeled in this study, the gamma-carboxy-glutamic acid-containing domains of PZ and FXa enable them to bind to the same phospholipid surfaces on platelet and other membranes, with optimal proximity for the inhibition of FXa by the complexed ZPI.