Identification of suitable reference genes for RT-qPCR studies in human parathyroid tissue glandular cells

Identifying a proper reference gene allows us to understand fundamental changes in many biological processes. Normalization during gene expression analyses is essential for every tissue/cell type, including parathyroid tissue glandular cells. Quantitative method of gene expression analyses via qRT-PCR method provides the accurate examination of every target gene. There are limited reports to present commonly used reference genes in human parathyroid tissues rather than for glandular cell types. This study aims to determine and compare the most stable to least stable genes for parathyroid tissue cells. 43 human parathyroid tissue obtained from primary and secondary hyperparathyroidism patients and glandular cells isolated enzymatically by the removal of extracellular matrix components. After extraction of the total RNA, cDNA synthesis was performed, then qRT-PCR evaluated 14 candidate reference genes. Stability was determined by RefFinder software (Delta ct, BestKeeper, Genorm, and NormFinder algorithms), and the outcome was evaluated for five groups. Even if assessed with different groups, the most stable genes were RPLP0 and GAPDH, while the CLTC and RNA 18S were the least stable. We have confirmed the comprehensive ranking of the most stable three genes alone with the NormFinder algorithm to understand intergroup variation and found out that RPLP0>GAPDH>PGK1. Lastly, comparisons of relative target gene (GCM2) expression revealed similar expression patterns for the most stable reference genes. The most stable reference gene is recommended for the stages where stability is evaluated using the results of four different approaches using RefFinder. We aspire for this study to assist future research to conduct thorough assessments of appropriate reference genes before engaging in gene expression analyses for parathyroid tissue.

Stable Reference Genes for qPCR Analysis in BM-MSCs Undergoing Osteogenic Differentiation within 3D Hyaluronan-Based Hydrogels

Reverse transcription quantitative polymerase chain reaction (RT-qPCR) enables the monitoring of changes in cell phenotype via the high-throughput screening of numerous genes. RT-qPCR is a fundamental approach in numerous research fields, including biomaterials, yet little attention has been given to the potential impact of 3D versus monolayer (2D) cell culture and to the requirement for a constant validation of the multiple steps of gene expression analysis. The aim of this study is to use high-quality RNA to identify the most suitable reference genes for RT-qPCR analysis during the osteogenic differentiation of human bone marrow mesenchymal stem/stromal cells (BM-MSCs). BM-MSCs are cultured under osteogenic conditions for 28 days in 2D or within hyaluronic acid hydrogels (3D). RNA is subject to quality controls and is then used to identify the most stable reference genes using geNorm, NormFinder, and the ∆Cq method. The effect of the reverse transcriptase is investigated, as well as the expression of osteogenic-related markers. This study shows marked differences in the stability of reference genes between 2D (RPLP0/GAPDH) and 3D (OAZ1/PPIA) culture, suggesting that it is critical to choose appropriate reference genes for 3D osteogenic cell cultures. Thus, a thorough validation under specific experimental settings is essential to obtain meaningful gene expression results.

Disruption of the ribosomal P complex leads to stress-induced autophagy

The human ribosomal P complex, which consists of the acidic ribosomal P proteins RPLP0, RPLP1, and RPLP2 (RPLP proteins), recruits translational factors, facilitating protein synthesis. Recently, we showed that overexpression of RPLP1 immortalizes primary cells and contributes to transformation. Moreover, RPLP proteins are overexpressed in human cancer, with the highest incidence in breast carcinomas. It is thought that disruption of the P complex would directly affect protein synthesis, causing cell growth arrest and eventually apoptosis. Here, we report a distinct mechanism by which cancer cells undergo cell cycle arrest and induced autophagy when RPLP proteins are downregulated. We found that absence of RPLP0, RPLP1, or RPLP2 resulted in reactive oxygen species (ROS) accumulation and MAPK1/ERK2 signaling pathway activation. Moreover, ROS generation led to endoplasmic reticulum (ER) stress that involved the EIF2AK3/PERK-EIF2S1/eIF2α-EIF2S2-EIF2S3-ATF4/ATF-4- and ATF6/ATF-6-dependent arms of the unfolded protein response (UPR). RPLP protein-deficient cells treated with autophagy inhibitors experienced apoptotic cell death as an alternative to autophagy. Strikingly, antioxidant treatment prevented UPR activation and autophagy while restoring the proliferative capacity of these cells. Our results indicate that ROS are a critical signal generated by disruption of the P complex that causes a cellular response that follows a sequential order: first ROS, then ER stress/UPR activation, and finally autophagy. Importantly, inhibition of the first step alone is able to restore the proliferative capacity of the cells, preventing UPR activation and autophagy. Overall, our results support a role for autophagy as a survival mechanism in response to stress due to RPLP protein deficiency.

The effects of dietary fatty acids on the postprandial triglyceride-rich lipoprotein/apoB48 receptor axis in human monocyte/macrophage cells

Intestinally produced triglyceride-rich lipoproteins (TRL) play an important role in the progression of atherosclerosis. In this study, we investigated the relevance of monounsaturated fatty acid (MUFA) and saturated fatty acid (SFA) in postprandial TRL in affecting the transcriptional activity of the apolipoprotein-B48 receptor (ApoB48R) and its functionality in human monocyte/macrophage cells. Healthy male volunteers were administered four standardized high-fat meals containing butter, high-palmitic sunflower oil, olive oil (ROO) or a mixture of vegetable and fish oils (50 g/m(2) body surface area) to obtain a panel of postprandial TRL with gradual MUFA oleic acid-to-SFA palmitic acid ratios. The increase in this ratio was linearly associated with a decrease of ApoB48R up-regulation and lipid accumulation in THP-1 and primary monocytes. ApoB48R mRNA levels and intracellular triglycerides were also lower in the monocytes from volunteers after the ingestion of the ROO meal when compared to the ingestion of the butter meal. In THP-1 macrophages, the increase in the MUFA oleic acid-to-SFA palmitic acid ratio in the postprandial TRL was linearly correlated with an increase in ApoB48R down-regulation and a decrease in lipid accumulation. We also revealed that the nuclear receptor transcription factors PPARα, PPARβ/δ, and PPARγ and the PPAR-RXR transcriptional complex were involved in sensing the proportion of MUFA oleic acid and SFA palmitic acid, and these were also involved in adjusting the transcriptional activity of ApoB48R. The results of this study support the notion that MUFA-rich dietary fats may prevent excessive lipid accumulation in monocyte/macrophage cells by targeting the postprandial TRL/ApoB48R axis.

Hypoxia perturbs aryl hydrocarbon receptor signaling and CYP1A1 expression induced by PCB 126 in human skin and liver-derived cell lines

The aryl hydrocarbon receptor (AhR) is an important mediator of toxic responses after exposure to xenobiotics including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like polychlorinated biphenyls (PCBs). Activation of AhR responsive genes requires AhR dimerization with the aryl hydrocarbon receptor nuclear translocator (ARNT), a heterodimeric partner also shared by the hypoxia-inducible factor-1α (HIF-1α) protein. TCDD-stimulated AhR transcriptional activity can be influenced by hypoxia; however, it less well known whether hypoxia interferes with AhR transcriptional transactivation in the context of PCB-mediated AhR activation in human cells. Elucidation of this interaction is important in liver hepatocytes which extensively metabolize ingested PCBs and experience varying degrees of oxygen tension during normal physiologic function. This study was designed to assess the effect of hypoxia on AhR transcriptional responses after exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Exposure to 1% O2 prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pre-treatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity.