Current Molecular Medicine (v.17, #2)
Meet Our Associate Editor by Jianjun Chen (91-91).
Ethanolamine Metabolism in the Mammalian Gastrointestinal Tract: Mechanisms, Patterns, and Importance by J. Zhou, X. Xiong, K. Wang, L. Zou, D. Lv, Y. Yin (92-99).
Nutritional exchanges and cooperation between bacteria in the gastrointestinal tract and the mammalian host play an important role in health and disease. Ethanolamine is an essential dietary lipid nutrient for animals and is abundant in both intestinal and bacterial cell membranes. Ethanolamine can be utilized by intestinal eukaryotic cells via the cytidine phosphoethanolamine pathway for de novo synthesis of phosphatidylethanolamine, and certain bacteria are able to catabolize it as a major carbon and/or nitrogen source with the help of ethanolamine utilization proteins. In addition, ethanolamine utilization dramatically affects lipid metabolism and short-chain fatty acid biosynthesis. Ethanolamine metabolism plays a significant role in the renewal and proliferation of intestinal cells and intestinal inflammation, and ethanolamine may be a nutritional target to diagnose or treat diseases such as inflammatory bowel disease. This review summarizes the mechanisms of ethanolamine metabolism in the mammalian gastrointestinal tract and its influence on intestinal health and immunity, thus providing a theoretical reference for further studies on mammalian nutrition and disease.
What Can Pharmacological Models of Retinal Degeneration Tell Us? by M. H. Reisenhofer, J. M. Balmer, V. Enzmann (100-107).
Animal models with pharmacologically induced retinal degeneration including sodium iodate (NaIO3) and N-methyl-N-nitrosourea (MNU) have been extensively used in ophthalmic research to investigate retinal degeneration. NaIO3 induces degeneration of the retinal pigment epithelium (RPE) followed by photoreceptor (PRC) cell death, mimicking features of age-related macular degeneration. In contrast, MNU leads to rapid destruction of the PRCs only, enabling the use of the MNU model to investigate degeneration induced in retinitis pigmentosa. It has been shown that multiple cell death pathways are involved in the cell-specific effects of the toxins. Necrosis has been identified as the cause of the NaIO3-induced RPE loss. PRC degeneration in the described models is mainly induced by programmed cell death, indicated by the upregulation of conventional apoptosis initiator and effector caspases. However, recent research points to the additional involvement of caspase-independent processes as endoplasmic reticulum stress and calpain activation. Since there is still a substantial amount of contradictory hypotheses concerning triggers of cell death, the use of pharmacological models is controversial. Thereby, the advantages of such models like the application reaching across species and strains as well as modulation of onset and severity of damage are not exploited to a full extent. Thus, the present review aims to give more insight into the involved cell death pathways and discusses recent findings in the most widely used retinal degeneration models. It might facilitate further studies aiming to develop putative therapeutic approaches for retinal degenerative diseases including combinatory treatment with cell death inhibitors and cell transplantation therapy.
The Molecular Mechanisms of Thalidomide Teratogenicity and Implications for Modern Medicine by J. Knobloch, D. Jungck, A. Koch (108-117).
Thalidomide is a teratogen that affects many organs but primarily induces limb truncations like phocomelia. Rodents are thalidomide resistant. In the 1950s, this has led to misinterpretations of animal tests and to the fatal assumption that the drug was safe for pregnant women to use against morning sickness. The result was one of the biggest scandals in medical history: 10.000 and more infants with birth defects in Europe. Nonetheless, thalidomide still has its place in modern medicine as it has strong therapeutic potential: it has been approved by the FDA for multiple myeloma and erythema nodosum leprosum, and its anti-inflammatory, immunomodulatory and antiangiogenic activities are considered in many other refractory diseases. The aim is to develop derivatives that are not teratogenic but maintain the therapeutic potential. This requires detailed knowledge about the underlying molecular mechanisms. Much progress has been made in deciphering the teratogenic mechanisms in the last decade. Here, we summarize these mechanisms, explain thalidomide resistance of rodents, and discuss possible mechanisms that could explain why the drug primarily targets the developing limb in the embryo. We also summarize the most important therapeutic mechanisms. Finally, we discuss which therapeutic and teratogenic mechanisms do and do not overlap, and if there is a chance for the development of non-teratogenic thalidomide derivatives with therapeutic potential.
Molecular Basis of Human Diseases and Targeted Therapy Based on Small-Molecule Inhibitors of ER Stress-Induced Signaling Pathways by W. Rozpedek, A. Nowak, D. Pytel, J. Alan Diehl, I. Majsterek (118-132).
The Endoplasmic Reticulum (ER) provides a conserved protein quality control system and plays a fundamental role in cell growth and homeostasis. Disturbances in the ER homeostasis may originate especially from hypoxia, glucose deficiency, presence of mutant proteins, that directly impair protein folding capacity and after deposition of unfolded and misfolded proteins within ER lumen trigger ER stress conditions. This subsequently activates the Unfolded Protein Response (UPR) branches, which have a dual pro-adaptive or pro-apoptotic role depending on the severity and time of duration of ER stress conditions. This review is the first to offer a detailed overview on molecular mechanisms of all major ER stress-dependent signaling branches, that are activated through three specific ER transmembrane receptors of impaired protein folding: Protein kinase RNA (PKR)-like ER kinase (PERK), Inositol-requiring enzyme-1 (IRE1) and Activating transcription factor 6 (ATF6). Molecular crosstalk among ER transmembrane receptors-dependent pathways determines a final UPR response, but the recent data reported that especially PERK over-activation has a significant impact on the development and progression of a wide spectrum of disease entities. Based on these findings, small-molecules, highly specific PERK inhibitors may provide effective, groundbreaking treatment strategy against human diseases. However, after foregoing in vitro cellular and in vivo animal models conducted examination, supplementary investigations of PERK inhibitors are required for their further clinical use. Future research may answer the question of how to minimize toxicity and side effects of characterized small-molecule PERK inhibitors, that may be used, as breakthrough drugs, alone or in combination with currently known models of therapy.
Copy Number Variations with Isolated Fetal Ventriculomegaly by P. Hu, Y. Wang, R. Sun, L. Cao, X. Chen, C. Liu, C. Luo, D. Ma, W. Wang, X. Fu, W. Shi, S. Yi, K. Zhang, H. Liu, Z. Xu (133-139).
Background: Copy Number Variations (CNVs) are an important genetic cause of a number of neurodevelopmental disorders (NDs). However, the association between CNVs and the development and prognosis of fetal isolated mild ventriculomegaly (IMV) is unclear. Objectives: To investigate possible associations between CNVs and the development of fetal IMV. Methods: This retrospective study recruited 154 subjects with ultrasound-confirmed fetal IMV and 190 subjects in a control cohort who underwent a high-risk prenatal serum screening program. The exclusion criteria included fetus G-banding chromosomal abnormality or positive fetus TORCH infection. DNA samples from all 344 fetuses were examined by an SNP-array. Developmental outcomes were assessed during postnatal follow-up. Results: Fourteen pathogenic CNVs (pCNVs) were identified in 13 out of 154 IMV fetuses. Three pCNVs were found in 3 out of 190 subjects in the prenatal screening high-risk cohort, with a significant difference (P value=0.016, X2 test). Notably, the 14 pCNVs detected in the IMV cohort were all associated with neurodevelopmental disorders (NDs), including autism, intellectual disability. Among the 13 IMV fetuses carrying pCNVs, five subjects were found in the postnatal follow-up to manifest NDs, including two with autism and three with mild neurodevelopmental delay. The other 8 subjects consisted of three normal infants younger than 12-months old, two lost in the follow-up, and three with the termination of pregnancy. Out of 141 IMV subjects without detectable pCNVs, 123 subjects showed normal development, 16 were lost in the follow-up, 2 subjects terminated the pregnancy due to fetal hydrocephalus or congenital heart disease in the late fetus development. Conclusions: This study suggests an association between pCNVs and fetal IMV. pCNVs may be involved in the pathological process of fetal IMV and postnatal NDs. Identifying specific genomic alterations may provide an insight into pathogenetic mechanism and aid better diagnosis and prognosis of neurodevelopmental outcomes in fetal IMV.
The Role of Mitochondria-Associated Reactive Oxygen Species in the Amyloid β Induced Production of Angiogenic Factors b y ARPE-19 Cells by L. Wu, X. Tan, L. Liang, H. Yu, C. Wang, D. Zhang, A. Kijlstra, P. Yang (140-148).
Objective: This study aimed to investigate the mechanisms whereby Amyloidbeta (Aβ) induces the production of angiogenic factors by a human retinal pigment epithelial cell line (ARPE-19) cells. Methods: ARPE-19 cells obtained from the American Type Culture Collection (ATCC) were utilized in this study. The expression level of vascular endothelial growth factor (VEGF), Interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and complement activation fragments C3a and C5a were measured by Real-time quantitative PCR (RT-PCR) and Enzyme-linked immunosorbent assay (ELISA). The production of mitochondria-associated reactive oxygen species (ROS) was measured by flow cytometry. Results: The expression of VEGF, IL-8, MCP-1, C3a and C5a was significantly increased in Aβ-treated ARPE-19 cells. Mitochondria-associated ROS production was also significantly increased when exposed to Aβ. Inhibition of mitochondrial ROS with Diphenyleneiodonium chloride (DPI) markedly decreased the Aβ induced production of VEGF, IL-8, MCP-1, C3a and C5a by ARPE-19 cells. Anti-C3a or anti-C5a neutralizing antibodies did not have a detectable influence on the secretion of VEGF, IL-8 and MCP-1 by ARPE-19 cells upon stimulation with Aβ. Conclusion: Our results support the hypothesis that Aβ is involved in the pathogenesis of choroidal neovascularization (CNV) formation by promoting the production of the angiogenic cytokines VEGF, IL-8 and MCP-1 by RPE cells. Mitochondrial ROS was shown to play a role in the regulation of Aβ induced expression of these cytokines.
Hydroxytyrosol Attenuates LPS-Induced Acute Lung Injury in Mice by Regulating Autophagy and Sirtuin Expression by X. Yang, T. Jing, Y. Li, Y. He, W. Zhang, B. Wang, Y. Xiao, W. Wang, J. Zhang, J. Wei, R. Lin (149-159).
Background: Recently, the effects of hydroxytyrosol on autophagy during acute lung injury (ALI) have drawn increasing attention. Objective: We explored the underlying molecular mechanisms by which hydroxytyrosol exerts its anti-inflammatory effects in a murine model of ALI by up-regulating autophagy. Methods: Male BALB/c mice, challenged with intranasal instillations of LPS, were treated with or without hydroxytyrosol (HT, 100 mg/kg, intragastrically) 1 h prior to LPS exposure. Twenty-four hours later, lung and bronchoalveolar lavage (BAL) fluid samples were obtained for the determination of lung wet to dry weight (W/D) ratios, protein leakage levels, and differential counts of inflammatory cells in BAL fluid. LPS-induced cytokine activity, inflammatory factor levels, sirtuin (SIRT1/3/6) expression, mitogenactivated protein kinase (MAPK) activation, and autophagy marker expression in ALImice were examined by western blotting and staining methods. Molecular docking between HT and SIRT and MAPK was studied with a Sybyl/Surflex module. Results: LPS-stimulated SIRT inhibition, MAPK phosphorylation, and autophagy suppression were all notably abolished by HT administration. HT treatment significantly attenuated pulmonary edema and inflammatory cell infiltration into lung tissues, accompanied by decreased lung W/D ratios, protein concentrations, and inflammatory cell levels in BAL fluid. LPS driven release of inflammatory mediators, including TNF-α, IL-1β, IL-6, IL-10, and MCP-1, was strongly regulated by HT. Conclusions: The protective effect of HT on lung inflammation in ALI mice may be attributed to the promotion of autophagy, which is likely associated with the activation of the SIRT/MAPK signaling pathway. Importantly, this study provides new insight into the molecular mechanisms of HT and its therapeutic potential in the treatment of acute respiratory distress syndrome.
Expression of Dominant Negative K6W-Ubiquitin in the Lens Epithelium via an Adenoviral Vector Delays Posterior Capsule Opacification in a Rabbit Model by X. Bao, M. Hou, R. Peng, F. Luo, M. Wu (160-168).
Purpose: Ubiquitin is involved in cell proliferation and differentiation, and the objective of this study is to investigate the potential of dominant negative Ubiquitin (Ub) with a lysine to tryptophan mutation at the 6 position (K6W) through an adenoviral expression vector in the prevention of posterior capsule opacification (PCO) in a rabbit PCO model. Methods: Recombinant dominant negative K6W-Ub adenovirus (RAd-K6W-Ub) with green fluorescent protein (RAd-K6W-Ub/GFP) and RAd-GFP viruses (control) were generated with QBI-HEK 293A cells. New Zealand rabbits receiving lens phacoemulsification were given an intraoperative anterior chamber injection of the viruses. The images of anterior segment photography taken by a slit lamp biomicroscopy were analyzed by posterior capsule opacification manual software (POCOman) for PCO grading. The intraocular pressure (IOP) was detected with a non-contact tonometer (NCT). The expression of α-smooth muscle actin (α-SMA) was assessed by Western blotting. Cell migration ability in cultured rabbit's lens epithelial cells (LECs) was evaluated by scratch healing assay. Results: The expression of GFP and Ub in the lens epithelium was markedly upregulated after 48 hours vector injection. Eyes injected with RAd-K6W-Ub showed a significantly lower PCO degree compared with controls. Meanwhile, higher IOP and corneal edema was observed in groups with a higher RAd-K6W-Ub virus dosage. The expression of α-SMA was down-regulated in the RAd-K6W-Ub eyes as compared to controls at the 15th day after injection. Cell migration was inhibited by RAd-K6W-Ub infection. Conclusions: RAd-K6W-Ub at an appropriate dosage could inhibit the proliferation of LECs and the formation of PCO in rabbit models. However, a higher dosage of Rad- K6W-Ub viral vector caused toxic effects to the surrounding tissues, such as corneal edema and high IOP.