Fine-tuning cell organelle dynamics during mitosis by small GTPases / 医学前沿

During mitosis, the allocation of genetic material concurs with organelle transformation and distribution. The coordination of genetic material inheritance with organelle dynamics directs accurate mitotic progression, cell fate determination, and organismal homeostasis. Small GTPases belonging to the Ras superfamily regulate various cell organelles during division. Being the key regulators of membrane dynamics, the dysregulation of small GTPases is widely associated with cell organelle disruption in neoplastic and non-neoplastic diseases, such as cancer and Alzheimer's disease. Recent discoveries shed light on the molecular properties of small GTPases as sophisticated modulators of a remarkably complex and perfect adaptors for rapid structure reformation. This review collects current knowledge on small GTPases in the regulation of cell organelles during mitosis and highlights the mediator role of small GTPase in transducing cell cycle signaling to organelle dynamics during mitosis.

Brain structure morphology after being fixated with ethanol on electron microscope / Morfología de la estructura cerebral después de la fijación con etanol en microscopio electrónico

Fixation is one of the processes in preparing histology and pathology. The common material for fixation is buffered formalin including paraformaldehyde. However, the effect of the damaged cells, which is fixed for a long time, causes the research for other fixation materials to become necessary. In addition, paraformaldehyde is also harmful to human body and natural environment. Ethanol is one of the alternative fixation materials, which has been used for two hundred years. It has been used for many purposes, both in routine staining and immunohistochemistry. Nonetheless, no research confirms its effect on the electron microscope. The authors studied the effect of 50 % of ethanol on the cell membrane, organelles, and nucleus of Purkinje cells (Neuron purkinjense) observed on a light microscope and Transmitted Electron Microscope (TEM). Then it was compared to buffered formalin. In the light microscope, it shows that both of fixations have no different effects of the morphology of the cell membrane, cytoplasm, the nucleus of Purkinje cells and the neutrophils. We assume that our 50 % of ethanol concentration is almost the same as BF 10 % in the ability of hardening tissue and color absorption based on the previous study. In TEM, the structure of the cell membrane, organelles, and cytoplasm of Purkinje cell look broken in the cerebellum of 50 % of ethanol except for the nucleus. There was no significant difference diameter of the nucleus. It happened in general because of the shrinkage effect of ethanol. However, the authors recommend using 50 % of ethanol for routine staining.

La fijación es uno de los procesos en la preparación de muestras para histología y patología. El material más común para la fijación es la formalina tamponada. Sin embargo, el daño a las células que se mantienen en formalina durante mucho tiempo, hace necesario buscar otros materiales de fijación. Además, el paraformaldehido también es perjudicial para el cuerpo humano y el medio ambiente natural. El etanol es uno de los materiales de fijación alternativos que se ha utilizado durante muchos años, con diversos objetivos, tanto en la tinción de rutina como en la inmunohistoquímica. Sin embargo no se ha confirmdo su efecto con microscopio electrónico. Los autores estudiaron el efecto del 50 % de etanol sobre la membrana celular, los orgánulos y el núcleo de las células de Purkinje observados en un microscopio óptico y un microscopio de transmisión electrónico (TEM). Luego se comparó con la formalina tamponada. En el microscopio óptico se observó que ambas fijaciones no tienen efectos diferentes a la morfología de la membrana celular, el citoplasma, el núcleo de las células de Purkinje y los neutrófilos. Suponemos que nuestra concentración de 50 % de etanol es casi la misma que BF 10 % en la capacidad de endurecer el tejido y la absorción de color según el estudio anterior. En TEM, la estructura de la membrana celular, los orgánulos y el citoplasma de la célula de Purkinje presentaban daño en el cerebelo con un 50 % de etanol, a excepción del núcleo. No hubo diferencia significativa en el diámetro del núcleo. En general lo anterior se debió al efecto de contracción del etanol. En conclusión los autores recomiendan usar 50% de etanol para la tinción de rutina.

Mitochondrial Quality Control in the Heart: New Drug Targets for Cardiovascular Disease

Despite considerable efforts to prevent and treat cardiovascular disease (CVD), it has become the leading cause of death worldwide. Cardiac mitochondria are crucial cell organelles responsible for creating energy-rich ATP and mitochondrial dysfunction is the root cause for developing heart failure. Therefore, maintenance of mitochondrial quality control (MQC) is an essential process for cardiovascular homeostasis and cardiac health. In this review, we describe the major mechanisms of MQC system, such as mitochondrial unfolded protein response and mitophagy. Moreover, we describe the results of MQC failure in cardiac mitochondria. Furthermore, we discuss the prospects of 2 drug candidates, urolithin A and spermidine, for restoring mitochondrial homeostasis to treat CVD.

Microtubular Dysfunction and Male Infertility

The Role of Autophagy in Eosinophilic Airway Inflammation

Autophagy is a homeostatic mechanism that discards not only invading pathogens but also damaged organelles and denatured proteins via lysosomal degradation. Increasing evidence suggests a role for autophagy in inflammatory diseases, including infectious diseases, Crohn's disease, cystic fibrosis, and pulmonary hypertension. These studies suggest that modulating autophagy could be a novel therapeutic option for inflammatory diseases. Eosinophils are a major type of inflammatory cell that aggravates airway inflammatory diseases, particularly corticosteroid-resistant inflammation. The eosinophil count is a useful tool for assessing which patients may benefit from inhaled corticosteroid therapy. Recent studies demonstrate that autophagy plays a role in eosinophilic airway inflammatory diseases by promoting airway remodeling and loss of function. Genetic variant in the autophagy gene ATG5 is associated with asthma pathogenesis, and autophagy regulates apoptotic pathways in epithelial cells in individuals with chronic obstructive pulmonary disease. Moreover, autophagy dysfunction leads to severe inflammation, especially eosinophilic inflammation, in chronic rhinosinusitis. However, the mechanism underlying autophagy-mediated regulation of eosinophilic airway inflammation remains unclear. The aim of this review is to provide a general overview of the role of autophagy in eosinophilic airway inflammation. We also suggest that autophagy may be a new therapeutic target for airway inflammation, including that mediated by eosinophils.

Diverse Effects of Small Molecule Inhibitors on Actin Cytoskeleton Dynamics in HIV-1 Infection

The dynamics of the actin cytoskeleton plays a pivotal role in the process of cell division, the transportation of organelles, vesicle trafficking and cell movement. Human immunodeficiency virus type 1 (HIV-1) hijacks the actin dynamics network during the viral entry and migration of the pre-integration complex (PIC) into the nucleus. Actin dynamics linked to HIV-1 has emerged as a potent therapeutic target against HIV infection. Although some inhibitors have been intensely analyzed with regard to HIV-1 infection, their effects are sometimes disputed and the exact mechanisms for actin dynamics in HIV infection have not been well elucidated. In this study, the small molecules regulating HIV-1 infection from diverse inhibitors of the actin dynamic network were screened. Two compounds, including Chaetoglobosin A and CK-548, were observed to specifically bar the viral infection, while the cytochalasin family, 187-1, N-WASP inhibitor, Rho GTPase family inhibitors (EHop-016, CID44216842, and ML-141) and LIMK inhibitor (LIM domain kinase inhibitor) increased the viral infection without cytotoxicity within a range of ~ µM. However, previously known inhibitory compounds of HIV-1 infection, such as Latrunculin A, Jasplakinolide, Wiskostatin and Swinholide A, exhibited either an inhibitory effect on HIV-1 infection combined with severe cytotoxicity or showed no effects. Our data indicate that Chaetoglobosin A and CK-548 have considerable potential for development as new therapeutic drugs for the treatment of HIV infection. In addition, the newly identified roles of Cytochalasins and some inhibitors of Rho GTPase and LIMK may provide fundamental knowledge for understanding the complicated actin dynamic pathway when infected by HIV-1. Remarkably, the newly defined action modes of the inhibitors may be helpful in developing potent anti-HIV drugs that target the actin network, which are required for HIV infection.

Particulate Matter-Induced Aryl Hydrocarbon Receptor Regulates Autophagy in Keratinocytes

Particulate matter (PM), which refers to the mixture of particles present in the air, can have harmful effects. Damage to cells by PM, including disruption of organelles and proteins, can trigger autophagy, and the relationship between autophagy and PM has been well studied. However, the cellular regulators of PM-induced autophagy have not been well characterized, especially in keratinocytes. The Aryl Hydrocarbon Receptor (AhR) is expressed in the epidermis and is activated by PM. In this study, we investigated the role of the AhR in PM-induced autophagy in HaCaT cells. Our results showed that PM led to AhR activation in keratinocytes. Activation of the AhR-target gene CYP1A1 by PM was reduced by co-treatment with α-naphthoflavone (α-NF), an AhR inhibitor. We also evaluated activation of the autophagy pathway in PM-treated keratinocytes. In HaCaT cells, treatment with PM treatment led to the induction of microtubules-associated proteins light chain 3 (LC3) and p62/SQSTM1, which are essential components of the autophagy pathway. To study the role of the AhR in mediating PM-induced autophagy, we treated cells with α-NF or used an siRNA against AhR. Expression of LC3-ІІ induced by PM was decreased in a dose dependent manner by α-NF. Furthermore, knockdown of AhR with siAhR diminished PM-induced expression of LC3-ІІ and p62. Together, these results suggest that inhibition of the AhR decreases PM-induced autophagy. We confirmed these results using the autophagy-inhibitors BAF and 3-MA. Taken together, our results indicate that exposure to PM induces autophagy via the AhR in HaCaT keratinocytes.

Nrf2-Heme oxygenase-1 modulates autophagy and inhibits apoptosis triggered by elevated glucose levels in renal tubule cells

BACKGROUND: Autophagy is a highly balanced process in which lysosomes remove aged and damaged organelles and cellular proteins. Autophagy is essential to maintain homeostasis in the kidneys. METHODS: Using human renal tubule cells HK-2, we assessed the impact of high glucose (HG) on autophagy. We also evaluated the capability of sulforaphane (SFN) to protect the HK-2 cells from HG-induced apoptosis by modulating autophagy. RESULTS: SFN modulated autophagy and decreased apoptosis in the HK-2 cells that were cultured in 250 mM glucose medium for two days. The reactive oxygen species (ROS) levels increased, as expected, in the cells cultured in the 250 mM glucose medium. However, the SFN decreased the ROS levels in the HK-2 cells. The overexpression of heme oxygenase-1 (HO-1) by SFN decreased the expression of LC3 and beclin-1. LC3 and beclin-1 were involved in the downregulation of caspase-3 that was observed in the HG-induced cells. CONCLUSION: The activation of nuclear factor E2-related factor 2 (Nrf2)–HO–1 inhibited ROS expression and subsequently attenuated autophagy and cell apoptosis after HG injury was decreased. HG injury led to the activation of autophagy and HO-1 in order to combat oxidative stress and protect against cell apoptosis. Therefore, HO-1 activation can prevent ROS development and oxidative stress during HG injury, which considerably decreases autophagy and apoptosis.

Autophagy, Cellular Aging and Age-related Human Diseases

Macroautophagy/autophagy is a conserved degradation system that engulfs intracytoplasmic contents, including aggregated proteins and organelles, which is crucial for cellular homeostasis. During aging, cellular factors suggested as the cause of aging have been reported to be associated with progressively compromised autophagy. Dysfunctional autophagy may contribute to age-related diseases, such as neurodegenerative disease, cancer, and metabolic syndrome, in the elderly. Therefore, restoration of impaired autophagy to normal may help to prevent age-related disease and extend lifespan and longevity. Therefore, this review aims to provide an overview of the mechanisms of autophagy underlying cellular aging and the consequent disease. Understanding the mechanisms of autophagy may provide potential information to aid therapeutic interventions in age-related diseases.

Repeated restraint stress promotes hippocampal neuronal cell ciliogenesis and proliferation in mice / 한국실험동물학회지

Stress severely disturbs physiological and mental homeostasis which includes adult neurogenesis in hippocampus. Neurogenesis in hippocampus is a key feature to adapt to environmental changes and highly regulated by multiple cellular signaling pathways. The primary cilium is a cellular organelle, which acts as a signaling center during development and neurogenesis in adult mice. However, it is not clear how the primary cilia are involved in the process of restraint (RST) stress response. Using a mouse model, we examined the role of primary cilia in repeated and acute RST stress response. Interestingly, RST stress increased the number of ciliated cells in the adult hippocampal dentate gyrus (DG). In our RST model, cell proliferation in the DG also increased in a time-dependent manner. Moreover, the analysis of ciliated cells in the hippocampal DG with cell type markers indicated that cells that were ciliated in response to acute RST stress are neurons. Taken together, these findings suggest that RST stress response is closely associated with an increase in the number of ciliated neurons and leads to an increase in cell proliferation.

Can Controlling Endoplasmic Reticulum Dysfunction Treat Allergic Inflammation in Severe Asthma With Fungal Sensitization?

Severe asthma is a heterogeneous disease entity to which diverse cellular components and pathogenetic mechanisms contribute. Current asthma therapies, including new biologic agents, are mainly targeting T helper type 2 cell-dominant inflammation, so that they are often unsatisfactory in the treatment of severe asthma. Respiratory fungal exposure has long been regarded as a precipitating factor for severe asthma phenotype. Moreover, as seen in clinical definitions of allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitization (SAFS), fungal allergy-associated severe asthma phenotype is increasingly thought to have distinct pathobiologic mechanisms requiring different therapeutic approaches other than conventional treatment. However, there are still many unanswered questions on the direct causality of fungal sensitization in inducing severe allergic inflammation in SAFS. Recently, growing evidence suggests that stress response from the largest organelle, endoplasmic reticulum (ER), is closely interconnected to diverse cellular immune/inflammatory platforms, thereby being implicated in severe allergic lung inflammation. Interestingly, a recent study on this issue has suggested that ER stress responses and several associated molecular platforms, including phosphoinositide 3-kinase-δ and mitochondria, may be crucial players in the development of severe allergic inflammation in the SAFS. Defining emerging roles of ER and associated cellular platforms in SAFS may offer promising therapeutic options in the near future.

Primary Cilia as a Signaling Platform for Control of Energy Metabolism

Obesity has become a common healthcare problem worldwide. Cilia are tiny hair-like organelles on the cell surface that are generated and anchored by the basal body. Non-motile primary cilia have been considered to be evolutionary rudiments until a few decades, but they are now considered as important signaling organelles because many receptors, channels, and signaling molecules are highly expressed in primary cilia. A potential role of primary cilia in metabolic regulation and body weight maintenance has been suspected based on rare genetic disorders termed as ciliopathy, such as Bardet-Biedl syndrome and Alström syndrome, which manifest as obesity. Recent studies have demonstrated involvement of cilia-related cellular signaling pathways in transducing metabolic information in hypothalamic neurons and in determining cellular fate during adipose tissue development. In this review, we summarize the current knowledge about cilia and cilia-associated signaling pathways in the regulation of body metabolism.

Can Tissue Cilia Lengths and Urine Cilia Proteins Be Markers of Kidney Diseases? / 전남의대학술지

The primary cilium is an organelle which consists of a microtubule in the core and a surrounding cilia membrane, and has long been recognized as a “vestigial organelle”. However, new evidence demonstrates that the primary cilium has a notable effect on signal transduction in the cell and is associated with some genetic and non-genetic diseases. In the kidney, the primary cilium protrudes into the Bowman's space and the tubular lumen from the apical side of epithelial cells. The length of primary cilia is dynamically altered during the normal cell cycle, being shortened by retraction into the cell body at the entry of cell division and elongated at differentiation. Furthermore, the length of primary cilia is also dynamically changed in the cells, as a result and/or cause, during the progression of various kidney diseases including acute kidney injury and chronic kidney disease. Notably, recent data has demonstrated that the shortening of the primary cilium in the cell is associated with fragmentation, apart from retraction into the cell body, in the progression of diseases and that the fragmented primary cilia are released into the urine. This data reveals that the alteration of primary cilia length could be related to the progression of diseases. This review will consider if primary cilia length alteration is associated with the progression of kidney diseases and if the length of tissue primary cilia and the presence or increase of cilia proteins in the urine is indicative of kidney diseases.

Reactive oxygen species-mediated unfolded protein response pathways in preimplantation embryos

Excessive production of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress-mediated responses are critical to embryonic development in the challenging in vitro environment. ROS production increases during early embryonic development with the increase in protein requirements for cell survival and growth. The ER is a multifunctional cellular organelle responsible for protein folding, modification, and cellular homeostasis. ER stress is activated by a variety of factors including ROS. Such stress leads to activation of the adaptive unfolded protein response (UPR), which restores homeostasis. However, chronic stress can exceed the toleration level of the ER, resulting in cellular apoptosis. In this review, we briefly describe the generation and impact of ROS in preimplantation embryo development, the ROS-mediated activation mechanism of the UPR via the ER, and the subsequent activation of signaling pathways following ER stress in preimplantation embryos.

Implications of aging and the endoplasmic reticulum unfolded protein response on the molecular modality of breast cancer

The endoplasmic reticulum (ER) is an important subcellular organelle that is involved in numerous activities required to achieve and maintain functional proteins in addition to its role in the biosynthesis of lipids and as a repository of intracellular Ca²⁺. The inability of the ER to cope with protein folding beyond its capacity causes disturbances that evoke ER stress. Cells possess molecular mechanisms aimed at clearing unwanted cargo from the ER lumen as an adaptive response, but failing to do so navigates the system towards cell death. This systemic approach is called the unfolded protein response. Aging insults cells through various perturbations in homeostasis that involve curtailing ER function by mitigating the expression of its resident chaperones and enzymes. Here the unfolded protein response (UPR) cannot protect the cell due to the weakening of its protective arm, which exacerbates imbalanced homeostasis. Aging predisposed breast malignancy activates the UPR, but tumor cells maneuver the mechanistic details of the UPR, favoring tumorigenesis and thereby eliciting a treacherous condition. Tumor cells exploit UPR pathways via crosstalk involving various signaling cascades that usher tumor cells to immortality. This review aims to present a collection of data that can delineate the missing links of molecular signatures between aging and breast cancer.

Autophagy in Mycobacterium abscessus Infection

Autophagy is a self-degradative process that removes misfolded or aggregated proteins, clears damaged organelles, as well as eliminates intracellular pathogens playing a role in innate immunity. Mycobacterium abscessus (M. abscessus) has been reported as a causative organism in nearly 80% of the rapid growing mycobacteria (RGM) pulmonary disease. The strain exhibits two different colony types: the smooth (S) one which is considered wild-type and the rough (R) one which is the mutated strain. In accordance to the colony morphology, the S and R types display varying autophagic responses in the host cells with the R type inducing elevated autophagy compared to the S type. The major difference in the autophagy could be based on the bioactive molecules exposed on the surface of the S and R types. Though autophagy has a vital role to play in the clearance of intracellular pathogens, very little is known on the autophagy induced by M. abscessus. It has been known that the intracellular pathogens employ different strategies to evade the autophagic pathway and to survive within the host cells. This review summarizes the most up-to-date findings on autophagy induced by M. abscessus morphotypes and how M. abscessus evades the autophagic machinery to divide and thrive inside the host cells. In addition, the prospects of autophagic machinery in devising new anti-infective strategies against mycobacterial infection is also been discussed.

Autophagy in Mycobacterium abscessus Infection

Autophagy is a self-degradative process that removes misfolded or aggregated proteins, clears damaged organelles, as well as eliminates intracellular pathogens playing a role in innate immunity. Mycobacterium abscessus (M. abscessus) has been reported as a causative organism in nearly 80% of the rapid growing mycobacteria (RGM) pulmonary disease. The strain exhibits two different colony types: the smooth (S) one which is considered wild-type and the rough (R) one which is the mutated strain. In accordance to the colony morphology, the S and R types display varying autophagic responses in the host cells with the R type inducing elevated autophagy compared to the S type. The major difference in the autophagy could be based on the bioactive molecules exposed on the surface of the S and R types. Though autophagy has a vital role to play in the clearance of intracellular pathogens, very little is known on the autophagy induced by M. abscessus. It has been known that the intracellular pathogens employ different strategies to evade the autophagic pathway and to survive within the host cells. This review summarizes the most up-to-date findings on autophagy induced by M. abscessus morphotypes and how M. abscessus evades the autophagic machinery to divide and thrive inside the host cells. In addition, the prospects of autophagic machinery in devising new anti-infective strategies against mycobacterial infection is also been discussed.

Autophagy in the placenta

Autophagy is an evolutionarily conserved catalytic process by which cytoplasmic components including damaged macromolecules and organelles are degraded. The role of autophagy includes adaptive responses to nutrition deprivation or intracellular stimuli. Although autophagosomes were first observed in early 1960s, it was 1990s that autophagy-related genes in yeast were identified and studied. Nowadays, the molecular machinery of autophagy and signaling pathway to various stimuli are almost outlined. Dysregulation of autophagic activity has been implicated in many human diseases including neurodegenerative diseases, infection and inflammation, and malignancies. However, since current understanding of autophagy in placenta is just at the beginning, this paper aims to provide general information on autophagy (part I) and to summarize articles on autophagy in human placenta (part II). This review article will serve as a basis for further researches on autophagy in relation to human pregnancy and its complications.

Effects of exercise on obesity-induced mitochondrial dysfunction in skeletal muscle

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all associated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dynamic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochondria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in O₂ respiration and increase in oxidative stress) in skeletal muscle. The balance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mitochondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal muscle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle.

Mitochondrial Control of Innate Immunity and Inflammation

Mitochondria are key organelles involved in energy production, functioning as the metabolic hubs of cells. Recent findings emphasize the emerging role of the mitochondrion as a key intracellular signaling platform regulating innate immune and inflammatory responses. Several mitochondrial proteins and mitochondrial reactive oxygen species have emerged as central players orchestrating the innate immune responses to pathogens and damaging ligands. This review explores our current understanding of the roles played by mitochondria in regulation of innate immunity and inflammatory responses. Recent advances in our understanding of the relationship between autophagy, mitochondria, and inflammasome activation are also briefly discussed. A comprehensive understanding of mitochondrial role in toll-like receptor-mediated innate immune responses and NLRP3 inflammasome complex activation, will facilitate development of novel therapeutics to treat various infectious, inflammatory, and autoimmune disorders.