Active Cellular Process Research Articles

Multi-omics of in vitro aortic valve calcification.

Heart valve calcification is an active cellular and molecular process that partly remains unknown. Osteogenic differentiation of valve interstitial cells (VIC) is a central mechanism in calcific aortic valve disease (CAVD). Studying mechanisms in CAVD progression is clearly needed. In this study, we compared molecular mechanisms of osteogenic differentiation of human VIC isolated from healthy donors or patients with CAVD by RNA-seq transcriptomics in early timepoint (48 h) and by shotgun proteomics at later timepoint (10th day). Bioinformatic analysis revealed genes and pathways involved in the regulation of VIC osteogenic differentiation. We found a high amount of stage-specific differentially expressed genes and good accordance between transcriptomic and proteomic data. Functional annotation of differentially expressed proteins revealed that osteogenic differentiation of VIC involved many signaling cascades such as: PI3K-Akt, MAPK, Ras, TNF signaling pathways. Wnt, FoxO, and HIF-1 signaling pathways were modulated only at the early timepoint and thus probably involved in the commitment of VIC to osteogenic differentiation. We also observed a significant shift of some metabolic pathways in the early stage of VIC osteogenic differentiation. Lentiviral overexpression of one of the most upregulated genes (ZBTB16, PLZF) increased calcification of VIC after osteogenic stimulation. Analysis with qPCR and shotgun proteomics suggested a proosteogenic role of ZBTB16 in the early stages of osteogenic differentiation.

The Drama of Wallerian Degeneration: The Cast, Crew, and Script.

Significant advances have been made in recent years in identifying the genetic components of Wallerian degeneration, the process that brings the progressive destruction and removal of injured axons. It has now been accepted that Wallerian degeneration is an active and dynamic cellular process that is well regulated at molecular and cellular levels. In this review, we describe our current understanding of Wallerian degeneration, focusing on the molecular players and mechanisms that mediate the injury response, activate the degenerative program, transduce the death signal, execute the destruction order, and finally, clear away the debris. By highlighting the starring roles and sketching out the molecular script of Wallerian degeneration, we hope to provide a useful framework to understand Wallerian and Wallerian-like degeneration and to lay a foundation for developing new therapeutic strategies to treat axon degeneration in neural injury as well as in neurodegenerative disease.

TAK1 inhibition elicits mitochondrial ROS to block intracellular bacterial colonization

Mitogen-activated protein kinase kinase kinase 7 (MAP3K7), known as TAK1, is an intracellular signaling intermediate of inflammatory responses. However, a series of mouse Tak1 gene deletion analyses have revealed that ablation of TAK1 does not prevent but rather elicits inflammation, which is accompanied by elevation of reactive oxygen species (ROS). This has been considered a consequence of impaired TAK1-dependent maintenance of tissue integrity. Contrary to this view, here we propose that TAK1 inhibition-induced ROS are an active cellular process that targets intracellular bacteria. Intracellular bacterial effector proteins such as Yersinia's outer membrane protein YopJ are known to inhibit TAK1 to circumvent the inflammatory host responses. We found that such TAK1 inhibition induces mitochondrial-derived ROS, which effectively destroys intracellular bacteria. Two cell death-signaling molecules, caspase 8 and RIPK3, cooperatively participate in TAK1 inhibition-induced ROS and blockade of intracellular bacterial growth. Our results reveal a previously unrecognized host defense mechanism, which is initiated by host recognition of pathogen-induced impairment in a host protein, TAK1, but not directly of pathogens.

TAK1 Inhibition Elicits Mitochondrial ROS to Block Intracellular Bacterial Colonization

Mitogen activated protein kinase kinase kinase 7 (MAP3K7), known as TAK1, is an intracellular signaling intermediate of inflammatory responses. However, a series of mouse Tak1 gene deletion analysis has revealed that ablation of TAK1 does not prevent but rather elicits inflammation, which is accompanied by elevation of reactive oxygen species (ROS). These have been considered as consequences of non-physiological loss of TAK1. Contrary to this view, here we propose that TAK1 inhibition-induced ROS are an active cellular process that targets intracellular bacteria. Intracellular bacterial effector proteins such as Yersinia's outer membrane protein YopJ are known to inhibit TAK1 to circumvent the inflammatory host responses. We found that such TAK1 inhibition particularly induces mitochondrial-derived ROS, which effectively destroys intracellular bacteria. Our results reveal a previously unrecognized host defense mechanism linking inhibition of inflammatory signaling with mitochondrial ROS.

Presumptive heterophil extracellular traps recognized cytologically in nine reptile patients with inflammatory conditions

Background Neutrophil extracellular traps (NETs) represent a novel cellular mechanism of antimicrobial defense activity. Intravascular neutrophils produce extracellular web-like structures composed of chromatin, histones, and cytoplasmic granule proteins to attack and kill microbes. They may impact both pathogen and host; NETs correlate strongly with disseminated intravascular coagulation and mortality in critically ill humans. The mechanism was first discovered in human neutrophils in 2004. Presumptive heterophil extracellular traps (HETs) in a non-avian reptile species were first described in blood films of a gopher tortoise with systemic inflammation. Objective While prior reports are limited to blood film review and in vitro studies, this descriptive case series highlights the cytological identification of presumptive HETs in nine reptile patients. Methods Subjects included six gopher tortoises, one blood python (Python curtus), one Burmese python (P. bivittatus), and one desert king snake (Lampropeltis getula splendida). All six gopher tortoises (Gopherus polyphemus) had upper respiratory disease with bacterial etiology (including Helicobacter sp. and/or Mycoplasma sp.), and snakes had upper respiratory tract infection confirmed with serpentovirus (n = 2) or bacterial dermatitis (n = 1). Results Cytology samples with identified HETs included tissue imprints (n = 4), nasal discharge (n = 3), an oral swab (n = 1), and a fine needle aspirate of a skin lesion (n = 1). The identification of specific bacterial (n = 6) and/or viral pathogens (n = 2) was notable. Clinical relevance To the authors’ knowledge, this is the first report of presumptive HETs recognized in reptile cytology specimens, suggesting an active cellular process in vivo in response to systemic inflammation in non-avian reptiles, and contributing to further understanding of extracellular traps in these species.

Gla-rich Protein (GRP): A New Player In The Burden Of Vascular Calcification

Abstract Vascular calcification is a life-threatening complication of cardiovascular disease and an independent risk factor for morbidity and mortality. It is a complex and active cellular process that includes multiple players and regulators resembling physiological bone formation. Currently, it is generally accepted that our understanding of the molecular aetiology of vascular calcification remains incomplete. Endogenous inhibitors play a critical role in preventing vascular calcification. A relation between vitamin K and vascular calcification has been widely established and recently, the vitamin K-dependent protein, Gla-rich protein (GRP), was proposed to have an important role in vascular calcification inhibition, with clinical implications.

Elucidation of Resolvin and Protectin Sulfido‐Conjugated Mediators: New Pro‐Resolving and Tissue Regenerative Pathways

Resolution of inflammation is an active cellular and biochemical process mediated by autacoids. Here, we investigated self‐limited infectious exudates for novel bioactive chemical signals in tissue regeneration and resolution. Using spleens from E. coli infected mice, self‐resolving infectious exudates, human spleens and blood from sepsis patients we identified two new families of potent molecules. Characterization of their physical properties and isotope tracking demonstrated that the bioactive structures contained a docosahexaenoate backbone and sulfido‐conjugated triene or tetraene double bond systems. Activated human phagocytes converted 17‐hydro(peroxy)‐4Z,7Z,10Z,13Z,15E,19Z‐docosahexaenoic acid to these bioactive molecules. Regeneration of injured planaria was accelerated with nanomolar amounts of 16‐glutathionyl, 17‐hydroxy‐docosahexaenoic acid and 16‐cysteinylglycinyl, 17‐hydroxy‐docosahexaenoic acid (coined protectin conjugates in tissue regeneration) as well as 8‐glutathionyl, 7,17‐dihydroxy‐docosahexaenoic acid and 8‐cysteinylglycinyl, 7,17‐dihydroxy‐docosahexaenoic acid (coined resolvin conjugates in tissue regeneration). Each protectin and resolvin sulfido‐conjugate stimulated human macrophage bacterial phagocytosis, phagolysosomal acidification and efferocytosis. Together these results identify two novel pathways and structural elucidation of new resolution moduli. These pathways and mediators display host protective, pro‐resolving and tissue regenerative actions, properties essential for tissue homeostasis.

STAT6 EXPRESSION BY PERIPHERAL BLOOD LYMPHOCYTES IN BRONCHIAL ASTHMA

Abstract. The aim of present study was to determine the features of STAT6 and phospho-STAT6 (pSTAT6) expression in bronchial asthma (BA). Patients and methods. Eleven patients with allergic (atopic) steroidfree were examined, five healthy controls served as a control. Expression of proteins (STAT6 and pSTAT6) in peripheral blood lymphocytes was studied by Western blot analysis after cell lysis. Preparation of cell lysates and Western blotting were performed using a standard procedure (Amersham). Antibodies against pSTAT6 and STAT6 (manufactured by Cell Signaling) were used. Relative levels of specific proteins were analyzed using actin as a reference, by means of anti-actin antibody. Results. STAT6 phosphorylation was significantly increased in lymphocytes of patients with BA exacerbation, as compared to patients in remission and healthy group. The level of STAT6 was significantly higher compared to healthy persons and showed negative correlation with grade of air flow obstruction. Conclusion. STAT6 and their active form pSTAT6 may play a key role in BA pathophysiology. This study suggests atopic, steroid-free BA (in particular, on exacerbation) to be associated with active cellular inflammatory process, involving activation of STAT6, along with increased level of their active form (pSTAT6). The work was supported by Saint-Petersburg government grants: PD04-4.0-102 (Certificate N ASP604079).

Preconditioning stimulus of proteasome inhibitor enhances aggresome formation and autophagy in differentiated SH-SY5Y cells

The abnormal accumulation of protein aggregates is a dominant pathological feature common in neurodegenerative diseases. Autophagy contributes to the processing of aggregated proteins resistant to proteasomal degradation. Autophagic degradation is multi-step process, and especially aggresome formation is a specific and active cellular process for appropriate autophagy-mediated protein homeostasis mechanism. Here, we showed that preconditioning of cells with a non-toxic low dose of MG132 induced autophagy, using an in vitro experimental model that closely represents the characteristics of the autophagy pathway under proteasome inhibition. Clear and large aggresome-like protein accumulation was observed in the perinuclear region of differentiated SH-SY5Y cells with preconditioning stimulus. This results in up-regulation of autophagosome formation and turnover and degradation of intracellular ubiquitinated and p62-bound protein aggregates. Pretreatment with low dose of MG132 attenuated proteinopathy-related cytotoxicity. Together, our experimental model could provide a proper in vitro system for studying the autophagy-related pathophysiology of neurodegeneration, especially therapeutic targeting of intracellular aggresome-like aggregates formation.

How Do Immune Cells Support and Shape the Brain in Health, Disease, and Aging?

For decades, several axioms have prevailed with respect to the relationships between the CNS and circulating immune cells. Specifically, immune cell entry was largely considered to be pathological or to mark the beginning of pathology within the brain. Moreover, local inflammation associated with neurodegenerative diseases such Alzheimer's disease or amyotrophic lateral sclerosis, were considered similar in their etiology to inflammatory diseases, such as remitting relapsing-multiple sclerosis. The ensuing confusion reflected a lack of awareness that the etiology of the disease as well as the origin of the immune cells determines the nature of the inflammatory response, and that inflammation resolution is an active cellular process. The last two decades have seen a revolution in these prevailing dogmas, with a significant contribution made by the authors. Microglia and infiltrating monocyte-derived macrophages are now known to be functionally distinct and of separate origin. Innate and adaptive immune cells are now known to have protective/healing properties in the CNS, as long as their activity is regulated, and their recruitment is well controlled; their role is appreciated in maintenance of brain plasticity in health, aging, and chronic neurodevelopmental and neurodegenerative diseases. Moreover, it is now understood that the barriers of the brain are not uniform in their interactions with the circulating immune cells. The implications of these new findings to the basic understanding of CNS repair processes, brain aging, and a wide spectrum of CNS disorders, including acute injuries, Rett syndrome, Alzheimer's disease, and multiple sclerosis, will be discussed.

Cold Physical Plasma Treatment Alters Redox Balance in Human Immune Cells

Cold atmospheric pressure plasma is a promising tool for various biomedical applications. Particularly, treatment of cells and tissues in diseases such as chronic wounds possesses high potential. However, detailed knowledge of how plasma mediates its actions on cells is necessary to explore its potentially beneficial effects in clinical settings. Previous studies have shown that plasma induces oxidative stress. We confirmed this hypothesis by showing that plasma significantly oxidized glutathione (GSH), a major cellular reductant. In plasma-treated cells we found elevated levels of GSH, pointing to a change in cellular redox balance. Oxidative stress can induce apoptosis and plasma-mediated apoptosis has been shown before measuring phosphatidylserine exposure. Using primary human immune cells, we investigated what events precede this reaction. Apoptosis is an active cellular process and accordingly it was dependent on incubation temperature after treatment. Damage of mitochondria was linked to apoptosis previously and plasma treatment resulted in mitochondrial oxidation and reduced mitochondrial membrane potential. Further, we measured a treatment time dependent activation of executioner caspase 3 which is known to be crucially involved in apoptosis. Together, our results suggested that plasma-mediated oxidative stress reactions in eukaryotic cells are in line with the foregoing research in redox biology. Establishing this link will help anticipate results in future research and clinical studies involving cold atmospheric pressure plasmas.

A Novel Drosophila Model of Nerve Injury Reveals an Essential Role of Nmnat in Maintaining Axonal Integrity

Axons damaged by acute injury, toxic insults, or during neurodegenerative diseases undergo Wallerian or Wallerian-like degeneration, which is an active and orderly cellular process, but the underlying mechanisms are poorly understood. Drosophila has been proven to be a successful system for modeling human neurodegenerative diseases. In this study, we established a novel in vivo model of axon injury using the adult fly wing. The wing nerve highlighted by fluorescent protein markers can be directly visualized in living animals and be precisely severed by a simple wing cut, making it highly suitable for large-scale screening. Using this model, we confirmed an axonal protective function of Wld(S) and nicotinamide mononucleotide adenylyltransferase (Nmnat). We further revealed that knockdown of endogenous Nmnat triggered spontaneous, dying-back axon degeneration in vivo. Intriguingly, axonal mitochondria were rapidly depleted upon axotomy or downregulation of Nmnat. The injury-induced mitochondrial loss was dramatically suppressed by upregulation of Nmnat, which also protected severed axons from degeneration. However, when mitochondria were genetically eliminated from axons, upregulation of Nmnat was no longer effective to suppress axon degeneration. Together, these findings demonstrate an essential role of endogenous Nmnat in maintaining axonal integrity that may rely on and function by stabilizing mitochondria.

Sublytic Concentrations of Staphylococcus Aureus α-Toxin Trigger Na+/K+ Atpase Mediated Cell Shrinkage

Cell lysis can occur through the pathologic action of various membrane-targeting toxins, of which the pore-forming toxin Staphylococcus aureus α-toxin is a prominent example. Paradoxically, S. aureus α-toxin, which forms monovalent cation permeable channels in the host cell plasma membrane, has been observed to cause significant volume shrinkage in many cell types. In HeLa cells we note a ≈45% decrease in cell volume 30-60 mins post α-toxin treatment in both interphase and mitotic cells. We show that inhibition of the Na+/K+ ATPase pump with ouabain not only prevents the cell shrinkage, but leads to cell volume expansion after exposure to α-toxin. This suggests α-toxin mediated volume decrease occurs through the upregulation of Na+/K+ ATPase activity because the 3:2 export:import ratio of Na+:K+ leads to the loss of one osmolyte per cycle. We therefore conclude that α-toxin induced cell shrinkage is an active cellular process driven by the Na+/K+ ATPase and elucidate sub-lytic mechanisms of pore-forming toxin assault.

DNA Repair: Exploiting the Fanconi Anemia Pathway As a Potential Therapeutic Target

DNA repair is an active cellular process to respond to constant DNA damage caused by metabolic processes and environmental factors. Since the outcome of DNA damage is generally adverse and long term effects may contribute to oncogenesis, cells have developed a variety of DNA repair mechanisms, which operate depending on the type of DNA damage inflicted. At least 15 Fanconi anemia (FA) proteins interact in a common pathway involved in homologous recombination. Inherited homozygous mutations in any of these FA genes cause a rare disease, Fanconi anemia, characterized by congenital abnormalities, progressive bone-marrow failure and cancer susceptibility. Heterozygous germline FA mutations predispose to various types of cancer. In addition, somatic FA mutations have been identified in diverse cancer types. Evidence exists that cells deficient in the FA pathway become dependent on alternative pathways for survival. Additional inhibition of such alternative pathways is thus expected to result in cell death, creating a relationship of synthetic lethality. Identifying these relationships can reveal yet unknown mechanisms of DNA repair and new targets for therapy.

Calcific Aortic Stenosis

Calcific aortic stenosis is the most common indication for surgical valve replacement in the United States. For years this disease has been described as a passive degenerative process during which serum calcium attaches to the valve surface and binds to the leaflet to form nodules. Therefore, surgical treatment of this disease has been the approach toward relieving outflow obstruction in these patients. Recent studies demonstrate an association between atherosclerosis and its risk factors for aortic valve disease. In 2008, there are increasing number of epidemiology and experimental studies to provide evidence that this disease process is not a passive phenomena. There is an active cellular process that develops within the valve leaflet and causes a regulated bone formation to develop. If the atherosclerotic hypothesis is important in the initiation of aortic stenosis, then treatments used in slowing the progression of atherosclerosis may be effective in patients with aortic valve disease. This review will discuss the pathogenesis and the potential for medical therapy in the management of patients with calcific aortic stenosis by examining the lessons provided from the experimental research.

The pathophysiology of vascular calcification: are osteoclast-like cells the missing link?

There is increasing evidence to suggest that the initiation of vascular calcification is an active process involving vascular smooth muscle cell (VSMC) apoptosis and trans-differentiation into calcifying cells. This active process results in the deposition of an osteogenic extracellular matrix and may be exacerbated by a reduction in the levels of one or more native calcification inhibitors (such as fetuin A and pyrophosphate). Here, we present data which strongly suggest that the regression of vascular calcification might also be an active cellular process involving osteoclast-like cells. However, the presence of osteoclast like cells in the vascular wall is rather limited. To explain this rarity of osteoclast-like cells, we recently observed that the same factors, which promote the trans-differentiation of VSMCs into osteoblastlike cells are also capable of inhibiting the in vitro differentiation of monocytes/macrophages into osteoclast-like cells. An imbalance between osteoblast-like and osteoclast-like cell activities would therefore favour the occurrence of a pathological calcification process in vessel walls. Our new data are strongly evocative of a vascular remodelling process similar to that observed in bone tissue. To confirm this hypothesis, strategies for activating osteoclasts in the vascular wall (with a view to preventing or reversing vascular calcifications) are required.

Relationship Between Fetuin-A Concentration, Elevated Levels of Inflammatory Markers, and Arterial Wall Stiffness in End-Stage Kidney Disease

The risk of cardiovascular mortality is significantly heightened in chronic dialysis patients. Aortic wall stiffness, as reflected by aortic pulse-wave velocity (PWV), is a strong predictor of cardiovascular events. Loss of the aortic wall's elasticity is accelerated in dialysis patients because of calcifying medial arteriosclerosis, an active cellular process, controlled by calcification inducers and inhibitors. A pivotal role in the inhibition of calcium x phosphorus (Ca x P) precipitation is played by fetuin-A, a circulating plasma glycoprotein. In hemodialysis patients, lower fetuin-A concentrations were associated with increases in both cardiovascular and overall mortality. In our own study, a significant negative correlation was established between fetuin-A level and aortic PWV in chronic hemodialysis patients. The arterial-stiffening process was unaffected by the Ca x P product, but occurred independent of elevated interleukin-6 levels.

Activin A is an anticatabolic autocrine cytokine in articular cartilage whose production is controlled by fibroblast growth factor 2 and NF‐κB

Proteomic analysis has previously shown that activin A, a member of the transforming growth factor beta family, is produced by human articular cartilage. This study was undertaken to investigate whether activin A affects cartilage matrix catabolism and how its production is regulated. The effect of exogenous activin A on interleukin-1-induced aggrecanase-generated neoepitope production was assessed by Western blotting, using medium from human cartilage explants. Levels of activin A production were determined by enzyme-linked immunosorbent assay. For genes of interest, messenger RNA (mRNA) induction in cartilage explants or primary chondrocyte monolayers was assessed by reverse transcriptase-polymerase chain reaction. Activin A activity in cartilage explant medium was measured by incubating it with human dermal fibroblasts and determining the increase in phospho-Smad2 by Western blotting. Activin A (1-10 ng/ml) suppressed aggrecanase-mediated cleavage of aggrecan in human articular cartilage. Activin A mRNA and protein secretion were induced by dissection and culture of human or porcine articular cartilage. This activin A was biologically active. Its production was due to an active cellular process and was enhanced in osteoarthritic (OA) tissue. Activin A production on dissection was reduced by 80% by the fibroblast growth factor (FGF) receptor inhibitor PD173074 and by 70% by the IKK inhibitor BMS345541. Activin A is potentially an anticatabolic molecule in articular cartilage. Its expression is induced by wounding in an FGF-2- and NF-kappaB-dependent manner. OA cartilage produced more activin A than did normal cartilage in vitro.

Programmed cell death in intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is largely a process of destruction and failure of the extracellular matrix (ECM), and symptomatic IVD degeneration is thought to be one of the leading causes of morbidity or life quality deterioration in the elderly. To date, however, the mechanism of IVD degeneration is still not fully understood. Cellular loss from cell death in the process of IVD degeneration has long been confirmed and considered to contribute to ECM degradation, but the causes and the manners of IVD cell death remain unclear. Programmed cell death (PCD) is executed by an active cellular process and is extensively involved in many physiological and pathological processes, including embryonic development and human degenerative diseases. Thus, the relationship between PCD and IVD degeneration has become a new research focus of interest in recent years. By reviewing the available literature concentrated on PCD in IVD and discussing the methodology of detecting PCD in IVD cells, its inducing factors, the relationship of cell death to ECM degradation, and the potential therapy for IVD degeneration by modulation of PCD, we conclude that IVD cells undergo PCD via different signal transduction pathways in response to different stimuli, that PCD may play a role in the process of IVD degeneration, and that modulation of PCD might be a potential therapeutic strategy for IVD degeneration.

Reversibility of Calcitriol-Induced Medial Artery Calcification in Rats With Intact Renal Function

VC is an important clinical entity; however, very little information is available on its resolution. Induction and regression of calcitriol-induced VC was studied in 47 rats. After calcitriol withdrawal, there was a relatively rapid regression of VC mediated by an active cellular process. Vascular calcifications (VCs) represent an important risk factor for cardiovascular death. Although VCs are prevalent in relevant diseases (e.g., chronic kidney disease, osteoporosis, diabetes), the reversibility of extraskeletal calcifications is an unresolved issue. This study was conducted to investigate (1) the in vivo effect of calcitriol on VC and (2) whether calcitriol-induced VC would regress after suppression of calcitriol treatment. The calcifying effect of calcitriol was studied in four groups of rats (n = 8) that received calcitriol (1 mug/kg, IP) for 2, 4, 6, and 8 days. The reversibility of VC was studied in three additional groups (n = 5) treated with 1 mug/kg of calcitriol for 8 days that were subsequently killed 1, 2, and 9 weeks after the last calcitriol dose. Aortic VC was assessed by histology and by quantification of aortic calcium and phosphorus content. The aortic wall was studied by histology and immunohistochemistry. Statistical analysis was performed by ANOVA and t-tests. Calcitriol administration resulted in a time-dependent induction of VC, with aortic calcium and phosphorus being significantly increased at 6 and 8 days. Treatment with calcitriol for 8 days resulted in massive medial calcification of the aorta with a 10- to 30-fold increase in the aortic Ca and P content. After suppressing calcitriol administration, a progressive decrease in von Kossa staining and aortic Ca (from 32.8 +/- 2.5 to 9.3 +/- 1.8 mg/g of tissue, p < 0.001) and P (from 11.9 +/- 1.2 to 2.7 +/- 1.8 mg/g of tissue, p = 0.001) content was evidenced. Histology of the aortic wall showed monocytes adhered to the aortic endothelium and macrophages involved in the reabsorption of calcium deposits. Our results show that calcitriol treatment induces time-dependent VC. After calcitriol withdrawal, VC regress rapidly with aortic calcium and phosphorus decreasing by 75% in the course of 9 weeks. An active cellular process seems to be involved in regression of VC.