Activation of Jun N-terminal kinase/stress-activated protein kinase pathway by tumor necrosis factor alpha leads to intercellular adhesion molecule-1 expression

Influence of cold-stimulated adipocyte supernatant on the expression of adhesion-related molecules in Schwann cell line

Bell's palsy is the most common form of facial nerve palsy. This study aimed to explore the pathogenesis of Bell's palsy by investigating the effect of cold-stimulated adipocyte supernatant on adhesion molecule expression in Schwann cell line. Schwann cells were cultured in regular or adipocyte-conditioned medium and analyzed using RNA sequencing. The mRNA expression of Schwann cell adhesion molecules melanoma cell adhesion molecule (MCAM), protocadherin 9 (PCDH9), and intercellular cell adhesion molecule 1 (ICAM1) was determined using real-time reverse-transcription polymerase chain reaction. Differentially expressed genes were identified, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were conducted. Compared with Schwann cells in 37 °C, the expression of MCAM, PCDH9, and ICAM1 was downregulated in Schwann cells treated with cold-stimulated adipocyte supernatant compared with Schwann cells in 37 °C. Adipocytes subjected to cold exposure may weaken the adhesion capacity of Schwann cells and disrupt the local homeostasis of Schwann cell-axon interactions by affecting the expression of MCAM, PCDH9, and ICAM1, ultimately leading to the development of demyelinating lesions.

The Involvement of Cx43 in JNK1/2-Mediated Endothelial Mechanotransduction and Human Plaque Progression

Atherosclerotic lesions preferentially develop at bifurcations, characterized by non-uniform shear stress (SS). The aim of this study was to investigate SS-induced endothelial activation, focusing on stress-regulated mitogen-activated protein kinases (MAPK) and downstream signaling, and its relation to gap junction proteins, Connexins (Cxs). Human umbilical vein endothelial cells were exposed to flow ("mechanical stimulation") and stimulated with TNF-α ("inflammatory stimulation"). Phosphorylated levels of MAPKs (c-Jun N-terminal kinase (JNK1/2), extracellular signal-regulated kinase (ERK), and p38 kinase (p38K)) were quantified by flow cytometry, showing the activation of JNK1/2 and ERK. THP-1 cell adhesion under non-uniform SS was suppressed by the inhibition of JNK1/2, not of ERK. Immunofluorescence staining and quantitative real-time PCR demonstrated an induction of c-Jun and c-Fos and of Cx43 in endothelial cells by non-uniform SS, and the latter was abolished by JNK1/2 inhibition. Furthermore, plaque inflammation was analyzed in human carotid plaques (n = 40) using immunohistochemistry and quanti-gene RNA-assays, revealing elevated Cx43⁺ cell counts in vulnerable compared to stable plaques. Cx43⁺ cell burden in the plaque shoulder correlated with intraplaque neovascularization and lipid core size, while an inverse correlation was observed with fibrous cap thickness. Our results constitute the first report that JNK1/2 mediates Cx43 mechanoinduction in endothelial cells by atheroprone shear stress and that Cx43 is expressed in human carotid plaques. The correlation of Cx43⁺ cell counts with markers of plaque vulnerability implies its contribution to plaque progression.

Acute and Chronic Exposure to 900 MHz Radio Frequency Radiation Activates p38/JNK-mediated MAPK Pathway in Rat Testis

The use of electronic devices such as mobile phones has had a long stretch of rapid growth all over the world. Therefore, exposure to radio frequency radiation (RFR) has increased enormously. Here, we aimed to assess the balance between cell death and proliferation and also investigate the involvement of the JNK/p38 MAPK signaling pathway in the testis of rats exposed to 900 MHz RFR in acute and chronic periods (2 h/day, 5 days/week) for 1 or 10 weeks, respectively. The expression of proliferating cell nuclear antigen (PCNA), Bcl-xL, cleaved caspase-3, phosphorylated-JNK (p-JNK), and phosphorylated-p38 (p-p38) was analyzed in line with histopathology and TUNEL analysis in rat testis. There were no histopathological differences between sham and RFR groups in the acute and chronic groups. PCNA expression was not altered between groups in both periods. However, alterations for cleaved caspase-3 and Bcl-xL were observed depending on the exposure period. TUNEL analysis showed a significant increase in the RFR group in the acute period, whereas no difference in the chronic groups for the apoptotic index was reported. In addition, both p-p38 and p-JNK protein expressions increased significantly in RFR groups in both periods. Our study indicated that 900 MHz RFR might result in alterations during acute period exposure for several parameters, but this can be ameliorated in the chronic period in rat testis. Here, we also report the involvement of the p38/JNK-mediated MAPK pathway after exposure to 900 MHz RFR. Hence, this information might shed light in future studies toward detailed molecular mechanisms in male reproduction and infertility.

Bacterial Infections Affect Male Fertility: A Focus on the Oxidative Stress-Autophagy Axis

Numerous factors trigger male infertility, including lifestyle, the environment, health, medical resources and pathogenic microorganism infections. Bacterial infections of the male reproductive system can cause various reproductive diseases. Several male reproductive organs, such as the testicles, have unique immune functions that protect the germ cells from damage. In the reproductive system, immune cells can recognize the pathogen-associated molecular patterns carried by pathogenic microorganisms and activate the host's innate immune response. Furthermore, bacterial infections can lead to oxidative stress through multiple signaling pathways. Many studies have revealed that oxidative stress serves dual functions: moderate oxidative stress can help clear the invaders and maintain sperm motility, but excessive oxidative stress will induce host damage. Additionally, oxidative stress is always accompanied by autophagy which can also help maintain host homeostasis. Male reproductive system homeostasis disequilibrium can cause inflammation of the genitourinary system, influence spermatogenesis, and even lead to infertility. Here, we focus on the effect of oxidative stress and autophagy on bacterial infection in the male reproductive system, and we also explore the crosslink between oxidative stress and autophagy during this process.

TNF-α inhibits GDNF levels in Sertoli cells, through a NF-κB-dependent, HES1-dependent mechanism

BACKGROUND

Glial cell line-derived neurotrophic factor (GDNF) is a soluble molecule crucial for the regulation of the spermatogonial stem cells (SSC) of the testis. The effects of GDNF on target cells have been extensively described, but mechanisms underlying GDNF regulation are currently under investigation. In the nervous system, GDNF expression is regulated by pro-inflammatory cytokines including lipopolysaccharide (LPS), interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α) but the effect of these cytokines on GDNF expression in the testis is unclear.

OBJECTIVES

The aim of the present study was to investigate the impact of TNF-α on GDNF expression levels using primary murine Sertoli cells as experimental model.

MATERIAL AND METHODS

The expression of TNF-α-regulated genes including Gdnf in different culture conditions was determined by real-time PCR. GDNF protein levels were determined by ELISA. The activation of the NF-κb pathway and HES1 levels were assessed by Western Blot analysis and immunofluorescence. HES1 expression was downregulated by RNAi.

RESULTS

In primary Sertoli cells, TNF-α downregulates GDNF levels through a nuclear factor-κB (NF-κB)-dependent mechanism. Mechanistically, TNF-α induces the transcriptional repressor HES1 by a NF-Κb-dependent mechanism, which in turn downregulates GDNF.

DISCUSSION

Under physiological conditions, TNF-α is secreted by germ cells suggesting that this cytokine plays a role in the paracrine control of SSC niche by modulating GDNF levels. HES1, a well-known target of the Notch pathway, is implicated in the regulation of GDNF expression. In Sertoli cells, TNF-α and Notch signaling may converge at molecular level, to regulate the expression of HES1 and HES1- target genes, including GDNF.

CONCLUSIONS

Because of the importance of GDNF for spermatogonial stem cell self-renewal and proliferation, this data may give important insights on how cytokine signals in the testis modulate the expression of niche-derived factors.

The inflammatory mediators TNFα and nitric oxide arrest spermatogonia GC-1 cell cycle

During an inflammatory process of the testis, the network of somatic, immune, and germ cell interactions is altered leading to organ dysfunction. In testicular biopsies of infertile men, spermatogenesis impairment is associated with reduced spermatogonia proliferation, increased number of immune cells, and content of pro-inflammatory cytokines. TNFα-TNFR and nitric oxide (NO)-NO synthase systems are up-regulated in models of testicular damage and in human testis with maturation arrest. The purpose of this study was to test the hypothesis that TNFα-TNFR system and NO alter the function of spermatogonia in the inflamed testis. We studied the effect of TNFα and NO on GC-1 spermatogonia cell cycle progression and death by flow cytometry. GC-1 cells expressed TNFR1 and TNFR2 (immunofluorescence). TNFα (10 and 50 ng/ml) and DETA-Nonoate (0.5 and 2 mM), a NO releaser, increased the percentage of cells in S-phase of the cell cycle and reduced the percentage in G1, inducing also cell apoptosis. TNFα effect was not mediated by oxidative stress unlike NO, since the presence of N-acetyl-l-cysteine (2.5 and 5.0 mM) prevented NO induced cell cycle arrest and death. GC-1 spermatogonia overpass NO induced cell cycle arrest but no TNFα, since after removal of NO, spermatogonia progressed through the cell cycle. We propose TNFα and NO might contribute to impairment of spermatogenesis by preventing adequate functioning of the spermatogonia population. Our results showed that TNFα and NO impaired spermatogonia cell cycle, inducing GC-1 arrest in the S phase.

TRIM59 loss in M2 macrophages promotes melanoma migration and invasion by upregulating MMP-9 and Madcam1

The culture supernatant from macrophages overexpressing TRIM59 has a cytotoxic effect on melanoma, but the mechanism remains unclear. To investigate whether deletion of TRIM59 in macrophages affects the metastatic potential of melanoma cells, we polarized control and TRIM59-deficient bone marrow-derived macrophages to the M2 phenotype and collected the respective conditioned media (CM). Exposure to CM from TRIM59^-/--M2 cultures significantly promoted migration and invasion by B16-F0 and B16-F10 cells. Cytokine profiling indicated a ~15-fold increase in TNF-α production in CM from TRIM59^-/--M2 cultures, and neutralizing TNF-α activity abrogated the referred stimulatory effects on cell motility. Transcriptome analysis revealed significant upregulation of MMP-9 and Madcam1 in melanoma cells exposed to TRIM59^-/--M2 CM. Inhibitory experiments determined that these changes were also TNF-α-dependent and mediated by activation of ERK signaling. Independent knockdown of MMP9 and Madcam1 in B16-F10 cells impeded epithelial-mesenchymal transition and inhibited subcutaneous tumor growth and formation of metastatic lung nodules in vivo. These data suggest TRIM59 expression attenuates the tumor-promoting effect of tumor-associated macrophages, most of which resemble the M2 phenotype. Moreover, they highlight the relevance of TRIM59 in macrophages as a potential regulator of tumor metastasis and suggest TRIM59 could serve as a novel target for cancer immunotherapy.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Vascular Dysfunction in Alzheimer's Disease: A Prelude to the Pathological Process or a Consequence of It?

Alzheimer's disease (AD) is the most prevalent form of dementia. Despite decades of research following several theoretical and clinical lines, all existing treatments for the disorder are purely symptomatic. AD research has traditionally been focused on neuronal and glial dysfunction. Although there is a wealth of evidence pointing to a significant vascular component in the disease, this angle has been relatively poorly explored. In this review, we consider the various aspects of vascular dysfunction in AD, which has a significant impact on brain metabolism and homeostasis and the clearance of β-amyloid and other toxic metabolites. This may potentially precede the onset of the hallmark pathophysiological and cognitive symptoms of the disease. Pathological changes in vessel haemodynamics, angiogenesis, vascular cell function, vascular coverage, blood-brain barrier permeability and immune cell migration may be related to amyloid toxicity, oxidative stress and apolipoprotein E (APOE) genotype. These vascular deficits may in turn contribute to parenchymal amyloid deposition, neurotoxicity, glial activation and metabolic dysfunction in multiple cell types. A vicious feedback cycle ensues, with progressively worsening neuronal and vascular pathology through the course of the disease. Thus, a better appreciation for the importance of vascular dysfunction in AD may open new avenues for research and therapy.

c-Jun N-terminal kinase and p38 mitogen-activated protein kinase pathways link capacitation with apoptosis and seminal plasma proteins protect sperm by interfering with both routes†

The mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), and p38 MAP kinase (p38) signaling cascades are involved in triggering apoptosis in somatic cells. Given that spermatozoa are able to undergo apoptosis, we tested the hypothesis that these pathways might be functional in ram spermatozoa as two signal transduction mechanisms that contribute to the modulation of capacitation and apoptosis. Indirect immunofluorescence and western blot analysis evidenced the presence of JNK and p38 in ram spermatozoa. To verify the involvement of these enzymes in sperm physiology, we determined the effect of specific inhibitors of JNK or p38 on in vitro capacitation induced with either cAMP-elevating agents or epidermal growth factor (EGF). Both inhibitions reduced the EGF-induced capacitation with a decrease in the chlortetracycline capacitated-sperm pattern, protein tyrosine phosphorylation, phosphatidylserine externalization, caspase-3 and -7 activation, and the proportion of DNA-damaged spermatozoa. No significant changes were found in the high-cAMP capacitated samples. The addition of 3.4 mg/ml seminal plasma proteins (SPPs) to the EGF-containing samples, either alone or together with each inhibitor, resulted in a decreased proportion of capacitated sperm pattern, protein tyrosine phosphorylation, loss of plasma membrane integrity, and apoptotic alterations. Furthermore, SPPs significantly reduced the phosphorylation level of JNK and p38 MAPK (active forms). These findings show a relationship between capacitation and apoptosis, and represent a step forward in the knowledge of the SPP protective mechanism in spermatozoa.

Deletion of JNK2 prevents vitamin-D-deficiency-induced hypertension and atherosclerosis in mice

The c-Jun N-terminal kinase 2 (JNK2) signaling pathway contributes to inflammation and plays a key role in the development of obesity-induced insulin resistance and cardiovascular disease. Macrophages are key cells implicated in these metabolic abnormalities. Active vitamin D downregulates macrophage JNK activation, suppressing oxidized LDL cholesterol uptake and foam cell formation and promoting an anti-inflammatory phenotype. To determine whether deletion of JNK2 prevents high blood pressure and atherosclerosis known to be induced by vitamin D deficiency in mice, we generated mice with knockout of JNK2 in a background susceptible to diet-induced atherosclerosis (LDLR^-/-). JNK2^-/- LDLR^-/- and LDLR^-/- control mice were fed vitamin D-deficient chow for 8 weeks followed by vitamin D-deficient high fat diet (HFD) for 10 weeks and assessed before and after HFD. There was no difference in fasting glucose, cholesterol, triglycerides, or free fatty acid levels. However, JNK2^-/- mice, despite vitamin D-deficient diet, had 20-30mmHg lower systolic (SBP) and diastolic (DBP) blood pressure before HFD compared to control mice fed vitamin D-deficient diets, with persistent SBP differences after HFD. Moreover, deletion of JNK2 reduced HFD-induced atherosclerosis by 30% in the proximal aorta when compared to control mice fed vitamin D-deficient diets. We have previously shown that peritoneal macrophages obtained from LDLR^-/- mice fed vitamin D-deficient HFD diets have higher foam cell formation compared to those from mice on vitamin D-sufficient HFD. The increased total cellular cholesterol and modified cholesterol uptake in macrophages from mice on vitamin D-deficient HFD were blunted by deletion of JNK2. These data suggest that JNK2 signaling activation is necessary for the atherosclerosis and hypertension induced by vitamin D deficiency.

Flow signaling and atherosclerosis

Atherosclerosis rarely develops in the region of arteries exposed to undisturbed flow (u-flow, unidirectional flow). Instead, atherogenesis occurs in the area exposed to disturbed flow (d-flow, multidirectional flow). Based on these general pathohistological observations, u-flow is considered to be athero-protective, while d-flow is atherogenic. The fact that u-flow and d-flow induce such clearly different biological responses in the wall of large arteries indicates that these two types of flow activate each distinct intracellular signaling cascade in vascular endothelial cells (ECs), which are directly exposed to blood flow. The ability of ECs to differentially respond to the two types of flow provides an opportunity to identify molecular events that lead to endothelial dysfunction and atherosclerosis. In this review, we will focus on various molecular events, which are differentially regulated by these two flow types. We will discuss how various kinases, ER stress, inflammasome, SUMOylation, and DNA methylation play roles in the differential flow response, endothelial dysfunction, and atherosclerosis. We will also discuss the interplay among the molecular events and how they coordinately regulate flow-dependent signaling and cellular responses. It is hoped that clear understanding of the way how the two flow types beget each unique phenotype in ECs will lead us to possible points of intervention against endothelial dysfunction and cardiovascular diseases.

Targeting of proangiogenic signalling pathways in chronic inflammation

Angiogenesis is de novo capillary outgrowth from pre-existing blood vessels. This process not only is crucial for normal development, but also has an important role in supplying oxygen and nutrients to inflamed tissues, as well as in facilitating the migration of inflammatory cells to the synovium in rheumatoid arthritis, spondyloarthritis and other systemic autoimmune diseases. Neovascularization is dependent on the balance of proangiogenic and antiangiogenic mediators, including growth factors, cytokines, chemokines, cell adhesion molecules and matrix metalloproteinases. This Review describes the various intracellular signalling pathways that govern these angiogenic processes and discusses potential approaches to interfere with pathological angiogenesis, and thereby ameliorate inflammatory disease, by targeting these pathways.

2,3',4,4',5-Pentachlorobiphenyl Induces Inflammatory Responses in the Thyroid Through JNK and Aryl Hydrocarbon Receptor-Mediated Pathway

Polychlorinated biphenyls (PCBs) are durable and widely distributed environmental contaminants that can compromise the normal functions of multiple organs and systems; one important mechanism is the induction of inflammatory disorders. In this study, we explored the influences of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on inflammatory responses and its underlying mechanisms in the thyroid. Wistar rats were administered PCB118 intraperitoneally at 0, 10, 100, and 1000 μg/kg/d, 5 days a week for 13 weeks; rat thyroid FRTL-5 cells were treated with PCB118 (0, 0.25, 2.5, and 25 nM) for indicated time. Results revealed that PCB118 promoted the generation of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and intercellular adhesion molecule-1 (ICAM-1) in a time- and dose-related manner and decreased sodium/iodide symporter (NIS) protein expression. Moreover, stimulation with PCB118 resulted in the upregulation of the aryl hydrocarbon receptor (AhR)-responsive gene cytochrome P450 1A1 in FRTL-5 cells; whereas pretreatment with the AhR inhibitor α-naphthoflavone or AhR small interfering RNA (siRNA) suppressed AhR, CYP1A1, IL-6, and ICAM-1 and restored NIS expression. In vivo and in vitro studies also suggested that the c-Jun N-terminal kinase (JNK) pathway was activated on PCB118 exposure, and the experiments using siRNA for JNK partially blocked PCB118-induced upregulation of IL-6 and ICAM-1 and downregulation of NIS. Altogether, PCB118 stimulates production of IL-6, TNF-α, and ICAM-1 in the thyroid through AhR and JNK activations and subsequently interferes with NIS expression, resulting in the disruption of thyroid structure and function.

Tumor necrosis factor α-mediated restructuring of the Sertoli cell barrier in vitro involves matrix metalloprotease 9 (MMP9), membrane-bound intercellular adhesion molecule-1 (ICAM-1) and the actin cytoskeleton

The mammalian blood-testis barrier (BTB) restructures throughout spermatogenesis, thereby allowing developing germ cells to enter the adluminal compartment of the seminiferous epithelium. Previous studies have shown pro-inflammatory cytokines such as tumor necrosis factor α (TNFα) and interleukin-1α to be important regulators of Sertoli cell barrier/BTB function in vitro and in vivo. In this study, the effects of TNFα on Sertoli cell barrier function were assessed, with emphasis on changes in proteases and cell adhesion molecules following treatment. By immunoblotting and immunohistochemistry, MMP9 was found to be present in germ cells, localizing by and large to spermatocytes and spermatids in the adult rat testis. Following treatment of Sertoli cells with physiologically relevant consecutive doses of recombinant human TNFα (25 ng/ml), the steady-state levels of active-matrix metalloprotease 9 (MMP9), membrane-bound intercellular adhesion molecule (mICAM-1) and androgen receptor increased significantly. TNFα also downregulated the steady-state level of occludin, in agreement with earlier results that showed TNFα to disrupt Sertoli cell barrier/BTB function. In addition, TNFα affected the filamentous actin cytoskeleton in Sertoli cells, which appeared to be mediated by cortactin, a regulator of actin dynamics. Taken collectively, these findings imply that germ cells may be involved in BTB restructuring via the localized production of TNFα. These results also illustrate that barrier restructuring correlated with an increase in Sertoli cell mICAM-1, suggesting that it may be critical for adhesion as germ cells traverse the “opened” BTB.

Novel mechanisms of endothelial mechanotransduction

Atherosclerosis is a focal disease that develops preferentially where nonlaminar, disturbed blood flow occurs, such as branches, bifurcations, and curvatures of large arteries. Endothelial cells sense and respond differently to disturbed flow compared with steady laminar flow. Disturbed flow that occurs in so-called atheroprone areas activates proinflammatory and apoptotic signaling, and this results in endothelial dysfunction and leads to subsequent development of atherosclerosis. In contrast, steady laminar flow as atheroprotective flow promotes expression of many anti-inflammatory genes, such as Kruppel-like factor 2 and endothelial nitric oxide synthase and inhibits endothelial inflammation and athrogenesis. Here we will discuss that disturbed flow and steady laminar flow induce pro- and antiatherogenic events via flow type-specific mechanotransduction pathways. We will focus on 5 mechanosensitive pathways: mitogen-activated protein kinases/extracellular signal-regulated kinase 5/Kruppel-like factor 2 signaling, extracellular signal-regulated kinase/peroxisome proliferator-activated receptor signaling, and mechanosignaling pathways involving SUMOylation, protein kinase C-ζ, and p90 ribosomal S6 kinase. We think that clarifying regulation mechanisms between these 2 flow types will provide new insights into therapeutic approaches for the prevention and treatment of atherosclerosis.

The role of glycogen synthase kinase 3-β in immunity and cell cycle: implications in esophageal cancer

Esophageal cancer (EC) is one of the most aggressive gastrointestinal malignancies, possessing an insidious onset and a poor prognosis. Numerous transcription factors and inflammatory mediators have been reported to play a pivotal role in the initiation and progression of this cancer. However, the specifics of the signaling network responsible for said factors, especially which elements are the critical regulators, are still being elucidated. Glycogen synthesis kinases 3 (GSK3)β was originally regarded as a kinase regulating glucose metabolism. Accumulating evidence demonstrated that it also played an essential role in a variety of cellular processes including proliferation, differentiation, inflammation, motility, and survival by regulating various transcription factors such as c-Jun, AP-1, β-catenin, CREB, and NF-κB. Aberrant regulation of GSK3β has been shown to promote cell growth in some cancers, while suppressing it in others, and thus may play an important role in the development of EC. This review will discuss our current understanding of GSK3β signaling, and its control of the expression and activation of various transcription factors that mediate the inflammatory response. We will also explore some of the known mediators of EC progression, and based on current literature, elucidate the potential roles and implications of GSK3 in this disease.

TNF-α signalling and inflammation: interactions between old acquaintances

INTRODUCTION

Inflammation is a very important part of innate immunity and is regulated in many steps. One such regulating step is the cytokine network, where tumor necrosis factor α (TNF-α) plays one of the most important roles.

METHODS

A PubMed and Web of Science databases search was performed for studies providing evidences on the role of TNF-α in inflammation, apoptosis, and cancer.

RESULTS AND CONCLUSION

This review concisely summarizes the role of this pro-inflammatory cytokine during inflammation. It is focused mainly on TNF-α intracellular signaling and its influence on the typical inflammatory features in the organism. Being one of the most important pro-inflammatory cytokines, TNF-α participates in vasodilatation and edema formation, and leukocyte adhesion to epithelium through expression of adhesion molecules; it regulates blood coagulation, contributes to oxidative stress in sites of inflammation, and indirectly induces fever. The connection between TNF-α and cancer is mentioned as well.

Intercellular adhesion molecules (ICAMs) and spermatogenesis

BACKGROUND

During the seminiferous epithelial cycle, restructuring takes places at the Sertoli-Sertoli and Sertoli-germ cell interface to accommodate spermatogonia/spermatogonial stem cell renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation since developing germ cells, in particular spermatids, move 'up and down' the seminiferous epithelium. Furthermore, preleptotene spermatocytes differentiated from type B spermatogonia residing at the basal compartment must traverse the blood-testis barrier (BTB) to enter the adluminal compartment to prepare for meiosis at Stage VIII of the epithelial cycle, a process also accompanied by the release of sperm at spermiation. These cellular events that take place at the opposite ends of the epithelium are co-ordinated by a functional axis designated the apical ectoplasmic specialization (ES)-BTB-basement membrane. However, the regulatory molecules that co-ordinate cellular events in this axis are not known.

METHODS

Literature was searched at http://www.pubmed.org and http://scholar.google.com to identify published findings regarding intercellular adhesion molecules (ICAMs) and the regulation of this axis.

RESULTS

Members of the ICAM family, namely ICAM-1 and ICAM-2, and the biologically active soluble ICAM-1 (sICAM-1) are the likely regulatory molecules that co-ordinate these events. sICAM-1 and ICAM-1 have antagonistic effects on the Sertoli cell tight junction-permeability barrier, involved in Sertoli cell BTB restructuring, whereas ICAM-2 is restricted to the apical ES, regulating spermatid adhesion during the epithelial cycle. Studies in other epithelia/endothelia on the role of the ICAM family in regulating cell movement are discussed and this information has been evaluated and integrated into studies of these proteins in the testis to create a hypothetical model, depicting how ICAMs regulate junction restructuring events during spermatogenesis.

CONCLUSIONS

ICAMs are crucial regulatory molecules of spermatogenesis. The proposed hypothetical model serves as a framework in designing functional experiments for future studies.

GLP-1 analog liraglutide protects against oxidative stress and albuminuria in streptozotocin-induced diabetic rats via protein kinase A-mediated inhibition of renal NAD(P)H oxidases

Accumulating evidence has implicated that GLP-1 may have a beneficial effect on cardiovascular and renal diseases but the mechanism is not fully understood. Here we show that GLP-1 analog, liraglutide, inhibits oxidative stress and albuminuria in streptozotocin (STZ)-induced type 1 diabetes mellitus rats, via a protein kinase A (PKA)-mediated inhibition of renal NAD(P)H oxidases. Diabetic rats were randomly treated with subcutaneous injections of liraglutide (0.3 mg/kg/12 h) for 4 weeks. Oxidative stress markers (urinary 8-hydroxy-2'-deoxyguanosine and renal dihydroethidium staining), expression of renal NAD(P)H oxidase components, transforming growth factor-β (TGF-β), fibronectin and urinary albumin excretion were measured. In vitro effect of liraglutide was evaluated using cultured renal mesangial cells. Administration of liraglutide did not affect plasma glucose levels or body weights in STZ diabetic rats, but normalized oxidative stress markers, expression of NAD(P)H oxidase components, TGF-β, fibronectin in renal tissues and urinary albumin excretion, all of which were significantly increased in diabetic rats. In addition, in cultured renal mesangial cells, incubation with liraglutide for 48 h inhibited NAD(P)H-dependent superoxide production evaluated by lucigenin chemiluminescence in a dose-dependent manner. This effect was reversed by both PKA inhibitor H89 and adenylate cyclase inhibitor SQ22536, but not by Epac2 inhibition via its small interfering RNA. Liraglutide may have a direct beneficial effect on oxidative stress and diabetic nephropathy via a PKA-mediated inhibition of renal NAD(P)H oxidase, independently of a glucose-lowering effect.

Regulation of activin and inhibin in the adult testis and the evidence for functional roles in spermatogenesis and immunoregulation

Activin A provides a unique link between reproduction and immunity, which is especially significant in the adult testis. This cytokine, together with inhibin B and follistatin acting as regulators of activin A activity, is fundamentally involved in the regulation of spermatogenesis and testicular steroidogenesis. However, activin A also has a much broader role in control of inflammation, fibrosis and immunity. In the Sertoli cell, activin A is regulated by signalling pathways that normally regulate stress and inflammation, signalling pathways that intersect with the classical hormonal regulatory pathways mediated by FSH. Modulation of activin A production and activity during spermatogenesis is implicated in the fine control of the cycle of the seminiferous epithelium. The immunoregulatory properties of activin A also suggest that it may be involved in maintaining testicular immune privilege. Consequently, elevated activin A production within the testis during inflammation and infection may contribute to spermatogenic failure, fibrosis and testicular damage.

The blood-testis barrier and its implications for male contraception

The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the mammalian body. It divides the seminiferous epithelium into the basal and the apical (adluminal) compartments. Meiosis I and II, spermiogenesis, and spermiation all take place in a specialized microenvironment behind the BTB in the apical compartment, but spermatogonial renewal and differentiation and cell cycle progression up to the preleptotene spermatocyte stage take place outside of the BTB in the basal compartment of the epithelium. However, the BTB is not a static ultrastructure. Instead, it undergoes extensive restructuring during the seminiferous epithelial cycle of spermatogenesis at stage VIII to allow the transit of preleptotene spermatocytes at the BTB. Yet the immunological barrier conferred by the BTB cannot be compromised, even transiently, during the epithelial cycle to avoid the production of antibodies against meiotic and postmeiotic germ cells. Studies have demonstrated that some unlikely partners, namely adhesion protein complexes (e.g., occludin-ZO-1, N-cadherin-β-catenin, claudin-5-ZO-1), steroids (e.g., testosterone, estradiol-17β), nonreceptor protein kinases (e.g., focal adhesion kinase, c-Src, c-Yes), polarity proteins (e.g., PAR6, Cdc42, 14-3-3), endocytic vesicle proteins (e.g., clathrin, caveolin, dynamin 2), and actin regulatory proteins (e.g., Eps8, Arp2/3 complex), are working together, apparently under the overall influence of cytokines (e.g., transforming growth factor-β3, tumor necrosis factor-α, interleukin-1α). In short, a "new" BTB is created behind spermatocytes in transit while the "old" BTB above transiting cells undergoes timely degeneration, so that the immunological barrier can be maintained while spermatocytes are traversing the BTB. We also discuss recent findings regarding the molecular mechanisms by which environmental toxicants (e.g., cadmium, bisphenol A) induce testicular injury via their initial actions at the BTB to elicit subsequent damage to germ-cell adhesion, thereby leading to germ-cell loss, reduced sperm count, and male infertility or subfertility. Moreover, we also critically evaluate findings in the field regarding studies on drug transporters in the testis and discuss how these influx and efflux pumps regulate the entry of potential nonhormonal male contraceptives to the apical compartment to exert their effects. Collectively, these findings illustrate multiple potential targets are present at the BTB for innovative contraceptive development and for better delivery of drugs to alleviate toxicant-induced reproductive dysfunction in men.

Over-expression of mitogen-activated protein kinase phosphatase-2 enhances adhesion molecule expression and protects against apoptosis in human endothelial cells

BACKGROUND AND PURPOSE

We assessed the effects of over-expressing the dual-specific phosphatase, mitogen-activated protein (MAP) kinase phosphatase-2 (MKP-2), in human umbilical vein endothelial cells (HUVECs) on inflammatory protein expression and apoptosis, two key features of endothelial dysfunction in disease.

EXPERIMENTAL APPROACHES

We infected HUVECs for 40 h with an adenoviral version of MKP-2 (Adv.MKP-2). Tumour necrosis factor (TNF)-α-stimulated phosphorylation of MAP kinase and protein expression was measured by Western blotting. Cellular apoptosis was assayed by FACS.

KEY RESULTS

Infection with Adv.MKP-2 selectively abolished TNF-α-mediated c-Jun-N-terminal kinase (JNK) activation and had little effect upon extracellular signal-regulated kinase or p38 MAP kinase. Adv.MKP-2 abolished COX-2 expression, while induction of the endothelial cell adhesion molecules, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), two NFκB-dependent proteins, was not affected. However, when ICAM and VCAM expression was partly reduced by blockade of the NFκB pathway, Adv.MKP-2 was able to reverse this inhibition. This correlated with enhanced TNF-α-induced loss of the inhibitor of κB (IκB)α loss, a marker of NFκB activation. TNF-α in combination with NFκB blockade also increased HUVEC apoptosis; this was significantly reversed by Adv.MKP-2. Protein markers of cellular damage and apoptosis, H2AX phosphorylation and caspase-3 cleavage, were also reversed by MKP-2 over-expression.

CONCLUSIONS AND IMPLICATIONS

Over-expression of MKP-2 had different effects upon the expression of inflammatory proteins due to a reciprocal effect upon JNK and NFκB signalling, and also prevented TNF-α-mediated endothelial cell death. These properties may make Adv.MKP-2 a potentially useful future therapy in cardiovascular diseases where endothelial dysfunction is a feature.

Interleukin-1beta induces ICAM-1 expression enhancing leukocyte adhesion in human rheumatoid arthritis synovial fibroblasts: involvement of ERK, JNK, AP-1, and NF-kappaB

Interleukin-1beta (IL-1beta) has been shown to induce the expression of adhesion molecules on various cell types and contributes to inflammatory responses. However, the molecular mechanisms by which IL-1beta induced intercellular adhesion molecule (ICAM)-1 expression remain unclear in human rheumatoid arthritis synovial fibroblasts (RASFs). Here, we demonstrated that IL-1beta induces ICAM-1 gene expression via the de novo protein synthesis through transcription and translation, which is attenuated by pretreatment with actinomycin D and cycloheximide, respectively. IL-1beta-induced ICAM-1 expression, extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) phosphorylation, AP-1 activation, and nuclear factor-kappaB (NF-kappaB) p65 translocation were attenuated by the inhibitors of MEK1/2 (U0126), JNK (SP600125), AP-1 (tanshinone IIA), and NF-kappaB (helenalin) or transfection with respective short hairpin RNA plasmids. Moreover, IL-1beta-stimulated NF-kappaB p65 translocation was blocked by helenalin, but not by U0126 or SP600125, revealing that MAPKs and NF-kappaB pathways were independent on these responses. IL-1beta-stimulated AP-1 activation was blocked by U0126 or SP600125, revealing that ERK and JNK linked to AP-1 on these responses. IL-1beta-stimulated ICAM-1 gene expression was attenuated by pretreatment with U0126, SP600125, tanshinone IIA, or helenalin, revealed by ICAM-1 promoter assay and real-time RT-PCR analysis. Finally, up-regulation of ICAM-1 enhanced the adhesion of leukocytes to RASFs exposed to IL-1beta. These results suggest that in human RASFs, activation of ERK, JNK, AP-1, and NF-kappaB are essential for IL-1beta-induced ICAM-1 expression and leukocyte adhesion.

Glycyrrhetinic acid inhibits ICAM-1 expression via blocking JNK and NF-kappaB pathways in TNF-alpha-activated endothelial cells

AIM

To investigate the effects of glycyrrhetinic acid (GA), an active component extracted from the root of Glycyrrhizae glabra, on the expression of intercellular adhesion molecule-1 (ICAM-1) in tumor necrosis factor-alpha (TNF-alpha)-activated human umbilical vein endothelial cells (HUVEC).

METHODS

ICAM-1 mRNA and protein levels were detected using RT-PCR and cell enzyme-linked immunosorbent assays. The adherence of human monocytic THP-1 cells labeled with [(3)H]thymidine to HUVEC was determined by counting radioactivity with a scintillation counter. The activation of mitogen-activated protein kinases as well as the degradation of I kappaB and nuclear factor-kappaB (NF-kappaB) or phospho-c-Jun in the nucleus were detected by western blots. NF-kappaB binding activity was detected using electrophoretic mobility shift assay.

RESULTS

GA (50 and 100 micromol/L) significantly inhibits TNF-alpha-induced ICAM-1 mRNA and protein expressions, as well as THP-1 cell adhesiveness in HUVEC. GA selectively inhibited TNF-alpha-activated signal pathway of c-Jun N-terminal kinase (JNK), without affecting extracellular signal-regulated kinase 1/2 and p38. Furthermore, GA apparently inhibited I kappaB/NF-kappaB signaling system by preventing I kappaB degradation, NF-kappaB translocation, and NF-kappaB/DNA binding activity. Finally, pretreatment with GA or the inhibitors of NF-kappaB, JNK, and p38 reduced the ICAM-1 protein expression induced by TNF-alpha.

CONCLUSION

GA inhibits TNF-alpha-stimulated ICAM-1 expression, leading to a decrease in adherent monocytes to HUVEC. This inhibition is attributed to GA interruption of both JNK/c-Jun and I kappaB/NF-kappaB signaling pathways, which decrease activator protein-1 (AP-1) and NF-kappaB mediated ICAM-1 expressions. The results suggest that GA may provide a beneficial effect in treating vascular diseases associated with inflammation, such as atherosclerosis.

Involvement of MAPKs and NF-kappaB in tumor necrosis factor alpha-induced vascular cell adhesion molecule 1 expression in human rheumatoid arthritis synovial fibroblasts

OBJECTIVE

To investigate the roles of MAPKs and NF-kappaB in tumor necrosis factor alpha (TNFalpha)-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Human RASFs were isolated from synovial tissue obtained from patients with RA who underwent knee or hip surgery. The involvement of MAPKs and NF-kappaB in TNFalpha-induced VCAM-1 expression was investigated using pharmacologic inhibitors and transfection with short hairpin RNA (shRNA) and measured using Western blot, reverse transcriptase-polymerase chain reaction, and gene promoter assay. NF-kappaB translocation was determined by Western blot and immunofluorescence staining. The functional activity of VCAM-1 was evaluated by lymphocyte adhesion assay.

RESULTS

TNFalpha-induced VCAM-1 expression, phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK, and translocation of NF-kappaB were attenuated by the inhibitors of MEK-1/2 (U0126), p38 (SB202190), JNK (SP600125), and NF-kappaB (helenalin) or by transfection with their respective shRNA. TNFalpha-stimulated translocation of NF-kappaB into the nucleus and NF-kappaB promoter activity were blocked by Bay11-7082, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNFalpha in RASFs transfected with VCAM-1-Luc, and this promoter activity was inhibited by Bay11-7082, U0126, SB202190, and SP600125. Moreover, up-regulation of VCAM-1 increased the adhesion of lymphocytes to the RASF monolayer, and this adhesion was attenuated by pretreatment with helenalin, U0126, SP600125, or SB202190 prior to exposure to TNFalpha or by anti-VCAM-1 antibody before the addition of lymphocytes.

CONCLUSION

In RASFs, TNFalpha-induced VCAM-1 expression is mediated through activation of the p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB pathways. These results provide new insights into the mechanisms underlying cytokine-initiated joint inflammation in RA and may inspire new targeted therapeutic approaches.

Immunology of the Testis and Male Reproductive Tract

A large body of evidence points to the existence of a close, dynamic relationship between the immune system and the male reproductive tract, which has important implications for our understanding of both systems. The testis and the male reproductive tract provide an environment that protects the otherwise highly immunogenic spermatogenic cells and sperm from immunological attack. At the same time, secretions of the testis, including androgens, influence the development and mature functions of the immune system. Activation of the immune system has negative effects on both androgen and sperm production, so that systemic or local infection and inflammation compromise male fertility. The mechanisms underlying these interactions have begun to receive the attention from reproductive biologists and immunologists that they deserve, but many crucial details remain to be uncovered. A complete picture of male reproductive tract function and its response to toxic agents is contingent upon continued exploration of these interactions and the mechanisms involved.

Cytokines and chemokines in testicular inflammation: A brief review

A wide spectrum of data in the literature shows the relevance of cytokines as paracrine regulators of spermatogenesis and steroidogenesis in the normal testis. In this brief review, we highlight the relevance of cytokines in the testis during inflammation. This phenomenon involves complex and multiple interactions among immune and germ cells generally resulting in the alteration of spermatogenesis. The complexity of these cell interactions is multiplied because Sertoli and Leydig cells are also producers of pro- and anti-inflammatory cytokines and chemokines. Also, cytokines are pleiotropic and they exert opposite and/or redundant effects in different conditions. However, in spite of this bidirectional immunoregulatory function of cytokines, the mass of the data, reported from experiments of acute testicular inflammation, shows upregulation of interleukin (IL)-1beta, IL-1alpha, IL-6, and tumor necrosis factor alpha (TNF-alpha), which induce adverse effects on germ cells. In autoimmune orchitis, a chronic testicular inflammation, chemokines such as CCL2, CCL3, and CCL4 induce attraction and extravasation of immune cells within the testicular interstitium. These cells alter the normal immunosuppressor microenvironment principally through the secretion of proinflammatory cytokines, interferon-gamma initially, and IL-6 and TNF-alpha thereafter. Germ cells expressing TNFR1, IL-6R, and Fas increase in number and undergo apoptosis, through the TNF-alpha/TNFR1, IL-6/IL-6R, and Fas/Fas L systems. The knowledge of immune-germ and somatic testicular cell interactions will contribute to the understanding of the mechanisms by which chronic inflammatory conditions of the testis can disrupt the process of spermatogenesis.

An intracellular trafficking pathway in the seminiferous epithelium regulating spermatogenesis: a biochemical and molecular perspective

During spermatogenesis in adult rat testes, fully developed spermatids (i.e. spermatozoa) at the luminal edge of the seminiferous epithelium undergo "spermiation" at stage VIII of the seminiferous epithelial cycle. This is manifested by the disruption of the apical ectoplasmic specialization (apical ES) so that spermatozoa can enter the tubule lumen and to complete their maturation in the epididymis. At the same time, the blood-testis barrier (BTB) located near the basement membrane undergoes extensive restructuring to allow transit of preleptotene spermatocytes so that post-meiotic germ cells complete their development behind the BTB. While spermiation and BTB restructuring take place concurrently at opposite ends of the Sertoli cell epithelium, the biochemical mechanism(s) by which they are coordinated were not known until recently. Studies have shown that fragments of laminin chains are generated from the laminin/integrin protein complex at the apical ES via the action of MMP-2 (matrix metalloprotease-2) at spermiation. These peptides serve as the local autocrine factors to destabilize the BTB. These laminin peptides also exert their effects on hemidesmosome which, in turn, further potentiates BTB restructuring. Thus, a novel apical ES-BTB-hemidesmosome regulatory loop is operating in the seminiferous epithelium to coordinate these two crucial cellular events of spermatogenesis. This functional loop is further assisted by the Par3/Par6-based polarity protein complex in coordination with cytokines and testosterone at the BTB. Herein, we provide a critical review based on the latest findings in the field regarding the regulation of these cellular events. These recent findings also open up a new window for investigators studying blood-tissue barriers.

Extracellular inosine participates in tumor necrosis factor-alpha induced nitric oxide production in cultured Sertoli cells

Recent reports have described purinergic modulation of tumor necrosis factor-alpha (TNF-alpha) signaling in neutrophils and astrocytes. In Sertoli cells, both TNF-R1 and TNF-R2 TNF-alpha receptors are present and this cytokine modulates many functions of these cells related to the maintenance of spermatogenesis. Sertoli cells express distinct purinoreceptors and previous work has shown that these cells secrete extracellular nucleotides and their metabolites. In this work, we studied the possible role of extracellular purines in TNF-alpha signaling in cultured Sertoli cells. This cytokine increased inosine concentration from 30 min to 6 h, with no effect at 24 h. Both TNF-alpha and inosine increased nitrite accumulation and nitric oxide synthase activity. Erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), an adenosine deaminase inhibitor, abolished the TNF-alpha induced inosine increase, nitrite accumulation and nitric oxide synthase activity. These results suggest that extracellular inosine acts as intermediary in TNF-alpha stimulated nitric oxide production in cultured Sertoli cells.

Extracellular matrix and its role in spermatogenesis

In adult mammalian testes, such as rats, Sertoli and germ cells at different stages of their development in the seminiferous epithelium are in close contact with the basement membrane, a modified form of extracellular matrix (ECM). In essence, Sertoli and germ cells in particular spermatogonia are "resting" on the basement membrane at different stages of the seminiferous epithelial cycle, relying on its structural and hormonal supports. Thus, it is not entirely unexpected that ECM plays a significant role in regulating spermatogenesis, particularly spermatogonia and Sertoli cells, and the blood-testis barrier (BTB) constituted by Sertoli cells since these cells are in physical contact with the basement membrane. Additionally, the basement membrane is also in close contact with the underlying collagen network and the myoid cell layers, which together with the lymphatic network, constitute the tunica propria. The seminiferous epithelium and the tunica propria, in turn, constitute the seminiferous tubule, which is the functional unit that produces spermatozoa via its interaction with Leydig cells in the interstitium. In short, the basement membrane and the underlying collagen network that create the acellular zone of the tunica propria may even facilitate cross-talk between the seminiferous epithelium, the myoid cells and cells in the interstitium. Recent studies in the field have illustrated the crucial role of ECM in supporting Sertoli and germ cell function in the seminiferous epithelium, including the BTB dynamics. In this chapter, we summarize some of the latest findings in the field regarding the functional role of ECM in spermatogenesis using the adult rat testis as a model. We also high light specific areas of research that deserve attention for investigators in the field.

Profound effects of burn and ethanol on proinflammatory cytokines of the reproductive axis in the male mouse

Thermal injury is often associated with previous ethanol exposure, and close to 50% of patients admitted to a burn unit have a potentially high blood ethanol level. Cellular mechanisms by which ethanol and/or burn affect the hypothalamic-pituitary-gonadal (HPG) axis are not entirely understood. However, it is known that the proinflammatory cytokines, tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 influence negatively on the endocrine functions of the HPG. We report a time course study (6, 12, 24, and 48 hours) of the effects of ethanol, burn, or the combination of burn/ethanol on proinflammatory cytokines of the hypothalamus, pituitary and testes of male C57Bl/6 mice. We found that there were highly significant increases in each of these cytokines caused by ethanol, burn, and burn/ethanol compared with sham/vehicle (P < .001). This was true in hypothalamus, pituitary, and testes. Because these cytokines generally reduce reproductive function, it may be that proinflammatory cytokines of HPG axis mediate the deleterious effects of burn and/or ethanol on mammalian reproduction.

The complexity of signaling in host-pathogen interactions revealed by the Toxoplasma gondii-dependent modulation of JNK phosphorylation

The inhibition of apoptosis by Toxoplasma gondii is governed by its modulation of several signaling cascades including the NFkappaappaB and JNK pathways. This is evident in the dysregulation of JNK activation following treatment with UV and TNFalpha, both apoptogenic stimuli. Infection-mediated interference with the JNK cascade was found to be highly reproducible in HeLa cells. In light of emerging evidence regarding cross talk between the JNK and NFkappaB cascades, we examined the impact of infection in wild type and RelA/p65-/- mouse embryonic fibroblasts (MEF). Remarkably, parasite infection failed to significantly impact both UV and TNFalpha-mediated JNK phosphorylation in both cell lines suggesting a cell type specific effect. Furthermore siRNA-mediated knockdown of RelA/p65 failed to impact the parasite mediated effects on stimulus dependent activation of JNK in HeLa cells. Finally, the infection mediated suppression of JNK phosphorylation in HeLa cells did not result in decreased JNK kinase activity. Rather, the reduced levels of phospho-JNK in infected cells correlated with increased phosphatase activity noted by the partial rescue of the phenotype following treatment with okadaic acid. Taken together the results indicate that manipulation of the JNK pathway does not involve NFkappaB and is furthermore not a central component of the parasite enforced block of apoptosis. It further highlights the complexity of these systems and the danger of extrapolating results both within and across pathogen-host cell systems based on limited studies.

ICAM-1 expression in vaginal cells as a potential biomarker for inflammatory response

This study aimed to elucidate the mechanisms that may lead to an efficient strategy to induce a suitable host response of the vaginal mucosa upon exposure to intravaginally delivered exogenous compounds. It was hypothesized that the upregulation of intercellular adhesion molecule (ICAM)-1 gene expression may reflect the inflammatory response evoked by exogenous compounds. Major emphasis was placed on ethylenediamine tetraacetic acid (EDTA) which was added as a synergistic agent to conventional spermicidal agents or anti-HIV drugs. The levels of ICAM-1 mRNA were examined as a surrogate marker for inflammatory response in human vaginal epithelial cells upon exposure to EDTA or interleukin (IL)-1beta (i.e. positive control, 25 mM). The effects of estrogen on EDTA-induced ICAM-1 expression were also evaluated for the estrogen involvement in the inflammatory process of the vaginal mucosa. ICAM-1 expression in human vaginal cells (VK2/E6E7 cells) increased as EDTA concentration added to human vaginal cell lines increased. The effects of estrogen on EDTA-induced ICAM-1 expression in human vaginal epithelial cells were estrogen-concentration dependent; estrogen at lower concentrations (approximately 1-10 nM) did not affect ICAM-1 expression, whereas estrogen at higher concentrations (approximately 100 nM-1 microM) attenuated ICAM-1 expression. The influence of estrogen in ICAM-1 expression suggests the beneficial effects of estrogen on the regulation of vaginal homeostasis. Identification and quantification of specific surrogate markers for the inflammatory response evoked by exogenous compounds and their regulation by estrogen will lead to an efficient strategy against sexually transmitted diseases including AIDS.

Hypogonadal Mouse, a Model to Study the Effects of the Endogenous Lack of Gonadotropins on Apoptosis1

Testicular apoptosis is involved in the regulation of germ cell numbers, allowing optimal sperm production. Apoptosis has been described to occur in response to the absence of hormonal stimulation of the testis. Here we investigate the effect of the physiological lack of gonadotropins from birth using the hypogonadal (homozygous for the mutant allele Gnrh1(hpg)) mouse as a model. We pursued a concerted strategy using microarray analysis and RT-PCR to assess transcript levels, TUNEL to quantify the incidence of apoptosis, and Western blotting to assess the respective contribution of the extrinsic and intrinsic apoptotic pathways. Our results indicate a large increase in apoptosis of both somatic and germ cell compartments in the hpg testis, affecting Sertoli cells as well as germ cells of all ages. We confirmed our observations of Sertoli cell apoptosis using anti-Mullerian inhibiting substance staining and staining for cleaved fodrin alpha. In the somatic compartment, apoptosis is primarily regulated via the membrane receptor (extrinsic) apoptotic pathway, while in the germ cell compartment, regulation occurs via both the mitochondrial (intrinsic) and membrane receptor (extrinsic) apoptotic pathways, the latter potentially in a stage-specific manner. This study is the first report of spermatogonial apoptosis in response to gonadotropin deficiency as well as the first report of Sertoli cell apoptosis in response to gonadotropin deficiency in the mouse.

Vitamin E prevents ethanol-induced inflammatory, hormonal, and cytotoxic changes in reproductive tissues

Ethanol causes decreased function of the hypothalamic-pituitary-gonadal (HPG) axis. Ethanol resulted in inflammatory changes in HPG manifested by increased concentrations of pro-inflammatory cytokines. Since, such cytokines have deleterious effects on functions of HPG, it seemed possible that ethanol's suppressive action could be due, at least in part, to this inflammation. Since oxidative stress can cause inflammation, we have used the antioxidant vitamin E to test, whether reducing inflammation might protect reproductive functions from ethanol. Rats were fed an ethanol diet or pair fed identically without ethanol for a 3-week period. For the last 10 days, animals were given 30 IU/kg or 90 IU/kg or vehicle. Ethanol significantly increased hypothalamic, pituitary and testicular TNF-alpha and IL-6, all changes prevented by the higher dose of vitamin E. Also, ethanol induced changes in LHRH, LH, testosterone, and testicular germ cell apoptosis were similarly prevented by vitamin E. These data strikingly show that vitamin E protects the HPG from deleterious effects of ethanol and suggests that the mechanism of this protection might be both anti-inflammatory and antioxidant.

A dominant negative form of the transcription factor c-Jun affects genes that have opposing effects on lipid homeostasis in mice

c-Jun is a transcription factor activated by phosphorylation by the stress-activated protein kinase/c-Jun N-terminal kinase pathway in response to extracellular signals and cytokines. We show that adenovirus-mediated gene transfer of the dominant negative form of c-Jun (dn-c-Jun) in C57BL/6 mice increased greatly apoE hepatic mRNA and plasma levels, increased plasma cholesterol, triglyceride, and very low density lipoprotein levels, and resulted in the accumulation of discoidal high density lipoprotein particles. A similar but more severe phenotype was generated by overexpression of the mouse apoE in C57BL/6 mice, suggesting that dyslipidemia induced by dn-c-Jun was the result of apoE overexpression. Unexpectedly, infection of apoE(-/-) mice with adenovirus expressing dn-c-Jun reduced plasma cholesterol by 70%, suggesting that dn-c-Jun affected other genes that control plasma cholesterol levels. To identify these genes, we performed whole genome expression analysis (34,000 genes) of isolated livers from two groups of five apoE(-/-) mice, infected with adenoviruses expressing either the dn-c-Jun or the green fluorescence protein. Bioinformatic analysis and Northern blotting validation revealed that dn-c-Jun increased 40-fold the apoE mRNA and reduced by 70% the Scd-1 (stearoyl-CoA-desaturase 1) mRNA. The involvement of Scd-1 in lowering plasma cholesterol was confirmed by restoration of high cholesterol levels of apoE(-/-) mice following coinfection with adenoviruses expressing dn-c-Jun and Scd-1. In conclusion, dn-c-Jun appears to trigger two opposing events in mice that affect plasma cholesterol and triglyceride levels as follows: one results in apoE overexpression and triggers dyslipidemia and the other results in inhibition of Scd-1 and offsets dyslipidemia.

Involvement of MAPKs and NF-kappaB in LPS-induced VCAM-1 expression in human tracheal smooth muscle cells

Lipopolysaccharide (LPS) has been shown to induce the expression of adhesion molecules on airway epithelial and smooth cells and contributes to inflammatory responses. Here, the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) pathways for LPS-induced vascular cell adhesion molecule (VCAM)-1 expression were investigated in HTSMCs. LPS-induced expression of VCAM-1 protein and mRNA in a time-dependent manner, was significantly inhibited by inhibitors of MEK1/2 (U0126), p38 (SB202190), and c-Jun-N-terminal kinase (JNK; SP600125). The involvement of p42/p44 MAPK and p38 in these responses was further confirmed by that transfection with small interference RNAs (siRNA) direct against MEK, p42, and p38 significantly attenuated LPS-induced VCAM-1 expression. Consistently, LPS-stimulated phosphorylation of p42/p44 MAPK and p38 was attenuated by pretreatment with U0126 or SB202190, and transfection with these siRNAs, respectively. In addition, LPS-induced VCAM-1 expression was significantly blocked by a specific NF-kappaB inhibitor helenalin. LPS-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha was blocked by helenalin, U0126, SB202190, or SP600125. Moreover, the resultant enhancement of VCAM-1 expression increased the adhesion of polymorphonuclear cells to monolayer of HTSMCs which was blocked by pretreatment with helenalin, U0126, or SP600125 prior to LPS exposure. Taken together, these results suggest that in HTSMCs, activation of p42/p44 MAPK, p38, and JNK pathways, at least in part, mediated through NF-kappaB, is essential for LPS-induced VCAM-1 gene expression. These results provide new insight into the mechanisms of LPS action that bacterial toxins may promote inflammatory responses in the airway disease.

TNFR1-induced NF-kappaB, but not ERK, p38MAPK or JNK activation, mediates TNF-induced ICAM-1 and VCAM-1 expression on endothelial cells

Tumour necrosis factor (TNF) is a pro-inflammatory cytokine, whose primary targets include vascular endothelial cells. TNF-mediated adhesion molecule expression has been shown to play a central role in endothelial cells inflammatory responses and disorders such as atherosclerosis. However it is not fully understand how the TNF receptor subtypes, namely TNFR1 and TNFR2, regulate inflammatory responses in endothelial cells. The aim of this study was to elucidate the kinase signalling pathways that TNF receptors activate, and determine the pathways responsible for downstream expression of adhesion molecules, intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human endothelial cells. Using human umbilical vein endothelial cells (HUVEC), we demonstrated that TNF activates a range of mitogen-activated protein kinases (MAPKs), including the extracellular-regulated kinase (ERK) pathway and the p38MAPK and c-Jun N-terminal kinase (JNK) stress kinase pathways. Human endothelial cells express both TNF receptor subtypes at low levels, however using TNFR-specific agonistic agents, we uncovered that TNF acts through its TNFR1 receptor subtype to activate NF-kappaB transcriptional pathways. Further investigation revealed that ICAM-1 and VCAM-1 mRNA and protein are induced by TNFR1 (but not TNFR2) in a wholly NF-kappaB-dependent manner. These findings reveal for the first time that TNF stimulation of adhesion molecules ICAM-1 and VCAM-1 in human endothelial cells occurs through the TNFR1 subtype and is mediated by the NF-kappaB pathway, but not the ERK, p38MAPK or JNK kinase pathways.

Sertoli cells initiate testicular innate immune responses through TLR activation

TLRs play a crucial role in early host defense against invading pathogens. In the seminiferous epithelium, Sertoli cells are the somatic nurse cells that mechanically segregate germ cell autoantigens by means of the blood-tubular barrier and create a microenvironment that protects germ cells from both interstitial and ascending invading pathogens. The objective of this study was to examine TLR expression and their functional responses to specific agonists in mouse Sertoli cells. We measured the expression of TLR2, TLR4, TLR5, and TLR6 mRNAs and confirmed by FACS analysis the presence of proteins TLR2 and TLR5 on which we focused our study. Stimulation of Sertoli cells with macrophage-activating lipopeptide-2, agonist of TLR2/TLR6, and with flagellin, agonist of TLR5, induces augmented secretion of the chemokine MCP-1. To assess the functional significance of MCP-1 production following TLR stimulation, conditioned medium from either macrophage-activating lipopeptide-2 or flagellin-treated Sertoli cells was tested for in vitro chemotaxis assay, and a significant increase of macrophage migration was observed in comparison with unstimulated conditioned medium. Moreover, we studied the role of NF-kappaB and of MAPKs in regulating TLR-mediated MCP-1 secretion by using inhibitors specific for each transduction pathway and we demonstrated a pivotal role of the IkappaB/NF-kappaB and JNK systems. In addition, TLR2/TLR6 and TLR5 stimulation induces increased ICAM-1 expression in Sertoli cells. Collectively, this study demonstrates the novel ability of Sertoli cells to potentially respond to a wide variety of bacteria through TLR stimulation.

Cerivastatin reduces cytokine-induced surface expression of ICAM-1 via increased shedding in human endothelial cells

Activation of endothelial cells is an incipient process in atherogenesis and leads to induction of the cellular adhesion molecules ICAM-1 and VCAM-1. Their expression can be induced by cytokines as well as other inflammatory mediators. The effects of HMG-CoA reductase inhibitors (statins) include mediation of anti-inflammatory properties. The aim of this study was the comparison of cerivastatin and simvastatin-mediated effects on inflammation-induced ICAM-1 and VCAM-1 expression in human umbilical venous endothelial cells (HUVEC). In HUVEC, TNF-alpha induced ICAM-1 and VCAM-1 mRNA and surface expression. Co-incubation with cerivastatin, but not simvastatin reduced TNF-alpha-induced up-regulation of ICAM-1 surface expression whereas both statins reduced VCAM-1 surface expression; all reductions in surface expression correlated with an increase in the soluble forms of ICAM-1 and VCAM-1 in cell culture supernatants. Mevalonate and nonsteroidal isoprenoids significantly reversed protein expression and shedding. Both statins caused an aggravation of TNF-alpha-induced ICAM-1 and VCAM-1 mRNA expression which was dependent on RNA synthesis. The statin-mediated increase in ICAM-1 and VCAM-1 mRNA expression correlated with the degradation of IkappaBa. Nuclear translocation of p65 was not significantly affected by statin-treatment of cytokine-treated cells. We conclude that cerivastatin and simvastatin reduce TNF-alpha-induced up-regulation of ICAM-1 and VCAM-1 surface expression via increased protein shedding mediated by HMG-CoA reductase inhibition and subsequent isoprenoid depletion.

Transcriptional regulation of VCAM-1 expression by tumor necrosis factor-alpha in human tracheal smooth muscle cells: involvement of MAPKs, NF-kappaB, p300, and histone acetylation

Tumor necrosis factor-alpha (TNF-alpha) has been shown to induce the expression of adhesion molecules in airway resident cells and contribute to inflammatory responses. Here, the roles of mitogen-activated protein kinases (MAPKs) and NF-kappaB in TNF-alpha-induced expression of vascular cell adhesion molecule (VCAM)-1 were investigated in human tracheal smooth muscle cells (HTSMCs). TNF-alpha-enhanced expression of VCAM-1 protein and mRNA as well as phosphorylation of p42/p44 MAPK, p38, and JNK were significantly attenuated by inhibitors of MEK1/2 (U0126), p38 (SB202190), and JNK (SP600125). Transfection with dominant negative mutants of MEK1/2, ERK1, ERK2, p38, and JNK attenuated TNF-alpha-induced VCAM-1 expression. Furthermore, TNF-alpha-induced VCAM-1 expression was significantly blocked by a selective NF-kappaB inhibitor helenalin. TNF-alpha-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha was blocked by helenalin, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNF-alpha in HTSMCs transfected with VCAM-1-Luc, which was inhibited by helenalin, U0126, SB202190, and SP600125. Most surprisingly, VCAM-1 expression was also significantly blocked by a selective inhibitor of p300, curcumin. NF-kappaB transcription factor and p300 were associated with the VCAM-1 promoter, which was dynamically linked to histone H3 acetylation stimulated by TNF-alpha, as determined by chromatin immunoprecipitation assay. Moreover, the resultant enhancement of VCAM-1 expression increased the adhesion of polymorphonuclear cells (PMNs) to monolayer of HTSMCs, which was blocked by helenalin, U0126, SB202190, or SP600125. These results suggest that in HTSMCs, activation of MAPK pathways, NF-kappaB, and p300 is essential for TNF-alpha-induced VCAM-1 expression.

Tumour necrosis factor-alpha as a tumour promoter

It is becoming more evident that many aspects of tumour promotion arise from persistent and unresolving inflammation. One of the key molecules mediating the inflammatory processes in tumour promotion is the cytokine, tumour necrosis factor-alpha (TNF-alpha). Clinically, elevated serum concentrations and increased expression of TNF-alpha are present in various pre-neoplastic and malignant diseases, compared with serum and tissue from healthy individuals. Although over the last few decades high-dose administration of TNF-alpha has been used as a cytotoxic agent, recent pre-clinical cancer models have provided critical evidence to support the link between chronic, low level TNF-alpha exposure and the acquisition of pro-malignant phenotype (i.e., increased growth, invasion and metastasis). Furthermore, sophisticated cellular systems are being utilised to dissect the crucial role TNF-alpha plays in the communication of stromal/inflammatory cells and tumour cells. Understanding the intricate roles of TNF-alpha in the process of tumour promotion will assist in the development of novel cancer therapeutics.

Platelet-derived growth factor-BB-induced hypertrophy of peritubular smooth muscle cells is mediated by activation of p38 MAP-kinase and of Rho-kinase

Peritubular smooth muscle cells (PSMC) from rat testis in primary serum-free cultures unexpectedly undergo contraction and subsequent cell hypertrophy in response to the growth factor PDGF-BB, remaining stationary. The present study investigates the transduction pathways involved in the observed paradoxical upregulation of the differentiated phenotype and induction of hypertrophy in PSMC. PI3K, ERK, JNK, and p38 kinases, known to mediate PDGF-BB signaling in the canonic dedifferentiative and proliferative response of smooth muscle cells (SMC) were rapidly activated by PDGF-BB but only p38 remained activated after 2-day stimulation. Immunofluorescence and immunoblotting experiments showed that in 4-day treatment: (i) continuous inhibition of PI3K, of ERK, of JNK, failed to inhibit either cell enlargement and formation of prominent alpha-SM actin containing stress fibers or the typical increase in alpha-SM actin; (ii) when stimulated in the presence of the p38 inhibitor SB203580 both responses were significantly inhibited and cytofluorimetric analysis of cell size showed a remarkable reduction of the hypertrophic response. PDGF-BB was also found to activate the small GTPase RhoA and inhibition of Rho-dependent kinase ROCK by Y27632 counteracted the effects of PDGF-BB similarly to SB203580. Both the transcription factor ATF2 and the nucleosomal kinase MSK1, downstream targets of p38, were activated by PDGF-BB, but p38 inhibitor SB203580 inhibited only the phosphorylation of MSK1 which appeared unaffected by ROCK inhibitor Y27632. In concluding, p38 and the Rho-ROCK system were found to play prominent, probably independent roles in the upregulation of PSMC differentiated phenotype and induction of hypertrophy by PDGF-BB.

Mitogen-activated protein kinases, adherens junction dynamics, and spermatogenesis: a review of recent data

Mitogen-activated protein kinases (MAPKs) are important regulators of many cellular processes. In mammalian testes, these kinases are involved in controlling cell division, differentiation, survival and death, and are therefore critical to spermatogenesis. Recent studies have also illustrated their involvement in junction restructuring in the seminiferous epithelium, especially at the ectoplasmic specialization (ES), a testis-specific adherens junction (AJ) type. ES contributes to the adhesion between Sertoli cells at the blood-testis barrier, as well as between Sertoli and developing spermatids (step 9 and beyond) at the adluminal compartment. MAPKs regulate AJ dynamics in the testis via their effects on the turnover of junction-associated protein complexes, the production of proteases and protease inhibitors, and the cytoskeleton structure. In this review, roles of the three major MAPK members, namely extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK, in ES dynamics are critically discussed. An integrated model of how these three MAPKs regulate adhesion function in the seminiferous epithelium is also presented. This model will serve as the framework for future investigation in the field.

The kinase insert domain-containing receptor is an angiogenesis-associated antigen recognized by human cytotoxic T lymphocytes

Antigen-specific cancer immunotherapy directed toward tumor-nourishing angiogenic blood vessels holds the promise of high efficacy, low toxicity, and ease of application. To evaluate whether the human angiogenic kinase insert domain-containing receptor (KDR) can serve as a target for cellular immunotherapy, 19 peptide sequences with HLA-A*0201 motifs were selected by computer-based algorithms. Five peptides (KDR82-90, KDR288-297, KDR766-774, KDR1093-1101, KDR1035-1044) stimulated specific cytotoxic T lymphocytes (CTLs) from peripheral-blood mononuclear cells (PBMCs) of 3 HLA-A*0201 donors. The decapeptide KDR288-297 was efficient in sensitizing target cells for recognition by a CTL clone at a concentration of 10 nM. More important, KDR288-297-specific CTLs lysed target cells transfected with HLA-A2/KDR cDNAs and a range of HLA-matched KDR+ angiogenic endothelial cells (aECs) and also recognized CD34+ endothelial progenitor cells. The specificity of CTLs was further confirmed by tetramer assay and cold-target inhibition assay. In addition, ex vivo exposure of aECs to the inflammatory cytokines enhanced CTL reactivity, which is in keeping with up-regulated KDR and HLA class 1 expression. In Matrigel assays, recognition of aECs by specific CTLs triggered an antivascular effect. These findings provide the first proof of the antigenic property of KDR protein and may be useful for devising new immunotherapeutic approaches to human cancers.

Method for evaluating quality of cultured neonatal pig Sertoli cells

BACKGROUND

Sertoli cells (SC) in the testis secrete factors that nourish and immunoprotect developing spermatozoa, which have made them the focus of studies that aim to generate localized tolerance, particularly for transplantation and perhaps autoimmunity. Several methods have been described to isolate these cells, which include a two-step enzymatic digestion with limited assessment of the culture. Here we describe a one-step method, and a series of tests for determining purity, viability, and function of the cultured cells.

METHODS

We isolated SC from neonatal pigs using Liberase HI digestion. Viability and apoptosis of cultured cells were measured by flow cytometry with propidium iodide and annexin, respectively. Specific identification of the Sertoli type was made by immunodetection of Sox9, vimentin, and Mullerian inhibiting substance. Moreover, for functionality we were able to detect clusterin in the cultured cells by Western blot.

RESULTS

Our isolation method had a yield and purity similar to previous reports measured with two-step methods. Viability was 95.22 +/- 0.57% and apoptotic cells were 10.5 +/- 0.32% after 48 h in culture. At 7 days, practically all cells expressed Sox9, Mullerian inhibiting substance, clusterin, and vimentin.

CONCLUSIONS

We describe an alternative strategy for preparing and identifying cultured SC for further assays of metabolic activity or in transplantation models. Establishing a one-step Liberase-digestion method for isolation, evaluating viability and apoptosis by more sensitive methods, and detecting specific markers in culture can help to evaluate the quality of cultured cells. Specific cell markers for identifying SC may be critical when identifying SC outside the testis, in contrast with vimentin which is useful only for in situ cells.