The influence of infectious factors on dendritic cell apoptosis

Clusterin protects mature dendritic cells from reactive oxygen species mediated cell death

Dendritic cells (DCs) play a key role in the induction of the adaptive immune response. They capture antigens in peripheral tissues and prime naïve T lymphocytes, triggering the adaptive immune response. In the course of inflammatory processes DCs face stressful conditions including hypoxia, low pH and high concentrations of reactive oxygen species (ROS), among others. How DCs survive under these adverse conditions remain poorly understood. Clusterin is a protein highly expressed by tumors and usually associated with bad prognosis. It promotes cancer cell survival by different mechanisms such as apoptosis inhibition and promotion of autophagy. Here, we show that, upon maturation, human monocyte-derived DCs (MoDCs) up-regulate clusterin expression. Clusterin protects MoDCs from ROS-mediated toxicity, enhancing DC survival and promoting their ability to induce T cell activation. In line with these results, we found that clusterin is expressed by a population of mature LAMP3+ DCs, called mregDCs, but not by immature DCs in human cancer. The expression of clusterin by intratumoral DCs was shown to be associated with a transcriptomic profile indicative of cellular response to stress. These results uncover an important role for clusterin in DC physiology.

Apoptotic bodies: bioactive treasure left behind by the dying cells with robust diagnostic and therapeutic application potentials

Apoptosis, a form of programmed cell death, is essential for growth and tissue homeostasis. Apoptotic bodies (ApoBDs) are a form of extracellular vesicles (EVs) released by dying cells in the last stage of apoptosis and were previously regarded as debris of dead cells. Recent studies unraveled that ApoBDs are not cell debris but the bioactive treasure left behind by the dying cells with an important role in intercellular communications related to human health and various diseases. Defective clearance of ApoBDs and infected-cells-derived ApoBDs are possible etiology of some diseases. Therefore, it is necessary to explore the function and mechanism of the action of ApoBDs in different physiological and pathological conditions. Recent advances in ApoBDs have elucidated the immunomodulatory, virus removal, vascular protection, tissue regenerative, and disease diagnostic potential of ApoBDs. Moreover, ApoBDs can be used as drug carriers enhancing drug stability, cellular uptake, and targeted therapy efficacy. These reports from the literature indicate that ApoBDs hold promising potential for diagnosis, prognosis, and treatment of various diseases, including cancer, systemic inflammatory diseases, cardiovascular diseases, and tissue regeneration. This review summarizes the recent advances in ApoBDs-related research and discusses the role of ApoBDs in health and diseases as well as the challenges and prospects of ApoBDs-based diagnostic and therapeutic applications.

Up-regulation of autophagy and apoptosis of cochlear hair cells in mouse models for deafness

INTRODUCTION

Hearing loss is one of the most common sensory disorders. Recent findings have shown that the apoptotic program and autophagy are related to hearing loss. The aim of the study was to explore the effects of noise and cisplatin exposure on apoptosis and autophagy in the hair cells of the cochleae.

MATERIAL AND METHODS

C57BL/6 mice were randomly divided into 3 groups (n = 10 for each): the control group, the noise model group and the cisplatin model group. Auditory brainstem response (ABR) measurements were used to detect the hearing thresholds. TUNEL assay was used to evaluate cell apoptosis. Western blot and immunofluorescence were performed to examine the apoptosis- and autophagy-related proteins.

RESULTS

The mice exhibited substantial hearing loss after noise and cisplatin exposure. Additionally, more TUNEL positive cells were observed in the mice after noise and cisplatin exposure compared with the control group. Moreover, the protein expression levels of Beclin-1, LC3-II, Bax and cleaved caspase-3 were significantly increased, while the expression of Bcl-2 was notably decreased in the cochlea after noise (p = 0.0278, 0.0075, 0.0142, 0.0158, 0.0131 respectively) and cisplatin (p = 0.0220, 0.0075, 0.0024, 0.0161, 0.0452 respectively) exposure compared with the control group. Besides, the ratio of LC3-II/LC3-I was substantially higher in the mice treated by cisplatin (p = 0.0046) and noise (p = 0.0220) compared with the control group.

CONCLUSIONS

Our findings demonstrated for the first time that noise and cisplatin exposure promoted apoptosis and autophagy in the hair cells of the cochleae. This study provides new insights into the mechanisms of noise- or cisplatin-induced hearing loss.

Production of IFN-γ by splenic dendritic cells during innate immune responses against Francisella tularensis LVS depends on MyD88, but not TLR2, TLR4, or TLR9

Production of IFN-γ is a key innate immune mechanism that limits replication of intracellular bacteria such as Francisella tularensis (Ft) until adaptive immune responses develop. Previously, we demonstrated that the host cell types responsible for IFN-γ production in response to murine Francisella infection include not only natural killer (NK) and T cells, but also a variety of myeloid cells. However, production of IFN-γ by mouse dendritic cells (DC) is controversial. Here, we directly demonstrated substantial production of IFN-γ by DC, as well as hybrid NK-DC, from LVS-infected wild type C57BL/6 or Rag1 knockout mice. We demonstrated that the numbers of conventional DC producing IFN-γ increased progressively over the course of 8 days of LVS infection. In contrast, the numbers of conventional NK cells producing IFN-γ, which represented about 40% of non-B/T IFN-γ-producing cells, peaked at day 4 after LVS infection and declined thereafter. This pattern was similar to that of hybrid NK-DC. To further confirm IFN-γ production by infected cells, DC and neutrophils were sorted from naïve and LVS-infected mice and analyzed for gene expression. Quantification of LVS by PCR revealed the presence of Ft DNA not only in macrophages, but also in highly purified, IFN-γ producing DC and neutrophils. Finally, production of IFN-γ by infected DC was confirmed by immunohistochemistry and confocal microscopy. Notably, IFN-γ production patterns similar to those in wild type mice were observed in cells derived from LVS-infected TLR2, TLR4, and TLR2xTLR9 knockout (KO) mice, but not from MyD88 KO mice. Taken together, these studies demonstrate the pivotal roles of DC and MyD88 in IFN-γ production and in initiating innate immune responses to this intracellular bacterium.

Hyperoside decreases the apoptosis and autophagy rates of osteoblast MC3T3‑E1 cells by regulating TNF‑like weak inducer of apoptosis and the p38mitogen activated protein kinase pathway

Wear particles generated between the interface of joints and artificial joint replacements are one of the primary causes of aseptic loosening. The aim of the present study was to investigate the influence of titanium (Ti) particles on the apoptosis and autophagy of osteoblasts, and probe into the potential use of hyperoside (Hy) as a protector for osteoblasts in Ti particle-induced injury. MC3T3-E1 cells were divided into control, Ti, Hy-1+Ti and Hy-2+Ti groups. Cell viability was detected using a Cell Counting Kit-8 assay. Apoptosis and autophagy rates were determined using flow cytometry. Expression levels of apoptosis-associated genes, including caspase-3, apoptosis regulator BAX, apoptosis regulator Bcl-2 and cellular tumor antigen p53, in addition to autophagy-associated genes, including Beclin1 and microtubule-associated protein light chain 3 conversion LC3-II/I, were measured using reverse transcription-quantitative polymerase chain reaction and western blotting. Activation of the tumor necrosis factor ligand superfamily member 12 (TWEAK)-mitogen activated protein kinase 11 (p38) mitogen activated protein kinase (MAPK) pathway was observed by western blotting. The present study demonstrated that pretreatment with Hy was able to increase cell viability and proliferation, and decrease apoptosis and autophagy to protect MC3T3-E1 cells against Ti particle-induced damage. Activation of the TWEAK-p38 pathway contributed to the repair processes of treatment with Hy. The present results suggested that Hy protected osteoblasts against Ti particle-induced damage by regulating the TWEAK-p38 pathway, which suggested the potential of Hy as a protective agent for bones.

Prevalence of bacteria and fungi in samples of cornea preservation fluid

INTRODUCTION

Recipients of corneal transplants are at risk of healthcare-associated infections, which, apart from other causes of surgical site infections, may also occur as a result of the transfer of infected corneal tissue. In this study we assessed the risk of bacterial and fungal infections based on the results of routine microbiological testing of cornea preservation fluid samples.

MATERIAL AND METHODS

We examined a total of 725 samples of corneal preservation fluid, obtained during a period of 3 years (2011-2013). Corneal preservation fluid samples were cultured and identified in accordance with standard microbiological methods.

RESULTS

The analysis comprised 725 samples of corneal preservation fluid, of which 32 (4.4%) samples tested positively in microbiological cultures. In total, 34 strains of bacteria and fungi were cultured. Gram-positive bacteria, Gram-negative bacteria and fungi comprised 85.3%, 8.8% and 5.9% of these strains, respectively. Analysis of the susceptibility of the cultured bacterial isolates to gentamicin was also performed, as this antibiotic is present in the composition of corneal preservation fluid. Among the cultured bacterial strains, 10 (33.3%) were resistant to gentamicin. None of the 32 patients who received a cornea stored in preservation fluid contaminated with bacteria and/or fungi demonstrated infectious complications in the surgical site within 1 year following cornea transplantation.

CONCLUSIONS

We postulate that perioperative antibiotic prophylaxis in cornea transplant recipients is important in preventing bacterial infections derived from the donor cornea. We believe that the addition of an antifungal agent to commercially available cornea preservation fluids should also be considered.

Low risk HPV-6E6 induces apoptosis in bone marrow-derived dendritic cells

The present study assessed the subcellular localization and apoptotic potential of low-risk human papilloma virus 6E6 (HPV-6E6), expressed in bone marrow-derived dendritic cells (DCs). DCs were obtained from C57BL/6 mice and transfected with a pGFP-6E6 plasmid. The subcellular localization of E6 was determined by tracing green fluorescent protein (GFP) using fluorescence microscopy. Apoptosis was assessed by staining nuclei with DAPI and performing an apoptosis-based flow cytometry assay. The co-localization of E6 and p53 was also investigated using confocal microscopy. In addition, the expression of apoptosis-associated proteins was analyzed using immunoblotting. The results of the present study demonstrated that low-risk HPV-6E6 is predominantly localized in the cytoplasm of DCs. Furthermore, p53 was upregulated in DCs transfected with pGFP-6E6 and co-localized with GFP-6E6 in the cytoplasm. DCs transfected with a control pGFP plasmid did not undergo apoptosis, whereas cells transfected with pGFP-6E6 did, as indicated by the presence of cell debris and condensation of the nuclei. Furthermore, the expression of apoptosis-associated proteins, including p53, BCL2 associated X apoptosis regulator (Bax), BCL2 homologous antagonist/killer (Bak) and cytochrome c, were significantly higher in DCs expressing low-risk E6 than in control cells. Therefore, the current study demonstrated that low-risk HPV-6E6 is predominantly located in the cytoplasm of DCs and induces apoptosis. This may be an important mechanism that explains why low-risk HPV is unable to induce malignant transformation.

Effect of the saliva from different triatomine species on the biology and immunity of TLR-4 ligand and Trypanosoma cruzi-stimulated dendritic cells

Background

Triatomines are blood-sucking vectors of Trypanosoma cruzi, the causative agent of Chagas disease. During feeding, triatomines surpass the skin host response through biomolecules present in their saliva. Dendritic cells (DCs) play a crucial role in the induction of the protection to aggressive agents, including blood-sucking arthropods. Here, we evaluated if salivary components of triatomines from different genera evade the host immunity by modulating the biology and the function of LPS- or T. cruzi-stimulated DCs.

Methods

Saliva of Panstrongylus lignarius, Meccus pallidipennis, Triatoma lecticularia and Rhodnius prolixus were obtained by dissection of salivary glands and the DCs were obtained from the differentiation of mouse bone marrow precursors.

Results

The differentiation of DCs was inhibited by saliva of all species tested. Saliva differentially inhibited the expression of MHC-II, CD40, CD80 and CD86 in LPS-matured DCs. Except for the saliva of R. prolixus, which induced IL-6 cytokine production, TNF-α, IL-12 and IL-6 were inhibited by the saliva of the other three tested species and IL-10 was increased in all of them. Saliva per se, also induced the production of IL-12, IL-6 and IL-10. Only the saliva of R. prolixus induced DCs apoptosis. The presence of PGE₂ was not detected in the saliva of the four triatomines studied. Finally, T. cruzi invasion on DCs is enhanced by the presence of the triatomine saliva.

Conclusions

These results demonstrate that saliva from different triatomine species exhibit immunomodulatory effects on LPS and T. cruzi-stimulated DCs. These effects could be related to hematophagy and transmission of T. cruzi during feeding.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1890-x) contains supplementary material, which is available to authorized users.

Follistatin-like protein 1 contributes to dendritic cell and T-lymphocyte activation in nasopharyngeal carcinoma patients by altering nuclear factor κb and Jun N-terminal kinase expression

Follistatin‐like protein 1 (FSTL1) is a newly characterized protein that can regulate the immune response in various ways. Dendritic cells (DCs) are central to immune regulation. In this study, we explored the impact of FSTL1 on DC activity in nasopharyngeal carcinoma (NPC) patients. The surface expression of CD40, CD86, and HLA‐DR on DCs was analyzed and showed significantly elevated expression levels, indicating DC maturity. After FSTL1 was added to DCs collected from NPC patients (n = 50), controls (n = 47), and healthy donors (n = 10), interferon γ secretion and T‐cell receptor expression in cytotoxic T lymphocytes were also investigated. In the experimental groups, the expression of the critical immune protein nuclear factor (NF)‐κb was upregulated, whereas Jun N‐terminal kinase (JNK) was downregulated. Our findings demonstrate that FSTL1 plays a critical role in immune regulation, enhancing the antigen presentation ability of DCs by up‐regulating NF‐κb expression and down‐regulating JNK expression.