The apoptotic signaling pathway activated by Toll-like receptor-2

Vibrio cholerae cytolysin induces pro-inflammatory and death signals through novel TLR assembly

Vibrio cholerae cytolysin (VCC) is a potent exotoxin secreted by Vibrio cholerae, the etiological agent of the severe diarrheal disease cholera. VCC is a membrane-damaging pore-forming toxin by nature, and is well known for its ability to cause host cell death. Using wild type V. cholerae and VCC-deleted mutant variant of the bacteria, we show that VCC plays an important role in the inflammatory responses during infection in mice. This observation supports that VCC can function as a pathogen-associated molecular pattern (PAMP). Toll-like receptors (TLRs) are the key initiators of inflammation. Upon ligand recognition, TLR1 and TLR6 generally form heterodimers with TLR2 for triggering pro-inflammatory signals. In the present study, we show that VCC engages novel TLR1/4 heterodimer assembly, and elicits pro-inflammatory responses in both dendritic cells (DCs) and macrophages. Along with TLR1/4, VCC-induced pro-inflammatory response in macrophages also involves TLR2. It has been shown earlier that VCC is implicated in the V. cholerae-mediated killing of the immune cells following biofilm formation. Here we show that TLRs play an important role in VCC-mediated killing of DCs and macrophages following V. cholerae infection. Interestingly, we find that TLR1/4 signalling is specifically crucial for the VCC-induced inflammatory and death responses in DCs, as well as in mice. Additionally, we observe that similar to DCs and macrophages, TLR1/4-MyD88 play an important role in VCC-mediated inflammatory responses in another crucial immune cell type, neutrophils. Taken together, our study shows novel TLR heterodimer formation, differential recognition of the same ligand by different TLR combination in cell type-dependent manner, and their implications in the context of V. cholerae and VCC-induced immune cell death and mortality.

Intratumoral delivery of mRNA encoding the endogenous TLR2/6 agonist UNE-C1 induces immunogenic cell death and enhances antitumor activity

Introduction

Recent investigations have highlighted the intratumoral administration of Toll-like receptor (TLR) ligands as a promising approach to initiate localized immune responses and enhance antitumor immunity. However, the clinical application of these ligands is limited by their rapid dissemination from the tumor microenvironment, raising concerns about reduced effectiveness and systemic toxicity.

Methods

To address these challenges, our study focused on the intratumoral delivery of mRNA encoding UNE-C1, a TLR2/6 ligand known for its efficacy and low toxicity profile. We explored the potential of UNE-C1 to induce immunogenic cell death (ICD) through autocrine mechanisms, facilitated by the release of damage-associated molecular patterns (DAMPs) triggered by TLR2 activation.

Results

Our findings indicate that sensitivity to UNE-C1-induced cell death is dependent on the expression levels of TLR2 and the Fas-associated death domain (FADD) in cancer cells. Furthermore, we investigated the paracrine activation of dendritic cells (DCs) by UNE-C1 via TLR2 signaling, which primes a CD8+ T cell response essential for tumor regression.

Discussion

Our results advocate for the intratumoral delivery of UNE-C1 via mRNA therapy as a promising strategy for innovative antitumor treatments.

Stage-specific expression of Toll-like receptors in the seminiferous epithelium of mouse testis

Genes encoding Toll-like receptors (TLRs) are expressed by germ cells in the mouse testis. Nevertheless, the expression of TLRs by germ cells has only been demonstrated for TLR-3, TLR-9, and TLR-11. Furthermore, the expression of each TLR in relation to the stage of spermatogenesis remains uncertain. We aimed in the present study to examine the expression pattern of all TLRs in germ cells throughout the cycle of seminiferous epithelium in the adult mouse testis. Immunohistochemistry was used to evaluate the expression of TLRs. Results of the present study reveal the expression of TLRs by specific populations of germ cells. Expression of TLRs, except for TLR-7, at endosomal compartments, acrosomes, and/or residual bodies was another interesting and novel finding of the present study. We further demonstrate that the expression of TLR-1, -2, -3, -4, -5, -7, -11, -12, and -13 follows a distinct spatiotemporal pattern throughout the cycle of seminiferous epithelium. While TLR-1, -3, -5, -11, and -12 are expressed in all stages, TLR-4 is expressed only in early and middle stages of spermatogenic cycle. On the other hand, TLR-2, -7, and -13 are expressed only in early stage of spermatogenic cycle. Evidence demonstrating the expression of TLRs in a stage specific manner throughout spermatogenesis strengthen the hypothesis that the expression of various TLRs by germ cells is a developmentally regulated process. However, if TLRs play a role in the regulation of proliferation, growth, maturation, and differentiation of germ cells throughout the cycle of the seminiferous epithelium warrants further investigations.

Molluscan pleiotropic FADD involved in innate immune signaling and induces apoptosis

Fas-associated protein with death domain (FADD) was initially identified as a crucial adaptor protein in the apoptotic pathway mediated by death receptor (DR). Subsequently, many studies have confirmed that FADD plays a vital role in innate immunity and inflammatory responses in animals. However, the function of this pleiotropic molecule in mollusk species has not been well explored. In this study, we successfully verified the gene sequence of FADD in the Zhikong scallop (Chlamys farreri) and designated it as CfFADD. The CfFADD protein contains a conserved death effector and death domains. Phylogenetic analysis showed that CfFADD is a novel addition to the molluscan FADD family with a close evolutionary relationship with molluscan FADD subfamily proteins. CfFADD mRNA expression in various scallop tissues was significantly induced by challenge with pathogen-associated molecular patterns (lipopolysaccharide, peptidoglycan, and poly(I:C)), suggesting its role in innate immunity in scallops. Co-immunoprecipitation showed that CfFADD interacted with the scallop DR (tumor necrosis factor receptor) and a signaling molecule involved in the Toll-like receptor pathway (interleukin-1 receptor-associated kinase), confirming that CfFADD may be involved in DR-mediated apoptosis and innate immune signaling pathways. Further studies showed that CfFADD interacted with CfCaspase-8 and activated caspase-3. HEK293T cells exhibited distinct apoptotic features after transfection with a CfFADD-expression plasmid, suggesting a functional DR-FADD-caspase apoptotic pathway in scallops. Overexpression of CfFADD led to a significant dose-dependent activation of interferon β and nuclear factor-κB reporter genes, demonstrating the key role of CfFADD in innate immunity. In summary, our research has confirmed the critical roles of CfFADD in innate immunity and apoptosis and provides valuable information for developing comparative immunology theories.

Characterization and expression profiles of toll-like receptor genes (TLR2 and TLR5) in immune tissues of hybrid yellow catfish under bacterial infection

The yellow catfish (Pelteobagrus fulvidraco) is one of the most economically important freshwater species in Asia. However, pathogenic bacterial infections often cause high rates of mortality and economic losses in practical aquaculture. Previous studies in mammals have shown that Toll-like receptor 2 (TLR2) and Toll-like receptor 5 (TLR5) are involved in the recognition of cell wall components such as lipopolysaccharides and flagella of various bacteria, thereby acting as key regulators in the innate immunity response. However, TLR2 and TLR5 in yellow catfish have not been characterized. In the present study, TLR2 and TLR5 were examined through comparative genomic approaches. The gene structure, collinearity, protein spatial structure, and phylogenetic relationships were compared with those in multiple representative vertebrates. Meanwhile, quantitative real-time PCR was conducted to explore transcriptional changes in TLR2 and TLR5 in immune tissues after infection with exogenous A. hydrophila and E. tarda. The results demonstrated the presence of TLR2 and TLR5 in yellow catfish. However, a systematic analysis showed that TLR2 was not associated with the arrangement of diverse neighboring genes. The expression of hybrid yellow catfish TLR2 transcripts in multiple tissues (including liver, spleen, kidney, and intestine) was significantly up-regulated after infection with A. hydrophila and E. tarda, suggesting that hybrid yellow catfish TLR2 and TLR5 may participate in the immune process. Taken together, the results indicate that TLR2 and TLR5 are conserved in terms of evolution and possess significant antibacterial activity as well as regulatory properties in immune-related tissues and thus play key roles in host defense against pathogen invasion.

Biofilm-derived membrane vesicles exhibit potent immunomodulatory activity in Pseudomonas aeruginosa PAO1

Pathogenic bacteria form biofilms on epithelial cells, and most bacterial biofilms show increased production of membrane vesicles (MVs), also known as outer membrane vesicles in Gram-negative bacteria. Numerous studies have investigated the MVs released under planktonic conditions; however, the impact of MVs released from biofilms on immune responses remains unclear. This study aimed to investigate the characteristics and immunomodulatory activity of MVs obtained from both planktonic and biofilm cultures of Pseudomonas aeruginosa PAO1. The innate immune responses of macrophages to planktonic-derived MVs (p-MVs) and biofilm-derived MVs (b-MVs) were investigated by measuring the mRNA expression of proinflammatory cytokines. Our results showed that b-MVs induced a higher expression of inflammatory cytokines, including Il1b, Il6, and Il12p40, than p-MVs. The mRNA expression levels of Toll-like receptor 4 (Tlr4) differed between the two types of MVs, but not Tlr2. Polymyxin B significantly neutralized b-MV-mediated cytokine induction, suggesting that lipopolysaccharide of native b-MVs is the origin of the immune response. In addition, heat-treated or homogenized b-MVs induced the mRNA expression of cytokines, including Tnfa, Il1b, Il6, and Il12p40. Heat treatment of MVs led to increased expression of Tlr2 but not Tlr4, suggesting that TLR2 ligands play a role in detecting the pathogen-associated molecular patterns in lysed MVs. Taken together, our data indicate that potent immunomodulatory MVs are produced in P. aeruginosa biofilms and that this behavior could be a strategy for the bacteria to infect host cells. Furthermore, our findings would contribute to developing novel vaccines using MVs.

Exposure to nanopollutants (nZnO) enhances the negative effects of hypoxia and delays recovery of the mussels' immune system

Aquatic environments face escalating challenges from multiple stressors like hypoxia and nanoparticle exposure, with impact of these combined stressors on mussel immunity being poorly understood. We investigated the individual and combined effects of short-term and long-term hypoxia and exposure to zinc oxide nanoparticles (nZnO) on immune system of the mussels (Mytilus edulis). Hemocyte functional traits (mortality, adhesion capacity, phagocytosis, lysosomal abundance, and oxidative burst), and transcript levels of immune-related genes involved in pathogen recognition (the Toll-like receptors, the complement system components, and the adaptor proteins MyD88) were assessed. Short-term hypoxia minimally affected hemocyte parameters, while prolonged exposure led to immunosuppression, impacting hemocyte abundance, viability, phagocytosis, and defensin gene expression. Under normoxia, nZnO stimulated immune responses of mussel hemocytes. However, combined nZnO and hypoxia induced more pronounced and rapid immunosuppression than hypoxia alone, indicating a synergistic interaction. nZnO exposure hindered immune parameter recovery during post-hypoxic reoxygenation, suggesting persistent impact. Opposing trends were observed in pathogen-sensing and pathogen-elimination mechanisms, with a positive correlation between pathogen-recognition system activation and hemocyte mortality. These findings underscore a complex relationship and potential conflict between pathogen-recognition ability, immune function, and cell survival in mussel hemocytes under hypoxia and nanopollutant stress, and emphasize the importance of considering multiple stressors in assessing the vulnerability and adaptability of mussel immune system under complex environmental conditions of anthropogenically modified coastal ecosystems.

Okadaic acid enhances NfKB, TLR-4, caspase 3, ERK ½, c-FOS, and 8-OHdG signaling pathways activation in brain tissues of zebrafish larvae

This study was designed to investigate the potential neuronal damage mechanism of the okadaic acid (OA) in the brain tissues of zebrafish embryos by evaluating in terms of immunofluorescence of Nf KB, TLR-4, caspase 3, ERK ½, c-FOS and 8-OHdG signaling pathways. We also evaluated body malformations. For this purpose, zebrafish embryos were exposed to 0.5 μg/ml, 1 μg/ml and 2.5 μg/ml of OA for 5 days. After application, FITC/GFP labeled protein-specific antibodies were used in immunofluorescence assay for NfKB, TLR-4, caspase 3, ERK ½, c-FOS and 8-OHdG respectively. The results indicated that OA caused immunofluorescence positivity of NfKB, TLR-4, caspase 3, ERK ½, c-FOS and 8-OHdG in a dose-dependent manner in the brain tissues of zebrafish embryos. Pericardial edema (PE), nutrient sac edema (YSE) and body malformations, tail malformation, short tail and head malformation (BM) were detected in zebrafish embryos. These results suggest that OA induces neuronal damage by affecting the modulation of DNA damage, apoptotic, and inflammatory activities in the brain tissues of zebrafish embryos. The increase in signaling pathways shows that OA can cause damage in the structure and function of brain nerve cells. Our results provide a new basis for the comprehensive assessment of the neural damage of OA and will offer enable us to better understand molecular the mechanisms underlying the pathophysiology of OA toxicity.

Metabolic changes enhance necroptosis of type 2 diabetes mellitus mice infected with Mycobacterium tuberculosis

Previously, we found that Mycobacterium tuberculosis (Mtb) infection in type 2 diabetes mellitus (T2DM) mice enhances inflammatory cytokine production which drives pathological immune responses and mortality. In the current study, using a T2DM Mtb infection mice model, we determined the mechanisms that make T2DM mice alveolar macrophages (AMs) more inflammatory upon Mtb infection. Among various cell death pathways, necroptosis is a major pathway involved in inflammatory cytokine production by T2DM mice AMs. Anti-TNFR1 antibody treatment of Mtb-infected AMs from T2DM mice significantly reduced expression of receptor interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) (necroptosis markers) and IL-6 production. Metabolic profile comparison of Mtb-infected AMs from T2DM mice and Mtb-infected AMs of nondiabetic control mice indicated that 2-ketohexanoic acid and deoxyadenosine monophosphate were significantly abundant, and acetylcholine and pyridoxine (Vitamin B6) were significantly less abundant in T2DM mice AMs infected with Mtb. 2-Ketohexanoic acid enhanced expression of TNFR1, RIPK3, MLKL and inflammatory cytokine production in the lungs of Mtb-infected nondiabetic mice. In contrast, pyridoxine inhibited RIPK3, MLKL and enhanced expression of Caspase 3 (apoptosis marker) in the lungs of Mtb-infected T2DM mice. Our findings demonstrate that metabolic changes in Mtb-infected T2DM mice enhance TNFR1-mediated necroptosis of AMs, which leads to excess inflammation and lung pathology.

Validation and application of caged Z-DEVD-aminoluciferin bioluminescence for assessment of apoptosis of wild type and TLR2-deficient mice after ischemic stroke

Programmed cell death or apoptosis is a critically important mechanism of tissue remodeling and regulates conditions such as cancer, neurodegeneration or stroke. The aim of this research article was to assess the caged Z-DEVD-aminoluciferin substrate for in vivo monitoring of apoptosis after ischemic stroke in TLR2-deficient mice and their TLR2-expressing counterparts. Postischemic inflammation is a significant contributor to ischemic injury development and apoptosis, and it is modified by the TLR2 receptor. Caged Z-DEVD-aminoluciferin is made available for bioluminescence enzymatic reaction by cleavage with activated caspase-3, and therefore it is assumed to be capable of reporting and measuring apoptosis. Apoptosis was investigated for 28 days after stroke in mice which ubiquitously expressed the firefly luciferase transgene. Middle cerebral artery occlusion was performed to achieve ischemic injury, which was followed with magnetic resonance imaging. The scope of apoptosis was determined by bioluminescence with caged Z-DEVD-aminoluciferin, immunofluorescence with activated caspase-3, flow cytometry with annexin-V and TUNEL assay. The linearity of Z-DEVD-aminoluciferin substrate dose effect was shown in the murine brain. Z-DEVD-aminoluciferin was validated as a good tool for monitoring apoptosis following adequate adjustment. By utilizing bioluminescence of Z-DEVD-aminoluciferin after ischemic stroke it was shown that TLR2-deficient mice had lower post-stroke apoptosis than TLR2-expressing wild type mice. In conclusion, Z-DEVD-aminoluciferin could be a valuable tool for apoptosis measurement in living mice.

TLR2 mediates renal apoptosis in neonatal mice subjected experimentally to obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, tubular apoptosis, and interstitial fibrosis. Toll like receptors (TLRs) expressed on leukocytes, myofibroblasts and renal cells play a central role in acute inflammation. TLR2 is activated by endogenous danger signals in the kidney; its contribution to renal injury in early life is still a controversial topic. We analyzed TLR2 for a potential role in the neonatal mouse model of congenital obstructive nephropathy. Inborn obstructive nephropathies are a leading cause of end-stage kidney disease in children. Thus, newborn Tlr2-/- and wild type (WT) C57BL/6 mice were subjected to complete unilateral ureteral obstruction (UUO) or sham-operation on the 2nd day of life. The neonatal kidneys were harvested and analyzed at days 7 and 14 of life. Relative expression levels of TLR2, caspase-8, Bcl-2, Bax, GSDMD, GSDME, HMGB1, TNF, galectin-3, α-SMA, MMP-2, and TGF-β proteins were quantified semi-quantitatively by immunoblot analyses. Tubular apoptosis, proliferation, macrophage- and T-cell infiltration, tubular atrophy, and interstitial fibrosis were analyzed immunohistochemically. Neonatal Tlr2-/- mice kidneys exhibited less tubular and interstitial apoptosis as compared to those of WT C57BL/6 mice after UUO. UUO induced neonatally did trigger pyroptosis in kidneys, however to similar degrees in Tlr2-/- and WT mice. Also, tubular atrophy, interstitial fibrosis, tubular proliferation, as well as macrophage and T-cell infiltration were unremarkable. We conclude that while TLR2 mediates apoptosis in the kidneys of neonatal mice subjected to UUO, leukocyte recruitment, interstitial fibrosis, and consequent neonatal obstructive nephropathy might lack a TLR2 involvement.

Characterization and expression profiling of fadd gene in response to exogenous Aeromonas hydrophila or Edwardsiella tarda challenge in the hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × P. vachelli ♂)

In mammals, fas-associated protein with death domain (FADD) is involved in the process of cell apoptosis and plays a key role in innate immune signaling. Nevertheless, its detailed molecular mechanisms underlying apoptosis and immune responses to exogenous bacterial infections in teleosts remain largely unknown. In this study, a group of 60 hybrid yellow catfish (with the body weight of 25 ± 0.5 g) were used in subsequent experiments, we examined the expression profiling of fadd gene through comparative genomics and comparative immunological methods. Our results showed that fadd in the hybrid yellow catfish (hycfadd) exhibited similar gene and spatial structures to those in other vertebrates, and formed an independent clade in phylogeny. An expression pattern analysis revealed that hycfadd widely transcribed in various tissues, with the highest transcription level in the liver. Furthermore, expression profiling of hycfadd when intraperitoneally infected with 50 μL of exogenous Aeromonas hydrophila (2.0 × 107 CFU/mL) or Edwardsiella tarda (2.0 × 107 CFU/mL) within 48 h were significantly up-regulated in the kidney, spleen, liver and intestine. Important genes in the toll like receptor (tlr) 1-tlr2- myeloid differentiation primary response 88 (MyD88)-fadd-caspase (casp) 8 cascades of TLR signaling pathway in liver were significantly up-regulated after the A. hydrophila stimulation, suggesting that apoptosis through the TLR signaling pathway may have been triggered and activated, which were further verified in the liver, kidney, spleen, intestine and gill by a TUNEL assay. Overall, this study provides solid evidence for the bacterial induction of fadd-related apoptosis in teleosts.

Identification and characterization of toll-like receptor genes in silver pomfret (Pampus argenteus) and their involvement in the host immune response to Photobacterium damselae subsp. Damselae and Nocardia seriolae infection

Toll-like receptors (TLRs) are vital pattern recognition receptors that play a critical role in the innate immune response against pathogenic attack. Among the bacteria commonly found in the culture process of silver pomfret, Photobacterium damselae subsp. Damselae (PDD, gram-negative) and Nocardia seriolae (NS, gram-positive), can cause large-scale mortality in this fish species. However, there is currently no research on the role of TLRs in mediating the immune response of silver pomfret to these two bacterial infections. Therefore, in this study, we identified nine PaTLRs family members, including several fish-specific TLRs (TLR14 and TLR21). Phylogenetic analysis revealed that these PaTLRs genes could be classified into five subfamilies, namely TLR1, TLR3, TLR5, TLR7, and TLR11, indicating their evolutionary conservation. To further explore the interactions of TLR genes with immune-related mediators, protein and protein interaction network (PPI) results were generated to explain the association of TLR genes with TNF receptor-associated factor 6 (TRAF6) and other relevant genes in the MyD88-dependent pathway and NF-κb signaling pathway. Subsequently, RT-qPCR was conducted to verify the expression patterns of the nine TLR genes in the gills, skin, kidney, liver, and spleen of healthy fish, with most of the TLRs showing high expression levels in the spleen. Following infection with PDD and NS, these PaTLRs exhibited different expression patterns in the spleen, with PaTLR2, PaTLR3, PaTLR5, PaTLR7, PaTLR9, and PaTLR14 being significantly up-regulated. Furthermore, when spleen cells were treated with bacterial compositions, the majority of PaTLRs expression was up-regulated in response to Lipopolysaccharide (LPS) and lipophosphorylcholic acid (LTA) treatment, except for PaTLR21. Finally, changes in the expression levels of TLR-interacting genes were also observed under the stimulation of bacteria and bacterial compositions. The results of this study provide a preliminary reference for further understanding the mechanism of the innate immune response of the TLR gene family in silver pomfret and offer theoretical support for addressing the disease problems encountered during large-scale fish breeding.

A Supportive Role of Mesenchymal Stem Cells on Insulin-Producing Langerhans Islets with a Specific Emphasis on The Secretome

Type 1 Diabetes (T1D) is a chronic autoimmune disease characterized by a gradual destruction of insulin-producing β-cells in the endocrine pancreas due to innate and specific immune responses, leading to impaired glucose homeostasis. T1D patients usually require regular insulin injections after meals to maintain normal serum glucose levels. In severe cases, pancreas or Langerhans islet transplantation can assist in reaching a sufficient β-mass to normalize glucose homeostasis. The latter procedure is limited because of low donor availability, high islet loss, and immune rejection. There is still a need to develop new technologies to improve islet survival and implantation and to keep the islets functional. Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells with high plasticity that can support human pancreatic islet function both in vitro and in vivo and islet co-transplantation with MSCs is more effective than islet transplantation alone in attenuating diabetes progression. The beneficial effect of MSCs on islet function is due to a combined effect on angiogenesis, suppression of immune responses, and secretion of growth factors essential for islet survival and function. In this review, various aspects of MSCs related to islet function and diabetes are described.

Two genes related to apoptosis in the hepatopancreas of juvenile prawn, Macrobrachium nipponense: Molecular characterization and transcriptional response to nanoplastic exposure

Nanoplastics have been widely found in the global water environment, causing plastic pollution and affecting human beings and numerous organisms. Studies involving freshwater crustacean exposure to nanoplastics, however, are limited. In this study, juvenile prawns (Macrobrachium nipponense) were exposed to 75 nm polystyrene nanoplastics at different concentrations (0, 5, 10, 20, or 40 mg/L) for a 28-d chronic exposure experiment. To study the effects of exposure to nanoplastics on hepatopancreas cell apoptosis, C-Jun N-terminal kinase (JNK) and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) genes were selected, and hepatotoxic enzyme activities and Toll pathway- and apoptosis-related gene expression were determined. For the first time, full-length Mn-JNK and Mn-PIK3CA cDNAs were cloned from M. nipponense. Homologous comparisons showed that JNK and PIK3CA had conserved functional sequences. The apoptosis rate in the high-concentration nanoplastic group (40 mg/L) was significantly higher than in the low-concentration nanoplastic (5 mg/L) and control groups (0 mg/L). The alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamyl transpeptidase (GGT) and xanthine oxidase (XOD) enzyme activities in the hepatopancreas increased with exposure to higher concentrations of nanoplastics. In addition, the levels of apoptosis- and Toll pathway-related gene expression and JNK and PIK3CA gene expression were initially increased, then decreased with exposure to higher concentrations of nanoplastics. This study showed that polystyrene nanoplastics activate toll-related pathways leading to apoptosis and hepatopancreas damage, which provides theoretical support for future aquatic toxicological research.

The critical role of apoptosis in mesenchymal stromal cell therapeutics and implications in homeostasis and normal tissue repair

Mesenchymal stromal cells (MSCs) have been extensively tested for the treatment of numerous clinical conditions and have demonstrated good safety but mixed efficacy. Although this outcome can be attributed in part to the heterogeneity of cell preparations, the lack of mechanistic understanding and tools to establish cell pharmacokinetics and pharmacodynamics, as well as the poorly defined criteria for patient stratification, have hampered the design of informative clinical trials. We and others have demonstrated that MSCs can rapidly undergo apoptosis after their infusion. Apoptotic MSCs are phagocytosed by monocytes/macrophages that are then reprogrammed to become anti-inflammatory cells. MSC apoptosis occurs when the cells are injected into patients who harbor activated cytotoxic T or NK cells. Therefore, the activation state of cytotoxic T or NK cells can be used as a biomarker to predict clinical responses to MSC treatment. Building on a large body of preexisting data, an alternative view on the mechanism of MSCs is that an inflammation-dependent MSC secretome is largely responsible for their immunomodulatory activity. We will discuss how these different mechanisms can coexist and are instructed by two different types of MSC "licensing": one that is cell-contact dependent and the second that is mediated by inflammatory cytokines. The varied and complex mechanisms by which MSCs can orchestrate inflammatory responses and how this function is specifically driven by inflammation support a physiological role for tissue stroma in tissue homeostasis, and it acts as a sensor of damage and initiator of tissue repair by reprogramming the inflammatory environment.

Maintenance and recall of memory T cell populations against tuberculosis: Implications for vaccine design

Despite the widespread use of standardised drug regimens, advanced diagnostics, and Mycobacterium bovis Bacille-Calmette-Guérin (BCG) vaccines, the global tuberculosis (TB) epidemic remains uncontrollable. To address this challenge, improved vaccines are urgently required that can elicit persistent immunologic memory, the hallmark of successful vaccines. Nonetheless, the processes underlying the induction and maintenance of immunologic memory are not entirely understood. Clarifying how memory T cells (Tm cells) are created and survive long term may be a crucial step towards the development of effective T cell–targeted vaccines. Here, we review research findings on the memory T cell response, which involves mobilization of several distinct Tm cell subsets that are required for efficient host suppression of M. tuberculosis (Mtb) activity. We also summaries current knowledge related to the T cell response-based host barrier against Mtb infection and discuss advantages and disadvantages of novel TB vaccine candidates.

Characterization of TLR1 and expression profiling of TLR signaling pathway related genes in response to Aeromonas hydrophila challenge in hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × P. vachelli ♂)

Toll‐like receptor 1 (TLR1) mediates the innate immune response to a variety of microbes through recognizing cell wall components (such as bacterial lipoproteins) in mammals. However, the detailed molecular mechanism of TLR1 involved in pathogen immunity in the representative hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × P. vachelli ♂) has not been well studied. In the present study, we identified the TLR1 gene from the hybrid yellow catfish, and further comparative synteny data from multiple species confirmed that the TLR1 gene is highly conserved in teleosts. Phylogenetic analysis revealed distinguishable TLR1s in diverse taxa, suggesting consistence in evolution of the TLR1 proteins with various species. Structural prediction indicated that the three-dimensional structures of TLR1 proteins are relatively conserved among different taxa. Positive selection analysis showed that purifying selection dominated the evolutionary process of TLR1s and TLR1-TIR domain in both vertebrates and invertebrates. Expression pattern analysis based on the tissue distribution showed that TLR1 mainly transcribed in the gonad, gallbladder and kidney, and the mRNA levels of TLR1 in kidney were remarkably up-regulated after Aeromonas hydrophila stimulation, indicating that TLR1 participates in the inflammatory responses to exogenous pathogen infection in hybrid yellow catfish. Homologous sequence alignment and chromosomal location indicated that the TLR signaling pathway is very conserved in the hybrid yellow catfish. The expression patterns of TLR signaling pathway related genes (TLR1- TLR2 - MyD88 - FADD - Caspase 8) were consistent after pathogen stimulation, revealing that the TLR signaling pathway is triggered and activated after A. hydrophila infection. Our findings will lay a solid foundation for better understanding the immune roles of TLR1 in teleosts, as well as provide basic data for developing strategies to control disease outbreak in hybrid yellow catfish.

Role of mitochondrial outer membrane permeabilization during bacterial infection

Beyond the initial 'powerhouse' view, mitochondria have numerous functions in their mammalian cell and contribute to many physiological processes, and many of these we understand only partially. The control of apoptosis by mitochondria is firmly established. Many questions remain however how this function is embedded into physiology, and how other signaling pathways regulate mitochondrial apoptosis; the interplay of bacteria with the mitochondrial apoptosis pathway is one such example. The outer mitochondrial membrane regulates both import into mitochondria and the release of intermembrane, and in some situations also matrix components from mitochondria, and these mitochondrial components can have signaling function in the cytosol. One function is the induction of apoptotic cell death. An exciting, more recently discovered function is the regulation of inflammation. Mitochondrial molecules, both proteins and nucleic acids, have inflammatory activity when released from mitochondria, an activity whose regulation is intertwined with the activation of apoptotic caspases. Bacterial infection can have more general effects on mitochondrial apoptosis-regulation, through effects on host transcription and other pathways, such as signals controlled by pattern recognition. Some specialized bacteria have products that more specifically regulate signaling to the outer mitochondrial membrane, and to apoptosis; both pro- and anti-apoptotic mechanisms have been reported. Among the intriguing recent findings in this area are signaling contributions of porins and the sub-lethal release of intermembrane constituents. We will here review the literature and place the new developments into the established context of mitochondrial signaling during the contact of bacterial pathogens with human cells.

Sub-lethal signals in the mitochondrial apoptosis apparatus: pernicious by-product or physiological event?

One of the tasks of mitochondria is the rule over life and death: when the outer membrane is permeabilized, the release of intermembrane space proteins causes cell death by apoptosis. For a long time, this mitochondrial outer membrane permeabilization (MOMP) has been accepted as the famous step from which no cell returns. Recent results have however shown that this quite plainly does not have to be the case. A cell can also undergo only a little MOMP, and it can efficiently repair damage it has incurred in the process. There is no doubt now that such low-scale permeabilization occurs. A major unclarified issue is the biological relevance. Is small-scale mitochondrial permeabilization an accident, a leakiness of the apoptosis apparatus, perhaps during restructuring of the mitochondrial network? Is it attempted suicide, where cell death by apoptosis is the real goal but the stimulus failed to reach the threshold? Or, more boldly, is there a true biological meaning behind the event of the release of low amounts of mitochondrial components? We will here explore this last possibility, which we believe is on one hand appealing, on the other hand plausible and supported by some evidence. Recent data are consistent with the view that sub-lethal signals in the mitochondrial apoptosis pathway can drive inflammation, the first step of an immune reaction. The apoptosis apparatus is almost notoriously easy to trigger. Sub-lethal signals may be even easier to set off. We suggest that the apoptosis apparatus is used in this way to sound the call when the first human cell is infected by a pathogen.

Dietary Supplementation with Eucommia ulmoides Leaf Extract Improved the Intestinal Antioxidant Capacity, Immune Response, and Disease Resistance against Streptococcus agalactiae in Genetically Improved Farmed Tilapia (GIFT; Oreochromis niloticus)

A 7-week rearing trial was designed to investigate the effects of Eucommia ulmoides leaf extract (ELE) on growth performance, body composition, antioxidant capacity, immune response, and disease susceptibility of diet-fed GIFT. The results showed that dietary ELE did not affect growth performance or whole-body composition (p > 0.05). Compared with the control group, plasma ALB contents increased in the 0.06% dietary ELE group (p < 0.05), and plasma ALT and AST activities decreased in the 0.08% dietary ELE group (p < 0.05). In terms of antioxidants, compared with GIFT fed the control diet, 0.06% dietary ELE upregulated the mRNA expression levels of Nrf2 pathway-related antioxidant genes, including CAT and SOD (p < 0.05), and 0.06% and 0.08% dietary ELE upregulated the mRNA levels of Hsp70 (p < 0.05). In terms of immunity, 0.06% dietary ELE suppressed intestinal TLR2, MyD88, and NF-κB mRNA levels (p < 0.05). Moreover, the mRNA levels of the anti-inflammatory cytokines TGF-β and IL-10 were upregulated by supplementation with 0.04% and 0.06% dietary ELE (p < 0.05). In terms of apoptosis, 0.06% and 0.08% ELE significantly downregulated the expression levels of FADD mRNA (p < 0.05). Finally, the challenge experiment with S. agalactiae showed that 0.06% dietary ELE could inhibit bacterial infection, and significantly improve the survival rate of GIFT (p < 0.05). This study demonstrated that the supplementation of 0.04−0.06% ELE in diet could promote intestinal antioxidant capacity, enhance the immune response and ultimately improve the disease resistance of GIFT against Streptococcus agalactiae.

Thiram exposure in environment: A critical review on cytotoxicity

Thiram is used in large quantities in agriculture and may contaminate the environment by improper handling or storage in chemical plants and warehouses. A review of the literature has shown that thiram can affect different organs in animals and its toxic mechanisms can be elucidated in more detail at molecular level. We have summarized several impacts of thiram on animals: the effects of the perspectives of oxidative stress, mitochondrial damage, autophagy, apoptosis, and the IHH/PTHrP pathway on regulating abnormal skeletal development in particular tibial dyschondroplasia and kyphosis; angiogenesis inhibition was investigated from the perspective of angiogenesis factor inhibition, PI3K/AKT signaling pathway and CD147; the inhibition effect of thiram on fibroblasts and erythrocytes via the perspective of oxidative stress, mitochondrial damage and inhibition of growth factors in animal skin fibroblasts and erythrocytes; studied fertilized egg size, reduced fertility, neurodegeneration, and immune damage from the perspectives of CYP51 inhibition and dopamine-b-hydroxylase inhibition in the reproductive system, vitamin D deficiency in the nervous system, and inflammatory damage in the immune system; embryonic dysplasia in terms of thyroid hormone repression in animal embryonic development and repression of the SOX9a transcription factor. The elucidation of the mechanisms of toxicity of thiram on various organs of animals at molecular level will enable a more detailed understanding of the mechanisms of toxicity of thiram in animals and will facilitate the exploration of the treatment of thiram poisoning at molecular level.

Transcriptome-based biomarker gene screening and evaluation of the extracellular fatty acid-binding protein (Ex-FABP) on immune and angiogenesis-related genes in chicken erythrocytes of tibial dyschondroplasia

BACKGROUND

Tibial dyschondroplasia (TD) is a bone disorder in which dead chondrocytes accumulate as a result of apoptosis and non-vascularization in the tibial bone of broiler chickens. The pathogenicity of TD is under extensive research but is yet not fully understood. Several studies have linked it to apoptosis and non-vascularization in the tibial growth plate (GP). We conceived the idea to find the differentially expressed genes (DEGs) in chicken erythrocytes which vary in expression over time using a likelihood-ratio test (LRT). Thiram was used to induce TD in chickens, and then injected Ex-FABP protein at 0, 20, and 50 μg^.kg^-1 to evaluate its therapeutic effect on 30 screened immunity and angiogenesis-related genes using quantitative PCR (qPCR). The histopathology was also performed in TD chickens to explore the shape, circularity, arrangements of chondrocytes and blood vessels.

RESULTS

Clinical lameness was observed in TD chickens, which decreased with the injection of Ex-FABP. Histopathological findings support Ex-FABP as a therapeutic agent for the morphology and vascularization of affected chondrocytes in TD chickens. qPCR results of 10 immunity (TLR2, TLR3, TLR4, TLR5, TLR7, TLR15, IL-7, MyD88, MHCII, and TRAF6) and 20 angiogenesis-related genes (ITGAV, ITGA2, ITGB2, ITGB3, ITGA5, IL1R1, TBXA2R, RPL17, F13A1, CLU, RAC2, RAP1B, GIT1, FYN, IQGAP2, PTCH1, NCOR2, VAV-like, PTPN11, MAML3) regulated when Ex-FABP is injected to TD chickens.

CONCLUSION

Immunity and angiogenesis-related genes can be responsible for apoptosis of chondrocytes and vascularization in tibial GP. Injection of Ex-FABP protein to thiram induced TD chickens decrease the chondrocytes damage and improves vascularization.

Gardnerella vaginalis infection in pregnancy: Effects on placental development and neonatal outcomes

INTRODUCTION

Gardnerella vaginalis (GV)-associated bacterial vaginosis is recognised for its detrimental effects on pregnancy resulting in poor obstetric and neonatal outcomes. There is limited knowledge of the effects on placental histomorphology following GV infection in pregnancy. We investigated the effects of GV infection on the placenta, particularly with regards to the syncytiotrophoblasts and vascular development, and related these to neonatal outcomes.

METHODS

A prospective cohort study involving GV-positive pregnant women presented with abnormal vaginal discharge, with gestational age-matched healthy pregnant women controls. Placental sampling was performed upon delivery and examined histologically. Vascular endothelial growth factor-A (VEGF-A) and hypoxia-inducible factor-1α (HIF-1α) mRNA and protein expression were analysed by real-time PCR and immunohistochemistry respectively. The standard measures in neonatal outcomes were recorded.

RESULTS

Placentas from GV-positive mothers were found to have significant histological evidence of maternal and/or fetal inflammatory response compared with the controls (17/28: 60.7% vs 2/20: 10%) (p = 0.0011). There was an increase in the percentage of syncytial nuclear aggregates (SNAs) per villus (47.4 ± 11.09%) in placentas from GV-positive mothers (p < 0.0001). VEGF-A was significantly increased in specifically, the villous endothelial cells of placentas with GV infection, but no difference in the immunoexpression of HIF-1α in these cells between groups. However, these were not associated with adverse neonatal outcomes.

DISCUSSION

Increased placental VEGF-A expression associated with increased SNAs in pregnant women with GV infection of the genital tract may be an intrauterine response towards placental vascular remodeling, that may also serve as a protective role in moderating birth outcomes.

Vortioxetine ameliorates motor and cognitive impairments in the rotenone-induced Parkinson's disease via targeting TLR-2 mediated neuroinflammation

Parkinson's disease (PD) is characterized by motor and non-motor symptoms associated with dopaminergic and non-dopaminergic injury. Vortioxetine is a multimodal serotonergic antidepressant with potential procognitive effects. This study aimed to explore the effects of vortioxetine on motor functions, spatial learning and memory, and depression-like behavior in the rotenone-induced rat model of PD. Male Sprague-Dawley rats were daily administered with the rotenone (2 mg·kg^-1, s.c.) and/or vortioxetine (10 mg·kg^-1, s.c.) for 28 days. Motor functions (rotarod, catalepsy, open-field), depression-like behaviors (sucrose preference test), anxiety (elevated plus maze), and spatial learning and memory abilities (novel object recognition and Morris water maze) were evaluated in behavioral tests. Then immunohistochemical, neurochemical, and biochemical analysis on specific brain areas were performed. Vortioxetine treatment markedly reduced rotenone-induced neurodegeneration, improved motor and cognitive dysfunction, decreased depression-like behaviors without affecting anxiety-like parameters. Vortioxetine also restored the impaired inflammatory response and affected neurotransmitter levels in brain tissues. Interestingly, vortioxetine was thought to trigger a sort of dysfunction in basal ganglia as evidenced by increased Toll-like receptor-2 (TLR-2) and decreased TH immunoreactivity only in substantia nigra tissue of PD rats compared to the control group. The present study indicates that vortioxetine has beneficial effects on motor dysfunction as well as cognitive impairment associated with neurodegeneration in the rotenone-induced PD model. Possible mechanisms underlying these beneficial effects cover TLR-2 inhibition and neurochemical restoration of vortioxetine.

The cytotoxicity and apoptotic effects of verbascoside on breast cancer 4T1 cell line

BACKGROUND

Despite significant advancements in breast cancer therapy, novel drugs with lower side effects are still being demanded. In this regard, we investigated the anti-cancer features of verbascoside in 4 T1 mouse mammary tumor cell.

METHODS

First, MTT assay was performed with various concentrations (ranging between 5 to 200 μM) of verbascoside and IC50 was calculated. Then the expression of Bax, Bcl-2, and caspase-3 was evaluated in treated 4 T1 cells. In addition, we investigated the expression of TLR4, MyD88, and NF-κB to ascertain the underlying mechanism of the anti-proliferative feature of verbascoside. Also, flow cytometry followed by double PI and Annexin V was conducted to confirm the apoptosis-inducing effect of verbascoside.

RESULTS

Our results from MTT assay showed verbascoside inhibits proliferation of 4 T1 cancer cells (IC50 117 μM) while is safe for normal HEK293T cells. By qRT-PCR, we observed that verbascoside treatment (100, 117 and, 130 μM) increases the expression of caspase-3 and Bax while reduces the expression of Bcl-2. Also, verbascoside (100, 117 and, 130 μM) increased the expression of TLR4 only at 130 μM dose and the expression of MyD88 whereas reduced the expression of NF-κB at mRNA level. Flow cytometry analysis also confirmed verbascoside induces apoptosis in 4 T1 cells at 117 μM.

CONCLUSION

Taken together, our data showed verbascoside is a safe natural compound for normal cells while has apoptosis-inducing feature through TLR4 axis on 4 T1 cells.

Induction of Apoptotic Cell Death by Oral Streptococci in Human Periodontal Ligament Cells

Initiation and progression of oral infectious diseases are associated with streptococcal species. Bacterial infection induces inflammatory responses together with reactive oxygen species (ROS), often causing cell death and tissue damage in the host. In the present study, we investigated the effects of oral streptococci on cytotoxicity and ROS production in human periodontal ligament (PDL) cells. Streptococcus gordonii showed cell cytotoxicity in a dose- and time-dependent manner. The cytotoxicity might be due to apoptosis since S. gordonii increased annexin V-positive cells, and the cytotoxicity was reduced by an apoptosis inhibitor, Z-VAD-FMK. Other oral streptococci such as Streptococcus mitis, Streptococcus sanguinis, and Streptococcus sobrinus also induced apoptosis, whereas Streptococcus mutans did not. All streptococci tested except S. mutans triggered ROS production in human PDL cells. Interestingly, however, streptococci-induced apoptosis appears to be ROS-independent, as the cell death induced by S. gordonii was not recovered by the ROS inhibitor, resveratrol or n-acetylcysteine. Instead, hydrogen peroxide (H₂O₂) appears to be important for the cytotoxic effects of streptococci since most oral streptococci except S. mutans generated H₂O₂, and the cytotoxicity was dramatically reduced by catalase. Furthermore, streptococcal lipoproteins are involved in cytotoxicity, as we observed that cytotoxicity induced by the lipoprotein-deficient S. gordonii mutant was less potent than that by the wild-type and was attenuated by anti-TLR2-neutralizing antibody. Indeed, lipoproteins purified from S. gordonii alone were sufficient to induce cytotoxicity. Notably, S. gordonii lipoproteins did not induce H₂O₂ or ROS but cooperatively induced cell death when co-treated with H₂O₂. Taken together, these results suggest that most oral streptococci except S. mutans efficiently induce damage to human PDL cells by inducing apoptotic cell death with bacterial H₂O₂ and lipoproteins, which might contribute to the progression of oral infectious diseases such as apical periodontitis.

Cephalosporium curvulum lectin causes mycotic keratitis by initiating infection through MyD88 dependent cellular proliferation and apoptosis in human corneal epithelial cells

Physiological role of a core fucose specific lectin from Cephalosporium curvulum isolated from mycotic keratitis patient in mediating pathogenesis was reported earlier. CSL has opposite effects on HCECs, at the initiation of infection when lectin concentration is low, CSL induces proinflammatory response and at higher concentration it inhibits growth as the infection progresses. Here we delineate detailed mechanism of opposing effects of CSL by confirming the binding of CSL and anti TLR 2 and 4 antibodies to TLRs 2 and 4 purified from HCECs using Galectin-3 Sepharose 4B column. Further, the expression of signaling proteins were monitored by Western blotting and apoptosis assay. At concentration of 0.3 µg/ml, CSL induced the activation of TLR-2,-4 and adapter protein MyD88. CSL also induced the expression of transcription factors NFkB, C-Jun and proinflammatory cytokines like interleukins -6 and -8 essential in maintaining cell proliferation. In contrast at higher concentrations i.e. 5 µg/ml CSL induces apoptotic effect as evidenced by increase in early and late apoptotic population as demonstrated by Annexin V-PI assay. Western blotting revealed that CSL treated HCECs at higher concentration lead to MyD88 dependent expression of apoptotic proteins like FADD, Caspase -8 and -3. All these results are in line with and substantiate our earlier results that indeed CSL is involved in mediating host pathogen interactions by interacting with cell surface TLRs, activating downstream signaling pathways leading to pathogenesis. Findings are of clinical significance in developing carbohydrate based therapeutic strategy to control infection and the disease.

A High-Cholesterol Diet Increases Toll-like Receptors and Other Harmful Factors in the Rabbit Myocardium: The Beneficial Effect of Statins

BACKGROUND

A high-cholesterol diet (HCD) induces vascular atherosclerosis through vascular inflammatory and immunological processes via TLRs. The aim of this study is to investigate the mRNA expression of TLRs and other noxious biomarkers expressing inflammation, fibrosis, apoptosis, and cardiac dysfunction in the rabbit myocardium during (a) high-cholesterol diet (HCD), (b) normal diet resumption and (c) fluvastatin or rosuvastatin treatment.

METHODS

Forty-eight male rabbits were randomly divided into eight groups (n = 6/group). In the first experiment, three groups were fed with HCD for 1, 2 and 3 months. In the second experiment, three groups were fed with HCD for 3 months, followed by normal chow for 1 month and administration of fluvastatin or rosuvastatin for 1 month. Control groups were fed with normal chow for 90 and 120 days. The whole myocardium was removed; total RNA was isolated from acquired samples, and polymerase chain reaction, reverse transcription PCR and quantitative real-time PCR were performed.

RESULTS

mRNA of TLRs 2, 3, 4 and 8; interleukin-6; TNF-a; metalloproteinase-2; tissue inhibitor of metalloproteinase-1; tumor protein 53; cysteinyl aspartate specific proteinase-3; and brain natriuretic peptide (BNP) increased in HCD. Statins but not resumption of a normal diet decreased levels of these biomarkers and increased levels of antifibrotic factors.

CONCLUSIONS

HCD increases the levels of TLRs; inflammatory, fibrotic and apoptotic factors; and BNP in the rabbit myocardium. Atherogenic diets adversely affect the myocardium at a molecular level and are reversed by statins.

Doxorubicin-induced cardiotoxicity: An update on the molecular mechanism and novel therapeutic strategies for effective management

Doxorubicin (Dox) is a secondary metabolite of the mutated strain of Streptomyces peucetius var. Caesius and belongs to the anthracyclines family. The anti-cancer activity of Dox is mainly exerted through the DNA intercalation and inhibiting topoisomerase II enzyme in fast-proliferating tumors. However, Dox causes cumulative and dose-dependent cardiotoxicity, which results in increased risks of mortality among cancer patients and thus limiting its wide clinical applications. There are several mechanisms has been proposed for doxorubicin-induced cardiotoxicity and oxidative stress, free radical generation and apoptosis are most widely reported. Apart from this, other mechanisms are also involved in Dox-induced cardiotoxicity such as impaired mitochondrial function, a perturbation in iron regulatory protein, disruption of Ca2+ homeostasis, autophagy, the release of nitric oxide and inflammatory mediators and altered gene and protein expression that involved apoptosis. Dox also causes downregulation of DNA methyltransferase 1 (DNMT1) enzyme activity which leads to a reduction in the DNA methylation process. This hypomethylation causes dysregulation in the mitochondrial genes like peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1-alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (TFAM) unit in the heart. Apart from DNA methylation, Dox treatment also alters the micro RNAs levels and histone deacetylase (HDAC) activity. Therefore, in the current review, we have provided a detailed update on the current understanding of the pathological mechanisms behind the well-known Dox-induced cardiotoxicity. Further, we have provided some of the most plausible pharmacological strategies which have been tested against Dox-induced cardiotoxicity.

IRAK2, an IL1R/TLR Immune Mediator, Enhances Radiosensitivity via Modulating Caspase 8/3-Mediated Apoptosis in Oral Squamous Cell Carcinoma

Predicting and overcoming radioresistance are crucial in radiation oncology, including in managing oral squamous cell carcinoma (OSCC). First, we used RNA-sequence to compare expression profiles of parent OML1 and radioresistant OML1-R OSCC cells in order to select candidate genes responsible for radiation sensitivity. We identified IRAK2, a key immune mediator of the IL-1R/TLR signaling, as a potential target in investigating radiosensitivity. In four OSCC cell lines, we observed that intrinsically low IRAK2 expression demonstrated a radioresistant phenotype (i.e., OML1-R and SCC4), and vice versa (i.e., OML1 and SCC25). Next, we overexpressed IRAK2 in low IRAK2-expression OSCC cells and knocked it down in high IRAK2-expression cells to examine changes of irradiation response. After ionizing radiation (IR) exposure, IRAK2 overexpression enhanced the radiosensitivity of radioresistant cells and synergistically suppressed OSCC cell growth both in vitro and in vivo, and vice versa. We found that IRAK2 overexpression restored and enhanced radiosensitivity by enhancing IR-induced cell killing via caspase-8/3-dependent apoptosis. OSCC patients with high IRAK2 expression had better post-irradiation local control than those with low expression (i.e., 87.4% vs. 60.0% at five years, P = 0.055), showing that IRAK2 expression was associated with post-radiation recurrence. Multivariate analysis confirmed high IRAK2 expression as an independent predictor for local control (HR, 0.11; 95% CI, 0.016 – 0.760; P = 0.025). In conclusion, IRAK2 enhances radiosensitivity, via modulating caspase 8/3-medicated apoptosis, potentially playing double roles as a predictive biomarker and a novel therapeutic target in OSCC.

Effects of extended pharmacological disruption of zebrafish embryonic heart biomechanical environment on cardiac function, morphology, and gene expression

BACKGROUND

Biomechanical stimuli are known to be important to cardiac development, but the mechanisms are not fully understood. Here, we pharmacologically disrupted the biomechanical environment of wild-type zebrafish embryonic hearts for an extended duration and investigated the consequent effects on cardiac function, morphological development, and gene expression.

RESULTS

Myocardial contractility was significantly diminished or abolished in zebrafish embryonic hearts treated for 72 hours from 2 dpf with 2,3-butanedione monoxime (BDM). Image-based flow simulations showed that flow wall shear stresses were abolished or significantly reduced with high oscillatory shear indices. At 5 dpf, after removal of BDM, treated embryonic hearts were maldeveloped, having disrupted cardiac looping, smaller ventricles, and poor cardiac function (lower ejected flow, bulboventricular regurgitation, lower contractility, and slower heart rate). RNA sequencing of cardiomyocytes of treated hearts revealed 922 significantly up-regulated genes and 1,698 significantly down-regulated genes. RNA analysis and subsequent qPCR and histology validation suggested that biomechanical disruption led to an up-regulation of inflammatory and apoptotic genes and down-regulation of ECM remodeling and ECM-receptor interaction genes. Biomechanics disruption also prevented the formation of ventricular trabeculation along with notch1 and erbb4a down-regulation.

CONCLUSIONS

Extended disruption of biomechanical stimuli caused maldevelopment, and potential genes responsible for this are identified.

Proteomic analysis using isobaric tags for relative and absolute quantification technology reveals mechanisms of toxic effects of tris (1,3-dichloro-2-propyl) phosphate on RAW264.7 macrophage cells

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is one of the most commonly used organophosphorus flame retardants. Immuno-toxicity induced by TDCIPP is becoming of increasing concern. However, effects of TDCIPP on immune cells and mechanisms resulting in those effects are poorly understood. In this study, it was determined, for the first time, by use of isobaric tags for relative and absolute quantification (iTRAQ) based proteomic techniques expression of global proteins in RAW264.7 cells exposed to 10 μM TDCIPP. A total of 180 significantly differentially expressed proteins (DEPs) were identified. Of these, 127 were up-regulated and 53 were down-regulated. The DEPs associated with toxic effects of TDCIPP were then screened by use of Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes for enrichment analysis. Results showed that these DEPs were involved in a number of pathways including apoptosis, DNA damage, cell cycle arrest, immune-toxicity, and signaling pathways, such as the Toll-like receptor, PPAR and p53 signaling pathways. The complex regulatory relationships between different DEPs, which might play an important role in cell death were also observed in the form of a protein-protein interaction network. Meanwhile, mitochondrial membrane potential (MMP) in RAW264.7 cells after TDCIPP treatment was also analyzed, the collapse of the MMP was speculated to play an important role in TDCIPP induced apoptosis. Moreover, some of the important regulator proteins discovered in this study, such as Chk1, Aurora A, would provide novel insight into the molecular mechanisms involved in toxic responses to TDCIPP.

The influence on oxidative stress markers, inflammatory factors and intestinal injury-related molecules in Wahui pigeon induced by lipopolysaccharide

INTRODUCTION

The intestinal structure is the foundation for various activities and functions in poultry. An important question concerns the changes in the intestinal status under endotoxin stimulation. This study aimed to investigate the mechanism of intestinal injury induced by lipopolysaccharide (LPS) in Wahui pigeons.

METHODS

Thirty-six 28-day-old healthy Wahui pigeons were randomly divided into two groups. The experimental group was injected with LPS (100 μg/kg) once per day for five days, and the control group was treated with the same amount of sterile saline. Blood and the ileum were collected from pigeons on the first, third, and fifth days of the experiment and used for oxidative stress assessment, inflammatory factor detection, histopathological examination, and positive cell localization. In addition, intestinal injury indices and mRNA expression levels (tight junction proteins, inflammatory cytokines, and factors related to autophagy and apoptosis) were evaluated.

RESULTS

Villi in the ileum were shorter in the LPS group than in the control group, and D-lactic acid levels in the serum were significantly increased. Glutathione and catalase levels significantly decreased, but the malondialdehyde content in the serum increased. TNF-α and IL-10 were detected at higher levels in the serum, with stronger positive signals and higher mRNA expression levels, in the LPS group than in the control group. In addition, the levels of TLR4, MyD88, NF-κB, and HMGB1 in the inflammatory signaling pathway were also upregulated. Finally, the mRNA expression of Claudin3, Occludin, and ZO-1 was significantly decreased; however, that of Beclin1 and Atg5 was increased in the LPS group.

CONCLUSION

Ileal pathological changes and oxidative stress were caused by LPS challenge; it is proposed that this triggering regulates the inflammatory response, causing excessive autophagy and apoptosis, promoting intestinal permeability, and leading to intestinal injury in Wahui pigeons.

The impact of damage-associated molecules released from canine tumor cells on gene expression in macrophages

Dying or damaged cells that are not completely eradicated by the immune system release their intracellular components in the extracellular space. Aberrant exposure of the damage-associated molecules to the immune system is often associated with inflammation and cancer pathogenesis. Thus, elucidating the role of damage-associated molecules in inducing sterile immune responses is crucial. In this study, we show that prostaglandin E2 (PGE2) is produced in the supernatants from several types of canine necrotic tumor cell lines. Inhibition of PGE2 production by indomethacin, a potent inhibitor of cyclooxygenase (COX) enzymes, induces the expression of tumor necrosis factor (Tnf) mRNA in the necrotic tumor cell supernatants. These results comply with the previous observations reported in mouse cell lines. Furthermore, comprehensive ribonucleic acid-sequencing (RNA-seq) analysis revealed that three categories of genes were induced by the damage-associated molecules: (i) a group of PGE2-inducible genes, (ii) genes that promote inflammation and are suppressed by PGE2, and (iii) a group of genes not suppressed by PGE2. Collectively, our findings reveal the hitherto unknown immune regulatory system by PGE2 and damage-associated molecules, which may have clinical implications in inflammation and cancer.

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) versus adult T-cell leukemia/lymphoma (ATLL)

Objectives

Human T cell leukemia virus-1 (HTLV-1) infection may lead to one or both diseases including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) or adult T cell leukemia lymphoma (ATLL). The complete interactions of the virus with host cells in both diseases is yet to be determined. This study aims to construct an interaction network for distinct signaling pathways in these diseases based on finding differentially expressed genes (DEGs) between HAM/TSP and ATLL.

Results

We identified 57 hub genes with higher criteria scores in the primary protein–protein interaction network (PPIN). The ontology-based enrichment analysis revealed following important terms: positive regulation of transcription from RNA polymerase II promoter, positive regulation of transcription from RNA polymerase II promoter involved in meiotic cell cycle and positive regulation of transcription from RNA polymerase II promoter by histone modification. The upregulated genes TNF, PIK3R1, HGF, NFKBIA, CTNNB1, ESR1, SMAD2, PPARG and downregulated genes VEGFA, TLR2, STAT3, TLR4, TP53, CHUK, SERPINE1, CREB1 and BRCA1 were commonly observed in all the three enriched terms in HAM/TSP vs. ATLL. The constructed interaction network was then visualized inside a mirrored map of signaling pathways for ATLL and HAM/TSP, so that the functions of hub genes were specified in both diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05521-y.

Structural insights of macromolecules involved in bacteria-induced apoptosis in the pathogenesis of human diseases

Numbers of pathogenic bacteria can induce apoptosis in human host cells and modulate the cellular pathways responsible for inducing or inhibiting apoptosis. These pathogens are significantly recognized by host proteins and provoke the multitude of several signaling pathways and alter the cellular apoptotic stimuli. This process leads the bacterial entry into the mammalian cells and evokes a variety of responses like phagocytosis, release of mitochondrial cytochrome c, secretion of bacterial effectors, release of both apoptotic and inflammatory cytokines, and the triggering of apoptosis. Several mechanisms are involved in bacteria-induced apoptosis including, initiation of the endogenous death machinery, pore-forming proteins, and secretion of superantigens. Either small molecules or proteins may act as a binding partner responsible for forming the protein complexes and regulate enzymatic activity via protein-protein interactions. The bacteria induce apoptosis, attack the human cell and gain control over various types of cells and tissue. Since these processes are intricate in the defense mechanisms of host organisms against pathogenic bacteria and play an important function in host-pathogen interactions. In this chapter, we focus on the various bacterial-induced apoptosis mechanisms in host cells and discuss the important proteins and bacterial effectors that trigger the host cell apoptosis. The structural characterization of bacterial effector proteins and their interaction with human host cells are also considered.

Intrauterine Gardnerella vaginalis Infection Results in Fetal Growth Restriction and Alveolar Septal Hypertrophy in a Rabbit Model

Background: Gardnerella vaginalis (GV) is most frequently associated with bacterial vaginosis and is the second most common etiology causing intrauterine infection after Ureaplasma urealyticum. Intrauterine GV infection adversely affects pregnancy outcomes, resulting in preterm birth, fetal growth restriction, and neonatal pneumonia. The knowledge of how GV exerts its effects is limited. We developed an in vivo animal model to study its effects on fetal development. Materials and Methods: A survival mini-laparotomy was conducted on New Zealand rabbits on gestational day 21 (28 weeks of human pregnancy). In each dam, fetuses in the right uterine horn received intra-amniotic 0.5 × 102 colony-forming units of GV injections each, while their littermate controls in the left horn received sterile saline injections. A second laparotomy was performed seven days later. Assessment of the fetal pups, histopathology of the placenta and histomorphometric examination of the fetal lung tissues was done. Results: Three dams with a combined total of 12 fetuses were exposed to intra-amniotic GV, and 9 fetuses were unexposed. The weights of fetuses, placenta, and fetal lung were significantly lower in the GV group than the saline-inoculated control group [mean gross weight, GV (19.8 ± 3.8 g) vs. control (27.9 ± 1.7 g), p < 0.001; mean placenta weight, GV (5.5 ± 1.0 g) vs. control (6.5 ± 0.7 g), p = 0.027; mean fetal lung weight, GV (0.59 ± 0.11 g) vs. control (0.91 ± 0.08 g), p = 0.002. There was a two-fold increase in the multinucleated syncytiotrophoblasts in the placenta of the GV group than their littermate controls (82.9 ± 14.9 vs. 41.6 ± 13.4, p < 0.001). The mean alveolar septae of GV fetuses was significantly thicker than the control (14.8 ± 2.8 μm vs. 12.4 ± 3.8 μm, p = 0.007). Correspondingly, the proliferative index in the interalveolar septum was 1.8-fold higher in the GV group than controls (24.9 ± 6.6% vs. 14.2 ± 2.9%, p = 0.011). The number of alveoli and alveolar surface area did not vary between groups. Discussion: Low-dose intra-amniotic GV injection induces fetal growth restriction, increased placental multinucleated syncytiotrophoblasts and fetal lung re-modeling characterized by alveolar septal hypertrophy with cellular proliferative changes. Conclusion: This intra-amniotic model could be utilized in future studies to elucidate the acute and chronic effects of GV intrauterine infections.

Heat Shock Protein 27 Injection Leads to Caspase Activation in the Visual Pathway and Retinal T-Cell Response

Heat shock protein 27 (HSP27) is one of the small molecular chaperones and is involved in many cell mechanisms. Besides the known protective and helpful functions of intracellular HSP27, very little is known about the mode of action of extracellular HSP27. In a previous study, we showed that intravitreal injection of HSP27 led to neuronal damage in the retina and optic nerve after 21 days. However, it was not clear which degenerative signaling pathways were induced by the injection. For this reason, the pathological mechanisms of intravitreal HSP27 injection after 14 days were investigated. Histological and RT-qPCR analyses revealed an increase in endogenous HSP27 in the retina and an activation of components of the intrinsic and extrinsic apoptosis pathway. In addition, an increase in nucleus factor-kappa-light-chain-enhancer of activated B cells (NFκB), as well as of microglia/macrophages and T-cells could be observed. In the optic nerve, however, only an increased apoptosis rate was detectable. Therefore, the activation of caspases and the induction of an incipient immune response seem to be the main triggers for retinal degeneration in this intravitreal HSP27 model.

Molecular Mechanisms of Renal Progenitor Regulation: How Many Pieces in the Puzzle?

Kidneys of mice, rats and humans possess progenitors that maintain daily homeostasis and take part in endogenous regenerative processes following injury, owing to their capacity to proliferate and differentiate. In the glomerular and tubular compartments of the nephron, consistent studies demonstrated that well-characterized, distinct populations of progenitor cells, localized in the parietal epithelium of Bowman capsule and scattered in the proximal and distal tubules, could generate segment-specific cells in physiological conditions and following tissue injury. However, defective or abnormal regenerative responses of these progenitors can contribute to pathologic conditions. The molecular characteristics of renal progenitors have been extensively studied, revealing that numerous classical and evolutionarily conserved pathways, such as Notch or Wnt/β-catenin, play a major role in cell regulation. Others, such as retinoic acid, renin-angiotensin-aldosterone system, TLR2 (Toll-like receptor 2) and leptin, are also important in this process. In this review, we summarize the plethora of molecular mechanisms directing renal progenitor responses during homeostasis and following kidney injury. Finally, we will explore how single-cell RNA sequencing could bring the characterization of renal progenitors to the next level, while knowing their molecular signature is gaining relevance in the clinic.

Screening of toll-like receptor signaling pathway-related genes and the response of recombinant glutathione S-transferase A3 protein to thiram induced apoptosis in chicken erythrocytes

The expression of genes related to the Toll-like receptors (TLRs) signaling pathway were determined. Group A, B and C fed with basal diet and group D, E and F induced TD by feeding a basal diet containing 100 mg·kg-1 thiram. rGSTA3 protein was injected at 20 μg·kg-1 in group B, E and at 50 μg·kg-1 in C, F. Results suggested that lameness and death of chondrocytes were significant on day 14. TLRs signaling pathway related genes were screened based on the transcriptome enrichment, and validated on qPCR. IL-7, TLR2, 3, 4, 5, 7, 15, MyD88, MHC-II, MDA5 and TRAF6 were significantly (p < 0.05) expressed in group E and F as compared to group D on day 14 and 23. IL-7, MHCII, TRAF6, TLR3, TLR5, TLR7, and TLR15 determined insignificant in group D compared to group A on day 23. TD occur in an early phase and alleviated in the later period. rGSTA3 protein can prevent apoptosis and repair degraded chondrocytes.

Aspergillus niger lectin elicits MyD88 dependent proliferation and apoptosis at lower and higher doses in immortalized human corneal epithelial cells leading to pathogenesis

An L-fucose lectin, ANL from the corneal smears of a mycotic keratitis patient was reported earlier. Interaction of ANL with immortalized Human Corneal Epithelial Cells (HCECs) was studied in order to assign the role of ANL in pathogenesis. ANL showed strong binding to HCECs which could be blocked by L-fucose and mucin. At concentrations below 0.6 μg/mL ANL showed proliferative effect and highest at 0.07 μg/mL leading to expression of proinflammatory cytokines IL-6 and IL-8. ANL induced proinflammatory response is mediated by TLR-2,-4, MyD88, NFkB and C-Jun dependent signaling. In contrast, ANL at concentrations above 0.6 μg/mL showed growth inhibitory effect at 48 h with an IC50 of 2.75 μg/mL. Western blot analysis revealed that HCECs treated with ANL at lower concentration induced the expression of proinflammatory signaling proteins TLR-2, 4, MyD88, NFkB and C-Jun which maintain high cell proliferating state. At higher concentration ANL induced apoptotic effect in HCECs with an increase in early apoptotic population as demonstrated by Annexin V-PI assay. ANL induced the expression of apoptotic proteins FADD, Caspase 8 and -3 mediated by MyD88. These findings demonstrate implication of ANL in pathogenesis and the findings are of clinical significance in developing strategy for controlling the infection leading to mycotic keratitis.

Desoxyrhapontigenin attenuates neuronal apoptosis in an isoflurane-induced neuronal injury model by modulating the TLR-4/cyclin B1/Sirt-1 pathway

This study investigated the protective effect of desoxyrhapontigenin (DOP) against isoflurane (ISF)-induced neuronal injury in rats. Neuronal injury was induced in pups by exposing them to 0.75% ISF on postnatal day 7 with 30% oxygen for 6 h. The pups were treated with DOP 10 mg/kg, i.p., for 21 days after ISF exposure. The protective effect of DOP was estimated by assessing cognitive function using the neurological score and the Morris water maze. Neuronal apoptosis was assessed in the hippocampus using the TUNEL assay, and protein expression of caspase-3, Bax, and Bcl-2 was measured by Western blotting. The levels of cytokines and oxidative stress parameters were assessed by ELISA. Western blotting and RT-PCR were performed to measure the expression of NF-kB, TLR-4, Sirt-1, and cyclin B1 protein in the brain. The cognitive function and neurological function scores were improved in the DOP group compared with the ISF group. Moreover, DOP treatment reduced the number of TUNEL-positive cells and the expression of caspase-3, Bax, and Bcl-2 protein in the brains of rats with neuronal injury. The levels of mediators of inflammation and oxidative stress were reduced in the brain tissue of the DOP group. Treatment with DOP attenuated the protein expression of TLR-4, NF-kB, cyclin B1, and Sirt-1 in the brain tissue of rats with neuronal injury. In conclusion, DOP ameliorates neuronal apoptosis and improves cognitive function in rats with ISF-induced neuronal injury. Moreover, DOP treatment can prevent neuronal injury by regulating the TLR-4/cyclin B1/Sirt-1 pathway.

Integration of gene expression profile data to screen and verify immune-related genes of chicken erythrocytes involved in Marek's disease virus

Chicken erythrocytes participated in immunity, but the role of erythrocytes in the immunity of Marek's disease virus (MDV) has not been reported related to the immunity genes. The purpose of this study was to screen and verify the immune-related genes of chicken erythrocytes which could be proven as a biomarker in MDV. The datasets (GPL8764-Chicken Gene Expression Microarray) were downloaded from the GEO profile database for control and MDV infected chickens to obtain differentially expressed genes (DEGs) through bioinformatics methods. Kyoto Encyclopedia of Genes and Genomes (KEGG) was performed to find enriched pathways, including Gene Ontology (GO). Based on enriched pathways, the top 19 immune-related genes were screened-out and process further to construct the protein-protein interaction (PPI) networks. The screened genes were validated on RT-PCR and qPCR. Results suggested that the mRNA transcription of Toll-like receptors 2, 3, 4, 6 (TLR2, TLR3, TLR4, TLR6), major histocompatibility complex-II (MHCII), interleukin-7 (IL-7), interferon-βeta (IFN-β), chicken myelomonocytic growth factor (cMGF) and myeloid differentiation primary response 88 (MyD88) were significantly up-regulated. The expression of toll-like receptor 5, 7 (TLR5, TLR7) interleukin-12 (IL-12 p40), interleukin-13 (IL-13), and interferon-αlpha (IFN-α) were significantly down-regulated in the erythrocytes of the infected group (P < 0.05). In contrast, the expression of toll-like receptor-1, 15, 21 (TLR1, TLR15, TLR21), major histocompatibility complex I (MHCI) and Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) were not significant. In conclusion, it has been verified on qRT-PCR results that 19 immune-related genes, which included TLRs, cytokines and MHC have immune functions in MDV infected chickens.

Expression of TLR-2 in hepatocellular carcinoma is associated with tumour proliferation, angiogenesis and Caspase-3 expression

AIMS

Unlike other Toll-like receptors (TLRs), the role of toll like receptor 2 (TLR-2) in the pathogenesis of chronic liver disease and hepatocellular carcinoma (HCC) is not well studied. We, therefore, set out to investigate the expression of TLR-2 in different chronic liver disease states along with other markers of cell death, cellular proliferation and tissue vascularisation METHODS AND RESULTS: Immunohistochemistry was performed on liver tissue microarrays comprising hepatitis, cirrhosis and HCC patient samples using antibodies against TLR-2, Ki-67, Caspase-3 and VEGF. This was done in order to characterise receptor expression and translocation, apoptosis, cell proliferation and vascularisation. Cytoplasmic TLR-2 expression was found to be weak in 5/8 normal liver cases, 10/19 hepatitis cases and 8/21 cirrhosis patients. Moderate to strong TLR-2 expression was observed in some cases of hepatitis and cirrhosis. Both, nuclear and cytoplasmic TLR-2 expression was present in HCC with weak intensity in 11/41 cases, and moderate to strong staining in 19/41 cases. Eleven HCC cases were TLR-2 negative. Surprisingly, both cytoplasmic and nuclear TLR-2 expression in HCC were found to significantly correlate with proliferative index (r = 0.24 and 0.37), Caspase-3 expression (r = 0.27 and 0.38) and vascularisation (r = 0.56 and 0.23). Further, nuclear TLR-2 localisation was predominant in HCC, whereas cytoplasmic expression was more prevalent in hepatitis and cirrhosis. Functionally, treatment of HUH7 HCC cells with a TLR-2 agonist induced the expression of cellular proliferation and vascularisation markers CD34 and VEGF.

CONCLUSIONS

Our results demonstrate a positive correlation between the expression of TLR-2 and other markers of proliferation and vascularisation in HCC which suggests a possible role for TLR-2 in HCC pathogenesis.

Impact of novel N-aryl substituted piperamide on NF-kappa B translocation as a potent anti-neuroinflammatory agent

NF-kB translocation is the key point in the upstream neuroinflammatory pathways. It plays an import role in the pro-inflammatory chemokine, cytokine, and various enzyme expressions, consequently leading to the inflammatory response of the innate immune system. The NF-kB complex consists of structural homolog subunits, including c-Rel, RelB, p52, p65, and p50. Among the p65 subunit has a vital function of NF-kB translocation and DNA binding. NF-kB translocation may occur due to acetylation and phosphorylation LYS 310 and SER311 amino acids in chain A of the p65 subunit in response to IKK-α/β activity. Therefore, there are two ways to inhibit the NF-kB translocation, either directly blocking the active sites of IKK-α/β enzymes or protecting the LYS 310 and SER311 of p65 subunit from acetylation and phosphorylation. NF-kB translocation inhibitors can maintain the NF-kB complex in the inactive form inside the cytosol. In this study, we have designed and developed an NF-kB translocation inhibitor, D4. We have performed various in silico, in vitro and in situ studies on the anti-neuroinflammatory function of D4. It showed the ability to inhibit IKK-α/β in both genome and proteome levels and protect LYS310 of the p65 subunit of NF-kB from the acetylation process. Therefore, we can suggest D4 as the promising anti-neuroinflammatory agent with a function on the upstream process of inflammatory pathways.

Eklund K. Osteoarthritis and Toll-Like Receptors: When Innate Immunity Meets Chondrocyte Apoptosis

Osteoarthritis (OA) has long been viewed as a degenerative disease of cartilage, but accumulating evidence indicates that inflammation has a critical role in its pathogenesis. In particular, chondrocyte-mediated inflammatory responses triggered by the activation of innate immune receptors by alarmins (also known as danger signals) are thought to be involved. Thus, toll-like receptors (TLRs) and their signaling pathways are of particular interest. Recent reports suggest that among the TLR-induced innate immune responses, apoptosis is one of the critical events. Apoptosis is of particular importance, given that chondrocyte death is a dominant feature in OA. This review focuses on the role of TLR signaling in chondrocytes and the role of TLR activation in chondrocyte apoptosis. The functional relevance of TLR and TLR-triggered apoptosis in OA are discussed as well as their relevance as candidates for novel disease-modifying OA drugs (DMOADs).

In Vitro Model of Stretch-Induced Lung Injury to Study Different Lung Ventilation Regimens and the Role of Sedatives

BACKGROUND

Currently lung injury is managed conservatively through supportive care including mechanical ventilation. However, mechanical ventilation can also cause additional lung injury due to over-stretch along with atelectasis and cytokine release. Here we developed an in vitro mechanical ventilation model using cyclic stretch of lung epithelial cells to mimic high and low tidal volume (TV) ventilation strategy, so that we could use this platform for pathophysiology analysis and screening for therapeutic drugs.

METHOD

We subjected MLE-15 cells to the following treatments. 1) No treatment, 2) lipopolysaccharide (100 ng/mL) stimulation for 24 hours, 3) mechanical stretch initiated at 6-hour time point for 18 hours, 4) LPS stimulation at time point 0 hour, and mechanical stretch was added at 6-hour time point for 18 hours. Biaxial cyclic stretch with a triangular wave was given via the Flexcell FX-6000 tension system to mimic low and high TV. Anesthetics dexmedetomidine and propofol were also tested.

RESULT

Our high TV mimic stretch increased cell death, while low TV mimic stretch did not affect the degree of cell death. Using this system, we examined the effect of sedatives commonly used in intensive care units on cell death and found that dexmedetomidine attenuated necrosis associated with stretch.

CONCLUSION

We described the in vitro cyclic stretch system mimicking high and low TV ventilation. High TV mimetic was associated with increased cell death. Dexmedetomidine attenuated the degree of cell death.

PLF-1 (Proliferin-1) Modulates Smooth Muscle Cell Proliferation and Development of Experimental Intimal Hyperplasia

Background Although apoptosis and cell proliferation have been extensively investigated in atherosclerosis and restenosis postinjury, the communication between these 2 cellular events has not been evaluated. Here, we report an inextricable communicative link between apoptosis and smooth muscle cell proliferation in the promotion of vascular remodeling postinjury. Methods and Results Cathepsin K-mediated caspase-8 maturation is a key initial step for oxidative stress-induced smooth muscle cell apoptosis. Apoptotic cells generate a potential growth-stimulating signal to facilitate cellular mass changes in response to injury. One downstream mediator that cathepsin K regulates is PLF-1 (proliferin-1), which can potently stimulate growth of surviving neighboring smooth muscle cells through activation of PI3K/Akt/p38MAPK (phosphatidylinositol 3-kinase/protein kinase B/p38 mitogen-activated protein kinase)-dependent and -independent mTOR (mammalian target of rapamycin) signaling cascades. We observed that cathepsin K deficiency substantially mitigated neointimal hyperplasia by reduction of Toll-like receptor-2/caspase-8-mediated PLF-1 expression. Interestingly, PLF-1 blocking, with its neutralizing antibody, suppressed neointima formation and remodeling in response to injury in wild-type mice. Contrarily, administration of recombinant mouse PLF-1 accelerated injury-induced vascular actions. Conclusions This is the first study detailing PLF-1 as a communicator between apoptosis and proliferation during injury-related vascular remodeling and neointimal hyperplasia. These data suggested that apoptosis-driven expression of PLF-1 is thus a novel target for treatment of apoptosis-based hyperproliferative disorders.