Influence of Pasteurella multocida Toxin on the differentiation of dendritic cells into osteoclasts

Pasteurella multocida toxin - lessons learned from a mitogenic toxin

The gram-negative, zoonotic bacterium Pasteurella multocida was discovered in 1880 and found to be the causative pathogen of fowl cholera. Pasteurella-related diseases can be found in domestic and wild life animals such as buffalo, sheep, goat, deer and antelope, cats, dogs and tigers and cause hemorrhagic septicemia in cattle, rhinitis or pneumonia in rabbits or fowl cholera in poultry and birds. Pasteurella multocida does not play a major role in the immune-competent human host, but can be found after animal bites or in people with close contact to animals. Toxigenic strains are most commonly found in pigs and express a phage-encoded 146 kDa protein, the Pasteurella multocida toxin (PMT). Toxin-expressing strains cause atrophic rhinitis where nasal turbinate bones are destroyed through the inhibition of bone building osteoblasts and the activation of bone resorbing osteoclasts. After its uptake through receptor-mediated endocytosis, PMT specifically targets the alpha subunit of several heterotrimeric G proteins and constitutively activates them through deamidation of a glutamine residue to glutamate in the alpha subunit. This results in cytoskeletal rearrangement, proliferation, differentiation and survival of cells. Because of the toxin's mitogenic effects, it was suggested that it might have carcinogenic properties, however, no link between Pasteurella infections and cell transformation could be established, neither in tissue culture models nor through epidemiological data. In the recent years it was shown that the toxin not only affects bone, but also the heart as well as basically all cells of innate and adaptive immunity. During the last decade the focus of research shifted from signal transduction processes to understanding how the bacteria might benefit from a bone-destroying toxin. The primary function of PMT seems to be the modulation of immune cell activation which at the same time creates an environment permissive for osteoclast formation. While the disease is restricted to pigs, the implications of the findings from PMT research can be used to explore human diseases and have a high translational potential. In this review our current knowledge will be summarized and it will be discussed what can be learned from using PMT as a tool to understand human pathologies.

Recent Advances in Osteoclast Biological Behavior

With the progress of the aging population, bone-related diseases such as osteoporosis and osteoarthritis have become urgent problems. Recent studies have demonstrated the importance of osteoclasts in bone homeostasis, implying these will be an important mediator in the treatment of bone-related diseases. Up to now, several reviews have been performed on part of osteoclast biological behaviors such as differentiation, function, or apoptosis. However, few reviews have shown the complete osteoclast biology and research advances in recent years. Therefore, in this review, we focus on the origin, differentiation, apoptosis, behavior changes and coupling signals with osteoblasts, providing a simple but comprehensive overview of osteoclasts for subsequent studies.

Cross-protection of recombinant Pasteurella multocida toxin proteins against atrophic rhinitis in mice

Pasteurella multocida (P. multocida) infects the swine respiratory tract and mainly causes atrophic rhinitis (AR). Recently, many commercially inactivated and subunit vaccines have been used as preventive strategies. However, the best antigenic protein portion has not been selected, and the aluminum gel was used as the adjuvant, which may not induce full protection. P. multocida toxin (PMT) is the major virulence factor responsible for AR. PMT is a monomeric 146 kDa protein (approximately 1285 amino acids) encoded by the tox A gene. In this study, we expressed different fragments of recombinant PMT proteins, combined them with a water-in-oil-in-water adjuvant, and evaluated mice's immune response. The results indicated that the rPMT-C-immunized group showed significantly higher levels (p < 0.05) of IgG, IgG2a antibody and interferon-γ, IL-12 cytokine expression than other groups. Furthermore, vaccination with rPMT-C recombinant protein can provide homologous and heterologous protection against P. multocida challenge. In conclusion, our approach may be feasible for developing an effective subunit vaccine against atrophic rhinitis with a cost-down simple ingredient.

Plumbagin, a Biomolecule with (Anti)Osteoclastic Properties

Plumbagin is a plant-derived naphthoquinone that is widely used in traditional Asian medicine due to its anti-inflammatory and anti-microbial properties. Additionally, plumbagin is cytotoxic for cancer cells due to its ability to trigger reactive oxygen species (ROS) formation and subsequent apoptosis. Since it was reported that plumbagin may inhibit the differentiation of bone resorbing osteoclasts in cancer-related models, we wanted to elucidate whether plumbagin interferes with cytokine-induced osteoclastogenesis. Using C57BL/6 mice, we unexpectedly found that plumbagin treatment enhanced osteoclast formation and that this effect was most pronounced when cells were pre-treated for 24 h with plumbagin before subsequent M-CSF/RANKL stimulation. Plumbagin caused a fast induction of NFATc1 signalling and mTOR-dependent activation of p70S6 kinase which resulted in the initiation of protein translation. In line with this finding, we observed an increase in RANK surface expression after Plumbagin stimulation that enhanced the responsiveness for subsequent RANKL treatment. However, in Balb/c mice and Balb/c-derived RAW264.7 macrophages, these findings could not be corroborated and osteoclastogenesis was inhibited. Our results suggest that the effects of plumbagin depend on the model system used and can therefore either trigger or inhibit osteoclast formation.

Dendritic cells development into osteoclast-type APCs by 4T1 breast tumor T cells milieu boost bone consumption

Bone metastases occur in 70% of patients with advanced breast cancer, causing severe morbidity and increased mortality due to osteolytic lesions driven by osteoclasts (OCs) inside the bone marrow (BM) microenvironment. A reciprocal vicious cycle between bone remodeling system and the tumor itself is established by the release of growth factors stored in the mineralized matrix, which in turn feed the tumor, changing tumor behavior and growth. However, BM is not a passive host microenvironment for circulating tumor cells, but instead can be actively modified by the primary tumor before metastatic spread occurs. Indeed, we have shown that T cells specific for the 4T1 mammary carcinoma cell line, are characteristically RANKL⁺ IL-17F⁺ CD4⁺ T cells. Those cells arrive in the BM before metastatic cells and set the pre-metastatic niche. In the absence of T cell derived RANKL, there is no pre-metastatic osteolytic disease and bone metastases do not take place. Recently, dendritic cells (DCs), the main T cell partner at the beginning of the immune response, came into the spotlight as a potential source of OCs progenitors under inflammatory conditions. Regarding bone metastasis, nothing is currently known about DCs plasticity or even its partnership with tumor induced T cells for BM pre-metastatic niche formation. Here, we show that splenic CD11c⁺ DCs stimulated with 4T1 conditioned media (CM) efficiently differentiated into mature and activated multinucleated giant cells (DC-OC) expressing TRAP and IL-23 cytokine. More important, 4T1 CM derived DC-OCs build a positive loop which amplifies the osteolytic phenomena by maintaining the RANKL⁺ Th17 T cells and by its own osteoclastic activity. In conclusion, our results indicate that differentiation of OCs from DCs may be achievable in the bone pre osteolytic disease context representing an alternative OC differentiation pathway. Besides being induced by high levels of T cells pro osteoclastogenic cytokines, especially by RANKL, DC-OC keep a positive feedback loop towards osteolysis, maintaining the pro-osteoclastogenic T cell phenotype in the BM.

The Role of Innate Immunity in Pulmonary Infections

Innate immunity forms a protective line of defense in the early stages of pulmonary infection. The primary cellular players of the innate immunity against respiratory infections are alveolar macrophages (AMs), dendritic cells (DCs), neutrophils, natural killer (NK) cells, and innate lymphoid cells (ILCs). They recognize conserved structures of microorganisms through membrane-bound and intracellular receptors to initiate appropriate responses. In this review, we focus on the prominent roles of innate immune cells and summarize transmembrane and cytosolic pattern recognition receptor (PRR) signaling recognition mechanisms during pulmonary microbial infections. Understanding the mechanisms of PRR signal recognition during pulmonary pathogen infections will help us to understand pulmonary immunopathology and lay a foundation for the development of effective therapies to treat and/or prevent pulmonary infections.

Human dendritic cell-derived osteoclasts with high bone resorption capacity and T cell stimulation ability

Osteoclasts are typically differentiated from monocytes (Mo-OC). A subset of osteoclasts (DC-OC) that are differentiated from dendritic cells (DC) has been reported in the arthritic mice model. However, little information is available on DC-OC in humans. The present study applied both in vitro and in vivo experiments to determine the function and pathological significance of DC-OC. DC-OC were differentiated from human monocyte-derived DC and their bone resorption and antigen-presenting functions were investigated. Synovial tissue samples from patients with rheumatoid arthritis were examined for the presence and characteristics of DC-OC. DC-OC differentiated from DC in the presence of M-CSF and RANKL in vitro were demonstrated to be cathepsin K-positive and TRAP-positive multinucleated giant cells. The DC-OC showed stronger bone resorption ability than monocyte-derived osteoclast (Mo-OC) as observed with the pit formation assay. The DC-OC retained CD11c positivity and expressed costimulatory molecules, unlike Mo-OC. T-cells proliferated when co-cultured with DC-OC, but not with Mo-OC. The addition of abatacept to the cocultures reduced T-cell stimulating activity of DC-OC. Abatacept inhibited the differentiation of monocytes into Mo-OC but did not suppress the differentiation of DC into DC-OC. TRAP-positive and CD86-positive DC-OC were detected in the synovial membranes of rheumatoid arthritis patients but not in patients with osteoarthritis. Human DC-OC demonstrated T-cell stimulating activity in addition to osteolytic activity. We further observed this subset of osteoclasts in the inflammatory synovial membrane of patients with rheumatoid arthritis. Such deviations from normal bone metabolism contribute to the inflammation and bone destruction in chronic inflammatory diseases such as rheumatoid arthritis.

Efficacy of cascade-primed cell infusion as an adjuvant immunotherapy with concurrent chemotherapy for patients with non-small-cell lung cancer: A retrospective observational study with a 5-year follow-up

BACKGROUND

Clinical studies have shown the efficacy of combination therapy for various malignancies. In this study, the characteristics, safety and feasibility of use of cascade-primed (CAPRI) cells for the combination treatment of non-small-cell lung cancer (NSCLC) were evaluated both in vitro and in vivo.

METHODS

Sixty-five patients with stage II-IV NSCLC were recruited. Of these patients, 31 patients received CAPRI cell therapy combined with chemotherapy (CAPRI group), and the other 34 patients constituted the control group and received chemotherapy alone. This study primarily aimed to evaluate the overall survival (OS), progression-free survival (PFS), short-term responses and treatment efficacy.

RESULTS

CD83, CD1a, CD80 and CD86 marker levels were significantly upregulated in CAPRI cells. Interferon-γ expression levels were highest in CD3⁺CD8⁺ cells (33.77% ± 4.40%). Furthermore, interleukin-2 levels were highest in CD3⁺CD56⁺ cells (26.73% ± 6.63%), whereas perforin expression levels were similar in CD3⁺CD8⁺ and CD3⁺CD56⁺ cells. Furthermore, CAPRI cells had a better anti-tumor potential in CD3⁺CD56⁺ cells and displayed the highest expression levels of CD107a to H460 and A549 cell lines. The 5-year OS was significantly greater in the CAPRI group than in the control group (P = 0.008), and the PFS of two groups exhibited a significant difference (P = 0.007). Median OS (48 versus 31.6 months; P = 0.004) and PFS (48 versus 36.4 months; P = 0.016) differed between these two groups. Moreover, treatment-associated toxicities were mild and well-tolerated by patients with NSCLC.

CONCLUSION

CAPRI cell therapy potentially prolongs the survival of patients with NSCLC when combined with chemotherapy.

l-Serine Lowers the Inflammatory Responses during Pasteurella multocida Infection

Pasteurella multocida causes a variety of infectious diseases in various species of mammals and birds, resulting in enormous economic loss to the modern livestock and poultry industry. However, the mechanism of host-pathogen interaction is unclear. Here, we found that l-serine levels were significantly decreased in murine lungs infected with P. multocida.

Pasteurella multocida causes a variety of infectious diseases in various species of mammals and birds, resulting in enormous economic loss to the modern livestock and poultry industry. However, the mechanism of host-pathogen interaction is unclear. Here, we found that l-serine levels were significantly decreased in murine lungs infected with P. multocida. Exogenous l-serine supplementation significantly increased the survival rate of mice and decreased the colonization of P. multocida in the lungs of mice. Notably, l-serine decreased the macrophage- and neutrophil-mediated inflammatory responses in mice during P. multocida infection.