Lipid-laden partially-activated plasmacytoid and CD4-CD8a+ dendritic cells accumulate in tissues in elderly mice

Background - Aging is associated with a decline in lymphocyte function however, little is known about dendritic cell (DC) subsets and aging. Aging is also associated with increasing circulating lipid levels and intracellular lipid accumulation modulates DC function. Whether age-associated increases in lipid levels influence DC biology is unknown. Thus, the effects of aging on DC subsets were assessed in vivo using young adult and elderly C57BL/6 J mice. Results - Major age-related changes included increased CD11c+ DC numbers in lymph nodes, spleens and livers, but not lungs, and significantly increased proportions of plasmacytoid (pDC) and CD4-CD8α+ DCs in lymph nodes and livers. Other changes included altered pDC activation status (decreased CD40, increased MHC class-I and MHC class-II), increased lipid content in pDCs and CD4-CD8α+ DCs, and increased expression of key mediators of lipid uptake including lipoprotein lipase, scavenger receptors (CD36, CD68 and LRP-1) in most tissues. Conclusions - Aging is associated with organ-specific numerical changes in DC subsets, and DC activation status, and increased lipid content in pDCs and CD4-CD8α+ DCs. Up-regulation of lipoprotein lipase and scavenger receptors by lipid-rich pDCs and CD4-CD8α+ DCs suggests these molecules contribute to DC lipid accumulation in the elderly. Lipid accumulation and modulated activation in pDCs and CD4-CD8α+ DCs may contribute to the declining responses to vaccination and infection with age

Rescue of skeletal muscle α-actin–null mice by cardiac (fetal) α-actin

Skeletal muscle α-actin (ACTA1) is the major actin in postnatal skeletal muscle. Mutations of ACTA1 cause mostly fatal congenital myopathies. Cardiac α-actin (ACTC) is the major striated actin in adult heart and fetal skeletal muscle. It is unknown why ACTC and ACTA1 expression switch during development. We investigated whether ACTC can replace ACTA1 in postnatal skeletal muscle. Two ACTC transgenic mouse lines were crossed with Acta1 knockout mice (which all die by 9 d after birth). Offspring resulting from the cross with the high expressing line survive to old age, and their skeletal muscles show no gross pathological features. The mice are not impaired on grip strength, rotarod, or locomotor activity. These findings indicate that ACTC is sufficiently similar to ACTA1 to produce adequate function in postnatal skeletal muscle. This raises the prospect that ACTC reactivation might provide a therapy for ACTA1 diseases. In addition, the mouse model will allow analysis of the precise functional differences between ACTA1 and ACTC

Rapid copper acquisition by developing murine mesothelioma: Decreasing bioavailable copper slows tumor growth, normalizes vessels and promotes T cell infiltration

Copper, an essential trace element acquired through nutrition, is an important co-factor for pro-angiogenic factors including vascular endothelial growth factor (VEGF). Decreasing bioavailable copper has been used as an antiangiogenic and anti-cancer strategy with promising results. However, the role of copper and its potential as a therapy in mesothelioma is not yet well understood. Therefore, we monitored copper levels in progressing murine mesothelioma tumors and analyzed the effects of lowering bioavailable copper. Copper levels in tumors and organs were assayed using atomic absorption spectrophotometry. Mesothelioma tumors rapidly sequestered copper at early stages of development, the copper was then dispersed throughout growing tumor tissues. These data imply that copper uptake may play an important role in early tumor development. Lowering bioavailable copper using the copper chelators, penicillamine, trientine or tetrathiomolybdate, slowed in vivo mesothelioma growth but did not provide any cures similar to using cisplatin chemotherapy or anti-VEGF receptor antibody therapy. The impact of copper lowering on tumor blood vessels and tumor infiltrating T cells was measured using flow cytometry and confocal microscopy. Copper lowering was associated with reduced tumor vessel diameter, reduced endothelial cell proliferation (reduced Ki67 expression) and lower surface ICAM/CD54 expression implying reduced endothelial cell activation, in a process similar to endothelial normalization. Copper lowering was also associated with a CD4+ T cell infiltrate. In conclusion, these data suggest copper lowering is a potentially useful anti-mesothelioma treatment strategy that slows tumor growth to provide a window of opportunity for inclusion of other treatment modalities to improve patient outcomes

Single-nucleus RNA sequencing of pre-malignant liver reveals disease-associated hepatocyte state with HCC prognostic potential

Current approaches to staging chronic liver diseases have limited utility for predicting liver cancer risk. Here, we employed single-nucleus RNA sequencing (snRNA-seq) to characterize the cellular microenvironment of healthy and pre-malignant livers using two distinct mouse models. Downstream analyses unraveled a previously uncharacterized disease-associated hepatocyte (daHep) transcriptional state. These cells were absent in healthy livers but increasingly prevalent as chronic liver disease progressed. Copy number variation (CNV) analysis of microdissected tissue demonstrated that daHep-enriched regions are riddled with structural variants, suggesting these cells represent a pre-malignant intermediary. Integrated analysis of three recent human snRNA-seq datasets confirmed the presence of a similar phenotype in human chronic liver disease and further supported its enhanced mutational burden. Importantly, we show that high daHep levels precede carcinogenesis and predict a higher risk of hepatocellular carcinoma development. These findings may change the way chronic liver disease patients are staged, surveilled, and risk stratified

Actin Nemaline Myopathy Mouse Reproduces Disease, Suggests Other Actin Disease Phenotypes and Provides Cautionary Note on Muscle Transgene Expression

Mutations in the skeletal muscle α-actin gene (ACTA1) cause congenital myopathies including nemaline myopathy, actin aggregate myopathy and rod-core disease. The majority of patients with ACTA1 mutations have severe hypotonia and do not survive beyond the age of one. A transgenic mouse model was generated expressing an autosomal dominant mutant (D286G) of ACTA1 (identified in a severe nemaline myopathy patient) fused with EGFP. Nemaline bodies were observed in multiple skeletal muscles, with serial sections showing these correlated to aggregates of the mutant skeletal muscle α-actin-EGFP. Isolated extensor digitorum longus and soleus muscles were significantly weaker than wild-type (WT) muscle at 4 weeks of age, coinciding with the peak in structural lesions. These 4 week-old mice were ∼30% less active on voluntary running wheels than WT mice. The α-actin-EGFP protein clearly demonstrated that the transgene was expressed equally in all myosin heavy chain (MHC) fibre types during the early postnatal period, but subsequently became largely confined to MHCIIB fibres. Ringbinden fibres, internal nuclei and myofibrillar myopathy pathologies, not typical features in nemaline myopathy or patients with ACTA1 mutations, were frequently observed. Ringbinden were found in fast fibre predominant muscles of adult mice and were exclusively MHCIIB-positive fibres. Thus, this mouse model presents a reliable model for the investigation of the pathobiology of nemaline body formation and muscle weakness and for evaluation of potential therapeutic interventions. The occurrence of core-like regions, internal nuclei and ringbinden will allow analysis of the mechanisms underlying these lesions. The occurrence of ringbinden and features of myofibrillar myopathy in this mouse model of ACTA1 disease suggests that patients with these pathologies and no genetic explanation should be screened for ACTA1 mutations

Are macrophages, myeloid derived suppressor cells and neutrophils mediators of local suppression in healthy and cancerous tissues in aging hosts?

Lung cancer is one of the commonest cancers worldwide and the incidence of malignant mesothelioma, caused by asbestos, is growing to global epidemic proportions. Standard chemotherapy only extends life expectancy in both cancers by, at best, a few years thus there is an urgent need for new treatment options. There are long latency periods of 30–45 years between asbestos exposure and development of diagnosable mesothelioma, and between cigarette smoking initiation and lung cancer diagnosis. Young people diagnosed with lung cancer or mesothelioma are rare. Children exposed to asbestos have a lower risk of developing mesothelioma compared to adults (Reid et al., 2007) and most cases occur in patients over 60 years. The mechanisms underlying this lengthy process are poorly understood. However, one contributing factor may be the declining immune function associated with aging, termed immunosenescence (Fulop et al., 2010). While, an age-related decline in T cell function is believed to contribute to increased cancer incidence in the elderly, the role of innate immune cells in cancer development is not so clear. Age-related immune dysfunction may be further compromised by tumor-associated factors and impact on therapeutic approaches involving the immune system, including standard chemotherapy. Yet preclinical studies of anti-cancer therapies are almost inevitably conducted in young adult animals with intact immunity, and elderly patients are often excluded from clinical trials due to toxicity concerns

Intratumoral interleukin-2/agonist CD40 antibody drives CD4+ - independent resolution of treated-turmors and CD4+ -dependent systemic and memory responses

Targeting interleukin-2 (IL-2) and/or agonist anti-CD40 antibody (Ab) into tumors represents an effective vaccination strategy that avoids systemic toxicity and resolves treated-site tumors. Here, we examined IL-2 and/or anti-CD40 Ab-driven local versus systemic T cell function and the installation of T cell memory. Single tumor studies showed that IL-2 induced a potent CD4? and CD8? T cell response that was limited to the draining lymph node and treated-site tumor, and lymph node tumorspecific CD8? T cells did not upregulate CD44. A twotumor model showed that while IL-2-treated-site tumors resolved, distal tumors continued to grow, implying limited systemic immunity. In contrast, anti-CD40 Ab treatment with or without IL-2 expanded the systemic T cell response to non-draining lymph nodes, and distal tumors resolved. Tumor-specific T cells in lymph nodes of anti-CD40 Ab ± IL-2-treated mice upregulated CD44, demonstrating activation and transition to effector/memory migratory cells. While CD40-activated CD4? T cells were not required for eradicating treated-site tumors, they, plus CD8? T cells, were crucial for removing distal tumors. Rechallenge/depletion experiments showed that the effector/memory phase required the presence of previously CD40/IL-2-activated CD4? and CD8? T cells to prevent recurrence. These novel findings show that different T cell effector mechanisms can operate for the eradication of local treated-site tumors versus untreated distal tumors and that signaling through CD40 generates a whole of body, effector/memory CD4? and CD8? T cell response that is amplified and prolonged via IL-2. Thus, successful immunotherapy needs to generate collaborating CD4? and CD8? T cells for a complete long-term protective cure

IL-2/CD40-activated macrophages rescue age and tumor-induced T cell dysfunction in elderly mice

The role of macrophages and their interactions with T cells during aging is not well understood. We determined if activating elderly-derived macrophages could rescue age-related and tumor-induced T cell dysfunction. Healthy elderly (18–24 months) Balb/c contained significantly more splenic IL-10-secreting M2-macrophages and myeloid-derived suppressor cells than young (6–8 weeks) mice. Exposure to syngeneic mesothelioma or lung carcinoma-conditioned media polarized peritoneal macrophages into suppressive M2-macrophages regardless of age. Tumor-exposed, elderly, but not young-derived, macrophages produced high levels of IL-4 and could not induce T cell IFN-γ production. We attempted to rescue tumor-exposed macrophages with LPS/IFN-γ (M1 stimulus) or IL-2/agonist anti-CD40 antibody. Tumor-exposed, M1-stimulated macrophages retained high CD40 expression, yet TNF-α and IFN-γ production were diminished relative to non-tumor-exposed, M1-stimulated controls. These macrophages induced young and elderly-derived T cell proliferation however, T cells did not secrete IFN-γ. In contrast, tumor-exposed, IL-2/CD40-stimulated macrophages rescued elderly-derived T cell IFN-γ production, suggesting that IL-2/CD40-activated macrophages could rescue T cell immunity in aging hosts

Modulation of dendritic cell and T cell cross-talk during aging: The potential role of checkpoint inhibitory molecules

© 2017 Elsevier B.V. Dendritic cells (DCs) undergo continuous changes throughout life, and there is evidence that elderly DCs have a reduced capacity to stimulate T cells, which may contribute to impaired anti-tumour immune responses in elderly people with cancer. Changes in checkpoint inhibitory molecules/pathways during aging may be one mechanism that impairs the ability of elderly DCs to activate T cells. However, little is currently known regarding the combined effects of aging and cancer on DC and T cell inhibitory molecules/pathways. In this review, we discuss our current understanding of the influence of aging and cancer on key DC and T cell inhibitory molecules/pathways, the potential underlying cellular and molecular mechanisms contributing to their modulation, and the possibility of therapeutically targeting inhibitory molecules in elderly cancer patients