Transgenic Overexpression of Interleukin-1β Induces Persistent Lymphangiogenesis But Not Angiogenesis in Mouse Airways

These studies used bi-transgenic Clara cell secretory protein (CCSP)/IL-1β mice that conditionally overexpress IL-1β in Clara cells to determine whether IL-1β can promote angiogenesis and lymphangiogenesis in airways. Doxycycline treatment induced rapid, abundant, and reversible IL-1β production, influx of neutrophils and macrophages, and conspicuous and persistent lymphangiogenesis, but surprisingly no angiogenesis. Gene profiling showed many up-regulated genes, including chemokines (Cxcl1, Ccl7), cytokines (tumor necrosis factor α, IL-1β, and lymphotoxin-β), and leukocyte genes (S100A9, Aif1/Iba1). Newly formed lymphatics persisted after IL-1β overexpression was stopped. Further studies examined how IL1R1 receptor activation by IL-1β induced lymphangiogenesis. Inactivation of vascular endothelial growth factor (VEGF)-C and VEGF-D by adeno-associated viral vector-mediated soluble VEGFR-3 (VEGF-C/D Trap) completely blocked lymphangiogenesis, showing its dependence on VEGFR-3 ligands. Consistent with this mechanism, VEGF-C immunoreactivity was present in some Aif1/Iba1-immunoreactive macrophages. Because neutrophils contribute to IL-1β–induced lung remodeling in newborn mice, we examined their potential role in lymphangiogenesis. Triple-transgenic CCSP/IL-1β/CXCR2^−/− mice had the usual IL-1β-mediated lymphangiogenesis but no neutrophil recruitment, suggesting that neutrophils are not essential. IL1R1 immunoreactivity was found on some epithelial basal cells and neuroendocrine cells, suggesting that these cells are targets of IL-1β, but was not detected on lymphatics, blood vessels, or leukocytes. We conclude that lymphangiogenesis triggered by IL-1β overexpression in mouse airways is driven by VEGF-C/D from macrophages, but not neutrophils, recruited by chemokines from epithelial cells that express IL1R1.CME Accreditation Statement: This activity (“ASIP 2013 AJP CME Program in Pathogenesis”) has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Society for Clinical Pathology (ASCP) and the American Society for Investigative Pathology (ASIP). ASCP is accredited by the ACCME to provide continuing medical education for physicians.The ASCP designates this journal-based CME activity (“ASIP 2013 AJP CME Program in Pathogenesis”) for a maximum of 48 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.CME Disclosures: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose.IL-1β is a key inflammatory cytokine found in many pathologic conditions and is responsible for triggering multiple downstream inflammatory pathways.¹ Inhibiting IL-1 signaling by neutralizing antibodies or by blocking IL1R1 receptors is effective in treating inflammation in numerous pathologic conditions.² However, IL-1β can be a two-edged sword. Depending on the context, IL-1β is responsible for deleterious effects by amplifying inflammation and also for protective effects, for example, by activating the immune system during infection.³IL-1β has a main role in the remodeling of many tissues, including the airways and lungs. Overexpression of IL-1β in adult mouse airways and lungs results in pulmonary inflammation and the recruitment of inflammatory cells, including neutrophils, enlargement of distal airspaces, and the induction of mucous metaplasia and airway fibrosis.⁴ In neonatal mice, overexpression of IL-1β results in the disruption of lung development characteristic of bronchopulmonary dysplasia,^5,6 and this effect is mediated in part by integrins.^7,8 Furthermore, in addition to its known effects on remodeling of many tissue types, IL-1β has been reported to induce angiogenesis in several experimental models and in human diseases, including the eye, arthritic joints, and tumors, mediated in part by recruitment of leukocytes that release other inflammatory mediators.^9–14Blood vessels and lymphatics of airways show a wide repertoire of responses to different inflammatory stimuli. Various patterns of blood vessel enlargement and angiogenic sprouting are found in mice with chronic airway inflammation.^15–17 For the most part, the cellular and molecular mediators that drive vascular changes are still poorly understood, but numerous cytokines and chemokines, including IL-1β, are up-regulated in Mycoplasma pulmonis infection.^17–20 M. pulmonis-infected mice also show profound lymphangiogenesis, mediated by vascular endothelial growth factor receptor (VEGFR)-3 signaling.²¹ Because IL-1β can activate NF-κB pathways to up-regulate vascular endothelial growth factor (VEGF)-C and -D, ligands for VEGFR-3,^22,23 IL-1β could also be a candidate for driving lymphangiogenesis. IL-1β is also known to up-regulate VEGF-C in vitro, a VEGFR-3 ligand that can drive lymphangiogenesis.²⁴ However, it has been difficult to dissect the effects of individual cytokines in bacterial infection, and the effects of IL-1β alone in airways have not been examined.With this background, we took advantage of bi-transgenic (CCSP/IL-1β) mice in which IL-1β is overexpressed in airways by the rat Clara cell secretory protein (CCSP) promoter in a doxycycline (Dox)-inducible fashion.⁴ This model permitted us to study the effects of overexpression of IL-1β alone on lymphangiogenesis and angiogenesis.The goal of this study was to determine whether selective overexpression of IL-1β in adult mouse airways would induce growth or remodeling of blood vessels or lymphatic vessels and to determine the involved cells and molecules. We also sought to learn if vessel remodeling persisted after IL-1β was turned off and if VEGFR-3 signaling drove the lymphangiogenesis. To approach these issues, we stained blood vessels and lymphatics immunohistochemically in whole mounts of tracheas from CCSP/IL-1β mice treated with Dox. We also used immunohistochemistry to identify airway cells that stained for IL1R1. Because IL-1β induced leukocyte influx, including abundant neutrophils, we tested whether neutrophils were essential for the effects of IL-1β on lymphatic vessels by examining lymphangiogenesis in CXCR2^−/− mice crossed to CCSP/IL-1β mice.We found that overexpression of IL-1β in mouse airways produced neutrophil and macrophage influx, expression of inflammatory cytokines and chemokines, and long-lasting lymphangiogenesis, but not angiogenesis. IL1R1 receptors were abundant on epithelial basal cells and neuroendocrine cells, but not on lymphatics. Inactivation of VEGFR-3 ligands by soluble VEGFR-3 (VEGF-C/D Trap) from an adeno-associated viral (AAV) vector completely blocked the lymphangiogenesis, indicative of the necessity of VEGFR-3 ligands, VEGF-C and/or VEGF-D. VEGF-C immunoreactivity was present in some recruited macrophages, but the lymphangiogenesis did not require the influx of neutrophils.     

PSD-95 in CA1 Area Regulates Spatial Choice Depending on Age

Cognitive processes that require spatial information rely on synaptic plasticity in the dorsal CA1 area (dCA1) of the hippocampus. Since the function of the hippocampus is impaired in aged individuals, it remains unknown how aged animals make spatial choices. Here, we used IntelliCage to study behavioral processes that support spatial choices of aged female mice living in a group. As a proxy of training-induced synaptic plasticity, we analyzed the morphology of dendritic spines and the expression of a synaptic scaffold protein, PSD-95. We observed that spatial choice training in young adult mice induced correlated shrinkage of dendritic spines and downregulation of PSD-95 in dCA1. Moreover, long-term depletion of PSD-95 by shRNA in dCA1 limited correct choices to a reward corner, while reward preference was intact. In contrast, old mice used behavioral strategies characterized by an increased tendency for perseverative visits and social interactions. This strategy resulted in a robust preference for the reward corner during the spatial choice task. Moreover, training decreased the correlation between PSD-95 expression and the size of dendritic spines. Furthermore, PSD-95 depletion did not impair place choice or reward preference in old mice. Thus, our data indicate that while young mice require PSD-95-dependent synaptic plasticity in dCA1 to make correct spatial choices, old animals observe cage mates and stick to a preferred corner to seek the reward. This strategy is resistant to the depletion of PSD-95 in the CA1 area. Overall, our study demonstrates that aged mice combine alternative behavioral and molecular strategies to approach and consume rewards in a complex environment.SIGNIFICANCE STATEMENT It remains poorly understood how aging affects behavioral and molecular processes that support cognitive functions. It is, however, essential to understand these processes to develop therapeutic interventions that support successful cognitive aging. Our data indicate that while young mice require PSD-95-dependent synaptic plasticity in dCA1 to make correct spatial choices (i.e., choices that require spatial information), old animals observe cage mates and stick to a preferred corner to seek the reward. This strategy is resistant to the depletion of PSD-95 in the CA1 area. Overall, our study demonstrates that aged mice combine alternative behavioral and molecular strategies to approach and consume rewards in a complex environment. Second, the contribution of PSD-95-dependent synaptic functions in spatial choice changes with age.     

Adult trkB Signaling in Parvalbumin Interneurons is Essential to Prefrontal Network Dynamics

Inhibitory interneurons expressing parvalbumin (PV) are central to cortical network dynamics, generation of γ oscillations, and cognition. Dysfunction of PV interneurons disrupts cortical information processing and cognitive behavior. Brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (trkB) signaling regulates the maturation of cortical PV interneurons but is also implicated in their adult multidimensional functions. Using a novel viral strategy for cell-type-specific and spatially restricted expression of a dominant-negative trkB (trkB.DN), we show that BDNF/trkB signaling is essential to the integrity and maintenance of prefrontal PV interneurons in adult male and female mice. Reduced BDNF/trkB signaling in PV interneurons in the medial prefrontal cortex (mPFC) resulted in deficient PV inhibition and increased baseline local field potential (LFP) activity in a broad frequency band. The altered network activity was particularly pronounced during increased activation of the prefrontal network and was associated with changed dynamics of local excitatory neurons, as well as decreased modulation of the LFP, abnormalities that appeared to generalize across stimuli and brain states. In addition, our findings link reduced BDNF/trkB signaling in prefrontal PV interneurons to increased aggression. Together our investigations demonstrate that BDNF/trkB signaling in PV interneurons in the adult mPFC is essential to local network dynamics and cognitive behavior. Our data provide direct support for the suggested association between decreased trkB signaling, deficient PV inhibition, and altered prefrontal circuitry.SIGNIFICANCE STATEMENT Brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (trkB) signaling promotes the maturation of inhibitory parvalbumin (PV) interneurons, neurons central to local cortical dynamics, γ rhythms, and cognition. Here, we used a novel viral approach for reduced BDNF/trkB signaling in PV interneurons in the medial prefrontal cortex (mPFC) to establish the role of BDNF/trkB signaling in adult prefrontal network activities. Reduced BDNF/trkB signaling caused pronounced morphologic alterations, reduced PV inhibition, and deficient prefrontal network dynamics. The altered network activity appeared to manifest across stimuli and brain states and was associated with aberrant local field potential (LFP) activities and increased aggression. The results demonstrate that adult BDNF/trkB signaling is essential to PV inhibition and prefrontal circuit function and directly links BDNF/trkB signaling to network integrity in the adult brain.     

Nerve ultrasound in hereditary transthyretin amyloidosis: red flags and possible progression biomarkers

Journal of Neurology - Diagnostic delay of hereditary transthyretin amyloidosis (ATTRv, v for variant) prevents timely treatment and, therefore, concurs to the mortality of the disease. The aim of...     

Metachromatic leukodystrophy with late adult-onset: diagnostic clues and differences from other genetic leukoencephalopathies with dementia

Journal of Neurology -     

Stroke care in Italy at the time of the COVID-19 pandemic: a lesson to learn

Journal of Neurology - From March to May 2020, the Italian health care system, as many others, was almost entirely devoted to the fight against the COVID-19 pandemic. In this context, a number of...