Paternal nicotine exposure alters hepatic xenobiotic metabolism in offspring

Paternal environmental conditions can influence phenotypes in future generations, but it is unclear whether offspring phenotypes represent specific responses to particular aspects of the paternal exposure history, or a generic response to paternal \u27quality of life\u27. Here, we establish a paternal effect model based on nicotine exposure in mice, enabling pharmacological interrogation of the specificity of the offspring response. Paternal exposure to nicotine prior to reproduction induced a broad protective response to multiple xenobiotics in male offspring. This effect manifested as increased survival following injection of toxic levels of either nicotine or cocaine, accompanied by hepatic upregulation of xenobiotic processing genes, and enhanced drug clearance. Surprisingly, this protective effect could also be induced by a nicotinic receptor antagonist, suggesting that xenobiotic exposure, rather than nicotinic receptor signaling, is responsible for programming offspring drug resistance. Thus, paternal drug exposure induces a protective phenotype in offspring by enhancing metabolic tolerance to xenobiotics

Computergestützte Analyse mechanischer Beanspruchungen in Knochenadaptionsmodellen von Mäusen

Decomposed Zeichen konvertiert!Knochengewebe passt sich an seine mechanische Umgebung an. Dies geschieht mittels Knochengewebeformation und -resorption. Ein besseres Verständnis dieser Knochengewebe( re)modellierung könnte zu besserem Verständnis von Krankheiten und gezielteren Behandlungen führen. Ziel dieser Arbeit ist es, den Einfluss von statischer und dynamischer Belastung auf die lokale Knochen(re)modellierung zu untersuchen. Hierzu wurde der sechste Schwanzwirbel von 15 Wochen alten, weiblichen Mäusen in vivo mittels einer axialen Druckvorrichtung 4 Wochen lang belastet. Die Studie umfasste fünf Gruppen: scheinbelastet, statisch belastet, dynamisch belastet mit den Frequenzen 2 Hz, 5 Hz und 10 Hz. Die Knochenadaption wurde mittels in vivo Mikro-CT gemessen. Morphometrische Parameter der Knochen wurden berechnet, um eine mögliche Frequenzabhängigkeit der Knochenadaption zu analysieren. Mechanische Größen (Verzerrungsenergiedichte und deren Gradient), welche als Maß für direkte, mechanische Belastung an Osteozyten betrachtet werden, wurden mit lokalem Knochen(re)modellierungsverhalten korreliert. Poromikromechanische Modelle wurden angewendet, um den Porendruck in den Lakunen und den Flüssigkeitsstrom in den Canaliculi zu untersuchen. Die morphometrischen Parameter zeigten eine signifikant größere Adaption in den dynamisch belasteten Gruppen. Diese Ergebnisse deuten auf einen logarithmischen Zusammenhang zwischen Belastungsfrequenz und Knochenadaption hin. Höhere Werte der Verzerrungsenergiedichte und deren Gradienten führten zu einer erhöhten Formations- und verminderten Resorptionswahrscheinlichkeit. Trabekulärer und kortikaler Knochen zeigen leicht unterschiedliche Ansprechverhalten auf. Der ermittelte Porendruck in den Lakunen war größer als der hydrostatische Druck, der bekanntermaßen Knochenzellen stimuliert. Die berechneten Fließgeschwindigkeiten in den Canaliculi betrugen bis zu 120 m/s, waren jedoch nicht hoch genug um eigenständig Knochenzellen zu stimulieren. Zusammenfassend konnte gezeigt werden, dass eine dynamische Belastung notwendig ist, um Knochenadaption hervorzurufen. Um Letztere zu maximieren, sollte die Belastungsfrequenz im Bereich von 510 Hz liegen. Selten auftretende, stoßartige Belastung mit hohen Verzerrungsraten, könnte ein wichtiger Bestandteil von Knochenadaption sein. Hohe Verzerrungsraten führen zu hoher, direkter mechanischer Belastung und großem Porendruck in den Lakunen, was sich beides positiv auf die Knochenadaption auswirkt.Bone adapts to its mechanical environment by coupled (remodelling) and uncoupled (modelling) bone formation and resorption. A better understanding of bone (re)modelling could lead to insights into diseases and a more targeted disease treatment. The general objective of this thesis is to investigate the influence of static and dynamic mechanical loading on local bone (re)modelling behaviour. To that end, the sixth caudal vertebrae of 15-week-old female mice were loaded in vivo by means of an axial compression device over the course of 4 weeks. The study consisted of five groups, which diered in type of loading: sham-loaded, static loading, dynamic loading with 2 Hz, 5 Hz, and 10 Hz. Bone adaptation was measured with in vivo micro-CT scans. Trabecular and cortical bone regions were analysed independently. Bone morphometric parameters were computed to analyse a possible frequency dependency of bone adaptation. Mechanical quantities (strain energy density, SED, and its gradient), which are considered to be a measure of direct mechanical stress to an osteocyte, were correlated with local bone (re)modelling behaviour. Poromicromechanical models were applied to investigate lacunar pore pressure and canalicular fluid flow. Bone morphometric parameters showed significantly greater adaptation in the dynamicloading groups. These results suggest a logarithmic relation between loading frequency and bone adaptation. Greater SED and SED gradient values lead to an increase in formation and decrease in resorption probability. Trabecular and cortical bone show slightly dierent responses. The resulting lacunar pore pressure is greater than the hydrostatic pressure known to stimulate bone cells. The estimated canalicular fluid velocity is in the range of up to 120 m/s, but not great enough to stimulate bone cells by itself. The underlying theoretical concepts of pore pressure and fluid flow could be combined with viscoelastic material behaviour to further study frequency or strain rate dependency. In conclusion, it could be shown that dynamic loading is needed to induce bone adaptation.In order to maximize bone adaptation, a loading frequency from a certain range (510 Hz) is ideally applied. Infrequent impact loading with high strain rates could be a key component of bone adaptation. High strain rates cause greater direct mechanical strains and great lacunar pore pressure, which both influence bone adaptation positively.13

Mechano-Regulation of Trabecular Bone Adaptation Is Controlled by the Local in vivo Environment and Logarithmically Dependent on Loading Frequency

It is well-established that cyclic, but not static, mechanical loading has anabolic effects on bone. However, the function describing the relationship between the loading frequency and the amount of bone adaptation remains unclear. Using a combined experimental and computational approach, this study aimed to investigate whether trabecular bone mechano-regulation is controlled by mechanical signals in the local in vivo environment and dependent on loading frequency. Specifically, by combining in vivo micro-computed tomography (micro-CT) imaging with micro-finite element (micro-FE) analysis, we monitored the changes in microstructural as well as the mechanical in vivo environment [strain energy density (SED) and SED gradient] of mouse caudal vertebrae over 4 weeks of either cyclic loading at varying frequencies of 2, 5, or 10 Hz, respectively, or static loading. Higher values of SED and SED gradient on the local tissue level led to an increased probability of trabecular bone formation and a decreased probability of trabecular bone resorption. In all loading groups, the SED gradient was superior in the determination of local bone formation and resorption events as compared to SED. Cyclic loading induced positive net (re)modeling rates when compared to sham and static loading, mainly due to an increase in mineralizing surface and a decrease in eroded surface. Consequently, bone volume fraction increased over time in 2, 5, and 10 Hz (+15%, +21% and +24%, p ≤ 0.0001), while static loading led to a decrease in bone volume fraction (−9%, p ≤ 0.001). Furthermore, regression analysis revealed a logarithmic relationship between loading frequency and the net change in bone volume fraction over the 4 week observation period (R2 = 0.74). In conclusion, these results suggest that trabecular bone adaptation is regulated by mechanical signals in the local in vivo environment and furthermore, that mechano-regulation is logarithmically dependent on loading frequency with frequencies below a certain threshold having catabolic effects, and those above anabolic effects. This study thereby provides valuable insights toward a better understanding of the mechanical signals influencing trabecular bone formation and resorption in the local in vivo environment.ISSN:2296-418

Tissue-Level Regeneration and Remodeling Dynamics are Driven by Mechanical Stimuli in the Microenvironment in a Post-Bridging Loaded Femur Defect Healing Model in Mice

Bone healing and remodeling are mechanically driven processes. While the generalized response to mechanical stimulation in bone is well-understood, much less is known about the mechanobiology-regulating tissue-scale bone formation and resorption during the reparative and remodeling phases of fracture healing. In this study, we combined computational approaches in the form of finite element analysis and experimental approaches by using a loaded femoral defect model in mice to investigate the role of mechanical stimulation in the microenvironment of bone. Specifically, we used longitudinal micro-computed tomography to observe temporal changes in bone at different densities and micro-finite element analysis to map the mechanics of the microenvironment to tissue-scale formation, quiescence (no change in bone presence between time points), and resorption dynamics in the late reparative and remodeling phases (post bridging). Increasing levels of effective strain led to increasing conditional probability of bone formation, while decreasing levels of effective strain led to increasing probability of bone resorption. In addition, the analysis of mineralization dynamics showed both a temporal and effective strain level-dependent behavior. A logarithmic-like response was displayed, where the conditional probability of bone formation or resorption increased rapidly and plateaued or fell rapidly and plateaued as mechanical strain increased.ISSN:2296-634

Increased CRF signalling in a ventral tegmental area-interpeduncular nucleus-medial habenula circuit induces anxiety during nicotine withdrawal

Increased anxiety is a prominent withdrawal symptom in abstinent smokers, yet the neuroanatomical and molecular bases underlying it are unclear. Here we show that withdrawal-induced anxiety increases activity of neurons in the interpeduncular intermediate (IPI), a subregion of the interpeduncular nucleus (IPN). IPI activation during nicotine withdrawal was mediated by increased corticotropin releasing factor (CRF) receptor-1 expression and signalling, which modulated glutamatergic input from the medial habenula (MHb). Pharmacological blockade of IPN CRF1 receptors or optogenetic silencing of MHb input reduced IPI activation and alleviated withdrawal-induced anxiety; whereas IPN CRF infusion in mice increased anxiety. We identified a mesointerpeduncular circuit, consisting of ventral tegmental area (VTA) dopaminergic neurons projecting to the IPN, as a potential source of CRF. Knockdown of CRF synthesis in the VTA prevented IPI activation and anxiety during nicotine withdrawal. These data indicate that increased CRF receptor signalling within a VTA-IPN-MHb circuit triggers anxiety during nicotine withdrawal

Genetic and Epigenetic Variation, but Not Diet, Shape the Sperm Methylome

Paternal diet can impact metabolic phenotypes in offspring, but mechanisms underlying such intergenerational information transfer remain obscure. Here, we interrogate cytosine methylation patterns in sperm obtained from mice consuming one of three diets, generating whole genome methylation maps for four pools of sperm samples and for 12 individual sperm samples, as well as 61 genome-scale methylation maps. We find that epivariation, either stochastic or due to unknown demographic or environmental factors, was a far stronger contributor to the sperm methylome than was the diet consumed. Variation in cytosine methylation was particularly dramatic over tandem repeat families, including ribosomal DNA (rDNA) repeats, but rDNA methylation was strongly correlated with genetic variation in rDNA copy number and was not influenced by paternal diet. These results identify loci of genetic and epigenetic lability in the mammalian genome but argue against a direct role for sperm cytosine methylation in dietary reprogramming of offspring metabolism