ED Sciences de la Vie et de la Santé
Expression and role of the nerve growth factor NGF in pulmonary hypertension
by Clement BOUCHET (Centre de recherche Cardio-Thoracique de Bordeaux)
The defense will take place at 14h00 - Amphitéatre IHU LYRIC, Avenue du Haut Leveque, Site de l'hopital Xavier Arnozan, PTIB, 33600 Pessac
in front of the jury composed of
- Véronique MICHEL - Professeure des universités - Université de Bordeaux - Directeur de these
- Marie Elise TRUCHETET - Professeure des universités - praticienne hospitalière - Immunoconcept, CNRS UMR 5164 – Université de Bordeaux - Examinateur
- Xavier NOREL - Ingénieur de recherche - INSERM U1148, Université Paris XIII - Examinateur
- Boris MANOURY - Maître de conférences - INSERM UMR 1180, Université Paris-Saclay - Examinateur
- Sylvia COHEN-KAMINSKY - Directrice de recherche - Inserm U999 - Rapporteur
- Vincent LAGENTE - Professeur des universités - Institut NUMECAN, INSERM U1317, INRAE 1341, Université de Rennes - Rapporteur
Pulmonary hypertension (PH) is a severe disease characterized by an increase in mean pulmonary arterial pressure over 20mmHg at rest, compared with 14mmHg in healthy individuals. Ultimately, PH leads to right heart failure and death. In the absence of any curative treatment, identification of new therapeutic targets is a major challenge. In this context, a better understanding of PH development and progression is crucial. In our laboratory, one target of interest is the nerve growth factor or NGF, overexpressed in pulmonary arteries both in experimental and human PH, and playing a significant role in three major PH features: pulmonary arterial inflammation, reactivity and remodeling. First, we focused on possible mechanisms activated in PH that may contribute to NGF pulmonary arterial increased expression. We showed that pro-inflammatory cytokines whose expression are increased in PH, such as interleukin-1β (IL-1β) or Tumor necrosis factor-α, as well as oxidative stress can increase NGF expression and secretion by pulmonary arterial endothelial cells - EC- or smooth muscle cells -CML-. We showed that this secretion involved Transforming growth factor β1, which is secreted by both ECs and SMCs, and then acts in an autocrine manner on these cells to stimulate NGF secretion. We then studied the role of NGF in two major PH features: pulmonary arterial hyperreactivity and inflammation. Regarding hyperreactivity first, we showed that a chronic treatment with NGF (24h) led to pulmonary arterial hyperreactivity, by enhancing activity of connexin-43-dependent gap junctions in SMCs. In parallel, we showed that a shorter treatment with NGF (1h) also led to led to pulmonary arterial hyperreactivity, but in a connexin-43-independent manner, with deregulation of intracellular calcium signaling and increased sensitization of the contractile apparatus in SMCs. Regarding the link between NGF and inflammation, our results showed that in vivo, in a rat model of PH, a preventive treatment with anti-NGF blocking antibodies reduced pulmonary arterial monocyte/macrophage infiltration and inflammasome protein expression as well as both circulating and pulmonary levels of IL-1β. In vitro, we showed that NGF is able to attract monocytes, and that IL-1β plays an important role in pulmonary arterial remodeling, inflammation and endothelial dysfunction. In conclusion, this work has highlighted mechanisms contributing to NGF increased expression in PH and confirmed its involvement in the progression of the disease. The overall results obtained further support NGF as a therapeutic target of interest in this disease.
ED Sciences et environnements
Physiological response of grapevines to esca and interactions with the abiotic environment: nitrogen nutrition and water stress under controlled conditions
by Ninon DELL'ACQUA (SAVE - Santé et Agroécologie du VignoblE)
The defense will take place at 14h00 - Amphithéâtre Colette & Josy Bové INRAE Centre Nouvelle Aquitaine Bordeaux 71 Av. Edouard Bourlaux, 33140 Villenave-d'Ornon
in front of the jury composed of
- Cécile ROBIN - Directrice de recherche - UMR BIOGECO INRAE - Examinateur
- Yves GIBON - Directeur de recherche - UMR 1332 BFP INRAE - Examinateur
- Vivian ZUFFEREY - Chargé de recherche - Agroscope - Examinateur
- Marielle ADRIAN - Professeure des universités - Institut Universitaire de la Vigne et du Vin Jules Guyot - Rapporteur
- Thierry SIMONNEAU - Directeur de recherche - UMR LEPSE INRAE - Rapporteur
Perennial plant decline is a global phenomenon that has been observed for several decades and may become more severe and complex with climate change. This multifactorial process involves biotic and/or abiotic factors that, depending on how they occur and interact, can lead to the premature death of the plant. Cultivated perennial plants are not exempt from this phenomenon. In vineyards, an increase in vine mortality has been observed for several decades, leading to reduced yield. Studying the combination and timing of abiotic and biotic stresses is crucial to understanding the underlying mechanisms of vineyard decline. The aim of this thesis is to investigate, using an integrated approach, the response of cultivated grapevines (Vitis vinifera L. ssp. vinifera) to different stresses, including: a biotic stress known as esca, a complex and still poorly understood grapevine wood disease; an abiotic stress related to agricultural practices, nitrogen fertilization, which can be adjusted by growers; and an environmental stress, drought, which is becoming more problematic due to climate change. We investigated the relationship between stem growth dynamics, plant physiology, and xylem anatomy during esca pathogenesis in two susceptible grape varieties, 'Sauvignon blanc' and 'Cabernet Sauvignon'. We demonstrated that esca pathogenesis led to stem growth alterations associated with xylem occlusions, theoretical loss of conductivity, and the production of small functional vessels late in the season. The production of these new vessels allowed the resumption of gas exchange through the formation of new shoots, demonstrating the resilience capacity of the vine. Subsequently, we conducted a three-year experiment to investigate the impact of nitrogen deficiency or excess on the incidence of esca foliar symptoms, wood fungal community (via metabarcoding), as well as leaf and trunk metabolome and plant physiology in 'Sauvignon blanc' grapevines. We demonstrated that nitrogen deficiency has a negative and significant impact on the expression of esca foliar symptoms. Our integrated approach revealed that physiological and biochemical changes are induced by nitrogen nutrition, without affecting the wood fungal community. We also studied the effect of esca on the vulnerability of 'Sauvignon blanc' grapevines to drought and their resilience capacity. We showed that the expression of esca foliar symptoms delayed the response to drought. This antagonistic interaction between the two stresses was mainly due to the loss of transpiring leaf surface associated with esca development. Esca symptomatic vines thus experienced lower stress levels compared to asymptomatic vines, allowing for faster physiological recovery. Finally, preliminary work characterized the leaf metabolome associated with increasing severity of esca symptoms and identified a metabolic signature of an early stage of foliar symptoms not previously described. This thesis highlights the importance of integrating plant ecophysiology, metabolism, and mycobiome in understanding the processes involved in the decline of perennial plants, and the fundamental role that interactions between biotic and abiotic stresses can play in grapevine vulnerability and resilience to these different stresses.