Eric Honoré

Babesia divergens are tick-borne apicomplexan parasites infecting red blood cells of domestic and wild animals in Europe, as well as humans with important health burden. Previous findings indicate that PIEZO1 gain-of-function inherited mutations confer a significant protection against cerebral malaria. In this study, we further demonstrate that several Yoda1 analogs promoting PIEZO1 opening prevent B. divergens infection of human red blood cells in vitro . We identify several compounds with improved specificity for B. divergens, as compared to Plasmodium falciparum . IMPORTANCE: Babesia are apicomplexan parasites transmitted by tick bites that mainly infect animals, but some species such as Babesia divergens also infect people with dramatic outcomes. Babesiosis represents a threat for bovine production and is also an emerging human infectious disease in endemic regions. Like the malaria parasite Plasmodium , Babesia infects red blood cells (RBC) and causes hemolysis. Protection is currently based on drug treatments, tick control strategies, and animal vaccination. However, the indiscriminate use of prophylactic agents directly targeting the parasite is at risk to cause drug resistance, as observed for malaria. Here, we show that PIEZO1 activation in human RBC, taking advantage of newly synthesized Yoda1 analogs with enhanced efficacy and lower cytotoxicity, confers in vitro protection against Babesia infection.

With aging or osteoporosis, bone marrow adipogenesis is increased and inversely correlates with the loss of bone mass. Bone marrow adipocytes are derived from multipotent bone marrow mesenchymal stem cells (BMMSCs), which can differentiate into either fat or bone. BMMSCs are mechanosensitive cells, but how mechanical loading is implicated in the in vivo regulation of bone marrow adipogenesis and its impact on bone remodeling remain poorly understood. Here, we identify the mechanosensitive cationic channel Piezo1 in BMMSCs as a key suppressor of bone marrow adipogenesis by preventing local inflammation, thereby enhancing osteoblast differentiation and bone formation. Mice with a specific Piezo1 invalidation in BMMSCs exhibit osteoporosis and marrow adiposity, together with resistance to the beneficial effects of exercise on bone health. Accordingly, Piezo1-deficient BMMSCs in vitro preferentially differentiate into adipocytes rather than osteoblasts. Invalidation of Piezo1 in BMMSCs enhances the autocrine activation of CCR2 by Ccl2, which further induces lipocalin-2 (Lcn2) production via NF-κB activation, thereby promoting adipocyte differentiation. Conversely, Piezo1 opening induces Klf2 expression through CaMKII, preventing c-Jun activation, Ccl2 production and bone marrow adipogenesis. These findings demonstrate that Piezo1 activation in BMMSCs suppresses bone marrow adipogenesis to maintain bone strength by preventing the Ccl2-Lcn2 inflammatory autocrine loop, thus uncovering a previously unrecognized link between mechanotransduction, inflammation, and cell fate determination.

BACKGROUND: Pulmonary hypertension (PH) is a life-threatening and progressive yet incurable disease. The hallmarks of PH comprise (1) sustained contraction and (2) excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). A major stimulus to which PASMCs are exposed during PH development is altered mechanical stress, originating from increased blood pressure, changes in blood flow velocity, and a progressive stiffening of pulmonary arteries. Mechanosensitive ion channels, including Piezo1 (Piezo-type mechanosensitive ion channel component-1), perceive such mechanical stimuli and translate them into a variety of cellular responses, including contractility or proliferation. Thus, the objective of the present study was to elucidate the specific role of Piezo1 in PASMCs for PH development and progression. METHODS: The cell-type specific function of Piezo1 in PH was assessed in (1) PASMCs and lung tissues from patients with PH and (2) 2 mouse strains characterized by smooth muscle cell–specific, conditional Piezo1 knockout. Taking advantage of these strains, the smooth muscle cell–specific role of Piezo1 in PH development and progression was assessed in isolated, perfused, and ventilated mouse lungs, wire myography, and proliferation assays. Finally, in vivo function of smooth muscle cell–specific Piezo1 knockout was evaluated upon induction of chronic hypoxia–induced PH in these mice with insights into pulmonary vascular cell senescence. RESULTS: Compared with healthy controls, PASMCs from patients with PH featured an elevated Piezo1 expression and increased proliferative phenotype. Smooth muscle cell–specific Piezo1 deletion, as confirmed via quantitative real-time polymerase chain reaction and patch clamp recordings, prevented the hypoxia-induced increase in PASMC proliferation in mice. Moreover, Piezo1 knockout reduced hypoxic pulmonary vasoconstriction in isolated, perfused, and ventilated mouse lungs, endothelial-denuded pulmonary arteries, and hemodynamic measurements in vivo. Consequently, Piezo1 -deficient mice were considerably protected against chronic hypoxia–induced PH development with ameliorated right heart hypertrophy and improved hemodynamic function. In addition, distal pulmonary capillaries were preserved in the Piezo1-knockout mice, associated with a lower number of senescent endothelial cells. CONCLUSIONS: This study provides evidence that Piezo1 expressed in PASMCs is critically involved in the pathogenesis of PH by controlling pulmonary vascular tone, arterial remodeling, and associated lung capillary rarefaction due to endothelial cell senescence.

An inherited gain-of-function variant (E756del) in the mechanosensitive cationic channel PIEZO1 was shown to confer a significant protection against severe malaria. Here, we demonstrate in vitro that human red blood cell (RBC) infection by Plasmodium falciparum is prevented by the pharmacological activation of PIEZO1. Yoda1 causes an increase in intracellular calcium associated with rapid echinocytosis that inhibits RBC invasion, without affecting parasite intraerythrocytic growth, division or egress. Notably, Yoda1 treatment significantly decreases merozoite attachment and subsequent RBC deformation. Intracellular Na⁺/K⁺ imbalance is unrelated to the mechanism of protection, although delayed RBC dehydration observed in the standard parasite culture medium RPMI/albumax further enhances the resistance to malaria conferred by Yoda1. The chemically unrelated Jedi2 PIEZO1 activator similarly causes echinocytosis and RBC dehydration associated with resistance to malaria invasion. Spiky outward membrane projections are anticipated to reduce the effective surface area required for both merozoite attachment and internalization upon pharmacological activation of PIEZO1. Globally, our findings indicate that the loss of the typical biconcave discoid shape of RBCs, together with an altered optimal surface to volume ratio, induced by PIEZO1 pharmacological activation prevent efficient P. falciparum invasion.

Thyroid hormone (TH) is a thermogenic activator with anti-obesity potential. However, systemic TH administration has no obvious clinical benefits on weight reduction. Herein we selectively delivered triiodothyronine (T3) to adipose tissues by encapsulating T3 in liposomes modified with an adipose homing peptide (PLT3). Systemic T3 administration failed to promote thermogenesis in brown and white adipose tissues (WAT) due to a feedback suppression of sympathetic innervation. PLT3 therapy effectively obviated this feedback suppression on adrenergic inputs, and potently induced browning and thermogenesis of WAT, leading to alleviation of obesity, glucose intolerance, insulin resistance, and fatty liver in obese mice. Furthermore, PLT3 was much more effective than systemic T3 therapy in reducing hypercholesterolemia and atherosclerosis in apoE-deficient mice. These findings uncover WAT as a viable target mediating the therapeutic benefits of TH and provide a safe and efficient therapeutic strategy for obesity and its complications by delivering TH to adipose tissue.

An inherited gain-of–function variant (E756 del) in the mechanosensitive cationic channel PIEZO1 was recently shown to confer a significant protection against severe malaria. Here, we demonstrate in vitro that human red blood cell (RBC) infection by Plasmodium falciparum is prevented by the pharmacological activation of PIEZO1. The PIEZO1 activator Yoda1 inhibits RBC invasion, without affecting parasite intraerythrocytic growth, division or egress. RBC dehydration, echinocytosis and intracellular Na ⁺ /K ⁺ imbalance are unrelated to the mechanism of protection. Inhibition of invasion is maintained, even after a prolonged wash out of Yoda1. Similarly, the chemically unrelated activators Jedi1 and Jedi2 potently inhibit parasitemia, further indicating a PIEZO1-dependent mechanism. Notably, Yoda1 treatment significantly reduced RBC surface receptors of P. falciparum , and decreased merozoite attachment and subsequent RBC deformation. Altogether these data indicate that the pharmacological activation of Piezo1 in human RBCs inhibits malaria infection by impairing P. falciparum invasion.