Biology subjects

Radaelli, E.

Publications and source records attributed to Radaelli, E..

6 recordsLinked to original sources

bioRxiv2024

FLASH proton reirradiation, with or without hypofractionation, mitigates chronic toxicity in the normal murine intestine, skin, and bone.

Background and purposeThe normal tissue sparing afforded by FLASH radiotherapy (RT) is being intensely investigated for potential clinical translation. Here, we studied the effects of FLASH proton RT (F-PRT) in the reirradiation setting, with or without hypofractionation. Chronic toxicities in three murine models of normal tissue toxicity including the intestine, skin, and bone were investigated. Materials and methodsIn studies of the intestine, single-dose irradiation was performed with 12 Gy of Standard proton RT (S-PRT), followed by a second dose of 12 Gy of F-PRT or S-PRT. Additionally, a hypofractionation scheme was applied in the reirradiation setting (3 x 6.4 Gy of F-PRT or S-PRT, given every 48 hrs). In studies of skin/bone of the murine leg, 15 Gy of S-PRT was followed by hypofractionated reirradiation with F-PRT or S-PRT (3 x 11 Gy). ResultsCompared to reirradiation with S-PRT, F-PRT reduced intestinal fibrosis and collagen deposition in the reirradiation setting and significantly increased survival rate, demonstrating its protective effects on intestinal tissues. In previously irradiated leg tissues, reirradiation with hypofractionated F-PRT created transient dermatitis that fully resolved in contrast to reirradiation with hypofractionated S-PRT. Lymphedema was also alleviated after a second course of radiation with F-PRT, along with significant reductions in the accumulation of fibrous connective tissue in the skin compared to mice reirradiated with S-PRT. The delivery of a second course of fractionated S-PRT induced tibial fractures in 83.3% of the mice, whereas only 20% of mice reirradiated with F-PRT presented with fractures. ConclusionThese studies provide the first evidence of the sparing effects of F-PRT, in the setting of hypofractionated reirradiation. The results support FLASH as highly relevant to the reirradiation regimen where it exhibits significant potential to minimize chronic complications for patients undergoing RT.

cell biology↗

bioRxiv2022

Mitochondrial defects leading to arrested spermatogenesis and ferroptosis in a mouse model of Leigh Syndrome

Impaired spermatogenesis and male infertility are common manifestations of mitochondrial diseases, but the underlying mechanisms are unclear. Here we show that mice deficient for PARL, the mitochondrial rhomboid protease, a recently reported model of Leigh syndrome, develop postpubertal testicular atrophy caused by arrested spermatogenesis and germ cell death independently of neurodegeneration. Genetic modifications of PINK1, PGAM5, and TTC19, three major substrates of PARL with important roles in mitochondrial homeostasis, do not reproduce or modify this phenotype. PARL deficiency in testis mitochondria leads to severe mitochondrial electron transfer chain defects, alterations in Coenzyme Q biosynthesis and redox status, and abrogates GPX4 expression specifically in spermatocytes leading to massive ferroptosis, an iron-dependent regulated cell death modality characterized by uncontrolled lipid peroxidation. Thus, mitochondrial defects can initiate ferroptosis in vivo in specific cell types by simultaneous effects on GPX4 and Coenzyme Q. These results highlight the importance of ferroptosis and cell-type specific downstream responses to mitochondrial deficits with respect to specific manifestations of mitochondrial diseases.

cell biology↗

bioRxiv2022

Inflammatory monocytes promote pyogranuloma formation to counteract Yersinia blockade of host defense

Granulomas are organized immune cell aggregates that form in response to chronic infection or antigen persistence. Yersinia pseudotuberculosis (Yp) blocks innate inflammatory signaling and phagocytosis, inducing formation of neutrophil-rich pyogranulomas within lymphoid tissues. Here, we uncover that Yp triggers pyogranuloma formation within the murine intestinal mucosa, a site not known to contain such structures. Mice lacking circulating monocytes fail to form defined pyogranulomas, have defects in neutrophil activation, and succumb to Yp infection. Yersinia lacking the virulence factors that block phagocytosis did not induce pyogranulomas, indicating that intestinal pyogranulomas form in response to Yp disruption of phagocytosis. Notably, mutation of a single anti-phagocytic virulence factor, YopH, restored pyogranuloma formation and control of Yp infection in monocyte-deficient mice, demonstrating that monocytes override YopH-dependent blockade of innate immune defense. This work reveals an unappreciated site of Yersinia intestinal invasion, and defines host and pathogen drivers of intestinal granuloma formation.

microbiology↗

bioRxiv2021

RIPK1 activates distinct gasdermins in macrophages and neutrophils upon pathogen blockade of innate immune signalling

Injection of effector proteins to block host innate immune signalling is a common strategy used by many pathogenic organisms to establish an infection. Pathogenic Yersinia species for example inject the acetyltransferase YopJ into target cells to inhibit NF-{kappa}B and MAPK signalling. To counteract this, detection of YopJ activity in myeloid cells promotes the assembly of a RIPK1-caspase-8 death-inducing platform that confers antibacterial defence. While recent studies revealed that caspase-8 cleaves the pore-forming protein, gasdermin D (GSDMD) to trigger pyroptosis in macrophages, whether RIPK1 activates additional substrates downstream of caspase-8 to promote host defence is unclear. Here, we report that the related gasdermin family member gasdermin E (GSDME) is activated upon detection of YopJ activity in a RIPK1 kinase-dependent manner. Specifically, GSDME promotes neutrophil pyroptosis and IL-1{beta} release, which is critical for anti-Yersinia defence. During in vivo infection, IL-1{beta} neutralisation increases bacterial burden in wild type but not Gsdme-deficient mice. Thus, our study establishes GSDME as an important mediator that counteracts pathogen blockade of innate immune signalling.

immunology↗

bioRxiv2021

IL-33 promotes innate lymphoid cell-dependent IFN-γ production required for innate immunity to Toxoplasma gondii

IL-33 is an alarmin required for resistance to the parasite Toxoplasma gondii, but its role in innate resistance to this infection is unclear. T. gondii infection promotes increased stromal cell expression of IL-33 and levels of parasite replication correlate with IL-33 release. In response to infection, a subset of innate lymphoid cells (ILC) emerges composed of IL-33R+ NK cells and ILC1s. In Rag-/- mice, where NK cells and ILC1 provide an innate mechanism of resistance to T. gondii, the loss of IL-33R reduced ILC responses and increased parasite replication. Furthermore, administration of IL-33 to Rag-/- mice resulted in a marked decrease in parasite burden, increased production of IFN-{gamma} and the recruitment and expansion of inflammatory monocytes associated with parasite control. These protective effects of exogenous IL-33 were dependent on endogenous IL-12p40 and the ability of IL-33 to enhance ILC production of IFN-{gamma}. These results highlight that IL-33 synergizes with IL-12 to promote ILC-mediated resistance to T. gondii.

immunology↗

bioRxiv2018

Parl Deficiency In Mouse Causes Coenzyme Q Depletion, Complex III Defects, And Leigh-Like Syndrome

The mitochondrial intramembrane rhomboid protease Parl has been implicated in diverse functions in vitro, but its physiological role in vivo remains unclear. Here we show that Parl ablation in mouse causes a striking necrotizing encephalomyelopathy similar to Leigh syndrome, a mitochondrial disease characterized by disrupted energy production. Mice with conditional Parl deficiency in the nervous system, but not in muscle, develop a similar phenotype as germline Parl knockouts demonstrating the vital role of Parl in neurological homeostasis. Genetic modification of two major Parl substrates, Pink1 and Pgam5, do not modify this severe neurological phenotype. Parl-/- brain mitochondria are affected by defects in Complex III activity and in coenzyme Q biosynthesis. Parl is necessary for the stable expression of Ttc19, required for Complex III activity, and of Coq4, essential in coenzyme Q biosynthesis. Thus, Parl plays a previously overseen constitutive role in the maintenance of the respiratory chain in the nervous system, and its deficiency causes progressive mitochondrial dysfunction and Leigh-like syndrome.

molecular biology↗