Study of Biological Effects Induced in Solid Tumors by Shortened-Duration Thermal Ablation Using High-Intensity Focused Ultrasound.

The HIFU ablation technique is limited by the long duration of the procedure, which results from the large difference between the size of the HIFU beam's focus and the tumor size. Ablation of large tumors requires treating them with a sequence of single HIFU beams, with a specific time interval in-between. The aim of this study was to evaluate the biological effects induced in a malignant solid tumor of the rat mammary gland, implanted in adult Wistar rats, during HIFU treatment according to a new ablation plan which allowed researchers to significantly shorten the duration of the procedure. We used a custom, automated, ultrasound imaging-guided HIFU ablation device. Tumors with a 1 mm thickness margin of healthy tissue were subjected to HIFU. Three days later, the animals were sacrificed, and the HIFU-treated tissues were harvested. The biological effects were studied, employing morphological, histological, immunohistochemical, and ultrastructural techniques. Massive cell death, hemorrhages, tissue loss, influx of immune cells, and induction of pro-inflammatory cytokines were observed in the HIFU-treated tumors. No damage to healthy tissues was observed in the area surrounding the safety margin. These results confirmed the efficacy of the proposed shortened duration of the HIFU ablation procedure and its potential for the treatment of solid tumors.

E3 ubiquitin ligase RNF2 protects polymerase ι from destabilization.

Human DNA polymerase ι (Polι) belongs to the Y-family of specialized DNA polymerases engaged in the DNA damage tolerance pathway of translesion DNA synthesis that is crucial to the maintenance of genome integrity. The extreme infidelity of Polι and the fact that both its up- and down-regulation correlate with various cancers indicate that Polι expression and access to the replication fork should be strictly controlled. Here, we identify RNF2, an E3 ubiquitin ligase, as a new interacting partner of Polι that is responsible for Polι stabilization in vivo. Interestingly, while we report that RNF2 does not directly ubiquitinate Polι, inhibition of the E3 ubiquitin ligase activity of RNF2 affects the cellular level of Polι thereby protecting it from destabilization. Additionally, we indicate that this mechanism is more general, as DNA polymerase η, another Y-family polymerase and the closest paralogue of Polι, share similar features.

Impaired iron recycling from erythrocytes is an early hallmark of aging.

Aging affects iron homeostasis, as evidenced by tissue iron loading and anemia in the elderly. Iron needs in mammals are met primarily by iron recycling from senescent red blood cells (RBCs), a task chiefly accomplished by splenic red pulp macrophages (RPMs) via erythrophagocytosis. Given that RPMs continuously process iron, their cellular functions might be susceptible to age-dependent decline, a possibility that has been unexplored to date. Here, we found that 10- to 11-month-old female mice exhibit iron loading in RPMs, largely attributable to a drop in iron exporter ferroportin, which diminishes their erythrophagocytosis capacity and lysosomal activity. Furthermore, we identified a loss of RPMs during aging, underlain by the combination of proteotoxic stress and iron-dependent cell death resembling ferroptosis. These impairments lead to the retention of senescent hemolytic RBCs in the spleen, and the formation of undegradable iron- and heme-rich extracellular protein aggregates, likely derived from ferroptotic RPMs. We further found that feeding mice an iron-reduced diet alleviates iron accumulation in RPMs, enhances their ability to clear erythrocytes, and reduces damage. Consequently, this diet ameliorates hemolysis of splenic RBCs and reduces the burden of protein aggregates, mildly increasing serum iron availability in aging mice. Taken together, we identified RPM collapse as an early hallmark of aging and demonstrated that dietary iron reduction improves iron turnover efficacy.

G3BPs tether the TSC complex to lysosomes and suppress mTORC1 signaling.

Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress activation of the metabolic master regulator mechanistic target of rapamycin complex 1 (mTORC1) by amino acids and insulin. Like the TSC complex, G3BP1 deficiency elicits phenotypes related to mTORC1 hyperactivity. In the context of tumors, low G3BP1 levels enhance mTORC1-driven breast cancer cell motility and correlate with adverse outcomes in patients. Furthermore, G3bp1 inhibition in zebrafish disturbs neuronal development and function, leading to white matter heterotopia and neuronal hyperactivity. Thus, G3BPs are not only core components of SGs but also a key element of lysosomal TSC-mTORC1 signaling.

GSK3ß Controls mTOR and Prosurvival Signaling in Neurons.

Glycogen synthase kinases-3ß (GSK3ß) is a key regulator of cell homeostasis. In neurons, GSK3ß contributes to control of neuronal transmission and plasticity. Despite extensive studies in non-neuronal cells, crosstalk between GSK3ß and other signaling pathways remains not well defined in neurons. In the present study, we report that GSK3ß positively affected the activity of effectors of mammalian target of rapamycin complex 1 (mTORC1) and complex 2 (mTORC2), in mature neurons in vitro and in vivo. GSK3ß also promoted prosurvival signaling and attenuated kainic acid-induced apoptosis. Our study identified GSK3ß as a positive regulator of prosurvival signaling, including the mTOR pathway, and indicates the possible neuroprotective role of GSK3ß in models of pharmacologically induced excitotoxicity.

Tuberous sclerosis complex neuropathology requires glutamate-cysteine ligase.

INTRODUCTION: Tuberous sclerosis complex (TSC) is a genetic disease resulting from mutation in TSC1 or TSC2 and subsequent hyperactivation of mammalian Target of Rapamycin (mTOR). Common TSC features include brain lesions, such as cortical tubers and subependymal giant cell astrocytomas (SEGAs). However, the current treatment with mTOR inhibitors has critical limitations. We aimed to identify new targets for TSC pharmacotherapy. RESULTS: The results of our shRNA screen point to glutamate-cysteine ligase catalytic subunit (GCLC), a key enzyme in glutathione synthesis, as a contributor to TSC-related phenotype. GCLC inhibition increased cellular stress and reduced mTOR hyperactivity in TSC2-depleted neurons and SEGA-derived cells. Moreover, patients' brain tubers showed elevated GCLC and stress markers expression. Finally, GCLC inhibition led to growth arrest and death of SEGA-derived cells. CONCLUSIONS: We describe GCLC as a part of redox adaptation in TSC, needed for overgrowth and survival of mutant cells, and provide a potential novel target for SEGA treatment.

Bcl-2 and Bax proteins are increased in neocortical but not in thalamic apoptosis following devascularizing lesion of the cerebral cortex in the rat: an immunohistochemical study.

The hypothesis that devascularization of somatosensory and motor cortex causes apoptosis in infarcted regions and in the linked thalamic nuclei was evaluated. To unravel whether Bcl-related proteins, known to regulate apoptosis, participate in neuronal and glial responses to devascularization, we analyzed immunohistochemically the distribution and intensity of staining of Bcl-2 and Bax proteins at different time points after lesion. Both early (up to 6 h) and late (1-7 days) responses were studied. Devascularization led to rapid (within hours) apoptosis in the cortex and to a delayed (within 3-7 days) apoptosis in thalamic nuclei. In control groups, Bcl-2 and Bax immunoreactivity (IR) was detected in neurons and oligodendrocytes but not in astrocytes or microglia. Following devascularization, Bcl-2 IR and Bax IR increased in neurons before the onset of the apoptosis. In the ischemic focus, the increase reached maximal values 3 h after the lesion. The increase was of slower onset in the penumbra zone (24 h and after), a region in which both proteins were induced in astrocytes also. The change of Bax IR intensity exceeded four times that of Bcl-2 at all time points investigated, indicating a diminution of Bcl-2/Bax ratio that may direct neurons to apoptotic pathway. In numerous neurons, an increase of IR in the cytoplasm was accompanied by induction of nuclear staining. No changes of Bcl-2 and Bax IR were found in thalamic nuclei. Our results point to different mechanisms underlying apoptosis of cortical and thalamic neurons. Nuclear appearance of Bcl-2 and Bax suggests they possess regulatory role of gene expression changes triggered by cortical infarct.