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Repurposing therapeutic agents with existing clinical data is a common strategy for developing radiation countermeasures. IEPA (imidazolyl ethanamide pentandioic acid) is an orally bioavailable small molecule pseudopeptide with myeloprotective properties, a good clinical safety profile, and stable chemical characteristics facilitating stockpiling. Here, we evaluated IEPA's radiomitigative efficacy in the hematopoietic subsyndrome of acute radiation syndrome (H-ARS) using total-body irradiation (TBI) models in C57BL/6J mice and WAG/RijCmcr rats, applying various posology schemes and introducing syringe feeding of the IEPA formulation in the pudding. Additionally, we assessed IEPA in the delayed effects of acute radiation exposure (DEARE) model after partial-body irradiation (PBI) in WAG/RijCmcr rats. Endpoints included survival, body weight, hematology, and pulmonary parameters, depending on the model. Results from mouse and rat TBI models demonstrated survival improvements with repeated IEPA dosing at 10 mg/kg, with the largest benefits observed in the bi-daily (BID) treatment over the 30-day ARS phase in female rats. Survival across PBI-DEARE subsyndromes was comparable between IEPA and vehicle groups, though IEPA improved pulmonary parameters in female rats during the lung-DEARE phase. Sex-related differences in response to irradiation and IEPA were noted, with females showing a survival advantage. IEPA treatment is compatible with Neulasta® (Pegfilgrastim; PEG-G-CSF); adequately powered studies are needed to confirm the trend toward improved survival over standard care alone. IEPA is a promising development candidate as a medical countermeasure against the effects of acute radiation syndrome. Further confirmatory studies in small and large animal models should validate the robustness and translatability of preliminary rodent data on IEPA's radiomitigative efficacy. [ABSTRACT FROM AUTHOR]

Lymphangioleiomyomatosis (LAM) is a rare genetic lung disease. Unfortunately, treatment with the mTORC1 inhibitor Rapamycin only slows disease progression, and incomplete responses are common. Thus, there remains an urgent need to identify new targets for the development of curative LAM treatments. Nitazoxanide (NTZ) is an orally bioavailable antiprotozoal small molecule drug approved for the treatment of diarrhea caused by Giardia lamblia or Cryptosporidium parvum in children and adults, with a demonstrated mTORC1 inhibitory effect in several human cell lines. NTZ's excellent safety profile characterized by its more than 20 years of clinical use makes it a promising candidate for repurposing. Our rationale for this study was to further investigate NTZ's effect using in vitro and in vivo LAM models and to elucidate the underlying molecular mechanism beyond mTORC1 inhibition. For this purpose, we investigated cell proliferation, cell viability, and changes in protein phosphorylation and expression in primary human cell cultures derived from LAM lung samples before translating our results into a syngeneic mouse model utilizing Tsc2-null cells. NTZ reduced cell growth for all tested cell lines at a dose of about 30 µM. Lower doses than that had no effect on cell viability, but doses above 45 µM lowered the viability by about 10 to 15% compared to control. Interestingly, our western blot revealed no inhibition of mTORC1 and only a mild effect on active ß-Catenin. Instead, NTZ had a pronounced effect on reducing pAkt. In the mouse model, prophylactic NTZ treatment via the intraperitoneal and oral routes had some effects on reducing lung lesions and improving body weight retention, but the results remain inconclusive. [ABSTRACT FROM AUTHOR]

Tyrosine hydroxylase (TH) is the rate‐limiting enzyme in dopamine biosynthesis catalyzing the tetrahydrobiopterin (BH4)—dependent hydroxylation of tyrosine to L‐DOPA. Here, we analyzed 25 TH variants associated with various degrees of dopa‐responsive dystonia and evaluate the effect of each variant on protein stability, activity and cellular localization. Furthermore, we investigated the physical interaction between TH and human wildtype (wt) GTP cyclohydrolase 1 (GTPCH) and the effect of variants on this interaction. Our in vitro results classify variants according to their resistance to proteinase K digestion into three groups (stable, intermediate, unstable). Based on their cellular localization, two groups of variants can be identified, variant group one with cytoplasmic distribution and variant group two forming aggregates. These aggregates do not correlate with loss of enzymatic activity but nevertheless might be a good target for molecular chaperones. Unfortunately, no obvious correlation between the half‐life of a variant and its enzymatic activity or between solubility, stability and enzymatic activity of a given variant could be found. Excitingly, some variants disrupt the physical interaction between TH and human wildtype GTPCH, thereby interfering with enzymatic activity and offering new druggable targets for therapy. Taken together, our results highlight the importance of an in‐depth molecular analysis of each variant in order to be able to classify groups of disease variants and to find specific therapies for each subgroup. Stand‐alone in silico analyses predict less precise the effect of specific variants and should be combined with other in vitro analyses in cellular model systems. [ABSTRACT FROM AUTHOR]