PI(18:1/18:1) is a SCD1-derived lipokine that limits stress signaling.

Cytotoxic stress activates stress-activated kinases, initiates adaptive mechanisms, including the unfolded protein response (UPR) and autophagy, and induces programmed cell death. Fatty acid unsaturation, controlled by stearoyl-CoA desaturase (SCD)1, prevents cytotoxic stress but the mechanisms are diffuse. Here, we show that 1,2-dioleoyl-sn-glycero-3-phospho-(1'-myo-inositol) [PI(18:1/18:1)] is a SCD1-derived signaling lipid, which inhibits p38 mitogen-activated protein kinase activation, counteracts UPR, endoplasmic reticulum-associated protein degradation, and apoptosis, regulates autophagy, and maintains cell morphology and proliferation. SCD1 expression and the cellular PI(18:1/18:1) proportion decrease during the onset of cell death, thereby repressing protein phosphatase 2 A and enhancing stress signaling. This counter-regulation applies to mechanistically diverse death-inducing conditions and is found in multiple human and mouse cell lines and tissues of Scd1-defective mice. PI(18:1/18:1) ratios reflect stress tolerance in tumorigenesis, chemoresistance, infection, high-fat diet, and immune aging. Together, PI(18:1/18:1) is a lipokine that links fatty acid unsaturation with stress responses, and its depletion evokes stress signaling.

Small molecule inhibitors of the mitochondrial ClpXP protease possess cytostatic potential and re-sensitize chemo-resistant cancers.

The human mitochondrial ClpXP protease complex (HsClpXP) has recently attracted major attention as a target for novel anti-cancer therapies. Despite its important role in disease progression, the cellular role of HsClpXP is poorly characterized and only few small molecule inhibitors have been reported. Herein, we screened previously established S. aureus ClpXP inhibitors against the related human protease complex and identified potent small molecules against human ClpXP. The hit compounds showed anti-cancer activity in a panoply of leukemia, liver and breast cancer cell lines. We found that the bacterial ClpXP inhibitor 334 impairs the electron transport chain (ETC), enhances the production of mitochondrial reactive oxygen species (mtROS) and thereby promotes protein carbonylation, aberrant proteostasis and apoptosis. In addition, 334 induces cell death in re-isolated patient-derived xenograft (PDX) leukemia cells, potentiates the effect of DNA-damaging cytostatics and re-sensitizes resistant cancers to chemotherapy in non-apoptotic doses.

Metabolic implication of tigecycline as an efficacious second-line treatment for sorafenib-resistant hepatocellular carcinoma.

Sorafenib represents the current standard of care for patients with advanced-stage hepatocellular carcinoma (HCC). However, acquired drug resistance occurs frequently during therapy and is accompanied by rapid tumor regrowth after sorafenib therapy termination. To identify the mechanism of this therapy-limiting growth resumption, we established robust sorafenib resistance HCC cell models that exhibited mitochondrial dysfunction and chemotherapeutic crossresistance. We found a rapid relapse of tumor cell proliferation after sorafenib withdrawal, which was caused by renewal of mitochondrial structures alongside a metabolic switch toward high electron transport system (ETS) activity. The translation-inhibiting antibiotic tigecycline impaired the biogenesis of mitochondrial DNA-encoded ETS subunits and limited the electron acceptor turnover required for glutamine oxidation. Thereby, tigecycline prevented the tumor relapse in vitro and in murine xenografts in vivo. These results offer a promising second-line therapeutic approach for advanced-stage HCC patients with progressive disease undergoing sorafenib therapy or treatment interruption due to severe adverse events.

Screening of wild ruminants from the Kaunertal and other alpine regions of Tyrol (Austria) for vector-borne pathogens.

Knowledge about vector-borne pathogens important for human and veterinary medicine in wild ruminants in Tyrol (Austria) is scarce. Blood samples from Alpine ibex (Capra ibex; n = 44), Alpine chamois (Rupicapra rupicapra; n = 21), roe deer (Capreolus capreolus; n = 18) and red deer (Cervus elaphus; n = 6) were collected over a period of 4 years (2015-2018) in four regions in North Tyrol, with a primary focus on the Kaunertal. Blood spots on filter paper were tested for the presence of DNA of vector-borne pathogens (Anaplasmataceae, Piroplasmida, Rickettsia and filarioid helminths). Anaplasma phagocytophilum and Babesia capreoli were detected in two of 89 (2.3%) blood samples. Rickettsia spp., Theileria spp. and filarioid helminths were not documented. One Alpine chamois was positive for A. phagocytophilum and B. capreoli. Moreover, an ibex from the Kaunertal region was positive for A. phagocytophilum. While the ibex was a kid less than 1 year old, the chamois was an adult individual. Further research is recommended to evaluate effects of climate change on infection rates of North Tyrolean wild ruminants by these pathogens and the distribution of their vectors.

Inhibition of Cyclin-Dependent Kinase 5: A Strategy to Improve Sorafenib Response in Hepatocellular Carcinoma Therapy.

Therapeutic options for patients with advanced-stage hepatocellular carcinoma (HCC) are very limited. The only approved first-line treatment is the multi-tyrosine kinase inhibitor sorafenib, which shows low response rates and severe side effects. In particular, the compensatory activation of growth factor receptors leads to chemoresistance and limits the clinical impact of sorafenib. However, combination approaches to improve sorafenib have failed. Here we investigate the inhibition of cyclin-dependent kinase 5 (Cdk5) as a promising combination strategy to improve sorafenib response in HCC. Combination of sorafenib with Cdk5 inhibition (genetic knockdown by short hairpin RNA or CRISPR/Cas9 and pharmacologic inhibition) synergistically impaired HCC progression in vitro and in vivo by inhibiting both tumor cell proliferation and migration. Importantly, these effects were mediated by a mechanism for Cdk5: A liquid chromatography-tandem mass spectrometry-based proteomic approach revealed that Cdk5 inhibition interferes with intracellular trafficking, a process crucial for cellular homeostasis and growth factor receptor signaling. Cdk5 inhibition resulted in an accumulation of enlarged vesicles and respective cargos in the perinuclear region, considerably impairing the extent and quality of growth factor receptor signaling. Thereby, Cdk5 inhibition offers a comprehensive approach to globally disturb growth factor receptor signaling that is superior to specific inhibition of individual growth factor receptors. Conclusion: Cdk5 inhibition represents an effective approach to improve sorafenib response and to prevent sorafenib treatment escape in HCC. Notably, Cdk5 is an addressable target frequently overexpressed in HCC, and with Dinaciclib, a clinically tested Cdk5 inhibitor is readily available. Thus, our study provides evidence for clinically evaluating the combination of sorafenib and Dinaciclib to improve the therapeutic situation for patients with advanced-stage HCC.

Design and synthesis of tailored human caseinolytic protease P inhibitors.

Human caseinolytic protease P (hClpP) is important for degradation of misfolded proteins in the mitochondrial unfolded protein response. We here introduce tailored hClpP inhibitors that utilize a steric discrimination in their core naphthofuran scaffold to selectively address the human enzyme. This novel inhibitor generation exhibited superior activity compared to previously introduced beta-lactones, optimized for bacterial ClpP. Further insights into the bioactivity and binding to cellular targets were obtained via chemical proteomics as well as proliferation- and migration studies in cancer cells.

Telomere shortening leads to earlier age of onset in ALS mice.

Telomere shortening has been linked to a variety of neurodegenerative diseases. Recent evidence suggests that reduced telomerase expression results in shorter telomeres in leukocytes from sporadic patients with amyotrophic lateral sclerosis (ALS) compared with healthy controls. Here, we have characterized telomere length in microglia, astroglia and neurons in human post mortem brain tissue from ALS patients and healthy controls. Moreover, we studied the consequences of telomerase deletion in a genetic mouse model for ALS. We found a trend towards longer telomeres in microglia in the brains of ALS patients compared to non-neurologic controls. Knockout of telomerase leading to telomere shortening accelerated the ALS phenotype inSOD1G93A-transgenic mice. Our results suggest that telomerase dysfunction might contribute to the age-related risk for ALS.