IntroductionMuscle symptoms in systemic sclerosis (SSc) may originate from altered skeletal muscle microcirculation, which can be investigated by means of blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI).MethodsAfter ethics committee approval and written consent, 11 consecutive SSc patients (5 men, mean age 52.6 years, mean SSc disease duration 5.4 years) and 12 healthy volunteers (4 men, mean age 45.1 years) were included. Subjects with peripheral arterial occlusive disease were excluded. BOLD MRI was performed on calf muscles during cuff-induced ischemia and reactive hyperemia, using a 3-T whole-body scanner (Verio, Siemens, Erlangen, Germany) and fat-suppressed single-short multi-echo echo planar imaging (EPI) with four different effective echo times. Muscle BOLD signal time courses were obtained for gastrocnemius and soleus muscles: minimal hemoglobin oxygen saturation (T2*min) and maximal T2* values (T2*max), time to T2* peak (TTP), and slopes of oxygen normalization after T2* peaking.ResultsThe vast majority of SSc patients lacked skeletal muscle atrophy, weakness or serum creatine kinase elevation. Nevertheless, more intense oxygen desaturation during ischemia was observed in calf muscles of SSc patients (mean T2*min -15.0%), compared with controls (-9.1%, P = 0.02). SSc patients also had impaired oxygenation during hyperemia (median T2*max 9.2% vs. 20.1%, respectively, P = 0.007). The slope of muscle oxygen normalization was significantly less steep and prolonged (TTP) in SSc patients (P<0.001 for both). Similar differences were found at a separate analysis of gastrocnemius and soleus muscles, with most pronounced impairment in the gastrocnemius.ConclusionsBOLD MRI demonstrates a significant impairment of skeletal muscle microcirculation in SSc.
Purpose To determine prevalence of paraproteinemic keratopathy (PPK) among patients with monoclonal gammopathy (MG). To evaluate interrelation between corneal and hematological parameters in patients with PPK. Methods Fifty-one patients with monoclonal gammopathy of undetermined significance (n = 19), smoldering multiple myeloma (n = 5) or multiple myeloma (n = 27) were prospectively included in this study. Best-corrected visual acuity, slit-lamp biomicroscopy, Scheimpflug tomography, in-vivo confocal laser scanning microscopy, optical coherence tomography and complete hematological workup were assessed. Results We identified n = 19 patients with bilateral corneal opacities compatible with PPK. PPK was newly diagnosed in 13 (29%) of 45 patients with a primary hematological diagnosis and in n = 6 patients without previous hematological diagnosis. The most common form was a discreet stromal flake-like PPK (n = 14 of 19). The median level of M-protein (p = 0.59), IgA (p = 0.53), IgG (p = 0.79) and IgM (p = 0.59) did not differ significantly between the patients with and without PPK. The median level of the FLC κ in serum of patients with kappa-restricted plasma cell dyscrasia was 209 mg/l in patients with PPK compared to 38.1 mg/l in patients without PPK (p = 0.18). Median level of FLC lambda in serum of patients with lambda-restricted plasma cell dyscrasia was lower in patients with PPK compared to patients without PPK (p = 0.02). Conclusion The PPK was mostly discreet, but its prevalence (29%) was higher than expected. Median level of the monoclonal paraprotein was not significantly higher in patients with PPK compared to patients without PPK. Our results suggest a lack of correlation between morphology and severity of the ocular findings and severity of the monoclonal gammopathy. Trial registration German Clinical Trial Register: DRKS00023893.
Introduction Although the therapeutic armamentarium against multiple myeloma has tremendously increased in recent years, it still remains an incurable disease. A highly promising novel anti-tumoral treatment strategy is to target specific non-redundant metabolic achilles heels of individual cancer entities. The semi-essential amino acid arginine can be synthesized from citrulline in most physiological tissues due to expression of the rate-limiting enzyme argininosuccinate synthetase 1 (ASS1). Various tumor entities do not express ASS1, therefore depend on the exogenous availability of arginine and pharmacological approaches to systemically deplete arginine are in phase I-III clinical development for such arginine-auxotrophic cancers. Cell death induction by arginine depletion can be dramatically enhanced by co-application of the arginine analogue canavanine. Canavanine can be used by the respective aminoacyl tRNA synthetase instead of arginine during protein translation and this leads to a highly toxic intracellular accumulation of misfolded proteins. In preliminary work we have seen that myeloma cells are largely arginine-auxotrophic and can be killed by arginine depletion and canavanine supplementation within hours, while ASS1 expressing cells are completely protected by their endogenous arginine rescue capability. Encouraging results of tumor control have already been seen in a murine myeloma model. Methods Human myeloma cell lines (NCI-H929_A2 and FD50, developed in our laboratory) were cultured and treated in RPMI-1640 medium with or without arginine. Protein levels were determinded by western blot analysis. Cell viability was measured by propidium iodide staining and flow cytometry analysis. RNA quantification was done by qRT-PCR. For autophagosome and aggresome quantification we used immunofluorescence staining (IF) and laser scanning microscopy (LSM). Results Arginine depletion and canavanine supplementation led to misfolded protein accumulation which was followed by massive apoptotic cell death. Both processes were further enhanced by co-treatment with the proteasome inhibitor bortezomib, indicated by an increase in intracellular polyubiquitinated proteins as well as higher cleaved caspase 3 levels and propidium-iodide positive cells after only 8-12 h in both tested cell lines. Unexpectedly, the endoplasmic reticulum (ER)-stress response was activated only very moderately. Expression of CHOP, a pro-apoptotic transcription factor that is highly translated under toxic ER stress, was not altered compared to control conditions. Tunicamycin-mediated induction of enhanced ER stress significantly improved the viability of arginine-starved and canavanine treated cells. This suggests that protein accumulation mainly takes place in the cytoplasm rather than the ER and tunicamycin might alleviate cell death by reduction of total protein translation. Despite severe arginine deficiency and induction of misfolded protein stress, the cells were not able to respond by an adequate upregulation of macroautophagy, as determined by an altered LC3 metabolism. The autophagic flux was significantly reduced compared to control conditions after 4-8 h of treatment. There was a strong induction of BAG3 and p62 proteins, which are both associated with chaperone-assisted autophagy as well as aggresome formation and are normally cleared via macroautophagy. Cytoplasmic aggresome formation was not detectable until onset of apoptosis. Also, no relevant modulation of phosphorylation of the autophagy inducer mTORC and the downstream kinase p70S6K1 was noted upon arginine depletion and canavanine co-treatment. Finally, ER stress induction via tunicamycin did not improve autophagic protein turnover, as determined by IF staining, LSM and western blot. Conclusions Arginine starvation in combination with canavanine supplementation induces fast and highly efficient cell death in arginine-auxotrophic myeloma cells. This novel strategy interferes with myeloma cellular metabolism by induction of misfolded protein accumulation. A relevant upregulation of potentially protective cellular strategies like ER stress responses, aggresome formation and autophagy are either not detectable or they remain insufficient. We hypothesize that our novel metabolic anti-tumor strategy is either too potent or too fast for the tumor cells to cope with its consequences. Disclosures No relevant conflicts of interest to declare.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.