Pegylated-liposomal Doxorubicin-induced Glomerular Thrombotic Microangiopathy.

Pegylated liposomal doxorubicin (PLD) has emerged as a recent innovation within the realm of antineoplastic agents, distinguished by its incorporation of doxorubicin within the liposomal bilayer. Given the low risk of cardiotoxicity, the clinical use of PLD has been expanding. We encountered a patient who underwent extended PLD therapy for recurrent malignancy and subsequently developed PLD-associated thrombotic microangiopathy, which was diagnosed by a detailed pathophysiological assessment. This case underscores the importance of considering thrombotic microangiopathy as a potential differential diagnosis in patients presenting with unexplained hypertension and renal impairment during prolonged PLD monotherapy.

Pembrolizumab-induced Acute Tubulointerstitial Nephritis Accompanying Fanconi Syndrome and Type 1 Renal Tubular Acidosis.

Pembrolizumab, an immune checkpoint inhibitor, is used to treat a variety of refractory malignancies. However, these agents are sometimes associated with immune-related adverse events. A 71-year-old woman received pembrolizumab-integrated chemotherapy to treat her recurrent mandibular gingival cancer. Five months after stopping pembrolizumab, she developed acute tubulointerstitial nephritis associated with Fanconi syndrome and type 1 renal tubular acidosis, which resolved with steroid therapy. We experienced a case of pembrolizumab-induced Fanconi syndrome and type 1 renal acidosis. We recommend follow-up of the tubular function in addition to the renal function even after discontinuation of pembrolizumab.

Fine-Tuning of Piezo1 Expression and Activity Ensures Efficient Myoblast Fusion during Skeletal Myogenesis.

Mechanical stimuli, such as stretch and resistance training, are essential in regulating the growth and functioning of skeletal muscles. However, the molecular mechanisms involved in sensing mechanical stress during muscle formation remain unclear. Here, we investigated the role of the mechanosensitive ion channel Piezo1 during myogenic progression of both fast and slow muscle satellite cells. We found that Piezo1 level increases during myogenic differentiation and direct manipulation of Piezo1 in muscle stem cells alters the myogenic progression. Indeed, Piezo1 knockdown suppresses myoblast fusion, leading to smaller myotubes. Such an event is accompanied by significant downregulation of the fusogenic protein Myomaker. In parallel, while Piezo1 knockdown also lowers Ca2+ influx in response to stretch, Piezo1 activation increases Ca2+ influx in response to stretch and enhances myoblasts fusion. These findings may help understand molecular defects present in some muscle diseases. Our study shows that Piezo1 is essential for terminal muscle differentiation acting on myoblast fusion, suggesting that Piezo1 deregulation may have implications in muscle aging and degenerative diseases, including muscular dystrophies and neuromuscular disorders.

MBNL1-Associated Mitochondrial Dysfunction and Apoptosis in C2C12 Myotubes and Mouse Skeletal Muscle.

We explored the interrelationship between a tissue-specific alternative splicing factor muscleblind-like 1 (MBNL1) and peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC-1α), B-cell lymphoma 2 (Bcl-2) or Bcl-2-associated X protein (Bax) in C2C12 myotubes and mouse skeletal muscle to investigate a possible physiological role of MBNL1 in mitochondrial-associated apoptosis of skeletal muscle. Expression level of PGC-1α and mitochondrial membrane potential evaluated by the fluorescence ratio of JC-1 aggregate to monomer in C2C12 myotubes were suppressed by knockdown of MBNL1. Conversely, the ratio of Bax to Bcl-2 as well as the apoptotic index in C2C12 myotubes was increased by MBNL1 knockdown. In plantaris muscle, on the other hand, not only the minimum muscle fiber diameter but also the expression level of MBNL1 and PGC-1α in of 100-week-old mice were significantly lower than that of 10-week-old mice. Furthermore, the ratio of Bax to Bcl-2 in mouse plantaris muscle was increased by aging. These results suggest that MBNL1 may play a key role in aging-associated muscle atrophy accompanied with mitochondrial dysfunction and apoptosis via mediating PGC-1α expression in skeletal muscle.

The Protective Effect of Brazilian Propolis against Glycation Stress in Mouse Skeletal Muscle.

We investigated the protective effect of Brazilian propolis, a natural resinous substance produced by honeybees, against glycation stress in mouse skeletal muscles. Mice were divided into four groups: (1) Normal diet + drinking water, (2) Brazilian propolis (0.1%)-containing diet + drinking water, (3) normal diet + methylglyoxal (MGO) (0.1%)-containing drinking water, and (4) Brazilian propolis (0.1%)-containing diet + MGO (0.1%)-containing drinking water. MGO treatment for 20 weeks reduced the weight of the extensor digitorum longus (EDL) muscle and tended to be in the soleus muscle. Ingestion of Brazilian propolis showed no effect on this change in EDL muscles but tended to increase the weight of the soleus muscles regardless of MGO treatment. In EDL muscles, Brazilian propolis ingestion suppressed the accumulation of MGO-derived advanced glycation end products (AGEs) in MGO-treated mice. The activity of glyoxalase 1 was not affected by MGO, but was enhanced by Brazilian propolis in EDL muscles. MGO treatment increased mRNA expression of inflammation-related molecules, interleukin (IL)-1ß, IL-6, and toll-like receptor 4 (TLR4). Brazilian propolis ingestion suppressed these increases. MGO and/or propolis exerted no effect on the accumulation of AGEs, glyoxalase 1 activity, and inflammatory responses in soleus muscles. These results suggest that Brazilian propolis exerts a protective effect against glycation stress by inhibiting the accumulation of AGEs, promoting MGO detoxification, and reducing proinflammatory responses in the skeletal muscle. However, these anti-glycation effects does not lead to prevent glycation-induced muscle mass reduction.

Lactate Stimulates a Potential for Hypertrophy and Regeneration of Mouse Skeletal Muscle.

The effects of lactate on muscle mass and regeneration were investigated using mouse skeletal muscle tissue and cultured C2C12 cells. Male C57BL/6J mice were randomly divided into (1) control, (2) lactate (1 mol/L in distilled water, 8.9 mL/g body weight)-administered, (3) cardio toxin (CTX)-injected (CX), and (4) lactate-administered after CTX-injection (LX) groups. CTX was injected into right tibialis anterior (TA) muscle before the oral administration of sodium lactate (five days/week for two weeks) to the mice. Oral lactate administration increased the muscle weight and fiber cross-sectional area, and the population of Pax7-positive nuclei in mouse TA skeletal muscle. Oral administration of lactate also facilitated the recovery process of CTX-associated injured mouse TA muscle mass accompanied with a transient increase in the population of Pax7-positive nuclei. Mouse myoblast-derived C2C12 cells were differentiated for five days to form myotubes with or without lactate administration. C2C12 myotube formation with an increase in protein content, fiber diameter, length, and myo-nuclei was stimulated by lactate. These observations suggest that lactate may be a potential molecule to stimulate muscle hypertrophy and regeneration of mouse skeletal muscle via the activation of muscle satellite cells.

Activation of adiponectin receptors has negative impact on muscle mass in C2C12 myotubes and fast-type mouse skeletal muscle.

This study investigated the effects of AdipoRon, which is an agonist for adiponectin receptor 1 (AdipoR1) and AdipoR2, on the protein content, myotube diameter, and number of nuclei per myotube of C2C12 cells and skeletal muscle mass in C57BL/6J mice. AdipoRon suppressed the protein content, myotube diameter, and number of nuclei per myotube of C2C12 cells of C2C12 myotubes in a dose-dependent manner. Adiponectin-associated decline of protein content, diameter, and number of nuclei per myotube in C2C12 myotubes was partially rescued by knockdown of AdipoR1 and/or AdipoR2. Phosphorylation level of AMPK showed a trend to be increased by AdipoRon. A significant increase in phosphorylation level of AMPK was observed at 20 µM AdipoRon. Knockdown of AdipoR1 and/or AdipoR2 rescued AdipoRon-associated decrease in protein content of C2C12 myotubes. AdipoRon-associated increase in phosphorylation level of AMPK in C2C12 myotubes was suppressed by knockdown of AdipoR1 and/or AdipoR2. Successive intravenous injections of AdipoRon into mice caused a decrease in the wet weight of plantaris muscle (PLA), but not in soleus muscle (SOL). Mean fiber cross-sectional area of PLA, but not of SOL, was significantly decreased by AdipoRon administration. On the one hand, the expression level of phosphorylated AMPK and ubiquitinated protein in SOL and PLA muscles was upregulated by AdipoRon administration. On the other hand, AdipoRon administration induced no changes in the expression level of puromycin-labeled proteins in both SOL and PLA muscles. Expression level of adiponectin in extensor digitorum longus (EDL) muscle was increased by aging, but not in SOL muscle. Aging had no effect on the expression level of AdipoR1 and AdipoR2 in both muscles. Phosphorylation level of AMPK in EDL was increased by aging, but not SOL muscle. Results from this study suggest that high level of circulating adiponectin may induce skeletal muscle atrophy, especially fast-type muscle.

AMPK Mediates Muscle Mass Change But Not the Transition of Myosin Heavy Chain Isoforms during Unloading and Reloading of Skeletal Muscles in Mice.

5'AMP-activated protein kinase (AMPK) plays an important role in the regulation of skeletal muscle mass and fiber-type distribution. However, it is unclear whether AMPK is involved in muscle mass change or transition of myosin heavy chain (MyHC) isoforms in response to unloading or increased loading. Here, we checked whether AMPK controls muscle mass change and transition of MyHC isoforms during unloading and reloading using mice expressing a skeletal-muscle-specific dominant-negative AMPKα1 (AMPK-DN). Fourteen days of hindlimb unloading reduced the soleus muscle weight in wild-type and AMPK-DN mice, but reduction in the muscle mass was partly attenuated in AMPK-DN mice. There was no difference in the regrown muscle weight between the mice after 7 days of reloading, and there was concomitantly reduced AMPKα2 activity, however it was higher in AMPK-DN mice after 14 days reloading. No difference was observed between the mice in relation to the levels of slow-type MyHC I, fast-type MyHC IIa/x, and MyHC IIb isoforms following unloading and reloading. The levels of 72-kDa heat-shock protein, which preserves muscle mass, increased in AMPK-DN-mice. Our results indicate that AMPK mediates the progress of atrophy during unloading and regrowth of atrophied muscles following reloading, but it does not influence the transition of MyHC isoforms.

Nuclear Accumulation of HSP70 in Mouse Skeletal Muscles in Response to Heat Stress, Aging, and Unloading With or Without Reloading.

The purpose of this study was to investigate the nuclear accumulation of heat shock protein 70 (HSP70), a molecular chaperonin in mouse skeletal muscle in response to aging, heat stress, and hindlimb unloading with or without reloading. Profiles of HSP70-specific nuclear transporter Hikeshi in skeletal muscles were also evaluated. Heat stress-associated nuclear accumulation of HSP70 was observed in slow soleus (SOL) and fast plantaris (PLA) muscles of young (10-week-old) mice. Mean nuclear expression level of HSP70 in slow medial gastrocnemius (MGAS) and PLA muscles of aged (100-week-old) mice increased ~4.8 and ~1.7 times, compared to that of young (10-week-old) mice. Reloading following 2-week hindlimb unloading caused accumulation of HSP70 in myonuclei in MGAS and PLA of young mice ( p < 0.05). However, reloading-associated nuclear accumulation of HSP70 was not observed in both types of muscles of aged mice. On the other hand, 2-week hindlimb unloading had no impact on the nuclear accumulation of HSP70 in both muscles of young and aged mice. Nuclear expression level of Hikeshi in both MGAS and PLA in mice was suppressed by aging. No significant changes in the nuclear Hikeshi in both muscles were induced by unloading with or without reloading. Results of this study indicate that the nuclear accumulation of HSP70 might show a protective response against cellular stresses in skeletal muscle and that the protective response may be suppressed by aging. Protective response to aging might depend on muscle fiber types.

Potential involvement of dietary advanced glycation end products in impairment of skeletal muscle growth and muscle contractile function in mice.

Diets enriched with advanced glycation end products (AGE) have recently been related to muscle dysfunction processes. However, it remains unclear whether long-term exposure to an AGE-enriched diet impacts physiological characteristics of skeletal muscles. Therefore, we explored the differences in skeletal muscle mass, contractile function and molecular responses between mice receiving a diet high in AGE (H-AGE) and low in AGE (L-AGE) for 16 weeks. There were no significant differences between L-AGE and H-AGE mice with regard to body weight, food intake or epididymal fat pad weight. However, extensor digitorum longus (EDL) and plantaris (PLA) muscle weights in H-AGE mice were lower compared with L-AGE mice. Higher levels of N ε -(carboxymethyl)-l-lysine, a marker for AGE, in EDL muscles of H-AGE mice were observed compared with L-AGE mice. H-AGE mice showed lower muscle strength and endurance in vivo and lower muscle force production of PLA muscle in vitro. mRNA expression levels of myogenic factors including myogenic factor 5 and myogenic differentiation in EDL muscle were lower in H-AGE mice compared with L-AGE mice. The phosphorylation status of 70-kDa ribosomal protein S6 kinase Thr389, an indicator of protein synthesis signalling, was lower in EDL muscle of H-AGE mice than that of L-AGE mice. These findings suggest that long-term exposure to an AGE-enriched diet impairs skeletal muscle growth and muscle contractile function, and that these muscle dysfunctions may be attributed to the inhibition of myogenic potential and protein synthesis.

Involvement of AMPK in regulating slow-twitch muscle atrophy during hindlimb unloading in mice.

AMPK is considered to have a role in regulating skeletal muscle mass. However, there are no studies investigating the function of AMPK in modulating skeletal muscle mass during atrophic conditions. In the present study, we investigated the difference in unloading-associated muscle atrophy and molecular functions in response to 2-wk hindlimb suspension between transgenic mice overexpressing the dominant-negative mutant of AMPK (AMPK-DN) and their wild-type (WT) littermates. Male WT (n = 24) and AMPK-DN (n = 24) mice were randomly divided into two groups: an untreated preexperimental control group (n = 12 in each group) and an unloading (n = 12 in each group) group. The relative soleus muscle weight and fiber cross-sectional area to body weight were decreased by ∼30% in WT mice by hindlimb unloading and by ∼20% in AMPK-DN mice. There were no changes in puromycin-labeled protein or Akt/70-kDa ribosomal S6 kinase signaling, the indicators of protein synthesis. The expressions of ubiquitinated proteins and muscle RING finger 1 mRNA and protein, markers of the ubiquitin-proteasome system, were increased by hindlimb unloading in WT mice but not in AMPK-DN mice. The expressions of molecules related to the protein degradation system, phosphorylated forkhead box class O3a, inhibitor of κBα, microRNA (miR)-1, and miR-23a, were decreased only in WT mice in response to hindlimb unloading, and 72-kDa heat shock protein expression was higher in AMPK-DN mice than in WT mice. These results imply that AMPK partially regulates unloading-induced atrophy of slow-twitch muscle possibly through modulation of the protein degradation system, especially the ubiquitin-proteasome system.

Mesoscopic structures of vermiculite and weathered biotite clays in suspension with and without cesium ions.

The effect of cesium (Cs) adsorption on the mesoscopic structure of the clay minerals vermiculite and weathered biotite (WB) in suspensions was elucidated by small-angle X-ray scattering (SAXS). The clay minerals form multilayered structures, and the Cs cations (Cs(+)) are strongly adsorbed in the interlayer space of the soil clays, in particular vermiculite and WB. SAXS was used to monitor the relationship between Cs(+) adsorption at the clay interlayers and the structural changes at length scales from 1 to 1000 Å. The variation in the distance between the neighboring clay sheets and the spatial arrangement of the clay sheets with and without Cs(+) were clarified. Our quantitative analyses revealed that the number of stacked layers of pure vermiculite was decreased by Cs(+) addition, whereas that of WB increased. Moreover, the average distance between the neighboring layers of vermiculite in suspension was larger than that of WB, which reflects the different conditions of Cs(+) intercalation. These findings provide fundamental insights that are important for predicting the environmental fate of radioactive Cs in contaminated regions and for developing methods for extracting Cs from soil.

Collective structural changes in vermiculite clay suspensions induced by cesium ions.

Following the Fukushima Daiichi nuclear disaster in 2011, Cs radioisotopes have been dispersed over a wide area. Most of the Cs has remained on the surface of the soil because Cs(+) is strongly adsorbed in the interlayer spaces of soil clays, particularly vermiculite. We have investigated the microscopic structure of an aqueous suspension of vermiculite clay over a wide length scale (1-1000 Å) by small-angle X-ray scattering. We determined the effect of the adsorption behavior of Cs(+) on the structural changes in the clay. It was found that the abruption of the clay sheets was induced by the localization of Cs(+) at the interlayer. This work provides important information for predicting the environmental fate of radioactive Cs in polluted areas, and for developing methods to extract Cs from the soil and reduce radioactivity.

AICAR-induced activation of AMPK negatively regulates myotube hypertrophy through the HSP72-mediated pathway in C2C12 skeletal muscle cells.

5'-AMP-activated protein kinase (AMPK) plays an important role as a negative regulator of skeletal muscle mass. However, the precise mechanism of AMPK-mediated regulation of muscle mass is not fully clarified. Heat shock proteins (HSPs), stress-induced molecular chaperones, are related with skeletal muscle adaptation, but the association between AMPK and HSPs in skeletal muscle hypertrophy is unknown. Thus, we investigated whether AMPK regulates hypertrophy by mediating HSPs in C2C12 cells. The treatment with AICAR, a potent stimulator of AMPK, decreased 72-kDa HSP (HSP72) expression, whereas there were no changes in the expressions of 25-kDa HSP, 70-kDa heat shock cognate, and heat shock transcription factor 1 in myotubes. Protein content and diameter were less in the AICAR-treated myotubes in those without treatment. AICAR-induced suppression of myotube hypertrophy and HSP72 expression was attenuated in the siRNA-mediated AMPKα knockdown myotubes. AICAR increased microRNA (miR)-1, a modulator of HSP72, and the increase of miR-1 was not induced in AMPKα knockdown condition. Furthermore, siRNA-mediated HSP72 knockdown blocked AICAR-induced inhibition of myotube hypertrophy. AICAR upregulated the gene expression of muscle Ring-finger 1, and this alteration was suppressed in either AMPKα or HSP72 knockdown myotubes. The phosphorylation of p70 S6 kinase Thr(389) was downregulated by AICAR, whereas this was attenuated in AMPKα, but not in HSP72, knockdown myotubes. These results suggest that AMPK inhibits hypertrophy through, in part, an HSP72-associated mechanism via miR-1 and protein degradation pathways in skeletal muscle cells.

Molecular and crystal structures of chitosan/HI type I salt determined by X-ray fiber diffraction.

The three-dimensional structure of chitosan/HI type I salt was determined by the X-ray fiber diffraction technique and linked-atom least-squares refinement method. Two polymer chains and four iodide ions (I(-)) crystallized in a monoclinic unit cell with dimensions a = 9.46(2), b = 9.79(2)], c (fiber axis)=10.33(2)A, beta = 105.2(2) degrees and a space group P2(1). Chitosan chains adopted an extended twofold helical conformation that was stabilized by O-3...O-5 hydrogen bonds, and the O-6 atom adopted nearly gt orientation. Polymer chains zigzag along the b-axis and directly connect to each other by N-2...O-6 hydrogen bonds. Two columns of iodide ions were shown to pack at the bending points of the zigzag sheets, and their locations are closely related to those of water columns in the hydrated chitosan. The iodide ions stabilized the salt structure by forming hydrogen bonds with the N-2 and O-6 atoms of the polymer chains together with an electrostatic interaction between N-2 and the iodide ions.