Slo1 deficiency impaired skeletal muscle regeneration and slow-twitch fibre formation.

BACKGROUND: It has been observed that Slo1 knockout mice have reduced motor function, and people with certain Slo1 mutations have movement problems, but there is no answer whether the movement disorder is caused by the loss of Slo1 in the nervous system, or skeletal muscle, or both. Here, to ascertain in which tissues Slo1 functions to regulate motor function and offer deeper insight in treating related movement disorder, we generated skeletal muscle-specific Slo1 knockout mice, studied the functional changes in Slo1-deficient skeletal muscle and explored the underlying mechanism. METHODS: We used skeletal muscle-specific Slo1 knockout mice (Myf5-Cre; Slo1flox/flox mice, called CKO) as in vivo models to examine the role of Slo1 in muscle growth and muscle regeneration. The forelimb grip strength test was used to assess skeletal muscle function and treadmill exhaustion test was used to test whole-body endurance. Mouse primary myoblasts derived from CKO (myoblast/CKO) mice were used to extend the findings to in vitro effects on myoblast differentiation and fusion. Quantitative real-time PCR, western blot and immunofluorescence approaches were used to analyse Slo1 expression during myoblast differentiation and muscle regeneration. To investigate the involvement of genes in the regulation of muscle dysfunction induced by Slo1 deletion, RNA-seq analysis was performed in primary myoblasts. Immunoprecipitation and mass spectrometry were used to identify the protein interacting with Slo1. A dual-luciferase reporter assay was used to identify whether Slo1 deletion affects NFAT activity. RESULTS: We found that the body weight and size of CKO mice were not significantly different from those of Slo1flox/flox mice (called WT). Deficiency of Slo1 in muscles leads to reduced endurance (~30% reduction, P < 0.05) and strength (~30% reduction, P < 0.001). Although there was no difference in the general morphology of the muscles, electron microscopy revealed a considerable reduction in the content of mitochondria in the soleus muscle (~40% reduction, P < 0.01). We found that Slo1 was expressed mainly on the cell membrane and showed higher expression in slow-twitch fibres. Slo1 protein expression is progressively reduced during muscle postnatal development and regeneration after injury, and the expression is strongly reduced during myoblast differentiation. Slo1 deletion impaired myoblast differentiation and slow-twitch fibre formation. Mechanistically, RNA-seq analysis showed that Slo1 influences the expression of genes related to myogenic differentiation and slow-twitch fibre formation. Slo1 interacts with FAK to influence myogenic differentiation, and Slo1 deletion diminishes NFAT activity. CONCLUSIONS: Our data reveal that Slo1 deficiency impaired skeletal muscle regeneration and slow-twitch fibre formation.

Characterization of organic anion transporting polypeptide 1b2 knockout rats generated by CRISPR/Cas9: a novel model for drug transport and hyperbilirubinemia disease.

Organic anion transporting polypeptide 1B1 and 1B3 (OATP1B1/3) as important uptake transporters play a fundamental role in the transportation of exogenous drugs and endogenous substances into cells. Rat OATP1B2, encoded by the Slco1b2 gene, is homologous to human OATP1B1/3. Although OATP1B1/3 is very important, few animal models can be used to study its properties. In this report, we successfully constructed the Slco1b2 knockout (KO) rat model via using the CRISPR/Cas9 technology for the first time. The novel rat model showed the absence of OATP1B2 protein expression, with no off-target effects as well as compensatory regulation of other transporters. Further pharmacokinetic study of pitavastatin, a typical substrate of OATP1B2, confirmed the OATP1B2 function was absent. Since bilirubin and bile acids are the substrates of OATP1B2, the contents of total bilirubin, direct bilirubin, indirect bilirubin, and total bile acids in serum are significantly higher in Slco1b2 KO rats than the data of wild-type rats. These results are consistent with the symptoms caused by the absence of OATP1B1/3 in Rotor syndrome. Therefore, this rat model is not only a powerful tool for the study of OATP1B2-mediated drug transportation, but also a good disease model to study hyperbilirubinemia-related diseases.

Calcium Homeostasis: A Potential Vicious Cycle of Bone Metastasis in Breast Cancers.

Cancers have been considered as one of the most severe health problems in the world. Efforts to elucidate the cancer progression reveal the importance of bone metastasis for tumor malignancy, one of the leading causes for high mortality rate. Multiple cancers develop bone metastasis, from which breast cancers exhibit the highest rate and have been well-recognized. Numerous cells and environmental factors have been believed to synergistically facilitate bone metastasis in breast cancers, from which breast cancer cells, osteoclasts, osteoblasts, and their produced cytokines have been well-recognized to form a vicious cycle that aggravates tumor malignancy. Except the cytokines or chemokines, calcium ions are another element largely released from bones during bone metastasis that leads to hypercalcemia, however, have not been well-characterized yet in modulation of bone metastasis. Calcium ions act as a type of unique second messenger that exhibits omnipotent functions in numerous cells, including tumor cells, osteoclasts, and osteoblasts. Calcium ions cannot be produced in the cells and are dynamically fluxed among extracellular calcium pools, intracellular calcium storages and cytosolic calcium signals, namely calcium homeostasis, raising a possibility that calcium ions released from bone during bone metastasis would further enhance bone metastasis and aggravate tumor progression via the vicious cycle due to abnormal calcium homeostasis in breast cancer cells, osteoclasts and osteoblasts. TRPs, VGCCs, SOCE, and P2Xs are four major calcium channels/routes mediating extracellular calcium entry and affect calcium homeostasis. Here we will summarize the overall functions of these four calcium channels in breast cancer cells, osteoclasts and osteoblasts, providing evidence of calcium homeostasis as a vicious cycle in modulation of bone metastasis in breast cancers.

Organic anion transport polypeptide 1b2 selectively affects the pharmacokinetic interaction between paclitaxel and sorafenib in rats.

Paclitaxel, a broad-spectrum antitumor drug, is widely used as a cytotoxic drug, while sorafenib as a multi-kinase inhibitor is a classic targeted drug. A number of clinical trials have combined paclitaxel and sorafenib for cancer treatment, with the expectation of better therapeutic effects. However, the toxicity and side effects in the treatment are significantly increased. In this report, the organic anion transport polypeptide 1b2 (Oatp1b2) overexpression cell model and the Oatp1b2 knockout (KO) rat model were used to investigate the drug-drug interactions (DDI) between paclitaxel and sorafenib. In Oatp1b2-overexpressed cells, sorafenib inhibited the uptake of paclitaxel in a concentration-dependent manner. In wild-type (WT) rats, sorafenib increased the systemic exposure and slowed the elimination of paclitaxel, resulting in DDI. In Oatp1b2 KO rats, however, the DDI disappeared. Interestingly, paclitaxel did not alter the pharmacokinetic profiles of sorafenib. Further studies found that sorafenib was not the substrate of Oatp1b2 in rats. In general, the combination of paclitaxel and sorafenib caused Oatp1b2-mediated DDI in vitro and in vivo, because sorafenib inhibited Oatp1b2 activity and affected the pharmacokinetic properties of paclitaxel. This study may provide useful information for understanding the role of OATP1B in paclitaxel-sorafenib interaction.

Diet-induced obese alters the expression and function of hepatic drug-metabolizing enzymes and transporters in rats.

Obesity increases the incidences of metabolic syndrome, including type 2 diabete, fatty liver, dyslipidemia, hyperglycemia, heart disease, hypertension and cancer. In particular, pharmacokinetics and pharmacodynamics of many drugs have changed in obese patients. However, little is known about the hepatic drug-metabolizing enzymes and transporters that are influenced by diet-induced obese. In this report, we established obesity and fatty liver models in male rats by high-fat diet. The expression profiles of drug-metabolizing enzymes and transporters were studied by quantitative real-timePCR and Western blotting analysis. The function of these enzymes and transporters were assessed by their substrates and cocktail methods. The expression and activity of phase I enzymes (CYP1A2, CYP2B1, CYP2C11, CYP3A1, CYP4A1 and FMO1) and phase II enzymes (UGT1A1, UGT1A3, UGT1A6, UGT1A9, UGT2B7, NAT1 and GSTT1) were decreased in the liver of obese rats. In addition, the mRNA levels of hepatic transporter Slco1a2, Slco1b2, Slc22a5, Abcc2, Abcc3, Abcb1a and Abcg2 decreased significantly in obese animals, while Abcb1b increased significantly. Furthermore, the decreased expression of hepatic phase I and II enzymes and transporter may be due to changes of Hnf4α, LXRα and FXR. In conclusion, the diet-induced obese altered the expression and function of hepatic drug-metabolizing enzymes and transporters in male rats, thereby impacting drug metabolism and pharmacokinetics.

Preclinical toxicology and toxicokinetic evaluation of ailanthone, a natural product against castration-resistant prostate cancer, in mice.

Ailanthone (AIL) has many biological activities including antimalarial, antiviral and anticancer. Our previous study also found that AIL targets p23 against castration-resistant prostate cancer. In this report, the preclinical safety of AIL was evaluated by acute toxicity, subacute toxicity and toxicokinetics in mice. In the acute toxicity study, the LD50 of AIL was 27.3 mg/kg, and severe pathological damages were mainly found in the liver and gastrointestinal tract. In the subacute toxicity study, mice were orally administered at doses of 2.5, 5 and 10 mg/kg for 28 days. The results showed the body weight of male mice in the 10 mg/kg dose group decreased, but that of female mice increased. Biochemical and histopathological analysis showed that AIL could cause steatohepatitis, splenomegaly, gastrointestinal mucosal damage and reproductive system abnormalities. In addition, AIL presented the reversible hematotoxicity. To determine the relationship between AIL toxicity and dose/exposure in vivo, toxicokinetics of AIL were carried out after a single oral dose of 15 mg/kg. The stomach was identified as the main target organ, followed by the intestine and kidney. On the basis of this study, the dose of 2.5 mg/kg had no adverse effect on mice. To sum up, this study is the first time to evaluate the systemic toxicity of AIL, which is useful for the further development of AIL.

Development and Characterization of MDR1 (Mdr1a/b) CRISPR/Cas9 Knockout Rat Model.

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) technology is widely used as a tool for gene editing in rat genome site-specific engineering. Multidrug resistance 1 [MDR1 (also known as P-glycoprotein)] is a key efflux transporter that plays an important role not only in the transport of endogenous and exogenous substances, but also in tumor MDR. In this report, a novel MDR1 (Mdr1a/b) double-knockout (KO) rat model was generated by the CRISPR/Cas9 system without any off-target effect detected. Western blot results showed that MDR1 was completely absent in the liver, small intestine, brain, and kidney of KO rats. Further pharmacokinetic studies of digoxin, a typical substrate of MDR1, confirmed the deficiency of MDR1 in vivo. To determine the possible compensatory mechanism of Mdr1a/b (-/-) rats, the mRNA levels of the CYP3A subfamily and transporter-related genes were compared in the brain, liver, kidney, and small intestine of KO and wild-type rats. In general, a new Mdr1a/b (-/-) rat model has been successfully generated and characterized. This rat model is a useful tool for studying the function of MDR1 in drug absorption, tumor MDR, and drug target validation.