Objective To establish an analytical method for the simultaneous determination of 18 perfluoroalkyl compounds(PFCs)in tea leaves using a quick,easy,cheap,effective,rugged,and safe(QuEChERS)method for sample pretreatment combined with ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).Methods The target analytes—18 PFCs—included 13 carboxylic acid PFCs(perfluorobutanoic acid[PFBA],perfluoropentanoic acid[PFPeA],perfluorohexanoic acid[PFHxA],perfluoroheptanoic acid[PFHpA],perfluorooctanoic acid[PFOA],perfluorononanoic acid[PFNA],perfluorodecanoic acid[PFDA],perfluoroundecanoic acid[PFUdA],perfluorododecanoic acid[PFTrDA],perfluorotridecanoic acid[PFTeDA],perfluorotetradecanoic acid[PFHxDA],perfluorohexadecanoic acid[PFHpS],and perfluorooctadecanoic acid[PFODA])and 5 sulfonic acid PFCs(perfluorobutanesulfonic acid[PFBS],perfluorohexanesulfonic acid[PFHxS],perfluoroheptanesulfonic acid[PFHpS],perfluorooctanesulfonic acid[PFOS],and perfluorodecanesulfonic acid[PFDS]).The QuEChERS pretreatment parameters were systematically optimized using the response surface methodology.The tea leave samples were extracted with an 80%acetonitrile solution and subsequently purified by adding a mixed absorbent consisting of 20 mg N-propyl-ethylenediamine(PSA),210 mg graphitized carbon black GCB),and 60 mg octadecylsilane(C18).The supernatant was concentrated by nitrogen blowing and subsequently re-dissolved in 50%methanol-2 mmol/L ammonium acetate solution.The re-dissolved solution was injected into the UHPLC-MS/MS for analysis.The target analytes were separated on an ACQUITY UPLC BEH C18 column(2.1 mm×50 mm,1.7 μm).The mobile phases consisted of methanol(phase A)and 2 mmol/L aqueous ammonium acetate(phase B),with a gradient elution procedure.The total running time was 18 min.The mass spectrometry analysis was conducted using an electrospray ionization source in negative ionization mode and multi-reaction monitoring(MRM),with quantification performed using the internal standard curve method.The greenness of the analytical method was assessed using Analytical GREEnness calculator(AGREE)and the Analytical Eco-Scale method(AES).Results Under the optimized conditions,the limits of detection(LODs)and limits of quantification(LOQs)of the method were 0.005 7-1.23 ng/g and 0.019-4.09 ng/g,respectively.The average recoveries of most target compounds were 71.1%-117.9%,with relative standard deviations(RSDs)below 15%.The AGREE index of the method was 0.49,and the AES score was 76.At least one PFC was detected in each of the 132 tea leave samples,and the detection rate of carboxylic acid PFC was higher than that of sulfonic acid PFC.The highest detection rates were observed for PFBA at 97.74%,PFHpA at 93.23%,and PFOA at 92.24%.In contrast,PFHpS,PFUdA,PFDoA,PFHxDA,and PFODA were not detected in the samples.Conclusion The proposed method has the advantages of simplicity,rapidity and sensitivity,and is suitable for the analysis of PFCs in tea leaves.The method has high greenness with minimal impact on the operator and the environment.The widespread presence of PFC contamination in tea leaves available in the market warrants strengthened monitoring and regulatory control.

Objective To observe the effect of a heavy load exercise on the ultrastructure,function and fission of skeletal muscle mitochondria in rats,and to analyze the changes of the phosphorylation expression of mitochondrial fission protein and upstream kinase at different times postexercise,and to explore the effect of acute heavy load exercise on mitochondrial fission in skeletal muscle of rats and its possible mechanism.Methods Forty-eight adult male Sprague-Dawley rats were randomly divided in-to a quiet control group(C,n=8)and an exercise group(E,n=40).Rats in the E group exercised on a treadmill down a 16° decline at 16 m/min for 90 min and were further divided into 0 h,12 h,24 h,48 h,and 72 h postexercise subgroups.Soleus muscle was isolated and mitochondria were ex-tracted at the corresponding time points after exercise.The ultrastructure of mitochondria in the soleus muscle was observed using transmission electron microscopy,and mitochondrial quantity and morphomet-ric analysis were conducted.Moreover,the colocalization and quantity of dynamin-related protein 1(Drp1)and cytochrome C oxidease subunit Ⅳ(COXⅣ)in the soleus muscle were detected using im-munofluorescence double-labeling techniques.Meanwhile,protein levels of soleus musclep-Drp1Ser616,p-Drp1Ser637,p-extracellular regulatory protein kinaseThr202/Tyr204(p-ERKThr202/Tyr204),p-protein kinaseAThr197(p-PKAThr197),and mitochondrial NADH of ubiquinone oxidoreductase subunit B8(NDUFB8)and ubiqui-nol-cytochrome C reductase core protein 2(UQCRC2)were determined by using Western blotting.An-other twenty-four rats were randomly divided into a DMSO group(CD),a U0126 group(CU),an Ex-ercise+DMSO group(ED),and an Exercise+U0126 group(EU).Six mice in each group were giv-en a single intra-bitoneal injection of DMSO or ERK inhibitor U0126 20 min before acute downhill running.Then,their phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 in soleus muscle were de-tected by Western blotting.Results(1)From 0 h to 48 h after exercise,the soleus muscle mitochon-dria showed swelling,rounding,and uneven distribution of mitochondria,among which the degree of mitochondrial damage was the most serious at 12 h and 24 h after exercise.Moreover,the protein ex-pression of NDUFB8 and UQCRC2 in the mitochondria fractions from soleus muscle was significantly lower at 12 h post-exercise(P<0.05).(2)The co-localization of Drp1 and COXⅣ in the skeletal muscle increased significantly at 12 h to 24 h after a heavy load exercise compared with group C and group E0(P<0.01).Moreover,the mitochondrial area,circumference,aspect ratio and Ferret diameter in the skeletal muscle were significantly lower at 12 h to 24 h postexercise(P<0.05).Meanwhile,the number of mitochondria was significantly higher at 24 h after exercise(P<0.01).(3)The phosphoryla-tion of ERKThr202/Tyr204,PKAThr197 and Drp1Ser616 was significantly higher at 24 h after exercise(P<0.01),while that of Drp1Ser637 was significantly lower at 48 h and 72 h post-exercise(P<0.01).However,the phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 were significantly down-regulated by U0126 treatment before exercise.Conclusion A session of heavy load exercise caused mitochondrial structure and function damage and induced mitochondrial fission in the skeletal muscle,and then to maintain the homeostasis of skeletal muscle cells by cleaving damaged mitochondria.The mechanism of promot-ing skeletal muscle repair may be related to the positive and negative regulation of Drp1 activity by the phosphorylation of Drp1Ser616 and Drp1Ser637,respectively.Among them,the activation of ERKThr202/Tyr204 mediates the phosphorylation activation of Drp1Ser616,but PKAThr197 is not an upstream kinase that medi-ates the inactivation of Drp1Ser637 phosphorylation.

Objective To observe the effect of a heavy load exercise on the ultrastructure,function and fission of skeletal muscle mitochondria in rats,and to analyze the changes of the phosphorylation expression of mitochondrial fission protein and upstream kinase at different times postexercise,and to explore the effect of acute heavy load exercise on mitochondrial fission in skeletal muscle of rats and its possible mechanism.Methods Forty-eight adult male Sprague-Dawley rats were randomly divided in-to a quiet control group(C,n=8)and an exercise group(E,n=40).Rats in the E group exercised on a treadmill down a 16° decline at 16 m/min for 90 min and were further divided into 0 h,12 h,24 h,48 h,and 72 h postexercise subgroups.Soleus muscle was isolated and mitochondria were ex-tracted at the corresponding time points after exercise.The ultrastructure of mitochondria in the soleus muscle was observed using transmission electron microscopy,and mitochondrial quantity and morphomet-ric analysis were conducted.Moreover,the colocalization and quantity of dynamin-related protein 1(Drp1)and cytochrome C oxidease subunit Ⅳ(COXⅣ)in the soleus muscle were detected using im-munofluorescence double-labeling techniques.Meanwhile,protein levels of soleus musclep-Drp1Ser616,p-Drp1Ser637,p-extracellular regulatory protein kinaseThr202/Tyr204(p-ERKThr202/Tyr204),p-protein kinaseAThr197(p-PKAThr197),and mitochondrial NADH of ubiquinone oxidoreductase subunit B8(NDUFB8)and ubiqui-nol-cytochrome C reductase core protein 2(UQCRC2)were determined by using Western blotting.An-other twenty-four rats were randomly divided into a DMSO group(CD),a U0126 group(CU),an Ex-ercise+DMSO group(ED),and an Exercise+U0126 group(EU).Six mice in each group were giv-en a single intra-bitoneal injection of DMSO or ERK inhibitor U0126 20 min before acute downhill running.Then,their phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 in soleus muscle were de-tected by Western blotting.Results(1)From 0 h to 48 h after exercise,the soleus muscle mitochon-dria showed swelling,rounding,and uneven distribution of mitochondria,among which the degree of mitochondrial damage was the most serious at 12 h and 24 h after exercise.Moreover,the protein ex-pression of NDUFB8 and UQCRC2 in the mitochondria fractions from soleus muscle was significantly lower at 12 h post-exercise(P<0.05).(2)The co-localization of Drp1 and COXⅣ in the skeletal muscle increased significantly at 12 h to 24 h after a heavy load exercise compared with group C and group E0(P<0.01).Moreover,the mitochondrial area,circumference,aspect ratio and Ferret diameter in the skeletal muscle were significantly lower at 12 h to 24 h postexercise(P<0.05).Meanwhile,the number of mitochondria was significantly higher at 24 h after exercise(P<0.01).(3)The phosphoryla-tion of ERKThr202/Tyr204,PKAThr197 and Drp1Ser616 was significantly higher at 24 h after exercise(P<0.01),while that of Drp1Ser637 was significantly lower at 48 h and 72 h post-exercise(P<0.01).However,the phosphorylated expressions of ERKThr202/Tyr204 and Drp1Ser616 were significantly down-regulated by U0126 treatment before exercise.Conclusion A session of heavy load exercise caused mitochondrial structure and function damage and induced mitochondrial fission in the skeletal muscle,and then to maintain the homeostasis of skeletal muscle cells by cleaving damaged mitochondria.The mechanism of promot-ing skeletal muscle repair may be related to the positive and negative regulation of Drp1 activity by the phosphorylation of Drp1Ser616 and Drp1Ser637,respectively.Among them,the activation of ERKThr202/Tyr204 mediates the phosphorylation activation of Drp1Ser616,but PKAThr197 is not an upstream kinase that medi-ates the inactivation of Drp1Ser637 phosphorylation.

Objective To explore the effect of 4-week repetitive downhill treadmill running on the mi-tochondrial structure,function,and autophagy in skeletal muscle of rats,so as to analyze the role of FKBP8-mediated mitophagy in exercise-induced mitochondrial damage in their skeletal muscles.Meth-ods Thirty-two male adult Sprague-Dawley rats were randomly divided into a 2-week quiet control group(2C group,n=8),a 4-week quiet control group(4C group,n=8),a 2-week exercise group(2E group,n=8)and a 4-week exercise group(4E group,n=8).Rats in 2E and 4E groups performed dai-ly 90-minute downhill treadmill running(-16°,16 m/min)5 days a week for two and four weeks,re-spectively.Then,they rested for 24 hours and received an exhaustive exercise test.Running distance and blood lactate were measured prior to and at the time of exercise cessation.Moreover,mitochondri-al ultrastructural changes in soleus muscles were observed by using a transmission electron microscope.The protein expression of mitochondrial succinate dehydrogenase subunit B(SDHB),cytochrome C oxi-dase subunit 1(MTCO1),FK506 binding protein 8(FKBP8)and microtubule associated protein 1 light chain 3(LC3)in the soleus muscle were measured using Western blotting.Meanwhile,the co-localiza-tion of FKBP8 with LC3 and cytochrome C oxidase subunit Ⅳ(COXⅣ)with LC3,lysosomal associat-ed membrane protein 2(LAMP2)were detected by the immunofluorescence double labeling technique.Results(1)The running distance of one exhaustive exercise and the blood lactate before and after the test in 2E group were significantly higher than 2C and 4E groups(P<0.05 or P<0.01),and the run-ning distance of 4E group was significantly higher than 4C group(P<0.01).However,there was no sig-nificant difference between 4E and 4C groups in the blood lactate before and after the exhaustive exer-cise test(P>0.05).(2)In both 2E and 4E groups,significant mitochondrial swelling and accumulation under cell membrane,as well as a number of mitophagosomes and mitophagolysosomes were observed,together with a significant reduce in the number of mitochondria(P<0.05),which was more severe in 2E group than 4E group.(3)The protein expression of mitochondrial SDHB and MTCO1 in 2E and 4E groups were lower than 2C and 4C groups,respectively,with significantly greater changes of these proteins in 4E group than 2E group(P<0.05 or P<0.01).(4)The protein expression of mitochondrial FKBP8 and LC3,as well as the co-localization of FKBP8 with LC3 and COXⅣ with LC3,LAMP2 in 2E and 4E groups were higher than 2C and 4C groups,respectively,with significantly greater changes in 4E group than 2E group(P<0.05 or P<0.01).Conclusion After 4-week downhill treadmill running,the structure,quantity and function of mitochondria in skeletal muscle are impaired.FKBP8-mediated mitophagy is activated,but is insufficient to degrade the damaged mitochondria,leading to muscular damage,as well as the increasing and falling down of running capacity.