Quercetin ameliorates oxidative stress-induced senescence in rat nucleus pulposus-derived mesenchymal stem cells via the miR-34a-5p/SIRT1 axis

BACKGROUND

Intervertebral disc degeneration (IDD) is a main contributor to low back pain. Oxidative stress, which is highly associated with the progression of IDD, increases senescence of nucleus pulposus-derived mesenchymal stem cells (NPMSCs) and weakens the differentiation ability of NPMSCs in degenerated intervertebral discs (IVDs). Quercetin (Que) has been demonstrated to reduce oxidative stress in diverse degenerative diseases.

AIM

To investigate the role of Que in oxidative stress-induced NPMSC damage and to elucidate the underlying mechanism.

METHODS

In vitro, NPMSCs were isolated from rat tails. Senescence-associated β-galactosidase (SA-β-Gal) staining, cell cycle, reactive oxygen species (ROS), real-time quantitative polymerase chain reaction (RT-qPCR), immunofluorescence, and western blot analyses were used to evaluated the protective effects of Que. Meanwhile the relationship between miR-34a-5p and Sirtuins 1 (SIRT1) was evaluated by dual-luciferase reporter assay. To explore whether Que modulates tert-butyl hydroperoxide (TBHP)-induced senescence of NPMSCs via the miR-34a-5p/SIRT1 pathway, we used adenovirus vectors to overexpress and downregulate the expression of miR-34a-5p and used SIRT1 siRNA to knockdown SIRT1 expression. In vivo, a puncture-induced rat IDD model was constructed, and X rays and histological analysis were used to assess whether Que could alleviate IDD in vivo.

RESULTS

We found that TBHP can cause NPMSCs senescence changes, such as reduced cell proliferation ability, increased SA-β-Gal activity, cell cycle arrest, the accumulation of ROS, and increased expression of senescence-related proteins. While abovementioned senescence indicators were significantly alleviated by Que treatment. Que decreased the expression levels of senescence-related proteins (p16, p21, and p53) and senescence-associated secreted phenotype (SASP), including IL-1β, IL-6, and MMP-13, and it increased the expression of SIRT1. In addition, the protective effects of Que on cell senescence were partially reversed by miR-34a-5p overexpression and SIRT1 knockdown. In vivo, X-ray, and histological analyses indicated that Que alleviated IDD in a puncture-induced rat model.

CONCLUSION

In summary, the present study provides evidence that Que reduces oxidative stress-induced senescence of NPMSCs via the miR-34a/SIRT1 signaling pathway, suggesting that Que may be a potential agent for the treatment of IDD.

Nucleus Pulposus Cells Induce M2 Polarization of RAW264.7 via CX3CL1/CX3CR1 Pathway and M2 Macrophages Promote Proliferation and Anabolism of Nucleus Pulposus Cells

Background

The mechanisms underlying M2 macrophage polarization induced by nucleus pulposus (NP) cells are unclear. The effects that M2-polarized macrophages have on NP cells are also controversial.

Methods

Transcriptome sequencing was performed to detect the gene change profiles between NP cells from ruptured intervertebral disc (IVD) and normal IVD. The main difference on biological activities between the two cell groups were analyzed by GO analysis and KEGG analysis. Virus transduction, flow cytometry, immunofluorescence, RT-PCR, western blot, CCK-8, TUNEL staining, and AO/EB staining were performed to explore the interactions between NP cells and RAW264.7 macrophages. Statistics were performed using SPSS26.

Results

801 upregulated and 276 downregulated genes were identified in NP cells from ruptured IVD in mouse models. According to GO and KEGG analysis, we found that the differentially expressed genes (DEG) were dominantly enriched in inflammatory response, extracellular matrix degradation, blood vessel morphogenesis, immune effector process, ossification, chemokine signaling pathway, macrophage activation, etc. CX3CL1 was one of the top 20% DEG, and we confirmed that both NP tissue and cells expressed remarkably higher level of CX3CL1 in mouse models (p < 0.001∗). Besides, we further revealed that both the recombinant CX3CL1 and NP cells remarkably induced M2 polarization of RAW264.7 (p < 0.001∗), respectively, while this effect was significantly reversed by si-CX3CL1 or JMS-17-2 (p < 0.001∗). Furthermore, we found that M2 macrophages significantly decreased the apoptosis rate (p < 0.001∗) and the catabolic gene levels (p < 0.001∗) of NP cells, while increased the viability, proliferation as well as the anabolic gene levels of NP cells (p < 0.01∗).

Conclusions

Via regulating CX3CL1/CX3CR1 pathway, NP cells can induce the M2 macrophage polarization. M2 polarized macrophages can further promote NP cell viability, proliferation, and anabolism, while inhibit NP cell apoptosis and catabolism.

Comparison of different segments in the fixation of thoracolumbar fractures: a Bayesian network meta-analysis

BACKGROUND

Posterior internal fixation (PIF) is commonly used in the treatment of thoracolumbar fracture (TLF), but there is still no standard for the number of fixed segments. The objective of this meta-analysis was to evaluate the efficacy and safety of short segment (SS), intermediate segment (IS) and long segment (LS) in the fixation of TLF.

METHODS

Two authors independently searched through PubMed, Embase, Cochrane Library and Web of Science for studies of thoracolumbar fracture treated by posterior internal fixation, which were published until the end of April 2021. The Aggregate Data Drug Information System (ADDIS) software was used for data evaluation according to the Markov chain Monte Carlo (MCMC) method based on the Bayesian theorem.

RESULTS

Nineteen trials evaluating a total of 970 patients were enrolled in these studies, of which 340 in the SS group, 429 in the IS group and 201 in the LS group. For anterior vertebral height ratio (AVHR), IS had the highest AVHR, LS had the second highest AVHR. IS also ranked first in reducing visual analogue scale (VAS), SS ranked second. For sagittal Cobb's angle (SCA), LS had the lowest SCA and IS had the second lowest SCA. In terms of adverse events, IS had the lowest implant failure rate and LS had the second lowest implant failure rate.

CONCLUSIONS

IS may be the most desirable treatment option for TLF in reducing SCA, implant failure rate, VAS, and improving AVHR. However, more randomized controlled trials are needed to verify these results.

[Outcome of vaginal birth after cesarean section in women with advanced maternal age]

Objective: To explore the perinatal outcome of vaginal birth after cesarean (VBAC) in women with advanced age. Methods: Totally 2 587 women delivered after one or two prior cesarean sections (gestational age≥28 weeks) in the First Affiliated Hospital of Kunming Medical University from July 2013 to February 2017. 909 trial of labor after cesarean(TOLAC) cases of singleton pregnancy with one prior cesarean section were studied retrospectively. According to the age, of the 909 TOLAC cases, 237 were the advanced age group, and 672 cases were the low age group. The maternal and neonatal outcomes between the two groups were compared. Results: The percentage of TOLAC in women with advanced age was 32.4% (237/731), and VBAC rate was 88.2% (209/237). The percentage of TOLAC in younger women was 36.2% (672/1 856), and VBAC rate was 82.4% (554/672). The difference of the TOLAC rate between the two groups was not significant (P>0.05), and the VBAC rate of the advanced age group was higher than the low age group (P<0.05). In the comparison of the two groups, the proportion of bachelor degree or above(55.7%,132/237), the prepregnancy BMI (22.4±3.0) kg/m(2), pregnant interval time (68.5±38.3) months, the proportion of gestational hypertension (8.4%,20/237), the proportion of gestational diabetes(34.6%,82/237) and the rate of the neonatal ICU admission (18.1%,43/237) in the advanced age group were higher than those of the low age group (P<0.05), respectively. And there were no significant differences in the rate of postpartum hemorrhage, the rate of postpartum hemorrhage≥1 500 ml, the rate of postpartum transfusion, puerperal morbidity, neonatal birth weight, neonatal 5 min Apgar score<7 score, umbilical artery blood pH<7.0, neonatal tracheal intubation and respiratory distress syndrome (all P>0.05). In all TOLAC cases, the rate of uterine rupture was 0.11%(1/909) and there was no maternal and neonatal death. Conclusion: VBAC is a safe and feasible way of delivery for singleton pregnancy after one prior cesarean section in women with advanced age.

[The outcome of trial of labor after cesarean section]

Objective: To explore the outcome of trial of labor after cesarean section(TOLAC). Methods: Totally 614 TOLAC were conducted in the First Affiliated Hospital of Kunming Medical University from July 2013 to June 2016. Among them, 586 cases of singleton pregnancy with one prior cesarean section(gestational age≥28 weeks)were studied retrospectively. The maternal and neonatal outcomes among the vaginal birth after cesarean(VBAC)group(481 cases), failed TOLAC group(105 cases)and the elective repeat cesarean section(ERCS)group(1 145 cases)were compared. Multiple logistic regression was used to determine the risk factors of admission to neonatal intensive care unit(NICU). Results: (1)The TOLAC rate was 29.62%(614/2 073)from July 2013 to June 2016, and the VBAC rate was 82.6%(507/614). The cesarean section rate was reduced by VBAC by 3.147%(507/16 112).(2)The comparison of adverse maternal outcomes: in the VBAC group, the postpartum hemorrhage volume was(431±299)ml, the rate of postpartum fever was 6.4%(31/481), the birth weight of the neonates was(3 085± 561)g, and the rate of large for gestational age was 2.9%(14/481). All were significantly lower than those in the failed TOLAC group and the ERCS group(P<0.05). There was no significant difference in other adverse maternal outcomes[the uterine rupture rate(0.2% ,1/481), the bladder injury rate(0), the proportion of postpartum hemorrhage volume≥1 500 ml(1.0%, 5/481), the blood transfusion rate(3.7%, 18/481)]and adverse perinatal outcomes[the rate of neonatal 5-minute Apgar score<7(0.4%, 21/481), the rate of umbilical arterial pH<7.0(0.6% , 3/481), the rate of the NICU admission and the perinatal mortality rate(12.3%, 59/481)]among the 3 groups(P>0.05). Multiple logistic regression showed no association between VBAC and admission to the NICU(OR=0.84, 95%CI: 0.58-1.21). The isolated risk factors for admission to the NICU were preterm birth(OR=16.71, 95% CI: 11.44-24.40), hypertensive disorder complicating pregnamcy(OR=3.89, 95% CI: 2.39-6.35), meconium stained amniotic fluid(OR=2.48, 95% CI: 1.62-3.80), small for gestational age(OR=2.00, 95% CI: 1.19-3.36)and diabetes mellitus(OR=1.69, 95% CI: 1.14-2.50). Conclusions: VBAC reduces cesarean section rate, with good outcomes in both mother and neonate. It is a safe and feasible way of labor in women with only one cesarean section history.

[Causal analysis and management strategies of 30-day unplanned revision surgery following single-stage posterior vertebral column resection for severe spinal deformity]

Objective: To investigate the causes of 30-day unplanned revision surgery following one-stage posterior vertebral column resection (PVCR) for severe spinal deformity and the methods of prevention and management. Methods: A total of 112 severe deformity patients underwent one-stage PVCR for surgical treatment in the 306(th) Hospital of People's Liberation Army from May 2010 to December 2015 were retrospectively reviewed. Six patients required reoperation within 30 days after PVCR, including 2 males and 4 females with average age of 21 years (ranging from 12 to 38 years). Four cases were congenital kyphoscoliosis, 1 was post-laminectomy kyphoscoliosis and 1 was post-tuberculous angular kyphosis. Three cases associated with preoperative neurologic deficit (Frankel C in 1 patient and D in 2 patients). The causes, management and outcomes of unplanned revision surgery within 30 days after PVCR were recorded. Results: The total incidence of unplanned revision surgery within 30 days following PVCR was 5.4% (6/112). There was 1 case due to cerebrospinal fluid leak, 5 cases with varying degrees of new neurologic deficits, the causes were as followed: dural buckling in 1 case, residual bone compression in 1 case, epidural hematoma compression in 2 cases, spinal subdural hematoma in 1 case. All the 6 cases underwent surgical exploration again, including further dural repair, decompression and hematoma clearance. After unplanned reoperation, 6 cases recovered completely. The average follow-up time after surgery was 30.8 months (ranging from 10 to 60 months). The major curve at coronal plane was improved from preoperative 87.7° to 34.2°, with a mean correction of 61.0% at final follow-up; the sagittal kyphosis curve was improved from preoperative 119.5° to 45.5°, with a mean correction of 61.9% at final follow-up. Two patients' neurological status improved from Frankel D to Frankel E, one patient's neurological status improved from Frankel C to Frankel E. Conclusions: One-stage PVCR could be an effective method for treatment of severe spinal deformity. The causes of 30-day unplanned reoperation after PVCR are as followed: cerebrospinal fluid leak, dural buckling, residual bone compression and hematoma compression. Timely surgical exploration can gain good clinical outcomes.

Expression of different-size transcripts from the clpP-clpX operon of Escherichia coli during carbon deprivation

Transcription of the clpP-clpX operon of Escherichia coli leads to the production of two different sizes of transcripts. In log phase, the level of the longer transcript is higher than the level of the shorter transcript. Soon after the onset of carbon starvation, the level of the shorter transcript increases significantly, and the level of the longer transcript decreases. The longer transcript consists of the entire clpP-clpX operon, whereas the shorter transcript contains the entire clpP gene but none of the clpX coding sequence. The RpoH protein is required for the increase in the level of the shorter transcript during carbon starvation. Primer extension experiments suggest that there is increased usage of the sigma(32)-dependent promoter of the clpP-clpX operon within 15 min after the start of carbon starvation. Expression of the clpP-clpX operon from the promoters upstream of the clpP gene decreases to a very low level by 20 min after the onset of carbon starvation. Various pieces of evidence suggest, though they do not conclusively prove, that production of the shorter transcript may involve premature termination of the longer transcript. The half-life of the shorter transcript is much less than that of the longer transcript during carbon starvation. E. coli rpoB mutations that affect transcription termination efficiency alter the ratio of the shorter clpP-clpX transcript to the longer transcript. The E. coli rpoB3595 mutant, with an RNA polymerase that terminates transcription with lower efficiency than the wild type, accumulates a lower percentage of the shorter transcript during carbon starvation than does the isogenic wild-type strain. In contrast, the rpoB8 mutant, with an RNA polymerase that terminates transcription with higher efficiency than the wild type, produces a higher percentage of the shorter clpP-clpX transcript when E. coli is in log phase. These and other data are consistent with the hypothesis that the shorter transcript results from premature transcription termination during production of the longer transcript.

Effects of nitric oxide on adenylyl cyclase stimulation in N18TG2 neuroblastoma cells

The addition of nitric oxide (NO), in the form of either donor compounds or nitric oxide gas, inhibits hormone-stimulated cAMP accumulation in N18TG2 cells. Hormone receptors and Gs are not targets of NO because forskolin-stimulated cAMP accumulation is also inhibited. The inhibitory effect of NO is not altered by pretreatment of cells with pertussis toxin, indicating that Gi is not mediating the effect of NO. cAMP accumulation in these cells is not altered by cell incubation with Ca++ ionophore or calmidazolium, indicating that calmodulin is not the target for NO. Experiments also rule out changes in phosphodiesterase or cGMP as mediators of the effect of NO. Cell incubation with superoxide dismutase in the presence or absence of catalase indicate that nitric oxide is the reactive species. The inhibitory action of nitric oxide is readily reversed, allowing full recovery of hormone and forskolin stimulation within 20 min of incubation in the absence of nitric oxide. The sum of the data indicate that NO targets either the adenylyl cyclase itself, or a regulatory component distinct from G proteins or calmodulin, to inhibit activation of the enzyme.

Nitric oxide, an endogenous regulator of Dictyostelium discoideum differentiation

We have previously demonstrated that nitric oxide (NO)-generating compounds inhibit D. discoideum differentiation by preventing the initiation of cAMP pulses (Tao, Y., Howlett, A. and Klein, C. (1996) Cell. Signal. 8, 37–43). In the present study, we demonstrate that cells produce NO at a relatively constant rate during the initial phase of their developmental cycle. The addition of oxyhemoglobin, an NO scavenger, stimulates cell aggregation, suggesting that NO has a negative effect on the development of aggregation competence. Starvation of cells in the presence of glucose, which has been shown to prevent the initiation of cAMP pulses (Darmon, M. and Klein, C. (1978) Dev. Biol. 63, 377–389), results in an increased production of NO. The inhibition of cell aggregation by glucose treatment can be reversed by oxyhemoglobin. These findings indicate that NO is a signaling molecule for D. discoideum cells and that physiological or environmental conditions that enhance external NO levels will delay the initiation of cAMP pulses, which are essential for cell differentiation.

Liver protein kinases in shock: I. Endotoxin administration inactivates protein kinase a in dog liver

Effects of endotoxin administration on protein kinase A (cAMP-dependent protein kinase) activity in dog liver were investigated. Hepatic protein kinase A was extracted and partially purified by acid precipitation, ammonium sulfate fraction, and DEAE-cellulose chromatography. Protein kinase A was eluted from DEAE-cellulose column with a linear NaCl gradient. Two peaks of protein kinase A, type I (eluted at low ionic strength) and type II (eluted at high ionic strength), were collected, and their activities were determined based on the rate of incorporation of [gamma-32P]ATP into histone. The results obtained 4 h after endotoxin administration (.5 mg/kg, intravenously) show that type I protein kinase A activity was unaffected, while type II protein kinase A activity was inhibited by 26-57%. Kinetic analysis of the data on type II protein kinase A reveals that the Vmax values for ATP, cAMP, and histone were decreased by 31, 39, and 36%, respectively; while the S.5 (substrate concentration required for half-maximal enzyme activity) values for ATP, cAMP, and histone were unaffected following endotoxin administration. These data indicate that endotoxin administration inhibits hepatic type II protein kinase A activity and the nature of inhibition is by a mechanism not competing with ATP, cAMP, and histone reactive sites. Since protein phosphorylation plays an important role in the regulation of cell metabolism and function, our finding may contribute to the understanding of hepatocellular dysfunction during endotoxin shock.

Changes in the activities of protein kinases A, C, and M in dog heart and liver following endotoxin administration

Changes in the activities of protein kinase A (cAMP-dependent), protein kinase C (Ca2+/phospholipid-dependent), and protein kinase M (Ca2+/calmodulin-dependent) in dog heart and liver were studied 4 hr following endotoxin injection. Protein kinases A and C were extracted and partially purified by DEAE-cellulose chromatography. Protein kinase M was extracted and partially purified by DEAE-cellulose, DEAE-Sephacel, and calmodulin-Sepharose chromatography. The results indicate that in the heart, both type I (eluted at low ionic strength) and type II (eluted at high ionic strength) protein kinase A activities were unchanged after endotoxin administration. Cardiac cytosolic protein kinase C activity was increased by 50% (p < 0.05) while the membrane-associated protein kinase C activity remained unaltered following endotoxin injection. Cardiac protein kinase M activity was decreased by 38.5% (p < 0.01) post endotoxin. In the liver, type I protein kinase A activity was unaffected while type II protein kinase A activity was decreased by 34% (p < 0.01) following endotoxin injection. Hepatic cytosolic and membrane-associated protein kinase C activities were inhibited by 37% (p < 0.01) and 53% (p < 0.01), respectively, 4 hr postendotoxin. Hepatic protein kinase M activity was decreased by 61% (p < 0.01) after endotoxin administration. These data indicate that the activities of various protein kinases in the heart and liver were modified by endotoxin administration. Since protein kinases regulate cell function through phosphorylation of various substrate proteins, a modification on protein kinase activities may contribute to the development of organ dysfunction in endotoxin shock.

Cloning and sequencing of the Bacillus megaterium spoIIA operon

The spoIIA operon of Bacillus megaterium has been cloned and the nucleotide sequence determined. The spoIIA sequence contains three open reading frames coding for putative proteins of 116 aa, 147 aa, and 253 aa; the first and the third genes are preceded by a ribosomal binding site. The genes are in the same order as those of B subtilis and B licheniformis. The deduced amino acid sequences of these three open reading frames show 78-92% homology with SpoIIAA, SpoIIAB and SpoIIAC of B subtilis and B licheniformis. Northern hybridization revealed that B megaterium also has two spoIIA transcripts, 1.77 kb and 2.92 kb, attaining maximum expression at t1 and t3, respectively. In addition, homology to a possible penicillin binding protein gene upstream and the first part of a spoVA operon downstream has been identified on the 3.34-kb fragment. The spoIIA and the downstream spoVA promoter regions are highly conserved among these three species. Sequence analysis of the spoVA promoter revealed a region upstream to the -35 that is highly conserved across Bacillus species.

Regulation of protein phosphorylation in Dictyostelium discoideum

We have examined the phosphorylation of the cyclic adenosine 3':5' monophosphate (cAMP) cell surface chemotactic receptor and a 36 kDa membrane-associated protein (p36) in Dictyostelium discoideum. The activity of CAR-kinase, the enzyme responsible for the phosphorylation of the cAMP receptor, was studied in plasma membrane preparations. It was found that, as in intact cells, the receptor was rapidly phosphorylated in membranes incubated with [gamma 32P] adenosine triphosphate (ATP) but only in the presence of cAMP. This phosphorylation was not observed in membranes prepared from cells which did not display significant cAMP binding activity. cAMP could induce receptor phosphorylation at low concentrations, while cyclic guanosine 3':5' monophosphate (cGMP) could elicit receptor phosphorylation only at high concentrations. Neither ConA, Ca2+, or guanine nucleotides had an effect on CAR-kinase. It was also observed that 2-deoxy cAMP but not dibutyryl cAMP induced receptor phosphorylation. The data suggest that the ligand occupied form of the cAMP receptor is required for CAR-kinase activity. Although the receptor is rapidly dephosphorylated in vivo, we were unable to observe its dephosphorylation in vitro. In contrast, p36 was rapidly dephosphorylated. Also, unlike the cAMP receptor, the phosphorylation of p36 was found to be regulated by the addition of guanine nucleotides. Guanosine diphosphate (GDP) enhanced the phosphorylation while guanosine triphosphate (GTP) decreased the radiolabeling of p36 indicating that GTP can compete with ATP for the nucleotide triphosphate binding site of p36 kinase. Thus was verified using radiolabeled GTP as the phosphate donor. Competition experiments with GTP gamma S, ATP, GTP, CTP, and uridine triphosphate (UTP) indicated that the phosphate donor site of p36 kinase is relatively non-specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties of CAR-kinase: the enzyme that phosphorylates the cAMP chemotactic receptor of D. discoideum

The cell surface cAMP chemotactic receptor of D. discoideum can be phosphorylated in partially purified plasma membrane preparations in a ligand-dependent manner. CAR-kinase, the enzyme responsible for receptor phosphorylation, was shown to be an integral membrane protein. It could utilize either ATP or GTP to phosphorylate the receptor, although ATP was much more efficient. The apparent affinity constant for ATP was approximately 20-25 microM. Maximum CAR-kinase activity was observed between pH 6.5 and pH7, and required the presence of Mg2+. Neither Mn2+ nor Ca2+ could substitute for that divalent cation. The enzyme was found to be sensitive to the ionic strength and temperature of the incubation reaction. Dephosphorylation of the receptor was not observed in the membrane preparations, indicating that the enhanced level of receptor phosphorylation that occurred upon ligand binding was not an indirect reflection of receptor dephosphorylation and subsequent incorporation of radiolabeled phosphate.

Localization of functional domains of the cAMP chemotactic receptor of Dictyostelium discoideum

The topography and functional domains of the cAMP chemotactic receptor of Dictyostelium discoideum were investigated by protease sensitivity to chymotrypsin. Proteolytic digestion of intact cells produced a 23-kDa fragment of the receptor that retained the photoaffinity label used to identify the receptor. Additionally, this fragment contained the sites phosphorylated by CAR-kinase, the enzyme that phosphorylates the ligand-occupied form of the receptor. The fragment was also found to be phosphorylated in response to cAMP stimulation of cells. Proteolytic digestion of either intact cells or membrane preparations did not appreciably alter the binding properties of the receptor, indicating that the domains which determine the cAMP binding pocket are likely to be transmembrane regions of the protein. Additionally, the sensitivity of down-regulated receptors to chymotrypsin digestion suggests that the initial loss of cAMP binding activity upon incubation of cells with high concentrations of ligand does not require receptor internalization.