Catalytically inactive DNA ligase IV promotes DNA repair in living cells.

DNA double strand breaks (DSBs) are induced by external genotoxic agents (ionizing radiation or genotoxins) or by internal processes (recombination intermediates in lymphocytes or by replication errors). The DNA ends induced by these genotoxic processes are often not ligatable, requiring potentially mutagenic end-processing to render ends compatible for ligation by non-homologous end-joining (NHEJ). Using single molecule approaches, Loparo et al. propose that NHEJ fidelity can be maintained by restricting end-processing to a ligation competent short-range NHEJ complex that 'maximizes the fidelity of DNA repair'. These in vitro studies show that although this short-range NHEJ complex requires DNA ligase IV (Lig4), its catalytic activity is dispensable. Here using cellular models, we show that inactive Lig4 robustly promotes DNA repair in living cells. Compared to repair products from wild-type cells, those isolated from cells with inactive Lig4 show a somewhat increased fraction that utilize micro-homology (MH) at the joining site consistent with alternative end-joining (a-EJ). But unlike a-EJ in the absence of NHEJ, a large percentage of joints isolated from cells with inactive Lig4 occur with no MH - thus, clearly distinct from a-EJ. Finally, biochemical assays demonstrate that the inactive Lig4 complex promotes the activity of DNA ligase III (Lig3).

Metabolism and elimination kinetics of mono-hydroxylated PAHs metabolites following single exposure to different combinations of PAH4 in rats.

The metabolism of polycyclic aromatic hydrocarbons (PAHs) and the elimination kinetics of their mono-hydroxylated metabolites (OH-PAHs) following single exposure to different combinations of four PAHs (PAH4) were studied. Male Sprague-Dawley rats were orally exposed to a single dose of benzo[a]pyrene (B[a]P) or PAH2 (B[a]P + chrysene), PAH3 (B[a]P + chrysene + benz[a]anthracene), and PAH4 (B[a]P + chrysene + B[a]A + benzo[b]fluoranthene) with each combination adjusted to the same dose of individual compound. OH-PAHs including 3-hydroxybenzo[a]pyrene, 3-hydroxychrysene, 3-hydroxybenz[a]anthracene, and 1-hydroxypyrene (1-OHP) were detected in serum and urine samples collected at six intervals over a 72-h period post-dosing. The hepatic mRNA levels of cytochrome P450 (CYPs) were determined to ascertain the expression induction of PAHs metabolic enzymes. Results showed OH-PAHs (except 1-OHP) peaked within 8 h in serum and were excreted from urine within 24-48 h. The serum and urinary concentration of 3-hydroxybenzo[a]pyrene was significantly increased after PAH4 exposure compared with other PAHs combinations. Inversely, urinary concentration of 3-hydroxychrysene was decreased after PAH4 exposure, and the kinetics of 3-hydroxybenz[a]anthracene or 1-OHP were not different depending on the PAHs combinations. Also, CYPs were markedly induced by PAHs. Notably, the induction levels of CYP1A1 and CYP1B1 were significantly higher after PAH4 exposure compared with B[a]P exposure. The results indicated the metabolism of B[a]P was accelerated after PAH4 exposure which might be partly due to the induction of CYPs. These results confirmed PAHs are rapidly metabolized and suggested potential interactions of PAHs may happen among PAH4 mixture.

[Comparative study on the essential composition content of commercial follow-up formula for young children with the requirements in the new national food safety standard in China from 2017 to 2022].

OBJECTIVE: To understand the distribution of the essential composition content of commercial follow-up formula for young children in China, to analyze the differences with the new requirements of national food safety standard, and to promote the implementation of the new national standard(GB 10767-2021). METHODS: The label information on the total of 483 follow-up formula for young children permitted from January 2017 to June 2022 were collected and recorded, the distribution of essential compositions were analyzed and compared with the new national food safety standard. RESULTS: Compared with GB 10767-2010, 23 essential compositions were revised in the new national standard, 2 new essential compositions, α-linolenic acid and carbohydrates, were required, and 8 minimum requirements and 4 maximum requirements were revised, 16 new maximum requirements were developed. The whole change of the new standard was major. Comparing with GB 10767-2021, there were 8 essential compositions in commercial products with 100% compliance rate and 9 with more than 95% compliance rate, the discordance rate of pantothenic acid, folic acid, vitamin C and Vitamin D was more than 20%, Vitamin D has the highest discordance rate 97.10%. CONCLUSION: Although the revision of the essential composition requirements in the new national standard is major, the compliance rate of almost essential compositions is high. A few of individual essential compositions in some commercial products cannot meet the new standards requirements, the main reason is those can not reach the increased new minimum requirements, especially on vitamin D.

Discovery and preclinical evaluations of WX-0593, a novel ALK inhibitor targeting crizotinib-resistant mutations.

ALK gene rearrangements are oncogenic drivers in approximately 5% of NSCLC. Crizotinib, a first generation ALK inhibitor, is widely prescribed for ALK-positive NSCLC in clinic. Resistance to crizotinib and other ALK inhibitors has been problematic. Addressing resistance, here we describe discovery and development of a novel, proprietary spirocyclic diamine-substituted aryl phosphine oxide series of inhibitors, which led to the identification of WX-0593 (16a) as a potent ALK inhibitor. WX-0593 inhibited the activity of both wild type and resistant mutants of ALK in vitro, showed strong antitumor activity in a crizotinib-resistant mouse PDX model. WX-0593 is currently under development in phase II/III clinical trials.

Perianal ulcerative tuberculosis: A case report.

Perianal tuberculosis (TB) is an extremely rare form of mycobacterial infection, in which the anal mucocutaneous junction becomes infected by autoinoculation from an active draining gastrointestinal tract infection. The case of a 73-year-old immunocompetent male patient, who came in with a refractory perianal ulcer is presented. The patient had no history of TB and his lab tests for TB were all negative. A chest X-ray showed streak and nodular opacities in both upper lungs. The ulcer was biopsied twice and a diagnosis of TB was finally rendered by histological examination with confirmatory Polymerase chain reaction (PCR). The lesion was finally cured by intensive anti-TB treatment. Perianal TB needs to be excluded in patients with a refractory perianal ulcer, including immunocompetent cases without TB history. Biopsies and microbiological tests should be performed for any suspicious lesion and repeated if there is high clinical concern. Consideration of differential diagnoses, especially inflammatory bowel disease, is essential. Early and sufficient antitubercular treatment should be initiated to minimize morbidity.

[Eating out of home of urban adults in eighteen provinces (autonomous regions, municipalities) of China in 2017].

OBJECTIVE: To analyze the eating out of home behavior of urban adults in China. METHODS: Samples were chosen from China Food Consumption Survey in 2017. A total of 17 234 participants aged 18 and above were included in the final analysis. The food frequency questionnaire were used to collect eating out of home status in the past week. χ~2 test was used to compare the difference in the rate of eating out of home and dining places among different groups. Non-parametric test was used to compare the differences in dining out times. RESULTS: The overall prevalence of eating out of home was 55.6% in urban adults aged in 2017. The average number of eating out of home was 2.8 times. The proportion of eating in hotels and restaurants was 36.0%. The proportion of eating in the canteen of school, workplace and other places was 19.8%. The rate of eating out of home and dining out times were higher among male, 18-44 years old, people with higher educational level and higher household income. The proportion of students eating in canteen was higher. The proportion of professional technicians and service staff eating in hotels and restaurants were higher. CONCLUSION: Eating out of home is more common among urban adults aged 18 and above in China. Young people aged 18-44 years old eat out more often in the past week. The proportion of people eating in hotels and restaurants is higher.

CXCL12 promotes proliferation of radial glia like cells after traumatic brain injury in rats.

To investigate the effect of CXCL12 on regeneration of radial glia like cells after traumatic brain injury (TBI). We randomly divided 48 rats into 4 groups: (1) the sham group, rats were performed craniotomy only, (2) the control group, saline were injected into the ipsilateral cortex after TBI, (3) the CXCL12 group, CXCL12 were injected, and (4) the CXCL12 + AMD3100 group, a mixture of CXCL12 and AMD3100 were injected. Seven days after TBI, the brain tissues were subjected to immunofluorescence double-labeled staining of BrdU/Nestin, BLBP/Nestin, BLBP/Vimentin, BLBP/SOX2, BLBP/CXCR4, BLBP/DCX. Western Blot assay was used to measure the levels of Nestin, BLBP, and Vimentin. Compared with the control group, CXCL12 treatment significantly increased the number of cells stained with BrdU/Nestin, BLBP/Nestin, and BLBP/Vimentin around the injured cortex and corpus callosum areas. CXCL12 + AMD3100 treatment significantly decreased the number of these cells compared with the CXCL12 treatment and control group. The protein levels of Nestin, BLBP, and Vimentin had the same change trends as those of the immunofluorescence staining. The BLBP/Vimentin positive cells presented with the astrocyte pattern around the injured cortex area but with the RGCs pattern around the injured corpus callosum area. The BLBP positive cells also expressed CXCR4 and SOX2. Altogether, CXCL12 promotes the proliferation of neural precursor cells after TBI by combing to its receptor, CXCR4. The proliferating neural precursor cells presents radial glial cell like cells. The RGCs-like cells can differentiate into immature neurons and promote the migration of immature neurons.

[Contamination of zearalenone and its dietary exposure assessment in coix seed in Shanghai].

OBJECTIVE: To analyze the zearalenone(ZEN) level in coix seed, and assess the risk of dietary exposure of ZEN in coix seed in Shanghai. METHODS: The ZEN contents of 147 coix seed samples collected in Shanghai were determined. The consumption data of 730 adults in Shanghai was collected by questionnaire survey with random sampling method. Dietary intake of ZEN from coix seed in Shanghai was simulated by Monte Carlo simulation. RESULTS: The total detection rate of ZEN in coix seed was 69. 39 %(102/147), with the content range of <1. 0-9361 µg/kg and the average value of 327. 7 µg/kg. The average exposure level of populations to ZEN in coix seed was 0. 0216 µg/(kg·d), which was much lower than the tolerable daily intake(TDI). The high exposure level(P95) of populations to ZEN in coix seed was 0. 0609 µg/(kg·d), which accounted for about 24% of TDI. There were about 1. 1% people with the dietary exposure to ZEN exceeding TDI on the basis of the ZEN contents in coix seed and consumption data of coix seed in Shanghai. CONCLUSION: The health risk of ZEN exposure of coix seed in Shanghai population is lower when taking coix seed regularly, and there are potential health risks when taking coix seed highly contaminated with ZEN at a higher dose for a long time.

Berberine attenuates XRCC1-mediated base excision repair and sensitizes breast cancer cells to the chemotherapeutic drugs.

Berberine (BBR) is a natural isoquinoline alkaloid, which is used in traditional medicine for its anti-microbial, anti-protozoal, anti-diarrhoeal activities. Berberine interacts with DNA and displays anti-cancer activities, yet its effects on cellular DNA repair and on synthetic treatments with chemotherapeutic drugs remain unclear. In this study, we investigated the effects of BBR on DNA repair and on sensitization of breast cancer cells to different types of DNA damage anti-tumoural drugs. We found BBR arrested cells in the cell cycle S phase and induced DNA breaks. Cell growth analysis showed BBR sensitized MDA-MB-231 cells to cisplatin, camptothecin and methyl methanesulfonate; however, BBR had no synergistic effects with hydroxurea and olaparib. These results suggest BBR only affects specific DNA repair pathways. Western blot showed BBR down-regulated XRCC1 expressions, and the rescued XRCC1 recovered the resistance of cancer cells to BBR. Therefore, we conclude that BBR interferes with XRCC1-mediated base excision repair to sensitize cancer cells to chemotherapeutic drugs. These finding can contribute to understanding the effects of BBR on cellular DNA repair and the clinical employment of BBR in treatment of breast cancer.

Inhibitory effect of recombinant human CXCL8(3-72)K11R/G31P on atherosclerotic plaques in a mouse model of atherosclerosis.

Context: Atherosclerosis is a chronic inflammatory disease in which the plaques were built up inside of the artery. Interleukin-8 (IL-8, CXCL8) is an inflammatory factor, known to play an important role in the development of atherosclerosis. G31P is an antagonist of the IL-8 receptor, which plays roles in vascular smooth muscle cell (VSMC) proliferation and migration. Objective: This study is to investigate the therapeutic effect of G31P on atherosclerosis through a mouse model. Materials and methods: A mouse model of atherosclerosis was generated through feeding the ApoE-/- mice with high fat diet for 12 weeks. G31P was injected subcutaneously into the mice. The levels of keratinocyte chemoattractant (KC), CXCR2, TNF-α, and IFN-γ were analyzed through ELISA. The expressions of MMP-2, MMP-9, PCNA, and Mef2a in aortic tissues were detected through RT-qPCR. In A7r5 cells, the levels of p-ERK, ROCK1, and ROCK2 were analyzed by western blot. Intracellular calcium levels were measured through Fluo-3 AM assay. Results and disccussion: G31P suppressed the abnormal lipid profile and decreased the levels of KC, MMP-2, MMP-9, PCNA, and Mef2a in a mouse model of atherosclerosis. In addition, G31P also inhibited the expressions of p-ERK, ROCK1, ROCK2, and decreased the calcium concentrations in A7r5 cells. Conclusions: These findings indicate the potential therapeutic effects of G31P in suppressing the development of atherosclerosis by antagonizing the IL-8 receptor. G31P inhibits the proliferation and migration of VSMCs through regulating the Rho-kinase, ERK, and calcium-dependent pathways.

Analysis of individual and combined estrogenic effects of bisphenol, nonylphenol and diethylstilbestrol in immature rats with mathematical models.

BACKGROUND: Traditional toxicological studies focus on individual compounds. However, this single-compound approach neglects the fact that the mixture exposed to human may act additively or synergistically to induce greater toxicity than the single compounds exposure due to their similarities in the mode of action and targets. Mixture effects can occur even when all mixture components are present at levels that individually do not produce observable effects. So the individual chemical effect thresholds do not necessarily protect against combination effects, an understanding of the rules governing the interactive effects in mixtures is needed. The aim of the study was to test and analyze the individual and combined estrogenic effects of a mixture of three endocrine disrupting chemicals (EDCs), bisphenol A (BPA), nonylphenol (NP) and diethylstilbestrol (DES) in immature rats with mathematical models. METHOD: In the present study, the data of individual estrogenic effects of BPA, NP and DES were obtained in uterotrophic bioassay respectively, the reference points for BPA, NP and DES were derived from the dose-response ralationship by using the traditional no observed adverse effect (NOAEL) or lowest observed adverse effect level (LOAEL) methods, and the benchmark dose (BMD) method. Then LOAEL values and the benchmark dose lower confidence limit (BMDL10) of single EDCs as the dose design basis for the study of the combined action pattern. Mixed prediction models, the 3 × 2 factorial design model and the concentration addition (CA) model, were employed to analyze the combined estrogenic effect of the three EDCs. RESULTS: From the dose-response relationship of estrogenic effects of BPA, NP and DES in the model of the prepuberty rats, the BMDL10(NOAEL) of the estrogenic effects of BPA, NP and DES were 90(120) mg/kg body weight, 6 mg/kg body weight and 0.10(0.25) µg/kg body weight, and the LOAEL of the the estrogenic effects of three EDCs were 240 mg/kg body weight, 15 mg/kg body weight and 0.50 µg/kg body weight, respectively. At BMDL10 doses based on the CA concept and the factorial analysis, the mode of combined effects of the three EDCs were dose addition. Mixtures in LOAEL doses, NP and DES combined effects on rat uterine/body weight ratio indicates antagonistic based on the CA concept but additive based on the factorial analysis. Combined effects of other mixtures are all additive by using the two models. CONCLUSION: Our results showed that CA model provide more accurate results than the factorial analysis, the mode of combined effects of the three EDCs were dose addition, except mixtures in LOAEL doses, NP and DES combined effects indicates antagonistic effects based on the CA model but additive based on the factorial analysis. In particular, BPA and NP produced combination effects that are larger than the effect of each mixture component applied separately at BMDL doses, which show that additivity is important in the assessment of chemicals with estrogenic effects. The use of BMDL as point of departure in risk assessment may lead to underestimation of risk, and a more balanced approach should be considered in risk assessment.

Nuclear PTEN interferes with binding of Ku70 at double-strand breaks through post-translational poly(ADP-ribosyl)ation.

PTEN is a tumor suppressor gene characterized as a phosphatase that antagonizes the phosphatidylinositol 3-kinase signaling pathway in the cytoplasm. Nuclear PTEN plays roles in chromosomal stability, in which the double-strand breaks (DSB) repair mediated by homologous recombination (HR) and non-homologous end joining (NHEJ) is critical. Herein, the role of nuclear PTEN in DSB repair and the underlying molecular mechanism was investigated in this study. Using human breast cancer BT549 and MDA-MB-231 cell lines, we reveal a specific feature of PTEN that controls poly(ADP-ribosyl)ation of Ku70 and interferes with binding of Ku70 at DSB. Plasmid-based end joining and reporter assays showed that nuclear PTEN restrained NHEJ efficacy. Electrophoretic mobility shift assays showed that nuclear PTEN impaired Ku70 complex binding to DSB by 3-fold. Co-immunoprecipitation assay showed PTEN regulated poly(ADP-ribosyl)ation of Ku70 instead of directly interacting with Ku70, while PTEN promoted the poly(ADP-ribosyl)ation of PARP1 and induced the degradation of PARP1 in PTEN-WT cells exposed to DSB agents. Of note, the role of PTEN in DSB repair mostly depends on its nuclear localization rather than its phosphatase activity. As a result, the absence of nuclear PTEN rather than phosphatase-negative PTEN confers cell hypersensitivity to anti-tumor DNA damage drugs. This finding contributes to understanding the effect of PTEN in repair of DSB and using defined anti-tumor DSB drugs to treat tumor cells with aberrant PTEN.

Discovery and optimization of selective FGFR4 inhibitors via scaffold hopping.

Introduction of a Michael acceptor on a flexible scaffold derived from pan-FGFR inhibitors has successfully yielded a novel series of highly potent FGFR4 inhibitors with selectivity over FGFR1. Due to reduced lipophilicity and aromatic ring count, this series demonstrated improved solubility and permeability. However, plasma instability and fast metabolism limited its potential for in vivo studies. Efforts have been made to address these problems, which led to the discovery of compound (-)-11 with improved stability, CYP inhibition, and good activity/selectivity for further optimization.

From a novel HTS hit to potent, selective, and orally bioavailable KDM5 inhibitors.

A high-throughput screening (HTS) of the Genentech/Roche library identified a novel, uncharged scaffold as a KDM5A inhibitor. Lacking insight into the binding mode, initial attempts to improve inhibitor potency failed to improve potency, and synthesis of analogs was further hampered by the presence of a C-C bond between the pyrrolidine and pyridine. Replacing this with a C-N bond significantly simplified synthesis, yielding pyrazole analog 35, of which we obtained a co-crystal structure with KDM5A. Using structure-based design approach, we identified 50 with improved biochemical, cell potency and reduced MW and lower lipophilicity (LogD) compared with the original hit. Furthermore, 50 showed lower clearance than 9 in mice. In combination with its remarkably low plasma protein binding (PPB) in mice (40%), oral dosing of 50 at 5mg/kg resulted in unbound Cmax ∼2-fold of its cell potency (PC9 H3K4Me3 0.96µM), meeting our criteria for an in vivo tool compound from a new scaffold.

CXCL12/CXCR4 Axis Improves Migration of Neuroblasts Along Corpus Callosum by Stimulating MMP-2 Secretion After Traumatic Brain Injury in Rats.

To investigate the effect of CXCL12 on migration of neural precursor cells after traumatic brain injury (TBI). We randomly divided 48 rats into four groups: (1) the sham group, rats were performed craniotomy only, (2) the control group, saline were injected into the ipsilateral cortex after TBI, (3) the CXCL12 group, CXCL12 were injected into the ipsilateral cortex after TBI, and (4) the CXCL12 + AMD3100 group, CXCL12 and AMD3100 were mixed together and injected into the ipsilateral cortex after TBI. At 7 days after TBI, the brain tissues were subjected to immunofluorescent double-labeled staining with the antibodies of CXCR4/DCX, MMP-2/DCX, MMP-2/GFAP, MMP-2/NeuN. Western blot assay was used to measure the protein levels of MMP-2. Compared with the control group, the number of CXCR4/DCX and MMP-2 positive cells around the injured corpus callosum area were significantly increased in the CXCL12 treatment group. The area occupied by these cells expanded and the shape changed from chain distribution to radial. CXCL12 + AMD3100 treatment significantly decreased the number and distribution area of CXCR4/DCX and MMP-2 positive cells compared with the CXCL12 treatment and control group. The DCX positive cells could not form chain or radial distribution. The protein expressions of MMP-2 had the similar change trends as the results of immunofluorescent staining. MMP-2 could be secreted by DCX, GFAP and NeuN positive cells. CXCL12/CXCR4 axis can improve the migration of the neuroblasts along the corpus callosum by stimulating the MMP-2 secretion of different types of cells.

Lead optimization of a pyrazolo[1,5-a]pyrimidin-7(4H)-one scaffold to identify potent, selective and orally bioavailable KDM5 inhibitors suitable for in vivo biological studies.

Starting with a lead [1,5-a]pyrimidin-7(4H)-one-containing molecule (1), we generated potent, selective and orally bioavailable KDM5 inhibitors. Using structure- and property-based approaches, we designed 48 with improved cell potency (PC9 H3K4Me3 EC50=0.34µM). Furthermore, 48 maintained suitable physiochemical properties and displayed an excellent pharmacokinetic (PK) profile in mice. When dosed orally in mice at 50mg/kg twice a day (BID), 48 showed an unbound maximal plasma concentration (Cmax) >15-fold over its cell EC50, thereby providing a robust chemical probe for studying KDM5 biological functions in vivo.

Identification of potent, selective KDM5 inhibitors.

This communication describes the identification and optimization of a series of pan-KDM5 inhibitors derived from compound 1, a hit initially identified against KDM4C. Compound 1 was optimized to afford compound 20, a 10nM inhibitor of KDM5A. Compound 20 is highly selective for the KDM5 enzymes versus other histone lysine demethylases and demonstrates activity in a cellular assay measuring the increase in global histone 3 lysine 4 tri-methylation (H3K4me3). In addition compound 20 has good ADME properties, excellent mouse PK, and is a suitable starting point for further optimization.

X-ray repair cross-complementing protein 1 (XRCC1) deficiency enhances class switch recombination and is permissive for alternative end joining.

DNA double-strand breaks (DSBs) are essential intermediates in Ig gene rearrangements: V(D)J and class switch recombination (CSR). In contrast to V(D)J recombination, which is almost exclusively dependent on nonhomologous end joining (NHEJ), CSR can occur in NHEJ-deficient cells via a poorly understand backup pathway (or pathways) often termed alternative end joining (A-EJ). Recently, several components of the single-strand DNA break (SSB) repair machinery, including XRCC1, have been implicated in A-EJ. To determine its role in A-EJ and CSR, Xrcc1 was deleted by targeted mutation in the CSR proficient mouse B-cell line, CH12F3. Here we demonstrate that XRCC1 deficiency slightly increases the efficiency of CSR. More importantly, Lig4 and XRCC1 double-deficient cells switch as efficiently as Lig4-deficient cells, clearly indicating that XRCC1 is dispensable for A-EJ in CH12F3 cells during CSR.

[Dietary intake and risk assessment of diisononyl phthalate (DINP) in Chinese population].

OBJECTIVE: To study DINP concentration level in the main food, evaluate DINP dietary intake level in Chinese population and its potential health risks. METHODS: Based on the deterministic assessment model, using concentration level of 25 kinds of food in 2011 - 2013 and Chinese national nutrition and health survey data in 2002, to calculate dietary intake of DINP in Chinese population. RESULTS: The average DINP concentration level in 24 kinds of foods was 0. 24 mg/kg, and the maximum value was 9. 55 mg/kg. In whole population, average dietary intake of DINP was 4. 39 µg/kg bw per day, only 2. 93% of TDI. The dietary intake of DINP in children aged 2 to 6 years old was highest, with an average of 8. 91 µg/kg bw per day, 5. 94% of the TDI. The dietary intake of DINP in children aged 7 to 12 years old was lower than 2 to 6 years old children, with an average of 6.53 µg/kg bw per day, 4. 35% of TDI. The dietary intake of DINP in high consumer(P97. 5) in all population was 8. 35 µg/kg bw per day, 5. 57% of the TDI. The range of dietary intake of DINP in high consumer (P97. 5) in each group (grouping by gender and age) was from 13. 84 to 5.44 µg/kg bw per day, which were all lower than the TDI. CONCLUSION: The dietary intake of DINP in different populations is considerably below the TDI and any health risk that would be expected to occur at this intake level is negligible.

CXCL12 inhibits cortical neuron apoptosis by increasing the ratio of Bcl-2/Bax after traumatic brain injury.

CXCL12 and its physiologic receptor CXCR4 are involved in controlling cell survival, proliferation and migration in adult tissues. This study aimed to investigate the effects of CXCL12 on cortical neuron apoptosis in rats after traumatic brain injury (TBI) and the potential mechanisms involved. At 3 days after TBI, in situ terminal transferase d-UTP nick-end labeling assay (TUNEL) showed that the apoptotic index (AI) deceased significantly in the CXCL12 treatment group compared with the control group (p < 0.05). Immunofluorescence double-labeled staining revealed that most of the TUNEL positive cells were NeuN positive neurons. The change trends of active caspase-3 expression were similar as those of the AI. The Bcl-2:Bax ratio was upregulated in the CXCL12 group compared with the control group. However, the effect of CXCL12 could be partially reverted by the additional use of AMD3100 (a kind of antagonist of CXCR4) (p < 0.05). Our results indicated that after TBI in rats CXCL12 combing CXCR4 receptors could inhibit the caspase-3 pathway by upregulating Bcl-2:Bax ratio, which protect neurons from apoptosis.