Identification of a Hippocampus-to-Zona Incerta Projection involved in Motor Learning.

Motor learning (ML), which plays a fundamental role in growth and physical rehabilitation, involves different stages of learning and memory processes through different brain regions. However, the neural mechanisms that underlie ML are not sufficiently understood. Here, a previously unreported neuronal projection from the dorsal hippocampus (dHPC) to the zona incerta (ZI) involved in the regulation of ML behaviors is identified. Using recombinant adeno-associated virus, the projections to the ZI are surprisingly identified as originating from the dorsal dentate gyrus (DG) and CA1 subregions of the dHPC. Furthermore, projection-specific chemogenetic and optogenetic manipulation reveals that the projections from the dorsal CA1 to the ZI play key roles in the acquisition and consolidation of ML behaviors, whereas the projections from the dorsal DG to the ZI mediate the retrieval/retention of ML behaviors. The results reveal new projections from the dorsal DG and dorsal CA1 to the ZI involved in the regulation of ML and provide insight into the stages over which this regulation occurs.

Predominance of the Blastocystis subtype ST5 among free-living sympatric rodents within pig farms in China suggests a novel transmission route from farms.

Blastocystis is a parasitic protist that can infect humans and various domestic and wild animals. However, there is limited research on the prevalence of this parasite among rodents, particularly those living in pig farm settings. Therefore, to investigate the occurrence, molecular characterization, and zoonotic potential of Blastocystis among rodents within pig farm environments, we conducted an investigation of 227 rodents and shrews from 34 pig farms located in Henan, Shaanxi, and Shanxi provinces of China using nested PCR of the SSU rRNA gene of Blastocystis. The potential transmission and public health implications were also assessed from a One Health perspective. Blastocystis was detected in 86 (37.9%) fecal samples. The highest infection rate was observed among Ruttus norvegicus (73.7%, 42/58), followed by Ruttus tanezumi (30.1%, 41/136), and Mus musculus (12.0%, 3/25). However, it was not detected among individuals with Apodemus agrarius (n = 1) and Crocidura shantungensis (n = 7). Five known zoonotic Blastocystis subtypes (ST1-ST5) were identified, with ST4 (51.2%, 44/86) and ST5 (40.7%, 35/86) being the predominant ones, followed by ST1 (3.5%, 3/86), ST3 (3.5%, 3/86), and ST2 (1.2%, 1/86). ST4 was prevalent among R. norvegicus (83.3%, 35/42), while ST5 dominated R. tanezumi (70.7%, 29/41). Furthermore, ST5 exhibited the widest distribution at pig farm level, accounting for 65.0% (13/20) of Blastocystis-positive pig farms. This investigation presents the first documented Blastocystis infection in R. tanezumi and M. musculus, highlighting the predominant presence of the zoonotic ST5 subtype in rodents for the first time. The results demonstrate that sympatric rodents can serve as natural reservoirs for Blastocystis and play a role in its transmission. These findings provide information on the dynamics of rodent transmission and emphasize the potential public health threat posed by zoonotic Blastocystis subtypes spillover from pig farms.

Correction to "Rapamycin Inhibits Osteoclastogenesis and Prevents LPS-Induced Alveolar Bone Loss by Oxidative Stress Suppression".

[This corrects the article DOI: 10.1021/acsomega.3c01289.].

Metagenomic analysis of gut microbiome and resistome of Whooper and Black Swans: a one health perspective.

BACKGROUND: With the promotion of "One Health," the health of animals and their impact on the environment have become major concerns recently. Widely distributed in China, the whooper swans (Cygnus cygnus) and black swans (Cygnus atratus) are not only important to the ecological environment, but they may also potentially influence public health security. The metagenomic approach was adopted to uncover the impacts of the gut microbiota of swans on host and public health. RESULTS: In this study, the intestinal microbiome and resistome of migratory whooper swans and captive-bred black swans were identified. The results revealed similar gut microbes and functional compositions in whooper and black swans. Interestingly, different bacteria and probiotics were enriched by overwintering whooper swans. We also found that Acinetobacter and Escherichia were significantly enriched in early wintering period swans and that clinically important pathogens were more abundant in black swans. Whooper swans and black swans are potential reservoirs of antibiotic resistance genes (ARGs) and novel ARGs, and the abundance of novel ARGs in whooper swans was significantly higher than that in black swans. Metagenomic assembly-based host tracking revealed that most ARG-carrying contigs originated from Proteobacteria (mainly Gammaproteobacteria). CONCLUSIONS: The results revealed spatiotemporal changes in microbiome and resistome in swans, providing a reference for safeguarding public health security and preventing animal epidemics.

Rapamycin Inhibits Osteoclastogenesis and Prevents LPS-Induced Alveolar Bone Loss by Oxidative Stress Suppression.

Periodontitis is a progressive inflammatory skeletal disease characterized by periodontal tissue destruction, alveolar bone resorption, and tooth loss. Chronic inflammatory response and excessive osteoclastogenesis play essential roles in periodontitis progression. Unfortunately, the pathogenesis that contributes to periodontitis remains unclear. As a specific inhibitor of the mTOR (mammalian/mechanistic target of rapamycin) signaling pathway and the most common autophagy activator, rapamycin plays a vital role in regulating various cellular processes. The present study investigated the effects of rapamycin on osteoclast (OC) formation in vitro and its effects on the rat periodontitis model. The results showed that rapamycin inhibited OC formation in a dose-dependent manner by up-regulating the Nrf2/GCLC signaling pathway, thus suppressing the intracellular redox status, as measured by 2',7'-dichlorofluorescein diacetate and MitoSOX. In addition, rather than simply increasing the autophagosome formation, rapamycin increased the autophagy flux during OC formation. Importantly, the anti-oxidative effect of rapamycin was regulated by an increase in autophagy flux, which could be attenuated by blocking autophagy with bafilomycin A1. In line with the in vitro results, rapamycin treatment attenuated alveolar bone resorption in rats with lipopolysaccharide-induced periodontitis in a dose-dependent manner, as assessed by micro-computed tomography, hematoxylin-eosin staining, and tartrate-resistant acid phosphatase staining. Besides, high-dose rapamycin treatment could reduce the serum levels of proinflammatory factors and oxidative stress in periodontitis rats. In conclusion, this study expanded our understanding of rapamycin's role in OC formation and protection from inflammatory bone diseases.

High glutamate concentration reverses the inhibitory effect of microglial adenosine 2A receptor on NLRP3 inflammasome assembly and activation.

NLRP3 inflammasome plays a crucial role in the innate immune system. Our group previously reported that the microglial adenosine 2A receptor (A2AR) regulates canonical neuroinflammation, which is affected by the glutamate concentration. However, the regulatory effect of A2AR on NLRP3 inflammasome and the effects of glutamate concentration remain unknown. Therefore, we aimed to investigate the regulatory effect of microglial A2AR on NLRP3 inflammasome assembly and activation as well as the effects of glutamate concentration on the inflammasome assembly and activation. Experiments were conducted on magnetically sorted primary microglia from P14 mice. The results showed that pharmacological A2AR activation ameliorated NLRP3 activation under no or low glutamate concentrations, but this effect was reversed by high glutamate concentrations. Moreover, the mRNA levels of NLRP3 inflammasome-related genes were not affected by A2AR activation or the glutamate concentration. We further demonstrated that A2AR activation inhibited the interaction between NLRP3 and caspase 1 under no or low glutamate concentrations while promoting their interaction under high glutamate concentrations. The oligomerization of ASC also showed a similar trend. In conclusion, our findings proved that the high glutamate concentration could reverse the inhibition of A2AR on NLRP3 inflammasome activation by modulating its assembly, which provides new insights into the regulatory effect of A2AR on neuroinflammation under different pathological conditions.

Does the Relationship Between Bone Cement and the Intravertebral Cleft of Kummell Disease Affect the Efficacy of PKP?

OBJECTIVE: To study the relationship between distribution of bone cement and intravertebral cleft of patients with Kummell disease on the clinical effect of percutaneous kyphoplasty (PKP). METHODS: According to the relationship between the distribution of bone cement and the cleft in the vertebrae, a total of 92 patients with Kummell disease who underwent PKP in our hospital were divided into 2 groups. Specifically, the bone cement of patients in group A was localized in the cleft of the vertebrae and did not infiltrate around the cleft, while that of group B patients not only filled the cleft of the vertebrae, but also distributed diffusely around the cleft of the vertebrae. The amount of bone cement injected, leakage rate, visual analogue scale (VAS) score, Oswestry Disability Index (ODI), and vertebral imaging changes before operation, and 2 days and 1 year after operation were compared between the 2 groups. RESULTS: The amount of bone cement injected and the permeability of bone cement in group B were higher than those in group A (P < 0.05). The scores of VAS and ODI in both groups were significantly improved after operation, but the two scores in group B were better than those in group A one year after operation. The height of anterior vertebral body and Cobb's angle of kyphosis in the 2 groups were significantly improved after operation, but 1 year after operation, those in group B were better than those in group A. CONCLUSIONS: PKP was an effective method for treating Kummell disease. At the same time, the relationship between the distribution of bone cement and the cleft in the vertebral body was an important factor affecting the curative effect after PKP. The effect of the distribution pattern of bone cement filled with intravertebral cleft and diffusely distributed around the fissures was better than that of bone cement confined in the vertebral cleft.

NLRP3 Inflammasome-Dependent Increases in High Mobility Group Box 1 Involved in the Cognitive Dysfunction Caused by Tau-Overexpression.

Tau hyperphosphorylation is a characteristic alteration present in a range of neurological conditions, such as traumatic brain injury (TBI) and neurodegenerative diseases. Treatments targeting high-mobility group box protein 1 (HMGB1) induce neuroprotective effects in these neuropathologic conditions. However, little is known about the interactions between hyperphosphorylated tau and HMGB1 in neuroinflammation. We established a model of TBI with controlled cortical impacts (CCIs) and a tau hyperphosphorylation model by injecting the virus encoding human P301S tau in mice, and immunofluorescence, western blotting analysis, and behavioral tests were performed to clarify the interaction between phosphorylated tau (p-tau) and HMGB1 levels. We demonstrated that p-tau and HMGB1 were elevated in the spatial memory-related brain regions in mice with TBI and tau-overexpression. Animals with tau-overexpression also had significantly increased nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation, which manifested as increases in apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), activating caspase-1 and interleukin 1 beta (IL-1ß) levels. In addition, NLRP3-/- mice and the HMGB1 inhibitor, glycyrrhizin, were used to explore therapeutic strategies for diseases with p-tau overexpression. Compared with wild-type (WT) mice with tau-overexpression, downregulation of p-tau and HMGB1 was observed in NLRP3-/- mice, indicating that HMGB1 alterations were NLRP3-dependent. Moreover, treatment with glycyrrhizin at a late stage markedly reduced p-tau levels and improved performance in the Y- and T-mazes and the ability of tau-overexpressing mice to build nests, which revealed improvements in spatial memory and advanced hippocampal function. The findings identified that p-tau has a triggering role in the modulation of neuroinflammation and spatial memory in an NLRP3-dependent manner, and suggest that treatment with HMGB1 inhibitors may be a better therapeutic strategy for tauopathies.

The Effect of PCDH15 Gene Variations on the Risk of Noise-induced Hearing Loss in a Chinese Population.

Noise-induced hearing loss (NIHL) is a complex disease caused by interactions between environmental and genetic factors. This study investigated whether genetic variability in protocadherin related 15 (PCDH15) underlies an increased susceptibility to the development of NIHL in a Chinese population. The results showed that compared with the TT genotype of rs11004085, CT/CC genotypes were associated with an increased risk of NIHL [adjusted odds ratio (OR) = 2.64; 95% confidence interval (CI): 1.14-6.11, P = 0.024]. Additionally, significant interactions between the rs11004085 and rs978842 genetic variations and noise exposure were observed in the high-level exposure groups (P < 0.05). Furthermore, the risk haplotype TAGCC was observed when combined with higher levels of noise exposure (P < 0.05). Thus, our study confirms that genetic variations in PCDH15 modify the susceptibility to NIHL development in humans.

Long-term exposure to diesel engine exhaust induced lung function decline in a cross sectional study.

To clarify the effects of lung function following exposure to diesel engine exhaust (DEE), we recruited 137 diesel engine testing workers exposed to DEE and 127 non-DEE-exposed workers as study subjects. We performed lung function tests and measured cytokinesis-block micronucleus (CBMN) cytome index and levels of urinary polycyclic aromatic hydrocarbons (PAHs) metabolites. There was a significant decrease of forced expiratory volume in 1 second (FEV1), ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/ FVC), maximal mid expiratory flow curve (MMF), forced expiratory flow at 50% of FVC (FEF50%), and forced expiratory flow at 75% of FVC (FEF75%) in the DEE-exposed workers than non-DEE-exposed workers (all p<0.05). Among all study subjects, the decreases of FEF75% were associated with the increasing levels of PAHs meta-bolites (p<0.05), and there were negative correlations between FEV1, FEV1/FVC, MMF, FEF50%, and FEF75% with CBMN cytome index (all p<0.05). Our results show that long-term exposure to DEE can induce lung function decline which shows mainly obstructive changes and influence of small airways function. The decreased lung function is associated with internal dosage of DEE exposure, and accompany with the increasing CBMN cytome index.

Development of Job Burden-capital Model of Occupational Stress: An Exploratory Study.

This study proposes a new framework as job burden-capital model for comprehensive assessment on occupational stress. 1618 valid samples were recruited from electronic manufacturing service industry in Hunan province by self-rated questionnaires after written consent. Structural equation model analysis was employed to verify the model by the data collected. The final fitting model has satisfactory fitting goodness (CMIN/DF=5.78, AGFI=0.937, NNFI=0.960, IFI=0.968, RMSEA=0.054). Both of the measurement model and structural model have acceptable path loadings. Job burden and capital could either directly affect occupational outcomes or indirectly influence them through personality. Multi-group structural equation model analyses indicate general applicability of the model to the basic features of such population. The job burden-capital model opens up new horizons for more in-depth study on occupational stress.

Establishment of a reference value for chromium in the blood for biological monitoring among occupational chromium workers.

The concentration of chromium in the blood (CrB) has been confirmed as a biomarker for occupational chromium exposure, but its biological exposure indices (BEIs) are still unclear, so we collected data from the years 2006 and 2008 (Shandong Province, China) to analyze the relationship between the concentration of chromium in the air (CrA) of the workplaces and CrB to establish a reference value of CrB for biological monitoring of occupational workers. The levels of the indicators for nasal injury, kidney (ß2 microglobulin (ß2-MG)), and genetic damages (8-hydroxy-deoxyguanosine (8-OHdG) and micronucleus (MN)) were measured in all subjects of the year 2011 (Henan Province, China) to verify the protective effect in this reference value of CrB. Compared with the control groups, the concentrations of CrA and CrB in chromium exposed groups were significantly higher (P < 0.05). Positive correlations were found between CrA and CrB in chromium exposed groups (r 2006 = 0.60, r 2008 = 0.35) in the years 2006 and 2008. According to the occupational exposure limitation of CrA (50 µg/m(3), China), the reference value of CrB was recommended to 20 µg/L. The levels of nasal injury, ß2-MG, 8-OhdG, and MN were not significantly different between the low chromium exposed group (CrB ≤ 20 µg/L) and the control group, while the levels of ß2-MG, 8-OHdG, and MN were statistically different in the high chromium exposed group than that in the control group. This research proved that only in occupational workers, CrB could be used as a biomarker to show chromium exposure in the environment. The recommended reference value of CrB was 20 µg/L.

How Work Organization Affects the Prevalence of WMSDs: A Case-control Study.

OBJECTIVE: In this study, we aimed at exploring the association between work-related musculoskeletal disorders (WMSDs) and work organization based on a case-control study. METHODS: A total of 1938 workers who claimed to suffer from WMSDs were selected from Beijing, Henan, Hubei, and the Guangdong province. The control group consisted of 2009 workers employed in similar industries without severe disease or musculoskeletal discomforts. We used a modified version of the questionnaire developed by the NMQ and the DMQ to investigate individual and work-related factors. RESULTS: A total of 13 variables (P<0.1) were selected by the chi-square test and finally, 7 variables entered into the equation, with 6 variables reaching statistical significance (P<0.05). The odds ratios (OR) of 'work changing with season' and 'sufficient rest time' did not reach 1 (0.749 and 0.441, respectively). In addition, 'sufficient rest time' seemed to be the stronger protective factor according to its higher standardized coefficient. And 'repetitive work every minute', 'constantly repetitive work' (every day), 'shortage of site personnel', and 'often switching shifts with others' seemed to be the risk factors. CONCLUSION: Work organization may have comprehensive effects on the occurrence of WMSDs. This pattern of associations suggests that further investigation into the mechanism of how work organization affects the prevalence of WMSDs is required.

Screening putative antigens as stimulators in the Mycobacterium bovis interferon-gamma release assay for cattle.

Bovine tuberculosis (BTB) represents not only a significant economic concern, but also an important public health problem. Currently, interferon-gamma (IFN-γ) release assays (IGRAs) are widely used as an adjunct to the tuberculin test (TST) for the diagnosis of BTB. A great number of international studies have demonstrated that the sensitivity of the IFN-γ assay, which uses purified protein derivatives (PPDs) as diagnostic reagents, is superior to that of the TST. However, there are concerns about its specificity, largely because of the cross reactivity of common antigens shared by pathogenic and non-pathogenic mycobacterial species. The use of pathogen-specific antigens theoretically offers the most effective way to improve the specificity of IGRAs. In this study, we evaluated the potential utility of 13 purified recombinant putative antigens, which are highly specific to the Mycobacterium tuberculosis complex, as diagnostic reagents in IGRAs. A CFP-10-ESAT-6 fusion protein (abbreviated CE) displayed the greatest potential, whereas four region of difference 2 (RD2) antigens, especially Rv1985c were identified as potential candidate antigens, and can be included in an IGRA cocktail, together with CE as stimulators in the IFN-γ release assay for the diagnosis of BTB.

[Development of an interferon-gamma ELISPOT for bovine tuberculosis].

We established an ELISPOT for bovine interferon-gamma (BoIFN-γ), and applied it in the diagnosis of bovine tuberculosis (bTB). Monoclonal antibodies that can bind with native BoIFN-γ were screened as the coating antibody and detecting antibody. After optimization of detecting conditions including coating antibody concentration, cell number, and detecting antibody concentration, the ELISPOT assay was established. Peripheral mononuclear cells (PBMCs) isolated from 30 cows were co-cultured with PPD, and detected with the ELISPOT assay. The optimal conditions of ELISPOT assay were 2.5 µg/mL coating antibody 2G5, 2.5 x 10(5) cells/well, and 1 µg/mL detecting antibody Bio-5E11. In these 30 cows tested both with the ELISPOT assay and the BOVIGAM kit, 11 cows were proved to be positive in ELISOPT assay with the sensitivity of 78.6%, and 12 cows were proved to be negative in ELISOPT assay with the specificity of 75%. The ELISPOT assay for BoIFN-γ could be used to detect bTB efficiently and it might be an alternative method for the diagnosis of bTB.

[Immunogenicity evaluation of Mycobacterium tuberculosis MPT83 protein and establishment of serological diagnostic method for bovine tuberculosis detection].

OBJECTIVE: The aim of this study was to express Mycobacterium tuberculosis MPT83 protein and to evaluate its immunogenicity in murine model as well as the serological diagnosis potential value for bovine tuberculosis. METHODS: The fragment of mpt83 gene was amplified and constructed into pET30a(+)-mpt83 recombinant plasmid. MPT83 fusion protein was purified with His affinity chromatography column from strain of BL21(DE3)-pET30a(+)-mpt83 after induced by IPTG, and then used to evaluate its immunogenicity in mice and the potential application in ELISA assay for the detection of bovine tuberculosis. RESULTS: SDS-PAGE and Western blot results show that MPT83 fusion protein was expressed successfully and possessed a good immunological reactivity. Flow cytometry (FCM) analysis displayed decreased expression of CD80 on dendritic cells and up-regulation of CD69 expression on both splenic CD4+ and CD8+ T cells. Meanwhile, more IL-4 specific secreting cell spots rather than those of IFN-γ were detected by ELISPOT assay in C57BL/6 mice injected with the fusion protein. Total 200 serum samples were detected by indirect ELISA based on MPT83 as antigen and the results showed 48.6% positive coincidence rate and 90% negative's compared to results of peripheral blood specific IFN-γ release assay in bovine tuberculosis detection. CONCLUSIONS: MPT83 fusion protein was expressed successfully with capability of eliciting Th2 immune response in mice and could be used for ELISA assay to detect bovine tuberculosis as a serological diagnosis antigen.

Biomarkers for lung epithelium injury in occupational hexavalent chromium-exposed workers.

OBJECTIVE: To evaluate whether Club (Clara) cell protein (CC16) and surfactant-associated protein D (SP-D) can be used as biomarkers for lung injury caused by chromium exposure. METHODS: The concentrations of chromium in the air (CrA), chromium in the blood (CrB), lung function, CC16, SP-D, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were detected in 91 chromium-exposed workers and 38 controls. RESULTS: In chromium-exposed group, the levels of CrA, CrB, SP-D, TNF-α, and IL-6 were significantly higher, whereas forced expiratory volume in one second (FEV1), FEV1/FVC, maximal expiratory flow (MEF), maximum ventilation volume (MVV), CC16, and CC16/SP-D were lower. Negative correlations were shown between CC16, SP-D or CC16/SP-D, and CrB or inflammatory cytokines (TNF-α and IL-6). Positive relationships were shown between CC16 or CC16/SP-D with indicators of lung function. Tobacco smoking and chromium exposure had synergic effects on lung injury. CONCLUSIONS: CC16, as an immunosuppressive protein, and CC16/SP-D can be used as sensitive and noninvasive biomarkers for lung injury. Smoking should be banned in chromium workplaces.

[Prokaryotic expression and immunological characteristics of Mycobacterium tuberculosis Rv1886c].

OBJECTIVE: Ag85B (Rv1886c) is secreted during the early stages of infection by Mycobacterium tuberculosis. The purpose of this study was probed into the immune response against Ag85B in vivo. METHODS: Ag85B was prokaryotic expressed and identified, its immunological characteristics were evaluated with indirect-ELSIA, Sandwich-ELISA and RESULTS: Ag85B was mainly expressed in form of inclusion body enzyme-linked immunospot assay (ELISPOT). confirmed by SDS-PAGE. Western blot analysis shows that the fusion protein had good specific reaction with serum of tuberculosis patient and serum of mice immunized with LM-Ag85B. C57BL/6 mice were subcutaneously immunized with Ag85B, the production of IFN-gamma and IL-4 in the spleen cells was determined by Sandwich ELISA, the level of IFN-gamma was significantly higher than that of IL-4 (P < 0.001) in the Ag85B immunization group, it indicated the protein induced Th1-tendency immune responses. Furthermore, purified protein derivative (PPD) used as coating antigen, antibody titer against Ag85B in murine serum reached 1:6400, it was demonstrated that Ag85B could also induce humoral immune responses. Additionally, C57BL/6 mice were intravenously immunized with M. tb H37Rv and bacillus Calmette-Guérin (BCG) respectively for 42 days, M. tb H37Rv group intended to induce Ag85B specific Th1 type immune response, and its ability of eliciting cellular immunity was significantly stronger than BCG group (P < 0.001). CONCLUSION: Ag85B can affectively induce strongly Th1-tendency immune response and humoral response. Whereas, BCG prime vaccination only can elicit low levels of Ag85B(240-259) specific immune response. The study laid foundation for probing the pathogenic mechanism, the development of novel vaccine and the establishment of clinical diagnostic method.

Generation and application of a 293 cell line stably expressing bovine interferon-gamma.

A stable mammalian cell line expressing highly active bovine interferon-gamma (BoIFN-γ) was generated using Flp recombinase-mediated integration. This recombinant 293 cell line (B1) efficiently secreted FLAG-tagged BoIFN-γ protein into the culture supernatant, as determined by ELISA and Western blot. The recombinant BoIFN-γ exhibited high anti-viral activity, suggesting that the 293 cells expressed BoIFN-γ that structurally and biologically resembled the natural protein. Two monoclonal antibodies (mAbs) with high affinity for the 293 cell-expressed BoIFN-γ were identified using this cell line, and these mAbs can be used for the development of diagnostic kits. Thus, this work demonstrates the successful generation of a 293 cell line that produces large quantities of highly active BoIFN-γ and demonstrates its potential application in the research of bovine infectious diseases.

Association of folate deficiency and selected tumor marker concentrations in long-term hexavalent chromium exposed population.

Both hexavalent chromium [Cr (VI)] exposure and folate deficiency have been associated with increased cancer risks. Our previous studies have found folate deficiency in Cr (VI) exposed population. Here the relationship between some tumor markers and folate status in long-term Cr (VI) exposure was investigated carefully to show the multiple aspects of Cr (VI) carcinogenesis. A group of 115 workers occupationally exposed to chromate and 60 matched, unexposed controls in Shandong province of China were recruited. Environmental and biological exposure assessments including personal exposure to airborne Cr and Cr contents in erythrocytes were performed. Serum folate, plasma total homocysteine (tHcy) and plasma carcinoembryonic antigen (CEA), neuron specific enolase (NSE), squamous cell carcinoma antigen (SCC), cytokeratin fragment antigen 21-1 (CYFRA 21-1), cancer antigen 72-4 (CA72-4), as well as α-fetoprotein (AFP) were measured. Smoking index (SI) was also calculated to discriminate possible confounding effects of smoking status. Serum folate level decreased significantly, while plasma tHcy, CEA, NSE, SCC, CYFRA21-1, CA72-4 and AFP concentrations increased significantly after Cr (VI) exposure. Meanwhile, plasma CEA, NSE and SCC were negatively correlated with serum folate. SI was negatively correlated with serum folate but positively correlated with plasma tHcy, CEA and NSE levels. Present study suggests that folate deficiency was associated with increased cancer risks and might be affected by smoking in Cr (VI) exposed population. Folate might play a key role in Cr (VI) carcinogenesis although further detailed investigations are needed to clarify the mechanism of this process.