ObjectiveTo investigate the molecular mechanisms by which salvianolic acid B （SalB） inhibits epithelial-mesenchymal transition （EMT） in non-small cell lung cancer （NSCLC） by downregulating phosphoribosylaminoimidazole carboxylase and phosphoribosylaminoimidazole succinocarboxamide synthetase （PAICS） expression. MethodsNSCLC A549 cells and normal bronchial epithelial cells （bronchial epithelium transformed with Ad12-SV40 2B， BEAS-2B） were used as models. Cell viability was assessed using the cell counting kit-8 （CCK-8） assay after treatment with SalB （0， 50， 100， 200， 300， 400， 500 μmol·L^-1 for 24 or 48 h to determine effective and safe intervention concentrations. Cell proliferation， cell cycle distribution， and apoptosis were evaluated by 5-ethynyl-2′-deoxyuridine （EdU） staining and flow cytometry， respectively. Wound healing and Transwell invasion assays were performed to assess cell migration and invasion. RNA sequencing combined with bioinformatic analysis was conducted to identify differentially expressed genes and functional enrichment. Molecular docking was used to predict the binding ability between SalB and PAICS， and the cellular thermal shift assay （CETSA） was performed to evaluate the effect of SalB on the thermal stability of the PAICS protein. Western blot （WB） was used to detect the effects of SalB on PAICS and EMT-related proteins （E-cadherin， N-cadherin， Vimentin， Snail， and Slug）. A functional rescue assay was conducted by PAICS overexpression via plasmid transfection. ResultsCompared with the control group， SalB inhibited A549 cell viability in a dose-dependent manner （P<0.05）， and the effective concentrations （≤300 μmol·L^-1） showed no significant cytotoxicity in BEAS-2B cells. Within this concentration range， SalB significantly inhibited A549 cell proliferation， migration， and invasion， and induced G₀/G₁ phase arrest and apoptosis （P<0.05）. Transcriptomic analysis showed that SalB significantly downregulated PAICS expression， and its functions were enriched in cell proliferation and EMT. Bioinformatic analysis indicated that PAICS is highly expressed in lung adenocarcinoma and is associated with poor prognosis （P<0.01）. Molecular docking showed that SalB has strong binding ability to PAICS （binding energy -9.1 kcal·mol^-1. CETSA results showed that SalB significantly increased the thermal stability of the PAICS protein （P<0.05）. WB results showed that， compared with the control group， SalB dose-dependently downregulated PAICS expression， upregulated E-cadherin， and downregulated N-cadherin， Vimentin， Snail， and Slug （P<0.05）. Functional rescue experiments showed that， compared with the empty vector group， PAICS overexpression significantly enhanced A549 cell proliferation， migration， and invasion， promoted cell cycle progression， and inhibited apoptosis （P<0.05）. Meanwhile， compared with the empty vector + SalB-H group， PAICS overexpression partially reversed the inhibitory effects of SalB on malignant phenotypes and EMT-related proteins （N-cadherin， Vimentin， Snail， and Slug）， and downregulated E-cadherin expression （P<0.05，P<0.01）， indicating that PAICS is a key functional target mediating the antitumor effects of SalB. ConclusionSalB effectively inhibits EMT progression and cell cycle progression in A549 cells by downregulating PAICS expression， thereby exerting anti-NSCLC effects. This study not only reveals that PAICS is a key functional target through which SalB regulates EMT， but also provides experimental evidence supporting SalB as a potential candidate drug for inhibiting NSCLC metastasis.

ObjectiveTo investigate the mechanisms by which eupatilin （Eup） inhibits proliferation， invasion， and metastasis of non-small cell lung cancer （NSCLC） through the enhancer of zeste homolog 2/histone H3 lysine 27 trimethylation （EZH2/H3K27me3） signaling pathway. MethodsIn vivo， a subcutaneous xenograft tumor model was established in nude mice using H1299 cells to evaluate the anti-NSCLC effects of Eup. Immunohistochemistry （IHC-P） was used to detect the expression of proliferation- and invasion/metastasis-related proteins， including proliferating cell nuclear antigen （PCNA）， matrix metalloproteinase-2 （MMP-2）， matrix metalloproteinase-9 （MMP-9）， and vascular endothelial growth factor A （VEGFA）. In vitro， cell counting kit-8 （CCK-8） assays were performed to determine the viability of H1299 cells treated with different concentrations of Eup （0-200 μmol·L^-1） and to select appropriate concentrations. Colony formation and 5-ethynyl-2′-deoxyuridine （EdU） assays were used to evaluate cell proliferation. Wound healing and invasion assays were conducted to assess cell migration and invasion. Human umbilical vein endothelial cell （HUVEC） angiogenesis assays were used to evaluate the effects of Eup on angiogenesis. Transcriptomic analysis was performed to identify the targets of Eup in H1299 cells and to explore its major functions. Molecular docking and molecular dynamics simulations were conducted to predict the binding affinity and interaction stability between Eup and its target proteins. Western blot was used to detect the effects of Eup on the expression levels of EZH2/H3K27me3 pathway-related proteins and proliferation- and invasion/metastasis-related proteins， including PCNA， MMP-2， MMP-9， and VEGFA. ResultsIn the subcutaneous xenograft model， compared with the model group， Eup treatment dose-dependently inhibited the growth of H1299 xenograft tumors， and the tumor inhibition rate was significantly increased （P<0.05）. IHC-P results showed that， compared with the model group， high-dose Eup significantly reduced the expression levels of PCNA， MMP-2， MMP-9， and VEGFA in vivo （P<0.05）. In vitro， compared with the control group， Eup inhibited the proliferation， invasion， and metastasis of NSCLC cells in a concentration-dependent manner. Transcriptomic analysis further showed that， compared with the control group， Eup significantly downregulated EZH2 expression， and its functional effects were associated with inhibition of tumor metastasis. Molecular docking and molecular dynamics simulations indicated that Eup exhibited strong binding affinity with EZH2 and stable interactions. Western blot results demonstrated that， compared with the model group， Eup significantly inhibited， in a dose-dependent manner， the expression levels of EZH2， H3K27me3， and proliferation- and invasion/metastasis-related proteins （PCNA， MMP-2， MMP-9， and VEGFA） in both in vivo and in vitro experiments （P<0.05）. In vitro， compared with the control group， overexpression of EZH2 via plasmid transfection partially reversed the inhibitory effects of Eup on the expression of key proteins involved in proliferation and invasion/metastasis in H1299 cells. ConclusionEup effectively inhibits the proliferation， migration， and invasion of H1299 cells both in vivo and in vitro. The underlying mechanism may be related to inhibition of the EZH2/H3K27me3 signaling pathway and downregulation of proliferation- and invasion/metastasis-related proteins， including PCNA， MMP-2， MMP-9， and VEGFA. Eup may serve as a potential therapeutic agent for suppressing proliferation and invasion/metastasis in NSCLC.

Lung cancer， particularly non-small cell lung cancer （NSCLC）， is the malignant tumor with the highest incidence and mortality in China and worldwide. In 2022， the global number of deaths reached 1.8 million， accounting for 18.7% of all cancer-related deaths， seriously threatening human health and life， and posing a severe challenge for prevention and treatment. Although treatment strategies for lung cancer have been continuously enriched in recent years， and progress has been made in targeted therapy and immunotherapy， long-term survival benefits remain limited due to primary or acquired drug resistance， low immune responsiveness， and chemotherapy-related toxicities. Therefore， there is an urgent need to explore safe and effective adjunctive therapeutic strategies. Traditional Chinese medicine （TCM）， with its advantages of holistic regulation and individualized syndrome differentiation， has played an increasingly prominent role in comprehensive cancer treatment. TCM holds that "Yang deficiency leads to accumulation" is a key pathogenesis of tumors. Based on the theory that "Yang transforms Qi， while Yin forms substance"， deficiency of Yang Qi results in impaired warming and transformation functions， leading to internal accumulation of Yin-cold. This is closely related to dysregulation of the immune microenvironment， "cold tumor" characteristics， and dysfunction of the neuroendocrine system in modern medicine. Accordingly， the therapeutic strategy of "warming Yang， supporting healthy Qi， and combating cancer" has gained increasing attention. In recent years， commonly used Yang-warming Chinese herbs， including Aconiti Lateralis Radix Praeparata， Zingiberis Rhizoma， Cinnamomi Cortex， Epimedii Folium， and Psoraleae Fructus， as well as their active constituents， have achieved notable progress in anti-lung cancer research by regulating multiple signaling pathways， inducing apoptosis， inhibiting metastasis， and reversing drug resistance. In addition， Yang-warming formulae such as Sini Tang and Yanghe Tang have shown promising effects in alleviating myelosuppression， improving cancer-related fatigue， managing malignant pleural effusion， and relieving cancer pain. These therapies exhibit toxicity-reducing and efficacy-enhancing effects， significantly improving patients' quality of life and survival benefits. To systematically summarize the roles and mechanisms of Yang-warming Chinese herbal medicines and compound formulae in lung cancer， this paper provides a comprehensive review of recent advances， aiming to offer insights for the clinical practice of TCM in the prevention and treatment of lung cancer.

ObjectiveTo investigate the molecular mechanisms by which salvianolic acid B （SalB） inhibits epithelial-mesenchymal transition （EMT） in non-small cell lung cancer （NSCLC） by downregulating phosphoribosylaminoimidazole carboxylase and phosphoribosylaminoimidazole succinocarboxamide synthetase （PAICS） expression. MethodsNSCLC A549 cells and normal bronchial epithelial cells （bronchial epithelium transformed with Ad12-SV40 2B， BEAS-2B） were used as models. Cell viability was assessed using the cell counting kit-8 （CCK-8） assay after treatment with SalB （0， 50， 100， 200， 300， 400， 500 μmol·L^-1 for 24 or 48 h to determine effective and safe intervention concentrations. Cell proliferation， cell cycle distribution， and apoptosis were evaluated by 5-ethynyl-2′-deoxyuridine （EdU） staining and flow cytometry， respectively. Wound healing and Transwell invasion assays were performed to assess cell migration and invasion. RNA sequencing combined with bioinformatic analysis was conducted to identify differentially expressed genes and functional enrichment. Molecular docking was used to predict the binding ability between SalB and PAICS， and the cellular thermal shift assay （CETSA） was performed to evaluate the effect of SalB on the thermal stability of the PAICS protein. Western blot （WB） was used to detect the effects of SalB on PAICS and EMT-related proteins （E-cadherin， N-cadherin， Vimentin， Snail， and Slug）. A functional rescue assay was conducted by PAICS overexpression via plasmid transfection. ResultsCompared with the control group， SalB inhibited A549 cell viability in a dose-dependent manner （P<0.05）， and the effective concentrations （≤300 μmol·L^-1） showed no significant cytotoxicity in BEAS-2B cells. Within this concentration range， SalB significantly inhibited A549 cell proliferation， migration， and invasion， and induced G₀/G₁ phase arrest and apoptosis （P<0.05）. Transcriptomic analysis showed that SalB significantly downregulated PAICS expression， and its functions were enriched in cell proliferation and EMT. Bioinformatic analysis indicated that PAICS is highly expressed in lung adenocarcinoma and is associated with poor prognosis （P<0.01）. Molecular docking showed that SalB has strong binding ability to PAICS （binding energy -9.1 kcal·mol^-1. CETSA results showed that SalB significantly increased the thermal stability of the PAICS protein （P<0.05）. WB results showed that， compared with the control group， SalB dose-dependently downregulated PAICS expression， upregulated E-cadherin， and downregulated N-cadherin， Vimentin， Snail， and Slug （P<0.05）. Functional rescue experiments showed that， compared with the empty vector group， PAICS overexpression significantly enhanced A549 cell proliferation， migration， and invasion， promoted cell cycle progression， and inhibited apoptosis （P<0.05）. Meanwhile， compared with the empty vector + SalB-H group， PAICS overexpression partially reversed the inhibitory effects of SalB on malignant phenotypes and EMT-related proteins （N-cadherin， Vimentin， Snail， and Slug）， and downregulated E-cadherin expression （P<0.05，P<0.01）， indicating that PAICS is a key functional target mediating the antitumor effects of SalB. ConclusionSalB effectively inhibits EMT progression and cell cycle progression in A549 cells by downregulating PAICS expression， thereby exerting anti-NSCLC effects. This study not only reveals that PAICS is a key functional target through which SalB regulates EMT， but also provides experimental evidence supporting SalB as a potential candidate drug for inhibiting NSCLC metastasis.

ObjectiveTo investigate the mechanisms by which eupatilin （Eup） inhibits proliferation， invasion， and metastasis of non-small cell lung cancer （NSCLC） through the enhancer of zeste homolog 2/histone H3 lysine 27 trimethylation （EZH2/H3K27me3） signaling pathway. MethodsIn vivo， a subcutaneous xenograft tumor model was established in nude mice using H1299 cells to evaluate the anti-NSCLC effects of Eup. Immunohistochemistry （IHC-P） was used to detect the expression of proliferation- and invasion/metastasis-related proteins， including proliferating cell nuclear antigen （PCNA）， matrix metalloproteinase-2 （MMP-2）， matrix metalloproteinase-9 （MMP-9）， and vascular endothelial growth factor A （VEGFA）. In vitro， cell counting kit-8 （CCK-8） assays were performed to determine the viability of H1299 cells treated with different concentrations of Eup （0-200 μmol·L^-1） and to select appropriate concentrations. Colony formation and 5-ethynyl-2′-deoxyuridine （EdU） assays were used to evaluate cell proliferation. Wound healing and invasion assays were conducted to assess cell migration and invasion. Human umbilical vein endothelial cell （HUVEC） angiogenesis assays were used to evaluate the effects of Eup on angiogenesis. Transcriptomic analysis was performed to identify the targets of Eup in H1299 cells and to explore its major functions. Molecular docking and molecular dynamics simulations were conducted to predict the binding affinity and interaction stability between Eup and its target proteins. Western blot was used to detect the effects of Eup on the expression levels of EZH2/H3K27me3 pathway-related proteins and proliferation- and invasion/metastasis-related proteins， including PCNA， MMP-2， MMP-9， and VEGFA. ResultsIn the subcutaneous xenograft model， compared with the model group， Eup treatment dose-dependently inhibited the growth of H1299 xenograft tumors， and the tumor inhibition rate was significantly increased （P<0.05）. IHC-P results showed that， compared with the model group， high-dose Eup significantly reduced the expression levels of PCNA， MMP-2， MMP-9， and VEGFA in vivo （P<0.05）. In vitro， compared with the control group， Eup inhibited the proliferation， invasion， and metastasis of NSCLC cells in a concentration-dependent manner. Transcriptomic analysis further showed that， compared with the control group， Eup significantly downregulated EZH2 expression， and its functional effects were associated with inhibition of tumor metastasis. Molecular docking and molecular dynamics simulations indicated that Eup exhibited strong binding affinity with EZH2 and stable interactions. Western blot results demonstrated that， compared with the model group， Eup significantly inhibited， in a dose-dependent manner， the expression levels of EZH2， H3K27me3， and proliferation- and invasion/metastasis-related proteins （PCNA， MMP-2， MMP-9， and VEGFA） in both in vivo and in vitro experiments （P<0.05）. In vitro， compared with the control group， overexpression of EZH2 via plasmid transfection partially reversed the inhibitory effects of Eup on the expression of key proteins involved in proliferation and invasion/metastasis in H1299 cells. ConclusionEup effectively inhibits the proliferation， migration， and invasion of H1299 cells both in vivo and in vitro. The underlying mechanism may be related to inhibition of the EZH2/H3K27me3 signaling pathway and downregulation of proliferation- and invasion/metastasis-related proteins， including PCNA， MMP-2， MMP-9， and VEGFA. Eup may serve as a potential therapeutic agent for suppressing proliferation and invasion/metastasis in NSCLC.

Lung cancer， particularly non-small cell lung cancer （NSCLC）， is the malignant tumor with the highest incidence and mortality in China and worldwide. In 2022， the global number of deaths reached 1.8 million， accounting for 18.7% of all cancer-related deaths， seriously threatening human health and life， and posing a severe challenge for prevention and treatment. Although treatment strategies for lung cancer have been continuously enriched in recent years， and progress has been made in targeted therapy and immunotherapy， long-term survival benefits remain limited due to primary or acquired drug resistance， low immune responsiveness， and chemotherapy-related toxicities. Therefore， there is an urgent need to explore safe and effective adjunctive therapeutic strategies. Traditional Chinese medicine （TCM）， with its advantages of holistic regulation and individualized syndrome differentiation， has played an increasingly prominent role in comprehensive cancer treatment. TCM holds that "Yang deficiency leads to accumulation" is a key pathogenesis of tumors. Based on the theory that "Yang transforms Qi， while Yin forms substance"， deficiency of Yang Qi results in impaired warming and transformation functions， leading to internal accumulation of Yin-cold. This is closely related to dysregulation of the immune microenvironment， "cold tumor" characteristics， and dysfunction of the neuroendocrine system in modern medicine. Accordingly， the therapeutic strategy of "warming Yang， supporting healthy Qi， and combating cancer" has gained increasing attention. In recent years， commonly used Yang-warming Chinese herbs， including Aconiti Lateralis Radix Praeparata， Zingiberis Rhizoma， Cinnamomi Cortex， Epimedii Folium， and Psoraleae Fructus， as well as their active constituents， have achieved notable progress in anti-lung cancer research by regulating multiple signaling pathways， inducing apoptosis， inhibiting metastasis， and reversing drug resistance. In addition， Yang-warming formulae such as Sini Tang and Yanghe Tang have shown promising effects in alleviating myelosuppression， improving cancer-related fatigue， managing malignant pleural effusion， and relieving cancer pain. These therapies exhibit toxicity-reducing and efficacy-enhancing effects， significantly improving patients' quality of life and survival benefits. To systematically summarize the roles and mechanisms of Yang-warming Chinese herbal medicines and compound formulae in lung cancer， this paper provides a comprehensive review of recent advances， aiming to offer insights for the clinical practice of TCM in the prevention and treatment of lung cancer.

Alzheimer’s disease (AD) is a central neurodegenerative disease characterized by progressive cognitive decline and memory impairment in clinical. Currently, there are no effective treatments for AD. In recent years, a variety of therapeutic approaches from different perspectives have been explored to treat AD. Although the drug therapies targeted at the clearance of amyloid β-protein (Aβ) had made a breakthrough in clinical trials, there were associated with adverse events. Neuroinflammation plays a crucial role in the onset and progression of AD. Continuous neuroinflammatory was considered to be the third major pathological feature of AD, which could promote the formation of extracellular amyloid plaques and intracellular neurofibrillary tangles. At the same time, these toxic substances could accelerate the development of neuroinflammation, form a vicious cycle, and exacerbate disease progression. Reducing neuroinflammation could break the feedback loop pattern between neuroinflammation, Aβ plaque deposition and Tau tangles, which might be an effective therapeutic strategy for treating AD. Traditional Chinese herbs such as Polygonum multiflorum and Curcuma were utilized in the treatment of AD due to their ability to mitigate neuroinflammation. Non-steroidal anti-inflammatory drugs such as ibuprofen and indomethacin had been shown to reduce the level of inflammasomes in the body, and taking these drugs was associated with a low incidence of AD. Biosynthetic nanomaterials loaded with oxytocin were demonstrated to have the capability to anti-inflammatory and penetrate the blood-brain barrier effectively, and they played an anti-inflammatory role via sustained-releasing oxytocin in the brain. Transplantation of mesenchymal stem cells could reduce neuroinflammation and inhibit the activation of microglia. The secretion of mesenchymal stem cells could not only improve neuroinflammation, but also exert a multi-target comprehensive therapeutic effect, making it potentially more suitable for the treatment of AD. Enhancing the level of TREM2 in microglial cells using gene editing technologies, or application of TREM2 antibodies such as Ab-T1, hT2AB could improve microglial cell function and reduce the level of neuroinflammation, which might be a potential treatment for AD. Probiotic therapy, fecal flora transplantation, antibiotic therapy, and dietary intervention could reshape the composition of the gut microbiota and alleviate neuroinflammation through the gut-brain axis. However, the drugs of sodium oligomannose remain controversial. Both exercise intervention and electromagnetic intervention had the potential to attenuate neuroinflammation, thereby delaying AD process. This article focuses on the role of drug therapy, gene therapy, stem cell therapy, gut microbiota therapy, exercise intervention, and brain stimulation in improving neuroinflammation in recent years, aiming to provide a novel insight for the treatment of AD by intervening neuroinflammation in the future.

BACKGROUND:More and more animal experiments and clinical studies have confirmed that electrical stimulation can promote the repair of peripheral nerve injury,but the specific mechanism is not yet fully understood. OBJECTIVE:To investigate the effect of electrical stimulation-induced miR-741-3p regulating Radil on Schwann cell migration. METHODS:(1)Twelve male SD rats were randomly divided into electrical stimulation group and control group.The electrical stimulation group received continuous electrical stimulation for 7 days after sciatic nerve compression injury,while the control group was not treated after sciatic nerve compression.The injured nerves were taken on day 7 after operation.The expression difference of miR-741-3p between the two groups was verified by fluorescence in situ hybridization.(2)The target genes of miR-741-3p were predicted by miRDB,TargetScan,and miRWalk databases.(3)Schwann cells were transfected with miR-741-3p mimetic and its control,miR-741-3p inhibitor and its control,Radil siRNA and its control,miR-741-3p inhibitor+Radil siRNA and miR-741-3p inhibitor+siRNA control.The transfection efficiency was detected by RT-PCR.The migration ability of Schwann cells was detected by Transwell chamber. RESULTS AND CONCLUSION:(1)The fluorescence intensity of miR-741-3p in the electrical stimulation group was lower than that in the control group.(2)The results of database prediction showed that 69 genes might be the target genes of miR-741-3p.Radil was one of the predicted target genes,which was mainly involved in cell adhesion and migration.(3)Compared with the miR-741-3p inhibitor control group,the number of Schwann cell migration increased in the miR-741-3p inhibitor group(P<0.05).Compared with the miR-741-3p mimic control group,the number of Schwann cell migration in the miR-741-3p mimic group decreased(P<0.05).Compared with the siRNA control group,the number of Schwann cell migration was decreased in the Radil siRNA group(P<0.05).(4)Compared with miR-741-3p inhibitor control group,the expression level of Radil was increased in miR-741-3p inhibitor group.Compared with miR-741-3p mimic control group,the expression level of Radil was decreased in miR-741-3p mimic group.(5)Compared with miR-741-3p inhibitor+siRNA control group,the number of Schwann cell migration was reduced in miR-741-3p inhibitor+Radil siRNA group(P<0.05).The results showed that electrical stimulation promoted the migration of Schwann cells by down-regulating miR-741-3p and targeting Radil gene.

Objective To investigate disparities in health levels among populations across different regions of China and analyze the relationship between these disparities and regional, social, and economic factors, and to provide recommendations to promote health equity. Methods Based on the data from the Seventh National Population Census, this study employed spatial autocorrelation analysis and the spatial Durbin model to conduct spatial and temporal analyses of the health status of the national population from 2012 to 2021, focusing on the regional distribution of health levels and related influencing factors. Results 1. Regional disparities: The mortality rate in Gansu Province rose from 6.05‰ in 2012 to 8.26‰ in 2021, whereas the mortality rate in eastern provinces such as Hainan Province was relatively low in 2021 (5.39‰). 2. Spatial clustering: The spatial correlation of mortality rates was weak (Moran's I: 0.134-0.245), and the high mortality clusters showed a shift from southwest to northeast region. 3. Influencing factors: Economic conditions, education quality, urbanization levels, and healthcare resources significantly impacted population mortality rates. Conclusion The present study identifies pronounced regional disparities in population health, providing a scientific basis for formulating targeted healthcare policies. Additionally, this study highlights the critical importance of spatial analysis in understanding and addressing public health issues to advance health equity.

Objective To explore the mediating role of activities of daily living (ADL) in pain and depressive symptoms in the elderly in China. Methods Utilizing the data from 2020 China Health and Retirement Longitudinal Study, 4403 Chinese elderly individuals aged ≥ 60 years old were selected as the research subjects. Depression Scale (CES-D 10) of the Center for Epidemiological Survey and ADL scale were used in the study. The PROCESS4.1 macro was used to test the mediating effect of daily living activities between pain and depressive symptoms, and the Bootstrap method was applied for verification of the mediating variables. Results A total of 2368 cases of depressive symptoms were detected in the elderly in China, with a detection rate of 53.78%. Pain was positively correlated with depressive symptoms (r=0.27, P<0.01), and activities of daily living were negatively correlated with pain and depressive symptoms (r=-0.27, -0.337, P<0.01). The results showed that the total effect value of pain on depressive symptoms was 0.33, the direct effect value was 0.24, and the mediating effect value of daily living activities was 0.09, accounting for 27.27%. Conclusion Pain and activities of daily living are important factors influencing depressive symptoms in the elderly, and activities of daily living play a partial mediating role in the relationship between pain and depressive symptoms in the elderly.