Danggui Buxue Decoction enhances the anticancer activity of gemcitabine and alleviates gemcitabine-induced myelosuppression

Exploration of the Active Component and Mechanisms of Shengyu Decoction Against Myelosuppression Using Network Pharmacology and in vitro Experimental Validation

Background

Chemotherapy-induced myelosuppression (CIM) is a common adverse reaction with a high incidence rate that seriously affects human health. Shengyu Decoction (SYD) is often used to treat CIM. However, its pharmacodynamic basis and therapeutic mechanisms remain unclear.

Purpose

This study aimed to clarify the active components and mechanisms of SYD in CIM.

Methods

LC-QTOF/MS was used to identify the absorbable components of SYD. A series of network pharmacology methods have been applied to explore hub targets and potential mechanisms. Molecular docking was used to identify the binding ability of potential active ingredients and hub targets. Finally, in vitro experiments were performed to validate these findings.

Results

In this study, 33 absorbable prototype components were identified using LC-QTOF/MS. A total of 62 possible targets of SYD in myelosuppression were identified. KEGG pathway enrichment analyses showed that some signaling pathways such as PI3K-Akt and HIF-1 may be the mechanisms by which it functions. Among them, we verified the PI3K-Akt pathway. 6 Hub proteins were screened by Protein-protein interaction (PPI) network analysis. Molecular docking results showed that four absorbable components in SYD showed good binding with six Hub targets. The effectiveness of the four predicted compounds and the mechanism were verified in vitro. It has also been shown that the active component could promote the proliferation of bone marrow stromal cells (BMSCs) and block apoptosis of BMSCs, which may be related to the PI3K-Akt pathway. This result is consistent with the network pharmacology approach and molecular docking predictions.

Conclusion

Our results provided not only the candidate active component of SYD, but also a new insights into mechanism of SYD in the treatment of CIM.

Mechanism of Danggui Buxue decoction in the treatment of myocardial infarction based on network pharmacology and experimental identification

Background

Myocardial infarction (MI) remains one of the major causes of high morbidity and mortality worldwide. Danggui Buxue Decoction (DBD)-an ancient Chinese herbal decoction-has been used to prevent coronary heart disease, which was called "chest palsy" in ancient clinics. However, the mechanism of DBD in the treatment of MI remains unclear. The aim of this study was to explore the effect and mechanism of DBD on MI by combining network pharmacology with in vivo experiments.

Materials and methods

First, public databases were used to identify the key active chemicals and possible targets of DBD. The MI targets were obtained from the Therapeutic Target Database, and the function of the target genes in relation to linked pathways was investigated. Subsequently, Cytoscape software was used to build a target-signaling pathway network. Finally, the efficacy of DBD therapy on MI was validated using in vivo investigations combined with molecular docking.

Results

In traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP), 27 bioactive compounds were screened from DBD. A total of 213 common targets were obtained, including 507 DBD targets and 2566 MI targets. Enrichment analysis suggests that PI3K/AKT is a potential signaling pathway for DBD-based protection. Immunofluorescence and protein blotting confirmed PI3K/AKT1, ERK2, and CASPASE-9 as the target proteins. Molecular docking analysis showed that quercetin, kaempferol, isoflavanones, isorhamnetin, hederagenin, and formononetin had high binding affinity to AKT1, ERK2, and CASPASE-9.

Conclusions

This study demonstrated that the therapeutic benefit of DBD on MI may be mediated via target proteins in the PI3K/AKT pathway, such as AKT1, ERK2, and CASPASE-9. Our study data can help to provide ideas and identify new treatment targets for MI.

Si Jun Zi decoction inhibits the growth of lung cancer by reducing the expression of PD-L1 through TLR4/MyD88/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Si Jun Zi decoction (SJZT) is a traditional Chinese medicine (TCM) formula with the effect of invigorating the spleen qi and replenishing qi. TCM believes that a strong spleen qi helps to strengthen lung qi. Lung cancer is often caused by a deficiency of lung qi. Based on this theory, TCM often applies SJZT to the treatment of lung cancer and has achieved remarkable results. However, the mechanism of SJZT in the treatment of lung cancer remains unclear and requires further study.

AIM OF THE STUDY

The main purpose of this study is to explore the mechanism of SJZT against lung cancer.

MATERIALS AND METHODS

In this study, the chemical constituents in SJZT were analyzed by UPLC-Q-Exactive-MS/MS. MTT and cell scratch test were used to determine the cell viability and inhibition of migration in vitro. The effect of SJZT on the expression of PD-L1 protein in A549 cells was detected by Western Blotting (WB). Apoptosis was detected by crystal violet staining. The mouse model of Lewis lung cancer was established in vivo, and the levels of serum TNF-α and IL-2 were detected by enzyme linked immunosorbent assay (ELISA). The protein levels of TLR4, MyD88, NF-κB and PD-L1 in tumor tissues of mice were detected by WB. Quantitative real-time PCR (qRT-PCR) was used to detect the levels of TLR4, MyD88, NF-κB and PD-L1 mRNA. Finally, hematoxylin and eosin (H&E) staining were used to detect the pathological status of tumor tissues in mice.

RESULTS

A total of 16 active chemical constituents were identified in SJZT. In vitro experiments showed that SJZT could inhibit the growth of A549, induce apoptosis and reduce the expression of PD-L1. In vivo experiments showed that SJZT regulated TLR4/MyD88/NF-κB signaling pathway, decreased the expression of PD-L1, and inhibited tumor growth.

CONCLUSIONS

SJZT inhibits the growth of lung cancer by regulating TLR4/MyD88/NF-κB signal pathway and reducing the expression of PD-L1.

Lipid-like gemcitabine diester-loaded liposomes for improved chemotherapy of pancreatic cancer

Gemcitabine (GEM) is a non-selective chemotherapeutic agent used in the treatment of pancreatic cancer. Its antitumor efficacy is limited by a short plasma half-life and severe adverse reactions. To overcome these shortcomings, four novel lipid-like GEM diesters were synthesized and encapsulated into liposomes. Through optimization, dimyristoyl GEM (dmGEM)-loaded liposomes (LipodmGEM) were successfully obtained with an almost complete encapsulation efficiency. Compared to free GEM, LipodmGEM showed enhanced cellular uptake and cell apoptosis, improved inhibition of cell migration on AsPC-1 cells and a greatly extended half-life (7.22 vs. 1.78 h). LipodmGEM succeeded in enriching the drug in the tumor (5.28 vs. 0.03 μmol/g at 8 h), overcoming a major shortcoming of GEM, showed excellent anticancer efficacy in vivo and negligible systemic toxicity, superior to GEM. Attractive as well, suspensions of LipodmGEM remained stable at 2-10 °C away from light for no <2 years. Our results suggest that LipodmGEM might become of high interest for treating pancreatic cancer while the simple strategy we reported might be explored as well for converting other antitumor drugs with high water-solubility and short plasma half-life into attractive nanomedicines.

Gemcitabine enhances pharmacokinetic exposure of the major components of Danggui Buxue Decoction in rat via the promotion of intestinal permeability and down-regulation of CYP3A for combination treatment of non-small cell lung cancer

CONTEXT

Danggui Buxue Decoction (DBD), a traditional Chinese medicine formula, has the potential to enhance the antitumor effect of gemcitabine in non-small cell lung cancer (NSCLC) treatment by increasing gemcitabine's active metabolites. However, whether gemcitabine affects the pharmacokinetics of DBD's major components remains unclear.

OBJECTIVE

This study evaluates the herb-drug interaction between DBD's major components and gemcitabine and validates the underlying pharmacokinetic mechanism.

MATERIALS AND METHODS

The pharmacokinetics of 3.6 g/kg DBD with and without a single-dose administration of 50 mg/kg gemcitabine was investigated in Sprague-Dawley rats. The effects of gemcitabine on intestinal permeability, hepatic microsomal enzymes in rat tissues, and CYP3A overexpressing HepG2 cells were determined using western blot analysis.

RESULTS

The combination of gemcitabine significantly altered the pharmacokinetic profiles of DBD's major components in rats. The Cmax and AUC of calycosin-7-O-β-d-glucoside notably increased through sodium-glucose transporter 1 (SGLT-1) expression promotion. The AUC of ligustilide and ferulic acid was also significantly elevated with the elimination half-life (t1/2) prolonged by 2.4-fold and 7.8-fold, respectively, by down-regulating hepatic CYP3A, tight junction proteins zonula occludens-1 (ZO-1) and occludin expression.

DISCUSSION AND CONCLUSIONS

Gemcitabine could modulate the pharmacokinetics of DBD's major components by increasing intestinal permeability, enhancing transporter expression, and down-regulating CYP3A. These findings provide critical information for clinical research on DBD as an adjuvant for NSCLC with gemcitabine and help make potential dosage adjustments more scientifically and rationally.

Danggui Buxue decoction alleviates cyclophosphamide-induced myelosuppression by regulating β-hydroxybutyric acid metabolism and suppressing oxidative stress

CONTEXT

Danggui Buxue Decoction (DBD) is an effective complementary medicine in alleviating myelosuppression after chemotherapy (MAC). However, its mechanism of action is elusive.

OBJECTIVE

To illustrate that regulating β-hydroxybutyric acid (β-OHB) metabolism and suppressing oxidative stress could be a potential mechanism of action for DBD in alleviating MAC.

MATERIALS AND METHODS

After HPLC quantification and dose testing (3, 6 and 10 g/kg, gavage) of DBD, Sprague-Dawley rats were divided into control, cyclophosphamide (CTX) (30 mg/kg CTX for 5 days, intraperitoneal administration) and CTX + DBD groups (6 g/kg DBD for 14 days, gavage). Blood cell counts, thigh bone histological examination, β-OHB levels, oxidative stress indices and HDAC1 activity were tested. The biological function of β-OHB was verified in vitro (hBMSC cells were incubated in culture mediums that contained 40 μM CTX and β-OHB in 0, 1, 2.5, 5, 10 mM) and in vivo (MAC rat model, 3 g/kg β-OHB for 14 days, gavage).

RESULTS

Rats in the CTX + DBD group showed upregulated blood cell counts (118-243%), β-OHB levels (495 nmol/mL in blood, 122 nmol/mg in marrow supernatant) and downregulated HDAC1 activity (59%), and oxidative stress indices (60-85%). In vitro, 5 mM β-OHB improved hBMSC cell migration (123%) and proliferation (131%). In vivo, rats treated with 3 g/kg β-OHB showed upregulated blood cell counts (121-182%) and downregulated HDAC1 activity (64%) and oxidative stress indices (65-83%).

DISCUSSION AND CONCLUSIONS

DBD, a traditional Chinese medicine, alleviates MAC by intervening in β-OHB metabolism and oxidative stress.

Evaluation of pharmacological and pharmacokinetic herb-drug interaction between irinotecan hydrochloride injection and Kangai injection in colorectal tumor-bearing mice and healthy rats

Introduction: Kangai (KA) injection, a Chinese herbal injection, is often used in combination with irinotecan (CPT-11) to enhance the effectiveness of anti-colorectal cancer treatment and alleviate side effects. However, the combined administration of this herb-drug pair remains controversial due to limited pre-clinical evidence and safety concerns. This study aimed to determine the pre-clinical herb-drug interactions between CPT-11 and KA injection to provide a reference for their clinical co-administration. Methods: In the pharmacological study, BALB/c mice with CT26 colorectal tumors were divided into four groups and treated with vehicle alone (0.9% saline), CPT-11 injection (100 mg/kg), KA injection (10 mL/kg), or a combination of CPT-11 and KA injection, respectively. The tumor volume of mice was monitored daily to evaluate the therapeutic effect. Daily body weight, survival rate, hematopoietic toxicity, immune organ indices, and gut toxicity were analyzed to study the adverse effects. Healthy Sprague-Dawley rats in the pharmacokinetic study were administered KA injection only (4 mL/kg), or a combination of CPT-11 injection (20 mg/kg) and KA injection, respectively. Six key components of KA injection (oxymatrine, matrine, ginsenoside Rb1, Rg1, Re, and astragaloside IV) in rat plasma samples collected within 24 h after administration were determined by LC-MS/MS. Results: The pharmacological study indicated that KA injection has the potential to enhance the anti-colorectal cancer efficacy of CPT-11 injection and alleviate the severe weight loss induced by CPT-11 injection in tumor-bearing mice. The pharmacokinetic study revealed that co-administration resulted in inhibition of oxymatrine metabolism in rats, evidenced by the significantly reduced Cmax and AUC0-t of its metabolite, matrine (p < 0.05), from 2.23 ± 0.24 to 1.38 ± 0.12 μg/mL and 8.29 ± 1.34 to 5.30 ± 0.79 μg h/mL, respectively. However, due to the similar efficacy of oxymatrine and matrine, this may not compromise the anti-cancer effect of this herb-drug pair. Discussion: This study clarified the pre-clinical pharmacology and pharmacokinetic benefits and risks of the CPT-11-KA combination and provided a reference for their clinical co-administration.

Ze-Qi decoction inhibits non-small cell lung cancer growth and metastasis by modulating the PI3K/Akt/p53 signaling pathway

Background

The Ze-Qi decoction (ZQD) is a traditional Chinese herbal formula commonly applied to treat lung cancer in China. This study aimed to assess the effective ingredients and molecular mechanisms of ZQD in treating non-small cell lung cancer (NSCLC) based on network pharmacology combined with experimental validation.

Methods

Network pharmacology, bioinformatics, and molecular docking analyses were conducted to explore the mechanism of ZQD for treating NSCLC, which was further confirmed by animal experiments.

Results

In total, 117 bioactive ingredients and 499 target proteins of ZQD were identified. Network pharmacology revealed 7 core active ingredients and 74 core target proteins. Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that the PI3K/Akt and p53 signaling pathways may be crucial in NSCLC treatment. Molecular docking analysis revealed that the seven crucial bioactive ingredients complexed with PI3K, Akt, and p53. The animal experiment results validated that ZQD treatment promoted cell apoptosis and cell cycle arrest, thereby inhibiting NSCLC growth and metastasis. Furthermore, ZQD treatment caused a significant increase in p53 and Bax, while leading to a distinct reduction in p-PI3K (Tyr317), p-Akt (Ser473), VEGFA, CD31, MMP2, MMP9, Bcl2, and CDK2.

Conclusions

ZQD inhibited the growth and metastasis of NSCLC subcutaneous tumors in C57BL/6J mice via the PI3K/Akt/p53 signaling pathway.

Analysis of adverse drug reactions/events of cancer chemotherapy and the potential mechanism of Danggui Buxue decoction against bone marrow suppression induced by chemotherapy

Objective: To analyze the clinical characteristics of adverse reactions/events based on chemotherapy in cancer patients, and then explore the potential mechanism of Danggui Buxue Decoction (DBD) against chemotherapy-induced bone marrow suppression (BMS). Methods: Retrospectively collected and evaluated were the clinical data of patients in a hospital who experienced adverse reactions/events brought on by chemotherapeutic medications between 2015 and 2022. We explored the potential mechanism of DBD against BMS using network pharmacology based on the findings of the adverse reactions/events analysis. Results: 151 instances (72.25%) experienced adverse reactions/events from a single chemotherapy medication. Besides, platinum-based medications produced the most unfavorable effects. The study also found that chemotherapy caused the highest number of cases of BMS, including platinum drugs. Consequently, BMS is the most prevalent adverse reaction disease caused by chemotherapy found in this part. According to network pharmacology findings, DBD can prevent BMS primarily involving 1,510 primary targets and 19 key active ingredients. Based on the enrichment analysis, PI3K-AKT, TNF, MAPK, and IL-17 signaling pathways made up the majority of the DBD-resisting BMS pathways. Molecular docking displayed that kaempferol, the major active ingredient of DBD, had the highest binding energy (-10.08 kJ mol-1) with PTGS2 (a key target of BMS). Conclusion: Cancer patients who received chemotherapy had a risk to develop BMS. Regular blood tests should be performed while taking medicine; early discovery and treatment can reduce a patient's risk of experiencing adverse reactions/events. Additionally, this study demonstrated that DBD, through a variety of targets and pathways, may be crucial in avoiding BMS.

Integrated transcriptomic and metabolomic profiles reveal the protective mechanism of modified Danggui Buxue decoction on radiation-induced leukopenia in mice

Leukopenia caused by radiation hinders the continuous treatment of cancers. Danggui Buxue Decoction (DBD) has been widely used in clinical owing to low toxicity and definite therapeutic effects to increase leukocytes. Meanwhile, icaritin (ICT) has also been proved to have the effect of boosting peripheral blood cells proliferation. However, there is no study to prove the efficacy of MDBD (Modified Danggui Buxue Decoction), a derivative herbal formula composed of DBD and ICT, in the treatment of radiation-induced leukopenia. In this study, we performed a model of 3.5 Gy whole-body radiation to induce leukopenia in mice. The results of pharmacodynamic studies demonstrated that MDBD could significantly increase the white blood cells in peripheral blood by improving the activity of bone marrow nuclear cells, reducing bone marrow damage, modulating spleen index, and regulating hematopoietic factors to alleviate leukopenia. We also analyzed the integrated results of metabolomics and transcriptomics and found that MDBD could relieve leukopenia and alleviate bone marrow damage by targeting steroid biosynthesis and IL-17 signaling pathway, in which the key genes are Jun, Cxcl2 and Egr1. Therefore, our study provides a basis for the effectiveness and compatibility in the combination of traditional Chinese medicine formula and small molecule drugs.

Crude polysaccharide from Danggui Buxue decoction enhanced the anti-tumor effect of gemcitabine by remodeling tumor-associated macrophages

Tumor-associated macrophages (TAMs) with an M2-phenotype mediate gemcitabine resistance to cancer by influencing the metabolic enzymes of gemcitabine and releasing competitive deoxycytidine (dC). Our previous studies showed that Danggui Buxue Decoction (DBD), a traditional Chinese medicinal recipe, enhances the anti-tumor activity of gemcitabine in vivo and alleviates gemcitabine-induced myelosuppression. However, the material basis and exact mechanism underlying its enhanced effects remain unclear. In this study, a bioactive polysaccharide consisting of arabinose, mannose, ribose, and glucose was isolated from DBD. In vivo results demonstrated that DBD crude polysaccharide (DBDP) ameliorated gemcitabine-induced immune system disorders. Moreover, DBDP improved the sensitivity of Lewis lung carcinoma-bearing mice to gemcitabine by reshaping the tumor-promoting M2-like macrophages into tumor-inhibiting M1-phenotypes. Furthermore, in vitro results further revealed that DBDP blocked the protective effects of TAMs and M2-macrophages against gemcitabine by inhibiting the excessive secretion of dC and decreasing the high expression of cytidine deaminase. In conclusion, our results demonstrated that DBDP, as the pharmacodynamic material basis of DBD, enhanced the anti-tumor activity of gemcitabine against lung cancer in vitro and in vivo, which was associated with remodeling of the M2-phenotype.

Relationship between HuR and tumor drug resistance

Human resistance protein R (HuR), also known as embryonic lethal abnormal visual-like protein (ELAVL1), is an RNA-binding protein widely expressed in vivo that affects the mRNA stability of targeted and is involved in post-transcriptional regulation. Recent studies have shown that HuR is aberrantly expressed in different human cancers and is an essential factor in poor clinical prognosis. The role of HuR in numerous tumors suggests that it could be a new target for tumor therapy and as a marker for efficacy and prognostic assessment. This review focuses on the relationship between HuR and drug resistance in different tumors and briefly describes the structure, function, and inhibitors of HuR. We summarize the mechanisms by which HuR causes tumor resistance and the molecular targets affected.

Danggui Buxue Tang potentiates the cytotoxicity of 5-fluorouracil on colorectal adenocarcinoma cells: A signaling mediated by c-Jun N-terminal kinase

Danggui Buxue Tang (DBT) is a well-known Chinese herbal recipe often prescribed in clinical treatment for menopausal and cardiovascular symptoms. 5-Fluorouracil (5-FU) is a chemotherapy drug that treats several cancers; however, it causes severe adverse effects and multidrug resistance. Combining natural medications can reduce the side effects of 5-FU use. Hence, we aimed to determine the role of DBT in strengthening the anticancer capabilities of 5-FU in a cultured colorectal adenocarcinoma cell line (HT-29 cell) and xenograft nude mice. HT-29 cells cultured with DBT did not exhibit cytotoxicity. However, co-administration of DBT with 5-FU significantly increased apoptosis and the expression of apoptotic markers. The inhibition of proliferation induced by DBT and 5-FU was shown to be mediated by c-Jun N-terminal kinase signaling. In addition, the potentiation effect of 5-FU and DBT was demonstrated in reducing tumor size, expressions of Ki67 and CD34 in HT-29 xenograft mice. This finding suggests that DBT can work with 5-FU as a novel chemotherapeutic strategy for treating colon cancer.

Mechanisms of Danggui Buxue Tang on Hematopoiesis via Multiple Targets and Multiple Components: Metabonomics Combined with Database Mining Technology

This study aimed to explore the mechanism of action of Danggui Buxue Tang (DBT) with its multiple components and targets in the synergistic regulation of hematopoiesis. Mouse models of hematopoiesis were established using antibiotics. Metabolomics was used to detect body metabolites and enriched pathways. The active ingredients, targets, and pathways of DBT were analyzed using system pharmacology. The results of metabolomics and system pharmacology were integrated to identify the key pathways and targets. A total of 515 metabolites were identified using metabolomics. After the action of antibiotics, 49 metabolites were markedly changed: 23 were increased, 26 were decreased, and 11 were significantly reversed after DBT administration. Pathway enrichment analysis showed that these 11 metabolites were related to bile secretion, cofactor biosynthesis, and fatty acid biosynthesis. The results of the pharmacological analysis showed that 616 targets were related to DBT-induced anemia, which were mainly enriched in biological processes, such as bile secretion, biosynthesis of cofactors, and cholesterol metabolism. Combined with the results of metabolomics and system pharmacology, we found that bile acid metabolism and biotin synthesis were the key pathways for DBT. Forty-two targets of DBT were related to these two metabolic pathways. PPI analysis revealed that the top 10 targets were CYP3A4, ABCG2, and UGT1A8. Twenty-one components interacted with these 10 targets. In one case, a target corresponds to multiple components, and a component corresponds to multiple targets. DBT acts on multiple targets of ABCG2, UGT1A8, and CYP3A4 through multiple components, affecting the biosynthesis of cofactors and bile secretion pathways to regulate hematopoiesis.

Utilizing Bioinformatics Technology to Explore the Potential Mechanism of Danggui Buxue Decoction against NSCLC

While lung cancer poses a serious threat to human health, non-small-cell lung cancer (NSCLC) is the most common type of lung cancer. Danggui Buxue Decoction (DBD) is a classical traditional antitumor medicine commonly used in China. However, the potential mechanism of DBD against NSCLC has not yet been expounded. Therefore, this study clarified the potential molecular mechanism and key targets of DBD in NSCLC treatment through several technological advances, such as network pharmacology, molecular docking, and bioinformatics. Firstly, the relative active ingredients and key DBD targets were analyzed, and subsequently, a drug-ingredient-target-disease network diagram was constructed for NSCLC treatment with DBD, resulting in the identification of five main active ingredients and ten core targets according to the enrichment degree. The enrichment analysis revealed that DBD can achieve the purpose of treating NSCLC through the AGE-RAGE signaling pathway in diabetic complications. Secondly, the molecular docking approach predicted that quercetin and hederagenin have the best working mechanisms with PDE3A and PTGS1, while the survival analysis results depicted that high PDE3A gene expression has a relatively poor prognosis for NSCLC patients (p < 0.05). Additionally, PDE3A is mainly distributed in the LU65 cell line that originated from Asian population. In summary, our study results showed that DBD can treat NSCLC through the synergistic correlation between multiple ingredients, multiple targets, and multiple pathways, thus effectively improving NSCLC prognosis. This study not only reflected the medicinal value of DBD but also provided a solid structural basis for future new drug developments and targeted therapies.

Anticonstriction Effect of MCA in Rats by Danggui Buxue Decoction

Objective: Danggui Buxue decoction (DBD), consisting of Angelicae Sinensis Radix (ASR) and Astragali Radix (AR), is a famous prescription with the function of antivasoconstriction. This study intends to probe its mechanisms on the relaxation of the middle cerebral artery (MCA).

Methods: Vascular tension of rat MCA was measured using a DMT620 M system. First, the identical series of concentrations of DBD, ASR, and AR were added into resting KCl and U46619 preconstricted MCA. According to the compatibility ratio, their dilatation effects were further investigated on KCl and U46619 preconstricted vessels. Third, four K⁺ channel blockers were employed to probe the vasodilator mechanism on KCl-contracted MCA. We finally examined the effects of DBD, ASR, and AR on the vascular tone of U46619-contracted MCA in the presence or absence of Ca²⁺.

Results: Data suggested that DBD, ASR, and AR can relax on KCl and U46619 precontracted MCA with no effects on resting vessels. The vasodilator effect of ASR was greater than those of DBD and AR on KCl-contracted MCA. For U46619-contracted MCA, ASR showed a stronger vasodilator effect than DBD and AR at low concentrations, but DBD was stronger than ASR at high concentrations. Amazingly, the vasodilator effect of DBD was stronger than that of AR at all concentrations on two vasoconstrictors which evoked MCA. The vasodilator effect of ASR was superior to that of DBD at a compatibility ratio on KCl-contracted MCA at low concentrations, while being inferior to DBD at high concentrations. However, DBD exceeded AR in vasodilating MCA at all concentrations. For U46619-constricted MCA, DBD, ASR, and AR had almost identical vasodilation. The dilation of DBD and AR on KCl-contracted MCA was independent of K⁺ channel blockers. However, ASR may inhibit the K⁺ channel opening partially through synergistic interactions with Gli and BaCl₂. DBD, ASR, and AR may be responsible for inhibiting [Ca²⁺]_out, while ASR and AR can also inhibit [Ca²⁺]_in.

Conclusion: DBD can relax MCA with no effects on resting vessels. The mechanism may be related to ASR’s inhibition of K_ATP and K_ir channels. Meanwhile, the inhibition of [Ca²⁺]_out by DBD, ASR, and AR as well as the inhibition of [Ca²⁺]_in by ASR and AR may contribute to dilate MCA.