miR-200a-3p inhibits the PDGF-BB-induced proliferation of VSMCs by affecting their phenotype-associated proteins

Accumulating evidence shows that the abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) can significantly affect the long-term prognosis of coronary artery bypass grafting. This study aimed to explore the factors affecting the proliferation, migration, and phenotypic transformation of VSMCs. First, we stimulated VSMCs with different platelet-derived growth factor-BB (PDGF-BB) concentrations, analyzed the expression of phenotype-associated proteins by Western blotting, and examined cell proliferation by scratch wound healing and the 5-ethynyl-2-deoxyuridine (EdU) assay. VSMC proliferation was induced most by PDGF-BB treatment at 20 ng/mL. miR-200a-3p decreased significantly in A7r5 cells stimulated with PDGF-BB. The overexpression of miR-200a-3p reversed the downregulation of α-SMA (p < 0.001) and the upregulation of vimentin (p < 0.001) caused by PDGF-BB. CCK8 and EdU analyses showed that miR-200a-3p overexpression could inhibit PDGF-BB-induced cell proliferation (p < 0.001). However, flow cytometric analysis showed that it did not significantly increase cell apoptosis. Collectively, the overexpression of miR-200a-3p inhibited the proliferation and migration of VSMCs induced by PDGF-BB, partly by affecting phenotypic transformation-related proteins, providing a new strategy for relieving the restenosis of vein grafts.

Single molecule magnet features in luminescent lanthanide coordination polymers with heptacoordinate Dy/Yb(III) ions as nodes

Two sets of 1D/2D lanthanide coordination polymers with formulas of Ln(oqa)3·2H2O [Hoqa = 2-(4-oxoquinolin-1(4H)-yl) acetic acid, Ln = Dy (1), Yb (2)] and Ln(oaa)2(HCOO)(H2O) [Hoaa = 2-(9-oxoacridin-10(9H)-yl) acetic acid, Ln = Dy (3), Yb (4)] have been synthesized and their physical properties were investigated. All four complexes are constructed from seven-coordinate lanthanide ions and corresponding organic linkers. The lanthanide ions in 1 and 2 adopt a pentagonal bipyramid coordination geometry, whereas the coordination geometry of lanthanide ions in 3 and 4 can be described as a capped octahedron. Slow magnetic relaxation behaviors were observed in these four products at a zero/non-zero static magnetic field. Complexes 1, 2 and 4 exhibit the characteristic emission of Ln(III) ions, whereas complex 3 shows ligand-based emission. Bright yellow light emission was also observed when a voltage was applied, demonstrating the potential of 1 for application in light-emitting diodes (LEDs). Compounds 3 and 4 are the first examples of lanthanide complexes based on Hoaa ligands.

Chitosan nanoparticles for sustained release of metformin and its derived synthetic biopolymer for bone regeneration

Background: There are considerable socioeconomic costs associated with bone defects, making regenerative medicine an increasingly attractive option for treating them. Chitosan is a natural biopolymer; it is used in approaches for sustained slow release and osteogenesis, and metformin has osteoinductivity. Our study aimed to synthesize chitosan and human serum albumin (HSA) with a metformin nanoformulation to evaluate the therapeutic effects of this nanoformulation on bone defects in vitro. Methods: A pluripotent differentiation assay was performed in vitro on mouse bone marrow mesenchymal stem cells (BMSCs). Cell Counting Kit-8 was used to detect whether metformin was toxic to BMSCs. The osteogenesis-related gene expression of osteocalcin (OCN) and osteoprotegerin (OPG) from BMSCs was tested by real-time polymerase chain reaction (PCR). HSA, metformin hydrochloride, and chitosan mixtures were magnetically stirred to finish the assembly of metformin/HSA/chitosan nanoparticles (MHC NPs). The MHC NPs were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FT-IR). To test the expression of OCN and OPG, western blot were used. MHC NPs were evaluated in vitro for their osteoinductivity using alkaline phosphatase (ALP). Results: BMSCs successfully differentiated into osteogenic and adipogenic lineages in vitro. According to real-time PCR, a 50 µM concentration of metformin promoted osteogenesis in BMSCs most effectively by upregulating the osteogenic markers OCN and OPG. The microstructure of MHC NPs was spherical with an average nanosize of 20 ± 4.7 nm and zeta potential of -8.3 mV. A blueshift and redshift were observed in MHC NPs following exposure to wavelengths of 1,600-1,900 and 2,000-3,700 nm, respectively. The encapsulation (%) of metformin was more than 90%. The simulation study showed that MHC NPs have good stability and it could release metformin slowly in vitro at room temperature. Upon treatment with the studied MHC NPs for 3 days, ALP was significantly elevated in BMSCs. In addition, the MHC NPs-treated BMSCs upregulated the expression of OPG and OCN, as shown by real-time PCR and western blot. Conclusion: MHC NPs have a stable metformin release effect and osteogenic ability. Therefore, as a derived synthetic biopolymer, it is expected to play a role in bone tissue regeneration.

[Generation and phenotypic characterization of S100A9 gene knockout mice by CRISPR/Cas9-mediated gene targeting]

S100 calcium binding protein A9 (S100A9) is involved in a variety of biological processes such as inflammation and tumor cell migration and invasion regulation. The purpose of this study was to construct S100A9 gene-edited mice by using CRISPR/Cas9 technology, thereby providing an animal model for exploring the biological functions of this gene. According to the S100A9 gene sequence, the single-stranded small guide RNA (sgRNA) targeting exons 2 and 3 was transcribed in vitro, and a mixture of Cas9 mRNA and candidate sgRNA was injected into mouse fertilized eggs by microinjection. Early embryos were obtained and transferred to surrogate mice, and F₀ mice were obtained and identified by PCR identification and gene sequencing. F₀ mice were further mated with wild-type C57BL/6 mice to obtain F₁ heterozygous mice, and then homozygous offspring were obtained through F₁ mice self-crossing. Real-time PCR, Western blot and immunohistochemistry (IHC) were used to verify the expression and distribution of S100A9. In order to observe the pathological changes of mouse lung tissue using HE staining, an allergic asthma model was induced by ovalbumin from chicken egg white (OVA). The results showed that the 2 492 bp of exons 2, 3 of the S100A9 gene was successfully knocked out, and S100A9^-/- mice with stable inheritance were obtained. Furthermore, it was found that S100A9 gene was highly expressed in the lung and spleen of wild-type mice. The expression of S100A9 mRNA and protein was not detected in the lung and spleen of S100A9^-/- mice. However, compared with wild-type mice, the lungs of S100A9^-/- mice showed a significantly worse inflammatory phenotype, and the proportion of eosinophils in bronchoalveolar lavage fluid (BALF) was significantly increased in response to the treatment of OVA. These results suggest we have successfully constructed a new strain of S100A9^-/- mice, and preliminarily confirmed that the lack of S100A9 function can aggravate airway inflammation in asthmatic mice, providing a new mouse model for further study of S100A9 gene function.

Folium Sennae and emodin reverse airway smooth muscle contraction

The objective of this project was to find a bronchodilatory compound from herbs and clarify the mechanism. We found that the ethanol extract of Folium Sennae (EEFS) can relax airway smooth muscle (ASM). EEFS inhibited ASM contraction, induced by acetylcholine, in mouse tracheal rings and lung slices. High-performance liquid chromatography assay showed that EEFS contained emodin. Emodin had a similar reversal action. Acetylcholine-evoked contraction was also partially reduced by nifedipine (a selective inhibitor of L-type voltage-dependent Ca²⁺ channels, LVDCCs), YM-58483 (a selective inhibitor of store-operated Ca²⁺ entry, SOCE), as well as Y-27632 (an inhibitor of Rho-associated protein kinase). In addition, LVDCC- and SOCE-mediated currents and cytosolic Ca²⁺ elevations were inhibited by emodin. Emodin reversed acetylcholine-caused increases in phosphorylation of myosin phosphatase target subunit 1. Furthermore, emodin, in vivo, inhibited acetylcholine-induced respiratory system resistance in mice. These results indicate that EEFS-induced relaxation results from emodin inhibiting LVDCC, SOCE, and Ca²⁺ sensitization. These findings suggest that Folium Sennae and emodin may be new sources of bronchodilators.

A universal aptasensing platform based on cryonase-assisted signal amplification and graphene oxide induced quenching of the fluorescence of labeled nucleic acid probes: application to the detection of theophylline and ATP

This study describes a universal fluorometric method for sensitive detection of analytes by using aptamers. It is based on the use of graphene oxide (GO) and cryonase-assisted signal amplification. GO is a strong quencher of FAM-labeled nucleic acid probes, while cryonase digests all types of nucleic acid probes. This makes the platform widely applicable to analytes for which the corresponding aptamers are available. Theophylline and ATP were chosen as model analytes. In the absence of targets, dye-labeled aptamers are in a flexible single strand state and adsorb on the GO. As a result, the probes are non-fluorescent due to the efficient quenching of dyes by GO. Upon the addition of a specific target, the aptamer/target complex desorbed from the GO surface and the probe becomes fluorescent. The released complex will immediately become a substrate for cryonase digestion and subsequently releasing the target to bind to another aptamer to initiate the next round of cleavage. This cyclic reaction will repeat again and again until all the related-probes are consumed and all fluorophores light up, resulting in significant fluorescent signal amplification. The detection limits are 47 nM for theophylline and 22.5 nM for ATP. This is much better than that of known methods. The assay requires only mix-and-measure steps that can be accomplished rapidly. In our perception, the detection scheme holds great promise for the design enzyme-aided amplification mechanisms for use in bioanalytical methods. Graphical abstract A cryonase-assisted signal amplification (CASA) method has been developed by using graphene oxide (GO) conjugated with a fluorophore-labeled aptamer for fluorescence signal generation. It has a large scope because it may be applied to numerous analytes.

Azithromycin inhibits muscarinic 2 receptor-activated and voltage-activated Ca2+ permeant ion channels and Ca2+ sensitization, relaxing airway smooth muscle contraction

Azithromycin (AZM) has been used for the treatment of asthma and chronic obstructive pulmonary disease (COPD); however, the effects and underlying mechanisms of AZM remain largely unknown. The effects of AZM on airway smooth muscles (ASMs) and the underlying mechanisms were studied using isometric muscle force measurements, the examination of lung slices, imaging, and patch-clamp techniques. AZM completely inhibited acetylcholine (ACH)-induced precontraction of ASMs in animals (mice, guinea pigs, and rabbits) and humans. Two other macrolide antibiotics, roxithromycin and Klaricid, displayed a decreased inhibitory activity, and the aminoglycoside antibiotics penicillin and streptomycin did not have an inhibitory effect. Precontractions were partially inhibited by nifedipine (selective inhibitor of L-type voltage-dependent Ca²⁺ channels (LVDCCs)), Pyr3 (selective inhibitor of TRPC3 and/or STIM/Orai channels, which are nonselective cation channels (NSCCs)), and Y-27632 (selective inhibitor of Rho-associated kinase (ROCK)). Moreover, LVDCC- and NSCC-mediated currents were inhibited by AZM, and the latter were suppressed by the muscarinic (M) 2 receptor inhibitor methoctramine. AZM inhibited LVDCC Ca²⁺ permeant ion channels, M2 receptors, and TRPC3 and/or STIM/Orai, which decreased cytosolic Ca²⁺ concentrations and led to muscle relaxation. This relaxation was also enhanced by the inhibition of Ca²⁺ sensitization. Therefore, AZM has potential as a novel and potent bronchodilator. The findings of this study improve the understanding of the effects of AZM on asthma and COPD.

Knockdown of KDM2A inhibits proliferation associated with TGF-β expression in HEK293T cell

Lysine-specific demethylase 2A (KDM2A, also known as JHDM1A or FBXL11) plays an important role in regulating cell proliferation. However, the mechanisms on KDM2A controlling cell proliferation are varied among cell types, even controversial conclusions have been drawn. In order to elucidate the functions and underlying mechanisms for KDM2A controlling cell proliferation and apoptosis, we screened a KDM2A knockout HEK293T cell lines by CRISPR-Cas9 to illustrate the effects of KDM2A on both biological process. The results indicate that knocking down expression of KDM2A can significantly weaken HEK293T cell proliferation. The cell cycle analysis via flow cytometry demonstrate that knockdown expression of KDM2A will lead more cells arrested at G2/M phase. Through the RNA-seq analysis of the differential expressed genes between KDM2A knockdown HEK293T cells and wild type, we screened out that TGF-β pathway was significantly downregulated in KDM2A knockdown cells, which indicates that TGF-β signaling pathway might be the downstream target of KDM2A to regulate cell proliferation. When the KDM2A knockdown HEK293T cells were transient-transfected with KDM2A overexpression plasmid or treated by TGF-β agonist hydrochloride, the cell proliferation levels can be partial or completely rescued. However, the TGF-β inhibitor LY2109761 can significantly inhibit the KDM2A WT cells proliferation, but not the KDM2A knockdown HEK293T cells. Taken together, these findings suggested that KDM2A might be a key regulator of cell proliferation and cell cycle via impacting TGF-β signaling pathway.

Semen cassiae Extract Inhibits Contraction of Airway Smooth Muscle

β₂-adrenoceptor agonists are commonly used as bronchodilators to treat obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), however, they induce severe side effects. Therefore, developing new bronchodilators is essential. Herbal plants were extracted and the extracts’ effect on airway smooth muscle (ASM) precontraction was assessed. The ethyl alcohol extract of semen cassiae (EESC) was extracted from Semen cassia. The effects of EESC on the ACh- and 80 mM K⁺-induced sustained precontraction in mouse and human ASM were evaluated. Ca²⁺ permeant ion channel currents and intracellular Ca²⁺ concentration were measured. HPLC analysis was employed to determine which compound was responsible for the EESC-induced relaxation. The EESC reversibly inhibited the ACh- and 80 mM K⁺-induced precontraction. The sustained precontraction depends on Ca²⁺ influx, and it was mediated by voltage-dependent L-type Ca²⁺ channels (LVDCCs), store-operated channels (SOCs), TRPC3/STIM/Orai channels. These channels were inhibited by aurantio-obtusin, one component of EESC. When aurantio-obtusin removed, EESC’s action disappeared. In addition, aurantio-obtusin inhibited the precontraction of mouse and human ASM and intracellular Ca²⁺ increases. These results indicate that Semen cassia-contained aurantio-obtusin inhibits sustained precontraction of ASM via inhibiting Ca²⁺-permeant ion channels, thereby, which could be used to develop new bronchodilators.

Generation and Role of Oscillatory Contractions in Mouse Airway Smooth Muscle

Background/Aims: Tetraethylammonium chloride (TEA) induces oscillatory contractions in mouse airway smooth muscle (ASM); however, the generation and maintenance of oscillatory contractions and their role in ASM are unclear. Methods: In this study, oscillations of ASM contraction and intracellular Ca2+ were measured using force measuring and Ca2+ imaging technique, respectively. TEA, nifedipine, niflumic acid, acetylcholine chloride, lithium chloride, KB-R7943, ouabain, 2-Aminoethoxydiphenyl borate, thapsigargin, tetrodotoxin, and ryanodine were used to assess the mechanism of oscillatory contractions. Results: TEA induced depolarization, resulting in activation of L-type voltage-dependent Ca2+ channels (LVDCCs) and voltage-dependent Na+ (VNa) channels. The former mediated Ca2+ influx to trigger a contraction and the latter mediated Na+ entry to enhance the contraction via activating LVDCCs. Meanwhile, increased Ca2+-activated Cl- channels, inducing depolarization that resulted in contraction through LVDCCs. In addition, the contraction was enhanced by intracellular Ca2+ release from Ca2+ stores mediated by inositol (1,4,5)-trisphosphate receptors (IP3Rs). These pathways together produce the contractile phase of the oscillatory contractions. Furthermore, the increased Ca2+ activated the Na+-Ca2+ exchanger (NCX), which transferred Ca2+ out of and Na+ into the cells. The former induced relaxation and the latter activated Na+/K+-ATPase that induced hypopolarization to inactivate LVDCCs causing further relaxation. This can also explain the relaxant phase of the oscillatory contractions. Moreover, the depolarization induced by VNa channels and NCX might be greater than the hypopolarization caused by Na+/K+-ATPase alone, inducing LVDCC activation and resulting in further contraction. Conclusions: These data indicate that the TEA-induced oscillatory contractions were cooperatively produced by LVDCCs, VNa channels, Ca2+-activated Cl- channels, NCX, Na+/K+ ATPase, IP3Rs-mediated Ca2+ release, and extracellular Ca2+.

Polygonum aviculare L. extract and quercetin attenuate contraction in airway smooth muscle

Because of the serious side effects of the currently used bronchodilators, new compounds with similar functions must be developed. We screened several herbs and found that Polygonum aviculare L. contains ingredients that inhibit the precontraction of mouse and human airway smooth muscle (ASM). High K⁺-induced precontraction in ASM was completely inhibited by nifedipine, a selective blocker of L-type voltage-dependent Ca²⁺ channels (LVDCCs). However, nifedipine only partially reduced the precontraction induced by acetylcholine chloride (ACH). Additionally, the ACH-induced precontraction was partly reduced by pyrazole-3 (Pyr3), a selective blocker of TRPC3 and stromal interaction molecule (STIM)/Orai channels. These channel-mediated currents were inhibited by the compounds present in P. aviculare extracts, suggesting that this inhibition was mediated by LVDCCs, TRPC3 and/or STIM/Orai channels. Moreover, these channel-mediated currents were inhibited by quercetin, which is present in P. aviculare extracts. Furthermore, quercetin inhibited ACH-induced precontraction in ASM. Overall, our data indicate that the ethyl acetate fraction of P. aviculare and quercetin can inhibit Ca²⁺-permeant LVDCCs, TRPC3 and STIM/Orai channels, which inhibits the precontraction of ASM. These findings suggest that P. aviculare could be used to develop new bronchodilators to treat obstructive lung diseases such as asthma and chronic obstructive pulmonary disease.

Nuciferine Relaxes Tracheal Rings via the Blockade of VDLCC and NSCC Channels

This study aimed to elucidate the mechanisms of nuciferine (a main aporphine alkaloid of lotus leaf extract), which can induce relaxation in contracted tracheal rings. Under Ca²⁺-free and 2 mM Ca²⁺ conditions, we found that nuciferine had no effect on the resting muscle tone of tracheal rings. In contrast, nuciferine relaxed high K⁺-contracted mouse tracheal rings in a dose-dependent manner and inhibited both Ca²⁺ influx and voltage-dependent L-type Ca²⁺ channel currents induced by high K⁺. Similarly, nuciferine also inhibited acetylcholine-induced contractions in mouse tracheal rings in a dose-dependent manner. Meanwhile, both acetylcholine-induced intracellular Ca²⁺ influx and whole-cell currents of nonselective cation channels were blocked by nuciferine. Together, the results indicate that nuciferine-induced relaxation in tracheal rings mainly occurred due to the inhibition of extracellular Ca²⁺ influx through the blockade of voltage-dependent L-type Ca²⁺ channels and/or nonselective cation channels. These results suggest that nuciferine has a therapeutic effect on respiratory diseases associated with the aberrant contraction of airway smooth muscles and/or bronchospasm.

Distinct Effects of Ca2+ Sparks on Cerebral Artery and Airway Smooth Muscle Cell Tone in Mice and Humans

The effects of Ca²⁺ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone, as well as the underlying mechanisms, are not clear. In this investigation, we elucidated the underlying mechanisms of the distinct effects of Ca²⁺ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone. In CASMCs, owing to the functional loss of Ca²⁺-activated Cl^- (Clca) channels, Ca²⁺ sparks activated large-conductance Ca²⁺-activated K⁺ channels (BKs), resulting in a decreases in tone against a spontaneous depolarization-caused high tone in the resting state. In ASMCs, Ca²⁺ sparks induced relaxation through BKs and contraction via Clca channels. However, the integrated result was contraction because Ca²⁺ sparks activated BKs prior to Clca channels and Clca channels-induced depolarization was larger than BKs-caused hyperpolarization. However, the effects of Ca²⁺ sparks on both cell types were determined by L-type voltage-dependent Ca²⁺ channels (LVDCCs). In addition, compared with ASMCs, CASMCs had great and higher amplitude Ca²⁺ sparks, a higher density of BKs, and higher Ca²⁺ and voltage sensitivity of BKs. These differences enhanced the ability of Ca²⁺ sparks to decrease CASMC and to increase ASMC tone. The higher Ca²⁺ and voltage sensitivity of BKs in CASMCs than ASMCs were determined by the β1 subunits. Moreover, Ca²⁺ sparks showed the similar effects on human CASMC and ASMC tone. In conclusions, Ca²⁺ sparks decrease CASMC tone and increase ASMC tone, mediated by BKs and Clca channels, respectively, and finally determined by LVDCCs.

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

The effects of hypertonic solution on airway smooth muscle (ASM) contraction and the underlying mechanisms are largely unknown. We found that hypertonic saline (HS) inhibited acetylcholine (ACh)-induced contraction of ASM from the mouse trachea and human bronchi. In single mouse ASM cells (ASMCs), ACh induced an increase in intracellular Ca²⁺ that was further enhanced by 5% NaCl, indicating that the HS-induced inhibition of ASM contraction was not mediated by a decrease in cytosolic Ca²⁺ . The Rho-associated kinase (ROCK) inhibitor Y-27632 relaxed ACh-induced precontraction of mouse tracheal rings. However, such inhibition was not observed after the relaxation induced by 5% NaCl. Moreover, the incubation of mouse tracheal rings with 5% NaCl decreased ACh-induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1. These data indicate that HS inhibits the contraction of ASM by inhibiting Ca²⁺ sensitization, not by decreasing intracellular Ca²⁺ .

Chloroquine inhibits Ca2+ permeable ion channels-mediated Ca2+ signaling in primary B lymphocytes

BACKGROUND

Chloroquine, a bitter tastant, inhibits Ca²⁺ signaling, resulting in suppression of B cell activation; however, the inhibitory mechanism remains unclear.

RESULTS

In this study, thapsigargin (TG), but not caffeine, induced sustained intracellular Ca²⁺ increases in mouse splenic primary B lymphocytes, which were markedly inhibited by chloroquine. Under Ca²⁺-free conditions, TG elicited transient Ca²⁺ increases, which additionally elevated upon the restoration of 2 mM Ca²⁺. The former were from release of intracellular Ca²⁺ store and the latter from Ca²⁺ influx. TG-induced release was inhibited by 2-APB (an inhibitor of inositol-3-phosphate receptors, IP₃Rs) and chloroquine, and TG-caused influx was inhibited by pyrazole (Pyr3, an inhibitor of transient receptor potential C3 (TRPC3) and stromal interaction molecule (STIM)/Orai channels) and chloroquine. Moreover, chloroquine also blocked Ca²⁺ increases induced by the engagement of B cell receptor (BCR) with anti-IgM.

CONCLUSIONS

These results indicate that chloroquine inhibits Ca²⁺ elevations in splenic B cells through inhibiting Ca²⁺ permeable IP₃R and TRPC3 and/or STIM/Orai channels. These findings suggest that chloroquine would be a potent immunosuppressant.

Chloroquine Inhibits Ca(2+) Signaling in Murine CD4(+) Thymocytes

BACKGROUND/AIMS

Bitter-tasting chloroquine can suppress T cell activation by inhibiting Ca(2+) signaling. However, the mechanism of inhibition remains largely unclear.

METHODS

In this study, CD4(+) T cells were isolated from the thymus, and the calcium content of CD4(+) thymocytes was measured using fura-2 AM and a TILL imaging system. Pyrazole-3 (Pyr3), thapsigargin (TG), and caffeine were used to assess the effects of chloroquine on the intracellular Ca(2+) content of CD4(+) T cells.

RESULTS

In murine CD4(+) thymocytes, chloroquine decreased the TG-triggered intracellular Ca(2+) increase in a dose-dependent manner. In the absence of chloroquine under Ca(2+)-free conditions (0 mM Ca(2+) and 0.5 mM EGTA), TG induced a transient Ca(2+) increase. After restoration of the extracellular Ca(2+) concentration to 2 mM, a dramatic Ca(2+) increase occurred. This elevation was completely blocked by chloroquine and was markedly inhibited by Pyr3, a selective antagonist of transient receptor potential C3 (TRPC3) channel and stromal interaction molecule (STIM)/Orai channel. Furthermore, the TG-induced transient Ca(2+) increase under Ca(2+)-free conditions was eliminated in the presence of chloroquine. Chloroquine also blocked the dialyzed inositol-1,4,5-trisphosphate (IP3)-induced intracellular Ca(2+) increase. However, chloroquine was not able to decrease the caffeine-induced Ca(2+) increase.

CONCLUSION

These data indicate that chloroquine inhibits the elevation of intracellular Ca(2+) in thymic CD4(+) T cells by inhibiting IP3 receptor-mediated Ca(2+) release from intracellular stores and TRPC3 channel-mediated and/or STIM/Orai channel-mediated Ca(2+) influx.

Involvement of large-conductance Ca2+-activated K+ channels in chloroquine-induced force alterations in pre-contracted airway smooth muscle

The participation of large-conductance Ca²⁺ activated K⁺ channels (BKs) in chloroquine (chloro)-induced relaxation of precontracted airway smooth muscle (ASM) is currently undefined. In this study we found that iberiotoxin (IbTx, a selective inhibitor of BKs) and chloro both completely blocked spontaneous transient outward currents (STOCs) in single mouse tracheal smooth muscle cells, which suggests that chloro might block BKs. We further found that chloro inhibited Ca²⁺ sparks and caffeine-induced global Ca²⁺ increases. Moreover, chloro can directly block single BK currents completely from the intracellular side and partially from the extracellular side. All these data indicate that the chloro-induced inhibition of STOCs is due to the blockade of chloro on both BKs and ryanodine receptors (RyRs). We also found that low concentrations of chloro resulted in additional contractions in tracheal rings that were precontracted by acetylcholine (ACH). Increases in chloro concentration reversed the contractile actions to relaxations. In the presence of IbTx or paxilline (pax), BK blockers, chloro-induced contractions were inhibited, although the high concentrations of chloro-induced relaxations were not affected. Taken together, our results indicate that chloro blocks BKs and RyRs, resulting in abolishment of STOCs and occurrence of contraction, the latter will counteract the relaxations induced by high concentrations of chloro.

Pharmacokinetics, bioavailability and PK/PD relationship of cefquinome for Escherichia coli in Beagle dogs

The pharmacokinetics and bioavailability of cefquinome in Beagle dogs were determined by intravenous (IV), intramuscular (IM) or subcutaneous (SC) injection at a single dose of 2 mg/kg body weight (BW). The minimum inhibitory concentrations (MIC) of cefquinome against 217 Escherichia coli isolated from dogs were also investigated. After IV injection, the plasma concentration-time curve of cefquinome was analyzed using a two-compartmental model, and the mean values of t1/2α (h), t1/2β (h), Vss (L/kg), ClB (L/kg/h) and AUC (μg·h/mL) were 0.12, 0.98, 0.30, 0.24 and 8.51, respectively. After IM and SC administration, the PK data were best described by a one-compartmental model with first-order absorption. The mean values of t1/2Kel , t1/2Ka , tmax (h), Cmax (μg/mL) and AUC (μg·h/mL) were corresponding 0.85, 0.14, 0.43, 4.83 and 8.24 for IM administration, 0.99, 0.29, 0.72, 3.88 and 9.13 for SC injection. The duration of time that drug levels exceed the MIC (%T > MIC) were calculated using the determined MIC90 (0.125 μg/mL) and the PK data obtained in this study. The results indicated that the dosage regimen of cefquinome at 2 mg/kg BW with 12-h intervals could achieve %T > MIC above 50% that generally produced a satisfactory bactericidal effect against E. coli isolated from dogs in this study.

6-Shogaol induces apoptosis in human leukemia cells through a process involving caspase-mediated cleavage of eIF2α

Background

6-Shogaol is a promising antitumor agent isolated from dietary ginger (Zingiber officinale). However, little is known about the efficacy of 6-shogaol on leukemia cells. Here we investigated the underlying mechanism of 6-shogaol induced apoptosis in human leukemia cells in vitro and in vivo.

Methods

Three leukemia cell lines and primary leukemia cells were used to investigate the apoptosis effect of 6-shogaol. A shotgun approach based on label-free proteome with LC-CHIP Q-TOF MS/MS was employed to identify the cellular targets of 6-shogaol and the differentially expressed proteins were analyzed by bioinformatics protocols.

Results

The present study indicated that 6-shogaol selectively induced apoptosis in transformed and primary leukemia cells but not in normal cells. Eukaryotic translation initiation factor 2 alpha (eIF2α), a key regulator in apoptosis signaling pathway, was significantly affected in both Jurkat and U937 proteome profiles. The docking results suggested that 6-shogaol might bind well to eIF2α at Ser51 of the N-terminal domain. Immunoblotting data indicated that 6-shogaol induced apoptosis through a process involving dephosphorylation of eIF2α and caspase activation–dependent cleavage of eIF2α. Furthermore, 6-shogaol markedly inhibited tumor growth and induced apoptosis in U937 xenograft mouse model.

Conclusion

The potent anti-leukemia activity of 6-shogaol found both in vitro and in vivo in our study make this compound a potential anti-tumor agent for hematologic malignancies.

6-Shogaol induces apoptosis in human hepatocellular carcinoma cells and exhibits anti-tumor activity in vivo through endoplasmic reticulum stress

6-Shogaol is an active compound isolated from Ginger (Zingiber officinale Rosc). In this work, we demonstrated that 6-shogaol induces apoptosis in human hepatocellular carcinoma cells in relation to caspase activation and endoplasmic reticulum (ER) stress signaling. Proteomic analysis revealed that ER stress was accompanied by 6-shogaol-induced apoptosis in hepatocellular carcinoma cells. 6-shogaol affected the ER stress signaling by regulating unfolded protein response (UPR) sensor PERK and its downstream target eIF2α. However, the effect on the other two UPR sensors IRE1 and ATF6 was not obvious. In prolonged ER stress, 6-shogaol inhibited the phosphorylation of eIF2α and triggered apoptosis in SMMC-7721 cells. Salubrinal, an activator of the PERK/eIF2α pathway, strikingly enhanced the phosphorylation of eIF2α in SMMC-7721 cells with no toxicity. However, combined treatment with 6-shogaol and salubrinal resulted in significantly increase of apoptosis and dephosphorylation of eIF2α. Overexpression of eIF2α prevented 6-shogaol-mediated apoptosis in SMMC-7721 cells, whereas inhibition of eIF2α by small interfering RNA markedly enhanced 6-shogaol-mediated cell death. Furthermore, 6-shogaol-mediated inhibition of tumor growth of mouse SMMC-7721 xenograft was associated with induction of apoptosis, activation of caspase-3, and inactivation of eIF2α. Altogether our results indicate that the PERK/eIF2α pathway plays an important role in 6-shogaol-mediated ER stress and apoptosis in SMMC-7721 cells in vitro and in vivo.

Reduced GABA(A) receptor α6 expression in the trigeminal ganglion alters inflammatory TMJ hypersensitivity

Trigeminal ganglia neurons express the GABA(A) receptor subunit alpha 6 (Gabrα6) but the role of this particular subunit in orofacial hypersensitivity is unknown. In this report the function of Gabrα6 was tested by reducing its expression in the trigeminal ganglia and measuring the effect of this reduction on inflammatory temporomandibular joint (TMJ) hypersensitivity. Gabrα6 expression was reduced by infusing the trigeminal ganglia of male Sprague Dawley rats with small interfering RNA (siRNA) having homology to either the Gabrα6 gene (Gabrα6 siRNA) or no known gene (control siRNA). Sixty hours after siRNA infusion the rats received a bilateral TMJ injection of complete Freund's adjuvant to induce an inflammatory response. Hypersensitivity was then quantitated by measuring meal duration, which lengthens when hypersensitivity increases. Neuronal activity in the trigeminal ganglia was also measured by quantitating the amount of phosphorylated ERK. Rats in a different group that did not have TMJ inflammation had an electrode placed in the spinal cord at the level of C1 sixty hours after siRNA infusion to record extracellular electrical activity of neurons that responded to TMJ stimulation. Our results show that Gabrα6 was expressed in both neurons and satellite glia of the trigeminal ganglia and that Gabrα6 positive neurons within the trigeminal ganglia have afferents in the TMJ. Gabrα6 siRNA infusion reduced Gabrα6 gene expression by 30% and significantly lengthened meal duration in rats with TMJ inflammation. Gabrα6 siRNA infusion also significantly increased p-ERK expression in the trigeminal ganglia of rats with TMJ inflammation and increased electrical activity in the spinal cord of rats without TMJ inflammation. These results suggest that maintaining Gabrα6 expression was necessary to inhibit primary sensory afferents in the trigeminal pathway and reduce inflammatory orofacial nociception.

Resistin level is positively correlated with thrombotic complications in Southern Chinese metabolic syndrome patients

BACKGROUND

The metabolic syndrome (MetS) has been found to be closely related with thrombotic diseases. The mechanism, however, is far from elucidated.

AIM

This study was designed to investigate the relationship between endogenous resistin and thrombosis mediating factors, as well as its potential effects on the gene expression of cardiovascular disease biomarkers.

METHODS

Ninety patients satisfied the MetS criteria, and 55 healthy subjects were recruited as part of a single-center clinical study. Plasma levels of resistin, tissue factor (TF), tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) were measured by enzymelinked immunosorbent assays. The effect of resistin on the expression of cardiovascular disease biomarkers in human umbilical vein endothelial cells (HUVEC) was assayed by gene microarray.

RESULTS

1) The average levels of resistin in MetS patients with or without acute myocardial or cerebral infarction were significantly higher than those of the controls. 2) The TF and TFPI increase was higher in MetS with infarction patients than in MetS patients. 3) In MetS with infarction patients, resistin was positively correlated with TF and PAI-1 (r=0.313, p=0.008; r=0.401, p=0.002, respectively). 4) In HUVEC, the microarray showed that apolipoprotein C-I, ACE, tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) and member 5 (CD40) genes expression were dramatically increased by resistin.

CONCLUSION

In patients with MetS, resistin is strongly associated with hypercoagulative and hypofibrinolitic activities. Moreover, resistin may induce thrombotic complications via mediating the lipoprotein metabolism and stimulating inflammation.

Anti-diabetic agents from natural products--an update from 2004 to 2009

Diabetes mellitus (DM), the third killer of the mankind health along with cancer, cardiovascular and cerebrovascular diseases, is one of the most challenging diseases facing health care professionals today. The World Health Organization (WHO) has declared that a DM epidemic is underway. Primary DM and its complications are costly to manage, not only for affected individuals, but also for healthcare systems around the world. Screening of anti-diabetic agents has been extensively investigated in the past decades. Natural products (NPs) have served as a major source of drugs for centuries, and about half of the pharmaceuticals in use today are derived from natural substances. Many natural products especially plants-derived medicines have been recommended for the treatment of DM. The present paper reviews NPs appeared in the literature with potential for DM and also identifies the research needs in this area. It mainly covers the time period from January 2004 to October 2008. The current review is divided into three major sections based on classification of the natural materials involved. The first part focuses on known and some new chemical entities isolated mainly from medicinal plants possessing anti-diabetic properties, including saponins, flavonoids, alkaloids, anthraquinones, terpenes, coumarins, phenolics, polysaccharides, and some other compounds. The second part summarizes crude extract of medicinal plants which are commonly used in the traditional Chinese medical system and have been demonstrated experimental or/and clinical anti-diabetic effectiveness, mainly including Leguminosae, Cucurbitaceae, Araliaceae, Liliaceae, Chenopodiaceae, Solanaceae, Compositae, Campanulaceae, Cornaceae, Rhamnaceae, Scrophulariaceae, Euphorbiaceae, Ginkgoceae, Gramineae, Myrtaceae, Sterculiaceae, Annonaceae, Labiatae, Crassulaceae, and Miscellaneous. The third part lists some compound formulae consisting of extracts of several plants that have been reported as beneficial for the treatment of DM, major involving Xiaokeling tablet, Ba-Wei-Di-Huang-Wan and Formula 1.

Oleanane-type triterpene glucuronides from the roots of Glycyrrhiza uralensis Fischer

Investigation of characteristic constituents of the roots of Glycyrrhiza uralensis Fischer led to isolation of four new triterpene glucuronides, namely uralsaponins C-F (1-4), an artificial product, namely the methyl ester of glycyrrhizin (5), as well as six known triterpene glucuronides (6-11). These new compounds were identified by 1D and 2D NMR spectroscopic analysis. The cytotoxicity of the selected compounds and their aglycones were evaluated against HeLa and MCF-7 cancer cell lines, and the preliminary structure-activity relationship was also elucidated.

Anticancer agents derived from natural products

Advances in the prevention and treatment of cancer require the continued development of novel and improved chemopreventive and chemotherapeutic agents. Throughout history, natural products have afforded a rich source of anticancer agents with diverse chemical structures and bioactivities. Recent technological and methodologic advances in structure elucidation, organic synthesis, and biological assay have resulted in the isolation and clinical evaluation of various novel anticancer agents. In this review, we will present the anticancer activities, mechanism of action, structure and activity relationships of six important anticancer agents from natural products, that is, taxol, betulinic acid, camptothecin, resveratrol, podophyllotoxin and curcumin.

High-speed separation and characterization of major constituents in Radix Paeoniae Rubra by fast high-performance liquid chromatography coupled with diode-array detection and time-of-flight mass spectrometry

A fast high-performance liquid chromatography (HPLC) method coupled with diode-array detection (DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) has been developed for rapid separation and sensitive identification of major constituents in Radix Paeoniae Rubra (RPR). The total analysis time on a short column packed with 1.8-microm porous particles was about 20 min without a loss in resolution, six times faster than the performance of a conventional column analysis (115 min). The MS fragmentation behavior and structural characterization of major compounds in RPR were investigated here for the first time. The targets were rapidly screened from RPR matrix using a narrow mass window of 0.01 Da to restructure extracted ion chromatograms. Accurate mass measurements (less than 5 ppm error) for both the deprotonated molecule and characteristic fragment ions represent reliable identification criteria for these compounds in complex matrices with similar if not even better performance compared with tandem mass spectrometry. A total of 26 components were screened and identified in RPR including 11 monoterpene glycosides, 11 galloyl glucoses and 4 other phenolic compounds. From the point of time savings, resolving power, accurate mass measurement capability and full spectral sensitivity, the established fast HPLC/DAD/TOFMS method turns out to be a highly useful technique to identify constituents in complex herbal medicines.

Molecular characterization and expression pattern of the porcine STARS, a striated muscle-specific expressed gene

STARS (striated muscle activator of Rho signaling) promotes the nuclear localization of MRTFs and mediates SRF transcription, which provides a potential muscle-specific mechanism for linking changes in the actin cytoskeleton structure with muscle gene expression. In this study, the full-length cDNA of the porcine STARS was cloned. The open reading frame of this gene contains 1,155 bp and encodes a protein of 384 amino acids, which is 79, 73, and 77% identical with human, mouse, and rat STARS genes, respectively. RT-PCR revealed that STARS is specifically expressed in heart and skeletal muscles. STARS is also distinctly different in different muscle developmental stages. The result indicates that its expression increased gradually from 33 dpc (days postcoitum) to postnatal muscles, and peaked 28 days postnatal. The porcine STARS was mapped to SSC4p13 using the somatic cell hybrid panel and the radiation hybrid panel IMpRH (LOD score 11.98). The data show that STARS is closely linked to marker SW871. A T/G single nucleotide polymorphism in the coding sequence, detected as Bsh1236I PCR-RFLP, displays allele frequency differences in six pig breeds.

Advances of modern chromatographic and electrophoretic methods in separation and analysis of flavonoids

Flavonoids, one of the largest groups of secondary metabolites, are widespread in vegetable crops such as herbs, fruits, vegetables, grains, seeds and derived foods such as juices, wines, oils, etc. They receive considerable attention due to their biological and physiological importance. Hundreds of publications on the analysis of flavonoids have appeared over the past decade. Traditional and more advanced techniques have come to prominence for sample preparation, separation, detection, and identification. This review intends to provide an updated, concise overview on the recent development and trends of separation, identification and quantification for flavonoids by modern chromatographic and spectrophotometric analytical techniques, including gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). The sample preparation before analysis is also briefly summarized.

Abscisic acid-specific binding sites in the flesh of developing apple fruit

Abscisic acid (ABA) specific-binding sites localized in the cytosol were identified and characterized in the flesh of developing apple (Malus pumila L. cv. Starkrimon) fruit. ABA binding activity was scarcely detectable in the microsomes but high ABA binding activity in the cytosolic fraction was detected. The ABA-binding sites possessed a protein nature with both active serine residues and thiol-groups of cysteine residues in their functional binding sites. ABA binding was shown to be saturable, reversible and of high affinity. A Scatchard plot provided evidence for two different ABA binding proteins, one with higher affinity (K(d)=2.3 nM) and the other with lower affinity (K(d)=58.8 nM). Phaseic acid, trans-ABA and (-)-ABA had essentially no affinity for the binding proteins, indicating their stereo-specificity to bind physiologically active cis-(+)-ABA. The time-course, pH- and temperature-dependence of the ABA-binding proteins were determined. It is hypothesized that the detected ABA-binding proteins may be putative ABA-receptors that mediate ABA signals during fruit development.

GABA(A) and 5-HT(3) receptors are involved in dorsal root reflexes: possible role in periaqueductal gray descending inhibition

The dorsal root reflex (DRR) is a measure of the central excitability of presynaptic inhibitory circuits in the spinal cord. Activation of the periaqueductal gray (PAG), a center for descending inhibition of spinal cord nociceptive transmission, induces release of variety of neurotransmitters in the spinal cord, including GABA and serotonin (5-HT). GABA has been shown to be involved in generation of DRRs. In this study, pharmacological agents that influence DRRs and their possible mechanisms were investigated. DRRs were recorded in anesthetized rats from filaments teased from the cut central stump of the left L(4) or L(5) dorsal root, using a monopolar recording electrode. Stimulating electrodes were placed either on the left sciatic nerve or transcutaneously in the left foot. Animals were paralyzed and maintained by artificial ventilation. Drugs were applied topically to the spinal cord. A total of 64 units were recorded in 34 Sprague-Dawley rats. Peripheral receptive fields were found for nine of these units. In these units, DRRs were evoked by brush, pressure, and pinch stimuli. Nine units were tested for an effect of electrical stimulation in the periaqueductal gray on the DRRs. In eight cases, DRR responses were enhanced following PAG stimulation. The background activity was 4.2 +/- 1.9 spikes/s (mean +/- SE; range: 0-97.7; n = 57). The responses to agents applied to the spinal cord were (in spikes/s): artificial cerebrospinal fluid, 7.1 +/- 3.6 (range: 0-86.9; n = 25); 0.1 mM GABA, 16.8 +/- 8.7 (range: 0-191.0; n = 22); 1.0 mM GABA, 116.0 +/- 26.5 (range: 0.05-1001.2; n = 50); and 1.0 mM phenylbiguanide (PBG), 68.1 +/- 25.3 (range: 0-1,073.0; n = 49). Bicuculline (0.5 mM, n = 27) and ondansetron (1.0 mM, n = 10) blocked the GABA and PBG effects, respectively (P < 0.05). Significant cross blockade was also observed. It is concluded that GABA(A) receptors are likely to play a key role in the generation of DRRs, but that 5-HT(3) receptors may also contribute. DRRs can be modulated by supraspinal mechanisms through descending systems.

Capsaicin responses in heat-sensitive and heat-insensitive A-fiber nociceptors

The recently cloned vanilloid receptor (VR1) is postulated to account for heat and capsaicin sensitivity in unmyelinated afferents. We sought to determine whether heat and capsaicin sensitivity also coexist in myelinated nociceptive afferents. Action potential (AP) activity was recorded from single A-fiber nociceptors that innervated the hairy skin in monkey. Before intradermal injection of capsaicin (10 microg/10 microl) into the receptive field, nociceptors were classified as heat-sensitive (threshold, </=53 degrees C, 1 sec) or heat-insensitive afferents and as mechanically sensitive (von Frey threshold, <6 bar) or mechanically insensitive afferents. All heat-sensitive afferents (n = 16) were insensitive to mechanical stimuli but responded to the intradermal injection of capsaicin (69 +/- 7 APs in 10 min). Responsiveness to mechanical stimuli, thermal stimuli, and capsaicin varied in their receptive fields; the majority of receptive field sites (24 of 36) were responsive to only one or two stimulus modalities, whereas only eight sites responded to all three modalities. For most heat-insensitive afferents, the activity induced by the capsaicin injection did not exceed the activity induced by needle insertion alone. However, the largest response to capsaicin (314 +/- 98 APs in 10 min) was observed for five afferents that were insensitive to heat as well as mechanical stimuli and therefore may be classified as cutaneous chemoreceptors. These results suggest that A-fiber nociceptors play a role in the pain and hyperalgesia associated with capsaicin injection. Our finding that a subgroup of capsaicin-sensitive A-fiber nociceptors are insensitive to heat predicts the existence of heat-insensitive capsaicin receptors.

Altered nociceptive neuronal circuits after neonatal peripheral inflammation

Nociceptive neuronal circuits are formed during embryonic and postnatal times when painful stimuli are normally absent or limited. Today, medical procedures for neonates with health risks can involve tissue injury and pain for which the long-term effects are unknown. To investigate the impact of neonatal tissue injury and pain on development of nociceptive neuronal circuitry, we used an animal model of persistent hind paw peripheral inflammation. We found that, as adults, these animals exhibited spinal neuronal circuits with increased input and segmental changes in nociceptive primary afferent axons and altered responses to sensory stimulation.

Electrophysiological assessment of the cutaneous arborization of Adelta-fiber nociceptors

Little is known about the relationship between the branching structure and function of physiologically identified cutaneous nociceptor terminals. The axonal arborization itself, however, has an impact on the afferent signal that is conveyed along the parent axon to the CNS. We therefore developed electrophysiological techniques to investigate the branching structure of cutaneous nociceptors. Single-fiber recordings were obtained from physiologically identified nociceptors that innervated the hairy skin of the monkey. Electrodes for transcutaneous stimulation were fixed at two separate locations inside the receptive field. For 32 Adelta-fiber nociceptors, distinct steps in latency of the recorded action potential were observed as the intensity of the transcutaneous electrical stimulus increased, indicating discrete sites for action potential initiation. The number of discrete latencies at each stimulation location ranged from 1 to 9 (3.7 +/- 0. 2; mean +/- SE) and the mean size of the latency step was 9.9 +/- 1. 0 ms (range: 0.4-89.1 ms). For seven Adelta fibers, collision techniques were used to locate the position of the branch point where the daughter fibers that innervated the two locations within the receptive field join the parent axon. To correct for changes in electrical excitability at the peripheral terminals, collision experiments between the two skin locations and between each skin location and a nerve trunk electrode were necessary. Nine branch points were studied in the seven Adelta fibers; the mean propagation time from the action potential initiation site to the branch point was 31 +/- 5 ms corresponding to a distance of 54 +/- 10 mm. Almost half of the daughter branches were unmyelinated. These results demonstrate that collision techniques can be used to study the functional anatomy of physiologically identified nociceptive afferent terminals. Furthermore these results indicate that some nociceptive afferents branch quite proximal to their peripheral receptive field. Occlusion of action potential activity can occur in these long branches such that the shorter branches dominate in the response to natural stimuli.

Nitric oxide mediates the central sensitization of primate spinothalamic tract neurons

Nitric oxide (NO) has been proposed to contribute to the development of hyperalgesia by activating the NO/guanosine 3',5'-cyclic monophosphate (cGMP) signal transduction pathway in the spinal cord. We have examined the effects of NO on the responses of primate spinothalamic tract (STT) neurons to peripheral cutaneous stimuli and on the sensitization of STT cells following intradermal injection of capsaicin. The NO level within the spinal dorsal horn was increased by microdialysis of a NO donor, 3-morpholinosydnonimine (SIN-1). SIN-1 enhanced the responses of STT cells to both weak and strong mechanical stimulation of the skin. This effect was preferentially on deep wide dynamic range STT neurons. The responses of none of the neurons tested to noxious heat stimuli were significantly changed when SIN-1 was administered. Intradermal injection of capsaicin increased dramatically the content of NO metabolites, NO-2/NO-3, within the dorsal horn. This effect was attenuated by pretreatment of the spinal cord with a nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). Sensitization of STT cells induced by intradermal injection of capsaicin was also prevented by pretreatment of the dorsal horn with the NOS inhibitors, L-NAME or 7-nitroindazole. Blockade of NOS did not significantly affect the responses of STT cells to peripheral stimulation in the absence of capsaicin injection. The data suggest that NO contributes to the development and maintenance of central sensitization of STT cells and the resultant mechanical hyperalgesia and allodynia after peripheral tissue damage or inflammation. NO seems to play little role in signaling peripheral stimuli under physiological conditions.

Nitric oxide-mediated spinal disinhibition contributes to the sensitization of primate spinothalamic tract neurons

This study concentrated on whether an increase in spinal nitric oxide (NO) diminishes inhibition of spinothalamic tract (STT) cells induced by activating the periaqueductal gray (PAG) or spinal glycinergic and GABAergic receptors, thus contributing to the sensitization of STT neurons. A reduction in inhibition of the responses to cutaneous mechanical stimuli induced by PAG stimulation was seen in wide dynamic range (WDR) STT cells located in the deep layers of the dorsal horn when these neurons were sensitized during administration of a NO donor, 3-morpholinosydnonimine (SIN-1), into the dorsal horn by microdialysis. In contrast, PAG-induced inhibition of the responses of high-threshold (HT) and superficial WDR STT cells was not significantly changed by spinal infusion of SIN-1. A reduction in PAG inhibition when STT cells were sensitized after intradermal injection of capsaicin could be nearly completely blocked by pretreatment of the dorsal horn with a NO synthase inhibitor, 7-nitroindazole. Moreover, spinal inhibition of nociceptive activity of deep WDR STT neurons elicited by iontophoretic release of glycine and GABA agonists was attenuated by administration of SIN-1. This change paralleled the change in PAG-induced inhibition. However, the inhibition of HT and superficial WDR cells induced by glycine and GABA release did not show a significant change when SIN-1 was administered spinally. Combined with our recent results, these data show that the effectiveness of spinal inhibition can be reduced by the NO/cGMP pathway. Thus disinhibition may constitute one mechanism underlying central sensitization.

Inhibition of primate spinothalamic tract neurons by spinal glycine and GABA is modulated by guanosine 3',5'-cyclic monophosphate

Our recent work has suggested that the nitric oxide/guanosine 3', 5'-cyclic monophosphate (NO/cGMP) signal transduction system contributes to central sensitization of spinothalamic tract (STT) neurons in part by influencing the descending inhibition of nociception resulting from stimulation in the periaqueductal gray. This study was designed to examine further whether activation of the NO/cGMP cascade reduces the inhibition of the activity of STT neurons mediated by spinal inhibitory amino acid (IAA) receptors. Responses of STT cells to noxious cutaneous stimuli were inhibited by iontophoresis of glycine and GABA agonists in anesthetized monkeys. Administration of 8-bromoguanosine-3',5'-cyclophosphate sodium (8-bromo-cGMP), a membrane permeable analogue of cGMP, either by microdialysis or by iontophoresis reduced significantly the IAA-induced inhibition of wide dynamic range (WDR) STT cells in the deep layers of the dorsal horn. The reduction in inhibition lasted for up to 1-1.5 h after the cessation of drug infusion. In contrast, IAA-induced inhibition of WDR STT cells in the superficial dorsal horn and high-threshold (HT) cells in superficial or deep layers was not significantly changed during 8-bromo-cGMP infusion. Iontophoresis of 8-bromo-cGMP onto STT cells produced the same actions as produced by microdialysis of this agent, but the effect was not as long-lasting nor as potent. Finally, an attenuation of the IAA receptor-mediated inhibition of STT cells produced by iontophoretic release of a NO donor, 3-morpholinosydnonimine, could be blocked by pretreatment of the spinal cord with a guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. These results suggest that an increased spinal cGMP level contributes to the sensitization of WDR STT neurons in the deep dorsal horn in part by down-regulating spinal IAA receptors. However, no evidence is provided in this study that the NO/cGMP cascade regulates IAA receptors on HT and superficial WDR neurons. Combined with the preceding studies, our data support the view that NO and cGMP function in the same signal transduction cascade and play an important role in central sensitization.

Polycaprolactone/glass bioabsorbable implant in a rabbit humerus fracture model

Research in improved materials and methods for internal fixation has centered on internal fixators made of bioabsorbable materials such as polylactic acid, polyglycolic acid, and polyparadioxanone. These materials have two problems: the first is a postoperative complication related to a delayed inflammatory response; and the second is low strength characteristics. An alternative material developed to alleviate these problems is a composite of phosphate glass fibers embedded in the polymer polycaprolactone, referred to as PCL. In this study, intramedullary pins made of PCL were compared to stainless steel pins in a rabbit humerus osteotomy model. Specimens were harvested at 0, 6, and 12 weeks postoperatively, radiographs and mechanical testing to failure were performed at each time interval, and tissue was examined microscopically at 6 and 12 weeks. Histologic results showed PCL pins to be well tolerated with minimal inflammation around the pin. Mechanical testing revealed the PCL fixation to be weaker initially than the stainless steel fixation. There was significant stress shielding of stainless-steel-healed rabbit humeri when compared to the PCL/bone humeri. All osteotomies immobilized with PCL healed with abundant periosteal callus production.

Involvement of protein kinase C in responses of rat dorsal horn neurons to mechanical stimuli and periaqueductal gray descending inhibition

The effects of a protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), on the activity and periaqueductal gray (PAG)-induced inhibition of rat dorsal horn neurons of the lumbar spinal cord were tested. A microdialysis fiber was placed through the dorsal horn for the purpose of local application of pharmacological agents. Extracellular single-unit recordings from dorsal horn neurons were made near the microdialysis fiber. TPA was tested on nociceptive dorsal horn cells. There was a significant increase in the background activity and responses to "brush", with no changes in responses to pressure and pinch stimuli. TPA also significantly blocked the PAG-induced inhibition of responses to brush, press, and pinch. These effects were eliminated by coadministration of the PKC inhibitor NPC-15437. The solvent, which contained dimethyl sulfoxide, was also tested for its effect on the responses to peripheral mechanical stimuli and PAG-induced inhibition of the dorsal horn neurons. There were no significant changes. This experiment suggests that activation of the PKC second messenger system might increase the activity of dorsal horn neurons and their responses to peripheral stimuli; in addition, the phorbol ester attenuated the PAG-induced descending inhibition of the dorsal horn neuron activity.

Involvement of cGMP in nociceptive processing by and sensitization of spinothalamic neurons in primates

Central sensitization of spinothalamic tract (STT) neurons in anesthetized monkeys after intradermal injection of capsaicin depends in part on disinhibition. Protein kinase C is suggested to participate in this process. The present study shows that the nitric oxide-cGMP (NO-cGMP) signal transduction system also contributes to sensitization of wide dynamic range (WDR) STT neurons located in the deep dorsal horn. The NO-cGMP system was activated by microdialysis administration into the dorsal horn of 8-bromo-cGMP, an analog of cGMP. Sensitization of STT cells by 8-bromo-cGMP increased the responses of deep WDR STT cells to both weak and strong mechanical stimulation of the skin and simultaneously attenuated the inhibition of the same neurons produced by stimulation in the periaqueductal gray (PAG). In contrast, WDR STT cells in the superficial dorsal horn and high-threshold (HT) STT cells in superficial or deep layers showed reduced responses to mechanical stimulation of the skin after infusion of 8-bromo-cGMP, and PAG inhibition of these neurons was unaffected. Sensitization of STT cells and the attenuation of PAG inhibition induced by intradermal injection of capsaicin were prevented by preteatment of the dorsal horn with a guanylate cyclase inhibitor, 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. The results support the hypothesis that activation of the NO-cGMP signal transduction system contributes to the sensitization of WDR STT neurons in the deep dorsal horn and helps explain why intradermal capsaicin injections often fail to sensitize superficial and HT STT cells. The results also support the idea that sensitization of STT cells is produced in part by disinhibition.

Effects of GABA and glycine receptor antagonists on the activity and PAG-induced inhibition of rat dorsal horn neurons

The effects of bicuculline and strychnine on the activity and periaqueductal gray (PAG)-induced inhibition of rat dorsal horn neurons of the lumbar spinal cord were tested. Extracellular single unit recordings were from 36 dorsal horn neurons near a microdialysis fiber passed through the spinal cord for drug application. The GABAA receptor antagonist, bicuculline, was tested on 19 cells, whereas the glycine receptor antagonist, strychnine, was tested on 17 cells. Both bicuculline and strychnine increased the background activity and responses to mechanical stimulation (BRUSH, PRESS, and PINCH) of the skin.06 They also significantly blocked the PAG-induced inhibition of responses to peripheral mechanical stimuli. This experiment suggests that the mechanism of PAG-induced descending inhibition of dorsal horn neuron activity involves GABA and/or glycine release in the spinal cord and that there is tonic release of these inhibitory neurotransmitters.

Inhibition of primate spinothalamic tract neurons by spinal glycine and GABA is reduced during central sensitization

1. In our previous work, we demonstrated that the glycinergic and GABAergic mechanisms that help mediate the descending inhibition from the periaqueductal gray exert a tonic modulation of nociceptive inputs through spinal glycine and gamma-aminobutyric acid (GABA) receptors. This study was designed to examine further possible changes in the inhibition of the activity of spinothalamic tract (STT) neurons mediated by spinal glycine and GABA receptors when STT cells are sensitized by intradermal injection of capsaicin, and to investigate the role of the protein kinase C (PKC) system in the functional modulation of these receptors. 2. Although the responses of STT cells to cutaneous mechanical stimuli were sensitized by intradermal injection of capsaicin, the inhibition of the responses of all STT cells tested to noxious cutaneous stimuli produced by iontophoretic release of glycine and GABA was significantly attenuated. The inhibition elicited by iontophoretic application of a GABAA agonist, muscimol, was reduced in some of the cells tested. 3. When the spinal cord dorsal horn was pretreated with a selective PKC inhibitor, 2,6-diamino-N-([1-oxotridecyl-2-piperidinyl]- methyl)hexanamide, by microdialysis, sensitization of STT cells by capsaicin injection and the accompanying attenuation of glycine- and GABA-induced inhibition were prevented. 4. Sensitization of STT cells to cutaneous mechanical stimuli was also induced by administration of the PKC activator, 12-O-tetradecanoylphorbol-13-acetate, into the spinal dorsal horn. The inhibition produced by iontophoretic release of glycine, GABA, and muscimol was found to be reduced in most cells examined when this phorbol ester was used. An inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, did not produce significant effects on cellular activity. 5. These results suggest that there is an activation of PKC in the spinal cord when STT neurons are sensitized after intradermal injection of capsaicin or administration of phorbol ester. This sensitization is likely to be involved in the development of allodynia and secondary hyperalgesia not only by enhancing the responses of excitatory amino acid receptors but also by desensitizing glycine and GABA receptors.

Involvement of alpha-2 adrenoceptors in the periaqueductal gray-induced inhibition of dorsal horn cell activity in rats

The noradrenergic system is considered to be one of the major descending analgesia systems originating in the brainstem. The relationship between the periaqueductal gray (PAG) and the descending noradrenergic system is of great interest. A projection from the PAG to the locus ceruleus and parabrachial region has been reported. It is possible that electrical stimulation of the PAG activates spinally projecting collaterals of the noradrenergic cells in A5, the locus ceruleus, subceruleus and A7/Kölliker-Fuse nucleus. The current experiments were designed to study the role of alpha-2 adrenoceptors on spinal cord dorsal Horn cells in PAG-induced inhibition. A microdialysis fiber was introduced into the dorsal horn of the lumbar enlargement for drug administration. An electrode was placed in the vicinity of the microdialysis fiber for extracellular single-unit recording. Recordings were made from a total of 35 cells from 22 Sprague-Dawley rats (270-360 g). When the PAG was stimulated, responses to mechanical stimuli applied to the skin (brush, press and pinch) were inhibited. When an alpha-2 adrenoceptor agonist (clonidine) was administered, the background activity and the responses of the cell to brush, press and pinch stimuli were decreased. In contrast, administration of alpha-2 adrenoceptor antagonists (idazoxan or yohimbine) increased the responses of the cell to brush, press and pinch stimuli. The background activity was also increased by idazoxan. The PAG-induced inhibition of the response to mechanical stimuli was reduced by idazoxan and yohimbine. These results suggest an involvement of alpha-2 adrenoceptors in the mechanism of PAG-induced inhibition of dorsal horn cell activity.

Possible role of protein kinase C in the sensitization of primate spinothalamic tract neurons

The responsiveness of spinal cord nociceptive neurons to innocuous mechanical stimuli can be increased by the release of excitatory amino acids (EAAs) and peptides attributable to an injury-induced barrage of impulses. This sensitization of spinal dorsal horn neurons can also result from administration of phorbol ester by microdialysis, presumably by direct activation of protein kinase C (PKC). This study was designed to examine the effects of central sensitization of spinothalamic tract (STT) neurons produced by intradermal injection of capsaicin on the descending inhibition driven from the periaqueductal gray (PAG) and the possible role of PKC in this process in anesthetized monkeys. Sensitization of responses of STT cells to mechanical stimuli was induced by intradermal injection of capsaicin. PAG inhibition was significantly attenuated when sensitization of responses to mechanical stimuli occurred. However, perfusion of the spinal cord with NPC15437 (a selective PKC inhibitor) by microdialysis could prevent the sensitization of the responses to mechanical stimuli and the reduction in PAG inhibition of these responses induced by capsaicin injection. Results similar to those produced by capsaicin injection were observed when a PKC activator, phorbol ester (12-O-tetradecanoylphorbol-13-acetate), was infused within the dorsal horn by microdialysis. An inactive phorbol ester (4 alpha-phorbol 12,13-didecanoate) had no effect. These results provide evidence that the activation of PKC contributes to the development of central sensitization in dorsal horn neurons produced by chemical stimulation with capsaicin. Attenuation of the effectiveness of PAG inhibition takes place when the sensitization of dorsal horn cells develops, and PKC may play a significant role in this process.

Antinociception and inhibition from the periaqueductal gray are mediated in part by spinal 5-hydroxytryptamine(1A) receptors

Although 5-hydroxytryptamine (5-HT) is known to be involved in the mediation of antinociception from the periaqueductal gray (PAG), its mode of action remains obscure. This investigation uses selective 5-HT(1A) receptor agonist and antagonist drugs in both behavioral and electrophysiological studies on antinociceptive mechanisms of the PAG of rats. Intraspinal administration of 8-hydroxy-dipropylaminotetralin hydrobromide (8-OH-DPAT), a selective 5-HT(1A) agonist, by microdialysis produced a dose-dependent antinociception in the radiant-heat paw withdrawal test. Dorsal horn neuronal activity was recorded extracellularly to test responses to noxious cutaneous stimuli when 8-OH-DPAT was administered iontophoretically, and it was observed that the noxious-evoked responses were inhibited in a current-related manner in all cells examined. The inhibitory effects elicited by 8-OH-DPAT could be selectively blocked by perfusion of the spinal cord with S-(--)-propranolol, a selective 5-HT(1A) antagonist. The antinociception produced by microinjection of morphine into the PAG was significantly attenuated in a dose-related manner by S-(--)-propranolol administered into the spinal cord. Similarly, the inhibition of dorsal horn neuronal responses to cutaneous mechanical stimuli produced by electrical stimulation in the PAG was reduced by S-(--)-propranolol administered into the spinal cord in the majority of cells tested. These data suggest that the release of 5-HT in the dorsal horn by stimulation in the PAG may act directly on spinal 5-HT(1A) receptors, resulting in inhibition of dorsal horn neurons. This is presumably one of the antinociceptive mechanisms of the descending serotonergic inhibitory pathway.

Role of GABA receptor subtypes in inhibition of primate spinothalamic tract neurons: difference between spinal and periaqueductal gray inhibition

1. gamma-Aminobutyric acid (GABA) is thought to inhibit both pre- and postsynaptically the transfer of nociceptive signals from primary afferent fibers to spinal dorsal horn sensory cells, including spinothalamic tract (STT) neurons. The inhibition can be mediated by both GABAA and GABAB receptors. We now attempt to characterize the synaptic inhibition of STT cells by spinal GABAA and GABAB receptors in anesthetized monkeys and to analyze the roles of these two receptor subtypes in the inhibition of STT cellular activity produced by stimulation in the periaqueductal gray (PAG). 2. Iontophoretic release of GABA or muscimol (a selective GABAA receptor agonist) onto STT cells elicited a profound and dose-related inhibition of the responses of all cells tested to noxious cutaneous stimuli. Only four cells (16.7%) were found to be inhibited when baclofen (a selective GABAB receptor agonist) was applied iontophoretically. However, a strong and dose-dependent inhibition of the responses to cutaneous mechanical and thermal stimuli was obtained in all cells examined when baclofen was administered into the dorsal horn through a microdialysis fiber. The inhibitory effects were mainly on nociceptive inputs. 3. The inhibition of cellular activity by GABAA and GABAB agonists could be selectively antagonized by specific antagonists applied through a microdialysis fiber. 4. The excitatory responses evoked by pulsed release of glutamic acid (GLUT) were also inhibited in a dose-related manner by iontophoretic application of GABA and muscimol, but not by baclofen. A high dose of baclofen administered by microdialysis resulted in only a small decrease in GLUT-evoked excitatory responses. 5. Infusion of GABAA and GABAB antagonists into the dorsal horn by microdialysis caused an increase in both background activity and responses to cutaneous stimuli, suggesting that there is a tonic GABAergic inhibition of STT cells. 6. The inhibition of responses to mechanical and thermal stimulation of the cutaneous excitatory receptive field resulting from stimulation in PAG was significantly antagonized in most of the STT cells tested when the GABAA antagonist bicuculline was infused into the spinal dorsal horn through a microdialysis fiber. In contrast, the inhibition produced by PAG stimulation in most of the cells examined was not significantly antagonized by the GABAB antagonists phaclofen or 3-amino-propyl(diethoxymethyl)phophinic acid (CGP35348) administered into the spinal dorsal horn by microdialysis. 7. Our results support the contention that GABAergic mechanisms in the spinal dorsal horn normally exert a tonic modulation of nociceptive inputs through both GABAA and GABAB receptors. The evidence provided here indicates that GABAA receptors located on primate STT neurons contribute to a postsynaptic inhibitory effect on the transmission of peripheral nociceptive inputs. A possible presynaptic GABAA action was not investigated. Our finding of a GABAB-receptor-mediated inhibition is consistent with the view that both pre- and postsynaptic GABAB receptors are involved in inhibitory modulation of spinal nociceptive transmission. Finally, it is suggested from this study that primate spinal GABAA, but not GABAB receptors, are involved in mediating the descending inhibition induced by PAG stimulation.

The role of 5-HT3 receptors in periaqueductal gray-induced inhibition of nociceptive dorsal horn neurons in rats

Electrical stimulation in the periaqueductal gray (PAG) can inhibit dorsal horn cell responses to both innocuous and noxious cutaneous stimuli. This inhibition is believed to be due to the release of serotonin (5-HT) into the dorsal horn of the spinal cord from descending axons of the nucleus raphe magnus and the adjacent reticular formation. It is still not clearly known which subtypes of 5-HT receptors are involved in the PAG-induced inhibition. Extracellular single-unit recordings of dorsal horn cell activity, in combination with drug administration through a microdialysis fiber, were used to test the role of 5-HT3 receptors in PAG-induced inhibition. The responses of the cells to mechanical stimulation of the skin (BRUSH, PRESS and PINCH) and to the same stimuli while stimulating PAG were recorded. When the 5-HT3 antagonist, ondansetron, was perfused through the microdialysis fiber, not only was the background activity of the cell increased, but also the responses to BRUSH, PRESS and PINCH stimuli. The PAG-induced inhibition of responses to the same stimuli was partially or completely blocked by ondansetron. Another 5-HT3 antagonist, zacopride, did not increase the background activity or responses to PRESS and PINCH, yet this agent, like ondansetron, blocked PAG inhibition. The 5-HT3 agonist, phenylbiguanide, inhibited the background activity and the responses to mechanical stimuli. These results suggest that 5-HT released in the dorsal horn by stimulation in the PAG excites inhibitory interneurons through 5-HT3 receptors, resulting in inhibition of dorsal horn neurons.