Antithrombotic effects of tetramethylpyrazine in in vivo experiments

Tetramethylpyrazine alleviates diabetes-induced high platelet response and endothelial adhesion via inhibiting NLRP3 inflammasome activation

BACKGROUND

The inflammatory state of diabetes promotes high platelet response and endothelial adhesion, which are the main risk factors for cardiovascular events. Tetramethylpyrazine (TMP) is an amide alkaloid isolated from the traditional Chinese medicine Rhizoma Ligustici Chuanxiong, which has been widely used in the clinical treatment of ischemic cardiovascular disease.

PURPOSE

This study aimed to investigate whether TMP could alleviate diabetes-induced high platelet response and endothelial adhesion and the underlying mechanisms.

METHODS

Type 2 diabetes mellitus (T2DM) rat model was established by high-fat feeding combined with low dose of streptozotocin. Rats in the TMP treatment group were administered with TMP (100 or 200 mg/kg) for 21 days. Cultured human umbilical vein endothelial cells (HUVECs) were stimulated with glucose (5.5 mM) to induce endothelial activation. The NOD-like receptor protein 3 (NLRP3) over- and low-expressing cell models were established via transfection of NLRP3 lentivirus plasmid into HUVECs. INF39 (25 mg/kg), a chemical inhibitor of NLRP3 inflammasome, was used to explore the role of NLRP3 in T2DM associated high platelet response and endothelial adhesion.

RESULTS

TMP effectively improved the prothrombotic phenotypes and inhibited the expression of vascular inflammatory factors and adhesion molecules in T2DM rats. TMP inhibited NLRP3 inflammasome and reduced the adhesion of HUVECs to platelets and monocytes in vitro. Over-expression of NLRP3 blocked the effect of TMP on HUVECs activation and adhesion, while TMP had no effect on NLRP3 low-expressing HUVECs. The NLRP3 inhibitor INF39 produced similar effects of TMP on diabetes-induced high platelet response, endothelial adhesion and vascular inflammation.

CONCLUSION

TMP ameliorates diabetes-induced high platelet response and endothelial adhesion via inhibiting NLRP3 inflammasome activation in T2DM rats, which provide a new basis for the clinical prevention and treatment of diabetes-associated cardiovascular events.

Tetramethylpyrazine nitrone improves motor dysfunction and pathological manifestations by activating the PGC-1α/Nrf2/HO-1 pathway in ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of upper and lower motor neurons that results in skeletal muscle atrophy, weakness and paralysis. Oxidative stress plays a key role in the pathogenesis of ALS, including familial forms of the disease arising from mutation of the gene coding for superoxide dismutase (SOD1). We have used the SOD1^G93A ALS mouse model to investigate the efficacy of 2-[[(1,1-dimethylethyl)oxidoimino]-methyl]-3,5,6-trimethylpyrazine (TBN), a novel tetramethylpyrazine derivative armed with a powerful free-radical scavenging nitrone moiety. TBN was administered to mice by intraperitoneal or intragastric injection after the onset of motor deficits. TBN slowed the progression of motor neuron disease as evidenced by improved motor performance, reduced spinal motor neuron loss and the associated glial response, and decreased skeletal muscle fiber denervation and fibrosis. TBN treatment activated mitochondrial antioxidant activity through the PGC-1α/Nrf2/HO-1 pathway and decreased the expression of human SOD1. These findings suggest that TBN holds promise as a therapeutic agent for ALS.

Tetramethylpyrazine Attenuates the Endotheliotoxicity and the Mitochondrial Dysfunction by Doxorubicin via 14-3-3γ/Bcl-2

Doxorubicin (Dox) with cardiotoxicity and endotheliotoxicity limits its clinical application for cancer. The toxicitic mechanism involves excess ROS generation. 14-3-3s have the protective effects on various injured tissues and cells. Tetramethylpyrazine (TMP) is an alkaloid extracted from the rhizome of Ligusticum wallichii and has multiple bioactivities. We hypothesize that TMP has the protective effects on vascular endothelium by upregulating 14-3-3γ. To test the hypothesis, Dox-induced endotheliotoxicity was used to establish vascular endothelium injury models in mice and human umbilical vein endothelial cells. The effects of TMP were assessed by determining thoracic aortic strips' endothelium-dependent dilation (EDD), as well as LDH, CK, caspase-3, SOD, CAT, GSH-Px activities and MDA level in serum, apoptotic rate, and histopathological changes of vascular tissue (in vivo). Also, cell viability, LDH and caspase-3 activities, ROS generation, levels of NAD⁺/NADH and GSH/GSSG, MMP, mPTP opening, and apoptotic rate were evaluated (in vitro). The expression of 14-3-3γ and Bcl-2, as well as phosphorylation of Bad (S112), were determined by Western blot. Our results showed that Dox-induced injury to vascular endothelium was decreased by TMP via upregulating 14-3-3γ expression in total protein and Bcl-2 expression in mitochondria, activating Bad (S112) phosphorylation, maintaining EDD, reducing LDH, CK, and caspase-3 activities, thereby causing a reduction in apoptotic rate, and histopathological changes of vascular endothelium (in vivo). Furthermore, TMP increased cell viability and MMP levels, maintained NAD⁺/NADH, GSH/GSSG balance, decreased LDH and caspase-3 activities, ROS generation, mPTP opening, and apoptotic rate (in vitro). However, the protective effects to vascular endothelium of TMP were significantly canceled by pAD/14-3-3γ-shRNA, an adenovirus that caused knockdown 14-3-3γ expression, or ABT-737, a specific Bcl-2 inhibitor. In conclusion, this study is the first to demonstrate that TMP protects the vascular endothelium against Dox-induced injury via upregulating 14-3-3γ expression, promoting translocation of Bcl-2 to the mitochondria, closing mPTP, maintaining MMP, inhibiting RIRR mechanism, suppressing oxidative stress, improving mitochondrial function, and alleviating Dox-induced endotheliotoxicity.

Tetramethylpyrazine suppresses HIF-1alpha, TNF-alpha, and activated caspase-3 expression in middle cerebral artery occlusion-induced brain ischemia in rats

AIM

To examine the detailed mechanisms underlying the inhibitory effect of tetramethylpyrazine (TMPZ) in inflammatory and apoptotic responses induced by middle cerebral artery occlusion (MCAO) in rats.

METHODS

MCAO-induced focal cerebral ischemia in rats was used in this study. The hypoxia-inducible factor-1alpha(HIF-1alpha), activation of caspase-3, and TNF-alpha mRNA transcription in ischemic regions were detected by immunoblotting and RT-PCR, respectively. Anti-oxidative activity was investigated using a thiobarbituric acid-reactive substance (TBARS) test in rat brain homogenate preparations.

RESULTS

We showed the statistical results of the infarct areas of solvent- and TMPZ (20 mg/kg)-treated groups at various distances from the frontal pole in MCAO-induced focal cerebral ischemia in rats. Treatment with TMPZ (20 mg/kg) markedly reduced the infarct area in all regions, especially in the third to fifth sections. MCAO-induced focal cerebral ischemia was associated with increases in HIF-1alpha and the activation of caspase-3, as well as TNF-alpha transcription in ischemic regions. These expressions were markedly inhibited by treatment with TMPZ (20 mg/kg). However, TMPZ (0.5-5 mmol/L) did not significantly inhibit TBARS reaction in rat brain homogenates.

CONCLUSION

The neuroprotective effect of TMPZ may be mediated at least by a portion of the inhibition of HIF-1alpha and TNF-alpha activations, followed by the inhibition of apoptosis formation (active caspase-3), resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, TMPZ treatment may represent an ideal approach to lowering the risk of or improving function in ischemia- reperfusion brain injury-related disorders.

Role of cGMP signals in tetramethylpyrazine induced relaxation of the isolated rat aortic strip

In the present study, role of guanosine-3',5'-cyclic monophosphate (cGMP) in the vasodilatation of tetramethylpyrazine (TMP), one of the active ingredients of the Chinese herb Chuang-xion, was investigated. We found that the TMP could decrease the vascular tone of isolated rat aorta precontracted with phenylephrine (10(-8) M) in a concentration-dependent manner from 10(-5) M to 10(-3) M. Also, the TMP-induced relaxation was reduced by 1H-(1,2,4)-oxadiazol-(4,3-a)-quinoxalin-1-one (ODQ) or methylene blue, the inhibitor of soluble guanylyl cyclase. Moreover, the vasodilative response to TMP was enhanced significantly in the presence of sildenafil, a well-known inhibitor of phosphodiestrase type 5 that is sensitive to cGMP. In addition, TMP could increase the cGMP level in the isolated aortic rings and TMP-induced vasodilatation was deleted by cGMP-dependent protein kinases (PKG) blockade. These results suggest that relaxation of rat aortic strip by TMP is induced in the cGMP-dependent manner.