Tetramethylpyrazine Protects Against Early Brain Injury and Inhibits the PERK/Akt Pathway in a Rat Model of Subarachnoid Hemorrhage

Food additives for the central nervous system, useful or harmful? An evidence-based review

OBJECTIVES

This review examines how food additives impact the central nervous system (CNS) focusing on the effects of sugars, artificial sweeteners, colorings, and preservatives.

METHODS

A literature search of PubMed, Scopus, and Web of Science was conducted for studies published since 2010. Key search terms included, food additives, neurotoxicity, cognition, and behavior.

RESULTS

It summarizes research findings on additives such as aspartame, stevia, methylene blue, azo dyes, sodium benzoate, and monosodium glutamate. It also covers mechanisms such as oxidative stress, neuroinflammation, and disruptions in neurotransmitter systems. Furthermore, it emphasizes the properties of natural compounds such as garlic (Allium sativum), tetramethylpyrazine, curcumin, licorice root extract (glycyrrhizin), and polyphenols in mitigating CNS damage caused by food additives.

DISCUSSION

Although ongoing studies are expanding our knowledge on the effects of these additives, future CNS research should focus on long-term investigations involving subjects to provide a more comprehensive understanding of the cumulative impacts of different additives and update regulatory standards based on new scientific findings.

A crosstalk between autophagy and apoptosis in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a severe condition that devastatingly harms human health and poses a financial burden on families and society. Bcl-2 Associated X-protein (Bax) and B-cell lymphoma 2 (Bcl-2) are two classic apoptotic markers post-ICH. Beclin 1 offers a competitive architecture with that of Bax, both playing a vital role in autophagy. However, the interaction between Beclin 1 and Bcl-2/Bax has not been conjunctively analyzed. This review aims to examine the crosstalk between autophagy and apoptosis in ICH by focusing on the interaction and balance of Beclin 1, Bax, and Bcl-2. We also explored the therapeutic potential of Western conventional medicine and traditional Chinese medicine (TCM) in ICH via controlling the crosstalk between autophagy and apoptosis.

Tetramethylpyrazine-derived polyurethane for improved hemocompatibility and rapid endothelialization

Thrombosis and intimal hyperplasia (IH) are the main factors affecting the long-term patency of small-diameter vascular grafts (SDVGs). Fabricating a confluent endothelial cell (EC) layer on surfaces with physiological elasticity to mimic vascular endothelium should be an effective strategy to prevent restenosis that is caused by thrombosis and IH. However, the vascular endothelialization process is time-consuming and always constrained by hemocompatibility of the vascular grafts, since excellent hemocompatibility could guarantee a sufficient time window for the endothelialization process. Tetramethylpyrazine (TMP)-derived polyurethane (PU) with improved hemocompatibility and accelerated endothelialization ability is synthesized by incorporating TMP moieties into PU backbones. Results show that TMP-contained PU films possess improved hemocompatibility by down-regulating platelet adhesion/activation and increasing the clotting time. Furthermore, the in vitro human umbilical vein endothelial cell (HUVEC) test demonstrates that the introduction of TMP can significantly promote HUVEC adhesion and proliferation, and thus accelerate luminal endothelialization of vascular grafts. Moreover, the TMP-containing PU films exhibit excellent biocompatibility especially for HUVECs, and their excellent, adjustable elasticity (1123%) guarantees compliance accommodation of vascular grafts. This newly synthesized TMP-containing material with multiple biological functions is expected to make up for the shortcomings of available SDVGs in clinical practice, and has significant potential in improving the long-term patency of SDVGs.

Tao-Hong-Si-Wu-Tang Improves the Depressive-like Behaviors in Mice Experiencing Perimenopausal Depression Through Modulating Activity of the Hypothalamic-Pituitary-Adrenal-Ovary Axis and Activating the BDNF-TrkB-CREB Signaling Pathway

Tao-Hong-Si-Wu-Tang (THSWT), a traditional Chinese herbal remedy, is commonly utilized for the treatment of female perimenopausal depression through regulating menstruation, but the mechanism remains unknown. In this study, ICR mice were randomly divided into six groups: low, medium, and high dose of THSWT (0.5, 1.5, and 4.5 g/kg), soy isoflavone (250 mg/kg), ovariectomy group, and control group. All mice, except the control group, had ovaries removed and were exposed to hypoxic stimulation for 28 days to establish a perimenopausal depression mice model. The mice, having unrestricted access to food and water, were administered THSWT treatment for a duration of 14 days. The Western blotting and Enzyme linked immunosorbent assay kits were used to determine protein and hormone levels, respectively. Experimental results showed that THSWT reduced the immobility time of mice from 150.8 s to 104.9 s in the tail suspension test, and it decreased the immobility time of mice from 165.7 s to 119.0 s in the forced swimming test, outperforming the results obtained with soy isoflavones. In addition, THSWT upregulated the protein expression of follicle-stimulating hormone receptor and downregulated the protein expression of corticotropin-releasing hormone-receptor 1 in the hippocampus. Compared with the oophorectomized group, treatment with THSWT decreased the levels of corticosterone and adrenocorticotropic hormone in serum by 173.7 and 23.4 ng/mL, respectively. These findings showed that THSWT could stimulate the perimenopausal nerve tissue and regulate the level of serum hormones in mice. THSWT exhibited promising potential as a viable alternative drug for hormone treatment of perimenopause in clinical use.

Therapeutic Potential of Natural Compounds in Subarachnoid Haemorrhage

Subarachnoid hemorrhage (SAH) is a common and fatal cerebrovascular disease with high morbidity, mortality and very poor prognosis worldwide. SAH can induce a complex series of pathophysiological processes, and the main factors affecting its prognosis are early brain injury (EBI) and delayed cerebral ischemia (DCI). The pathophysiological features of EBI mainly include intense neuroinflammation, oxidative stress, neuronal cell death, mitochondrial dysfunction and brain edema, while DCI is characterized by delayed onset ischemic neurological deficits and cerebral vasospasm (CVS). Despite much exploration in people to improve the prognostic outcome of SAH, effective treatment strategies are still lacking. In recent years, numerous studies have shown that natural compounds of plant origin have unique neuro- and vascular protective effects in EBI and DCI after SAH and long-term neurological deficits, which mainly include inhibition of inflammatory response, reduction of oxidative stress, anti-apoptosis, and improvement of blood-brain barrier and cerebral vasospasm. The aim of this paper is to systematically explore the processes of neuroinflammation, oxidative stress, and apoptosis in SAH, and to summarize natural compounds as potential targets for improving the prognosis of SAH and their related mechanisms of action for future therapies.

Acacetin inhibits activation of microglia to improve neuroinflammation after subarachnoid hemorrhage through the PERK signaling pathway mediated autophagy

PURPOSE

To explore the effect of acacetin on subarachnoid hemorrhage (SAH) and its possible mechanism.

METHODS

SAH model of rat was established, and intraperitoneally injected with three doses of acacetin. To verify the role of PERK pathway, we used the CCT020312 (PERK inhibitor) and Tunicamycin (activators of endoplasmic reticulum stress). The SAH score, neurological function score, brain edema content, and Evans blue (EB) exudate were evaluated. Western blot was used to determine the expression of inflammation-associated proteins and PERK pathway. The activation of microglia was also determined through Iba-1 detection. TEM and immunofluorescence staining of LC3B were performed to observe the autophagy degree of SAH rats after acacetin. Tunel/NeuN staining, HE and Nissl' staining were performed for neuronal damage.

RESULTS

Acacetin increased the neurological function score, reduce brain water content, Evans blue exudation and SAH scores. The microglia in cerebral cortex were activated after SAH, while acacetin could inhibit its activation, and decreased the expression of TNF-α and IL-6 proteins. The pathological staining showed the severe neuronal damage and increased neuronal apoptosis after SAH, while acacetin could improve these pathological changes. We also visualized the alleviated autophagy after acacetin. The expression of Beclin1 and ATF4 proteins were increased, but acacetin could inhibit them. Acacetin also inactivated PERK pathway, which could improve the neuronal injury and neuroinflammation after SAH, inhibit the microglia activation and the overactivated autophagy through PERK pathway.

CONCLUSION

Acacetin may alleviate neuroinflammation and neuronal damage through PERK pathway, thus having the protective effect on EBI after SAH.

Buyang Huanwu Decoction: A Traditional Chinese Medicine, Promotes Lactate-Induced Angiogenesis in Experimental Intracerebral Hemorrhage

Identifying the underlying mechanisms and exploring effective therapies for intracerebral hemorrhage (ICH) are urgently needed. Here, we aim to elucidate the potential roles and underlying mechanisms of Buyang Huanwu decoction (BYHWD) in ICH. In the first set of experiments, rats were randomly divided into five groups: Sham, ICH, ICH + sodium oxamate (OXA), ICH + BYHWD, and ICH + BYHWD + OXA. The lactate level around the hematoma was evaluated. PCNA+/vWF+ nuclei were observed. Additionally, an online bioinformatics analysis tool was used to predict the BYHWD druggable targets related to angiogenesis. Then, we validated these predictions. In the second set, exogenous sodium L-lactate (Lac) was infused into the intact brains of rats. Rats were randomly divided into three groups: Sham, Lac, and Lac + YC-1. The numbers of PCNA+/vWF+ nuclei and the expression of HIF-1α and VEGF were evaluated. In the first set of experiments, compared with the ICH group, the BYHWD group exhibited significantly increased numbers of PCNA+/vWF+ nuclei, and neurological dysfunction was markedly improved. Bioinformatics analysis revealed that the improvements caused by BYHWD indicated a role for the HIF-1α pathway. The HIF-1α and VEGF protein levels were upregulated after BYHWD administration. Moreover, we verified that lactate was involved in the predicted mechanisms. In the second set, lactate facilitated angiogenesis and HIF-1α and VEGF expression. Co-infusion with a HIF-1α inhibitor, YC-1, significantly inhibited these effects. Our data suggest that the pharmacological effects of BYHWD involve lactate-induced angiogenesis, these data may provide new evidence for its use in ICH.

Live and let die: signaling AKTivation and UPRegulation dynamics in SARS-CoVs infection and cancer

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the coronavirus disease 2019 (COVID-19) pandemic. Of particular interest for this topic are the signaling cascades that regulate cell survival and death, two opposite cell programs whose control is hijacked by viral infections. The AKT and the Unfolded Protein Response (UPR) pathways, which maintain cell homeostasis by regulating these two programs, have been shown to be deregulated during SARS-CoVs infection as well as in the development of cancer, one of the most important comorbidities in relation to COVID-19. Recent evidence revealed two way crosstalk mechanisms between the AKT and the UPR pathways, suggesting that they might constitute a unified homeostatic control system. Here, we review the role of the AKT and UPR pathways and their interaction in relation to SARS-CoV-2 infection as well as in tumor onset and progression. Feedback regulation between AKT and UPR pathways emerges as a master control mechanism of cell decision making in terms of survival or death and therefore represents a key potential target for developing treatments for both viral infection and cancer. In particular, drug repositioning, the investigation of existing drugs for new therapeutic purposes, could significantly reduce time and costs compared to de novo drug discovery.

Tetramethylpyrazine: A review on its mechanisms and functions

Ligusticum chuanxiong Hort (known as Chuanxiong in China, CX) is one of the most widely used and long-standing medicinal herbs in China. Tetramethylpyrazine (TMP) is an alkaloid and one of the active components of CX. Over the past few decades, TMP has been proven to possess several pharmacological properties. It has been used to treat a variety of diseases with excellent therapeutic effects. Here, the pharmacological characteristics and molecular mechanism of TMP in recent years are reviewed, with an emphasis on the signal-regulation mechanism of TMP. This review shows that TMP has many physiological functions, including anti-oxidant, anti-inflammatory, and anti-apoptosis properties; autophagy regulation; vasodilation; angiogenesis regulation; mitochondrial damage suppression; endothelial protection; reduction of proliferation and migration of vascular smooth muscle cells; and neuroprotection. At present, TMP is used in treating cardiovascular, nervous, and digestive system conditions, cancer, and other conditions and has achieved good curative effects. The therapeutic mechanism of TMP involves multiple targets, multiple pathways, and bidirectional regulation. TMP is, thus, a promising drug with great research potential.

Traditional Chinese medicine use in the pathophysiological processes of intracerebral hemorrhage and comparison with conventional therapy

Intracerebral hemorrhage (ICH) refers to hemorrhage caused by non-traumatic vascular rupture in the brain parenchyma, which is characterized by acute onset, severe illness, and high mortality and disability. The influx of blood into the brain tissue after cerebrovascular rupture causes severe brain damage, including primary injury caused by persistent hemorrhage and secondary brain injury (SBI) induced by hematoma. The mechanism of brain injury is complicated and is a significant cause of disability after ICH. Therefore, it is essential to understand the mechanism of brain injury after ICH to develop drugs to prevent and treat ICH. Studies have confirmed that many traditional Chinese medicines (TCM) can reduce brain injury by improving neurotoxicity, inflammation, oxidative stress (OS), blood-brain barrier (BBB), apoptosis, and neurological dysfunction after ICH. Starting from the pathophysiological process of brain injury after ICH, this paper summarizes the mechanisms by which TCM improves cerebral injury after ICH and its comparison with conventional western medicine, so as to provide clues and a reference for the clinical application of TCM in the prevention and treatment of hemorrhagic stroke and further research and development of new drugs.

The Roles of Tetramethylpyrazine During Neurodegenerative Disease

With the aging of the world population, neurodegenerative diseases are considered crippling diseases, which seriously affect the quality of life and are an increasing burden on society and the economy. As a major alkaloid in Ligusticum chuanxiong Hort, tetramethylpyrazine (TMP) plays an increasingly significant role during neurodegenerative diseases, including roles as an anti-inflammatory, antioxidative, antiplatelet citatory poisoning, and anti-inflammation. This review focuses on the latest advances in the roles and mechanisms of action of TMP in neurodegenerative diseases to stimulate new concepts and methods for the prevention and treatment of neurodegenerative diseases.

Possibilities of Using Phyto-Preparations to Increase the Adaptive Capabilities of the Organism of Test Animals in Swimming

Background: To study the possibilities of using phytopreparations to increase the adaptive capabilities of the animals on which the experiments were conducted in swimming. Methods: 100 mongrel male rats were divided into 5 groups of 20 animals in each one. For 30 days running, the animals were immersed for 10 min in a bath with water at a temperature of +4 °C. In addition to cold exposure, the animals of the first three groups were injected per os with stress protectors 30 min before the immersion in water. The rats of the first group received an inhibitor of the enzyme gamma-butyrobetaine hydroxylase, the second group was given an extract of Eleutherococcus, and the third group took an extract of Ligusticum wallichii. As a placebo, to control the effect of the stress protectors, the rats of the fourth group were injected per os with 0.9% NaCl solution, and the animals in the fifth group were not given any drugs. On days 1, 4 and 30 of the experiment, five randomly selected animals from each group were decapitated, the heart and liver were removed, and the activity of tissue enzymes—superoxide dismutase (SOD), glutathione peroxidase (GPO), alanine aminotransferase (ALT), and aspartate aminotransferase (AST)—was analyzed. Results: The animals in the control group displayed a decrease in the activity of most of the studied enzymes, increasing from the 1st to the 30th day of the experiment. The NaCl solution had practically no effect on the analyzed parameters. Against the use of the enzyme gamma-butyrobetaine hydroxylase inhibitor, the activity of the enzymes did not change as compared with the pre-intervention level. On the first day of ingestion, the effects of the Ligusticum wallichii extract were similar to those of the enzyme gamma-butyrobetaine hydroxylase inhibitor. On the 30th day of ingestion, the effects of the Eleutherococcus extract were practically indistinguishable from those of the enzyme gamma-butyrobetaine hydroxylase inhibitor. Conclusions: The data obtained suggest the presence of cytoprotective effects in the two phytopreparations that are similar to the enzyme gamma-butyrobetaine hydroxylase inhibitor. In this case, the effect of the extract of Ligusticum wallichii is more pronounced under the acute stress conditions, and the extract of Eleutherococcus, under the chronic stress conditions.

Rapid Screening and Quantitative Analysis of 74 Pesticide Residues in Herb by Retention Index Combined with GC-QQQ-MS/MS

In this research, a very practical QuEChERS-GC-MS/MS analytical approach for 74 pesticide residues in herb based on retention index was established. This novel analytical approach has two important technical advantages. One advantage is to quickly screen pesticide compounds in herbs without having to use a large number of pesticide standard substances at the beginning of the experiment. The other advantage is to assist in identifying the target pesticide compound accurately. A total of 74 kinds of pesticides were quickly prescreened in all chuanxiong rhizoma samples. The results showed that three kinds of pesticides were screened out in all the samples, including chlorpyrifos, fipronil, and procymidone, and the three pesticides were qualitatively and quantitatively determined. The RSD values for interday and intraday variation were acquired to evaluate the precision of the analytical approach, and the overall interday and intraday variations are not more than 1.97% and 3.82%, respectively. The variations of concentrations of the analyzed three pesticide compounds in sample CX16 are 0.74%-4.15%, indicating that the three pesticides in the sample solutions were stable in 48 h. The spiked recoveries of the three pesticides are 95.22%, 93.03%, and 94.31%, and the RSDs are less than ± 6.0%. The methodological verification results indicated the good reliability and accuracy of the new analytical method. This research work is a new application of retention index, and it will be a valuable tool to assist quickly and accurately in the qualitative and quantitative analysis of multipesticide residues in herbs.

A Novel Co-Crystal of Bexarotene and Ligustrazine Improves Pharmacokinetics and Tissue Distribution of Bexarotene in SD Rats

Bexarotene (BEX), a specific retinoic acid X receptor (RXR) agonist granted by Food and Drug Administration (FDA) approval for the clinical treatment of T cell lymphoma, has now been found to exert pharmacological effects in the nervous system, with low bioavailability and poor cerebral distribution limiting its application in treatment on neurological disorders. Pharmaceutical co-crystal was a helpful method to improve the bioavailability and tissue distribution of active pharmaceutical ingredients (APIs). Here, 2bexarotene-ligustrazine (2BEX-LIG), a novel co-crystal system of BEX and ligustrazine (LIG) of which with BEX is an API, was constructed with satisfactory stability and enhanced solubility. The pharmacokinetics characteristics of BEX were detected, and the results showed that the absolute bioavailability and the cerebral concentration of BEX in rats administrated with 2BEX-LIG were enhanced from 22.89% to 42.86% and increased by 3.4-fold, respectively, compared with those in rats administrated an equivalent of BEX. Hence, our present study indicated that the novel co-crystal of 2BEX-LIG contributed to improving BEX oral bioavailability and cerebral distribution, thereby providing significant advantages for clinical application of brain tumors and other neurological diseases.

Tetramethylpyrazine ameliorates isoflurane-induced cognitive dysfunction by inhibiting neuroinflammation via miR-150 in rats

Tetramethylpyrazine (TMP) has neuroprotective effects in the pathogenesis of some human diseases, such as Parkinson's disease. The present study aimed to investigate the role of TMP in isoflurane-induced cognitive dysfunction in rats, and further identify the mechanisms involved in the protective effects of TMP. The Morris water maze test was used to evaluate the cognitive function of rats exposed to isoflurane or treated with TMP. ELISA was conducted to evaluate the effects of isoflurane or TMP on neuroinflammation. The expression of microRNA-150 (miR-150) was measured using reverse transcription-quantitative PCR, and the potential target genes of miR-150 were predicted and verified. The impaired cognitive function induced by isoflurane in the rats was significantly ameliorated by treatment with TMP. In addition, TMP treatment in rats attenuated neuroinflammation caused by isoflurane. The expression of miR-150 was inhibited by isoflurane exposure, but was enhanced by TMP treatment in rats. Furthermore, the overexpression of miR-150 alleviated the isoflurane-induced cognitive dysfunction and neuroinflammation, while the neuroprotective effects of TMP were significantly abrogated by the knockdown of miR-150. AKT3 was a direct target of miR-150, and its mRNA expression was significantly decreased by the overexpression of miR-150 in isoflurane- and TMP-treated rats. These results demonstrated the protective effects of TMP against isoflurane-induced cognitive dysfunction, which were achieved by attenuating neuroinflammation via the regulation of the miR-150/AKT3 pathway. In addition, miR-150 may serve as a novel therapeutic target for the alleviation of cognitive dysfunction induced by anesthetics.

Increased microneedle-mediated transdermal delivery of tetramethylpyrazine to the brain, combined with borneol and iontophoresis, for MCAO prevention

The aim of this research was to improve transdermal delivery and distribution of tetramethylpyrazine (TMP) in the brain, by adding borneol (BN) and iontophoresis (ITP), and using microneedles (MN), to prevent middle cerebral artery occlusion (MCAO). BN was encapsulated into sulfobutylated-β-cyclodextrin (BN-SBE-β-CD), and then dispersed together with TMP. Four delivery groups were tested: passive (with no ITP and MN), ITP, MN, and MN combined with ITP (MN-ITP). In vitro transdermal fluxes of the drugs in those groups and in that corresponding order were 79.12 ± 14.5, 395.43 ± 12.37, 319.16 ± 29.99, and 1018.07 ± 108.92 μg/cm² (for TMP), and 39.34 ± 1.31, 202.81 ± 53.56, 715.47 ± 75.52, and 1088.60 ± 53.90 μg/cm² (for BN), respectively, which indicated that the use of MN-ITP greatly enhanced transdermal TMP and BN delivery compared to the other groups. The AUC_0-t for the combined use of TMP and BN drugs was measured using two in vivo studies, cutaneous microdialysis and pharmacodynamic, yielding increased folds of 3.69 and 1.98 in ITP, 6.05 and 2.73 in MN, and 12.43 and 7.47 in MN-ITP groups, respectively, as compared to those in the passive group. In addition, the combined use of TMP and BN increased TMP distribution in the heart and the brain, indicated by TMP C_max of 1.76- and 1.59-fold higher (p < 0.05), and TMP AUC_0-t of 1.50 times and 1.19-fold higher (p < 0.01), than with administration of TMP in absence of BN, respectively. The brain infarction area and IL-β expression in the MCAO rat were significantly decreased in the MN-ITP group, compared with the control group (p < 0.05). In conclusion, combination of MN and ITP resulted in a synergistic enhancement of transdermal delivery and distribution of TMP in the brain, when in combination with BN, thereby significantly decreasing the infarct volumes and improving the neurological scores of MCAO.

Preparation, preliminary pharmacokinetics and brain tissue distribution of Tanshinone IIA and Tetramethylpyrazine composite nanoemulsions

Objective: Tanshinone IIA (TSN) and Tetramethylpyrazine (TMP) were combined in a composite, oil-in-water nanoemulsions (TSN/TMP O/W NEs) was prepared to prolong in vitro and vivo circulation time, and enhance the bioavailability of TSN. Material and methods: Physicochemical characterization of TSN/TMP O/W NEs was characterized systematically. The in vitro dissolution and in vivo pharmacokinetic experiments of TSN/TMP O/W NEs were also evaluated. Result: A formulation was optimized, yielding a 32.5 nm average particle size, an encapsulation efficiency of over 95 %, and were spherical in shape as shown by TEM. TSN/TMP O/W NEs were shown to extend the release and availability in vitro compared to raw compounds. In pharmacokinetic study, the AUC_0→∞ and t_1/2 of the TSN/TMP O/W NEs were 481.50 mg/L*min and 346.39 min higher than TSN solution, respectively. Brain tissue concentration of TSN was enhanced with TSN/TMP O/W NEs over raw TSN and even TSN O/W NEs. Conclusions: Therefore, nanoemulsions are an effective carrier to increase encapsulation efficiency of drugs, improve bioavailability and brain penetration for TSN - which is further enhanced by pairing with the co-delivery of TMP, providing a promising drug delivery.

Tetramethylpyrazine ameliorates depression by inhibiting TLR4-NLRP3 inflammasome signal pathway in mice

Depression is a common but serious mental illness; meanwhile, it is also an inflammatory disorder. Toll-like receptor 4 (TLR4), as the pattern recognition receptor, has been shown to play a vital role in neuroinflammation. The nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome acts as an important signaling molecule downstream of TLR4 and can promote the maturation of inflammatory cytokines, such as interleukin-1β (IL-1β). Tetramethylpyrazine (TMP) is a natural compound with neuroprotective effects but with unknown mechanisms on its antidepressant-like effect. In this study, we hypothesized that TMP ameliorates depression may be through the inhibition of the TLR4-NF-κB-NLRP3 signal pathway. Our results have shown that chronic unpredictable mild stress (CUMS) that induced the decreased sucrose preference and increased immobile time was prominently reversed by TMP and fluoxetine. Additionally, we also found that CUMS induced the upregulation of proinflammatory cytokines; TLR4 and NLRP3-associated proteins were significantly suppressed by TMP in the prefrontal cortex and hippocampus. TMP also exhibited potent antioxidant effects and increased the monoamine levels in the serum and brain, such as increasing the activity of SOD and GSH-Px, and reducing the activity of MDA in the serum, and elevating the 5-HT and NE concentration in the serum and brain. Moreover, treatment with Cli-095 (TLR4 inhibitor) also markedly inhibited CUMS-induced depression-like behaviors. Taken together, our findings suggested that TMP exerted a potential antidepressant-like effect in CUMS mice, and the molecular mechanisms may relate to inhibit the TLR4-NF-κB-NLRP3 signaling pathway in the brain.

Tetramethylpyrazine Nitrone Reduces Oxidative Stress to Alleviate Cerebral Vasospasm in Experimental Subarachnoid Hemorrhage Models

Cerebral vasospasm is one of the deleterious complications after subarachnoid hemorrhage (SAH), leading to delayed cerebral ischemia and permanent neurological deficits or even death. Free radicals and oxidative stress are considered as crucial causes contributing to cerebral vasospasm and brain damage after SAH. Tetramethylpyrazine nitrone (TBN), a derivative of the clinically used anti-stroke drug tetramethylpyrazine armed with a powerful free radical scavenging nitrone moiety, has been reported to prevent brain damage from ischemic stroke. The present study aimed to investigate the effects of TBN on vasospasm and brain damage after SAH. Two experimental SAH models were used, a rat model by endovascular perforation and a rabbit model by intracisternal injection of autologous blood. The effects of TBN on SAH were evaluated assessing basilar artery spasm, neuronal apoptosis, and neurological deficits. TBN treatment significantly attenuated vasospasm, improved neurological behavior functions and reduced the number of apoptotic neurons in both the SAH rats and rabbits. Mechanistically, TBN suppressed the increase in 3-nitrotyrosine and 8-hydroxy-2-deoxyguanosine immuno-positive cells in the cortex of SAH rat brain. Western blot analyses indicated that TBN effectively reversed the altered expression of Bcl-2, Bax and cytochrome C, and up-regulated nuclear factor erythroid-derived 2-like 2 (Nrf2) and hemeoxygenase-1 (HO-1) protein expressions. In the in vitro studies, TBN inhibited H₂O₂-induced bEnd.3 cell apoptosis and reduced ROS generation. Additionally, TBN alleviated the contraction of rat basilar artery rings induced by H₂O₂ ex vivo. In conclusion, TBN ameliorated SAH-induced cerebral vasospasm and neuronal damage. These effects of TBN may be attributed to its anti-oxidative stress effect and up-regulation of Nrf2/HO-1.