Tetramethylpyrazine decreases hypothalamic glutamate, hydroxyl radicals and prostaglandin-E2 and has antipyretic effects

Analgesic Alkaloids Derived From Traditional Chinese Medicine in Pain Management

Chronic pain is one of the most prevalent health problems. The establishment of chronic pain is complex. Current medication for chronic pain mainly dependent on anticonvulsants, tricyclic antidepressants and opioidergic drugs. However, they have limited therapeutic efficacy, and some even with severe side effects. We turned our interest into alkaloids separated from traditional Chinese medicine (TCM), that usually act on multiple drug targets. In this article, we introduced the best-studied analgesic alkaloids derived from TCM, including tetrahydropalmatine, aloperine, oxysophocarpine, matrine, sinomenine, ligustrazine, evodiamine, brucine, tetrandrine, Stopholidine, and lappaconitine, focusing on their mechanisms and potential clinical applications. To better describe the mechanism of these alkaloids, we adopted the concept of drug-cloud (dCloud) theory. dCloud illustrated the full therapeutic spectrum of multitarget analgesics with two dimensions, which are “direct efficacy”, including inhibition of ion channels, activating γ-Aminobutyric Acid/opioid receptors, to suppress pain signal directly; and “background efficacy”, including reducing neuronal inflammation/oxidative stress, inhibition of glial cell activation, restoring the balance between excitatory and inhibitory neurotransmission, to cure the root causes of chronic pain. Empirical evidence showed drug combination is beneficial to 30–50% chronic pain patients. To promote the discovery of effective analgesic combinations, we introduced an ancient Chinese therapeutic regimen that combines herbal drugs with “Jun”, “Chen”, “Zuo”, and “Shi” properties. In dCloud, “Jun” drug acts directly on the major symptom of the disease; “Chen” drug generates major background effects; “Zuo” drug has salutary and supportive functions; and “Shi” drug facilitates drug delivery to the targeted tissue. Subsequently, using this concept, we interpreted the therapeutic effect of established analgesic compositions containing TCM derived analgesic alkaloids, which may contribute to the establishment of an alternative drug discovery model.

Prostaglandin Transporter OATP2A1/SLCO2A1 Is Essential for Body Temperature Regulation during Fever

Prostaglandin E₂ (PGE₂) in the hypothalamus is a principal mediator of the febrile response. However, the role of organic anion transporting polypeptide 2A1 (OATP2A1/SLCO2A1), a prostaglandin transporter, in facilitating this response is unknown. Here, we investigated the effect of Slco2a1 deficiency on the body core temperature (Tc) and on the PGE₂ concentration in hypothalamus interstitial fluid (C_isf) and CSF (C_csf) of lipopolysaccharide (LPS; 100 μg/kg, i.p.)-treated mice of both sexes. Slco2a1^-/- mice did not develop a febrile response. C_csf was increased in Slco2a1^+/+ and Slco2a1^-/- mice, and C_csf of Slco2a1^-/- mice was well maintained at 5 h after LPS injection (1160 pg/ml) compared with Slco2a1^+/+ mice (316 pg/ml). A microdialysis study revealed that C_isf peaked at 2 h after LPS injection in Slco2a1^+/+ mice (841 pg/ml), whereas the increase in C_isf was negligible in Slco2a1^-/- mice. The PGE₂ plasma concentration in Slco2a1^-/- mice (201 pg/ml) was significantly higher than that in Slco2a1^+/+ mice (54 pg/ml) at 1 h after LPS injection, whereas the two groups showed similar PGE₂ concentrations in the hypothalamus. Strong Oatp2a1 immunoreactivity was observed in F4/80-positive microglia and perivascular cells and in brain capillary endothelial cells. The changes in Tc and C_isf seen in LPS-injected Slco2a1^+/+ mice were partially attenuated in monocyte-/macrophage-specific Slco2a1^-/- (Slco2a1^Fl/Fl/LysM^Cre/+) mice. Thus, OATP2A1 facilitates the LPS-induced febrile response by maintaining a high level of C_isf, possibly by regulating PGE₂ secretion from F4/80-positive glial cells and/or facilitating PGE₂ transport across the blood-brain barrier. These findings suggest that OATP2A1 is a useful therapeutic target for neuroinflammation.SIGNIFICANCE STATEMENT Fever is a physiological response caused by pyrogen-induced release of prostaglandin E₂ (PGE₂) in the hypothalamus, which plays a central role in regulating the set-point of body temperature. However, it is unclear whether the prostaglandin transporter OATP2A1/SLCO2A1 is involved in this response. We show here that LPS-induced fever is associated with increased PGE₂ concentration in hypothalamus interstitial fluid (C_isf), but not in CSF (C_csf), by means of a microdialysis study in global Slco2a1-knock-out mice and monocyte-/macrophage-specific Slco2a1-knock-out mice. The results suggest that OATP2A1 serves as a regulator of C_isf in F4/80-positive glial cells. OATP2A1 was detected immunohistochemically in brain capillary endothelial cells and, therefore, may also play a role in PGE₂ transport across the blood-brain barrier.

Tetramethylpyrazine attenuates lipopolysaccharide-induced cardiomyocyte injury via improving mitochondrial function mediated by 14-3-3γ

Lipopolysaccharide (LPS) is one of the many reasons that can cause myocardial injury. Our previous works have demonstrated that 14-3-3γ could protect myocardium against LPS-induced injury. Tetramethylpyrazine (TMP), an alkaloid found in Chinese herbs, exerts myocardial protection in many ways with multiple targets. We hypothesized that the cardioprotection of TMP against LPS-induced injury is attributed to upregulation of 14-3-3γ and improvement of mitochondrial function. To test the hypothesis, we investigated the effects of TMP on LPS-induced injury to cardiomyocytes by determining cell viability, LDH and caspase-3 activities, reactive oxygen species and MMP levels, mPTP openness, and apoptosis rate. The expression of 14-3-3γ and Bcl-2, and the phosphorylation of Bad (S112) were examined by Western blot. LPS-induced injury to cardiomyocytes was attenuated by TMP via upregulating expression of 14-3-3γ, and Bcl-2 on mitochondria, activating Bad (S112) phosphorylation, increasing cell viability and MMP levels, decreasing LDH and caspase-3 activity, reactive oxygen species generation, mPTP opening and apoptosis rate. However, the cardioprotection of TMP was attenuated by pAD/14-3-3γ-shRNA, an adenovirus that knocked down intracellular 14-3-3γ expression. In conclusion, the cardioprotection of TMP against LPS-induced injury was through up-regulating the expression of 14-3-3γ, promoting the translocation of Bcl-2 to mitochondria, and improving the function of mitochondria.

Physiological Concentration of Prostaglandin E2 Exerts Anti-inflammatory Effects by Inhibiting Microglial Production of Superoxide Through a Novel Pathway

This study investigated the physiological regulation of brain immune homeostasis in rat primary neuron-glial cultures by sub-nanomolar concentrations of prostaglandin E2 (PGE₂). We demonstrated that 0.01 to 10 nM PGE₂ protected dopaminergic neurons against LPS-induced neurotoxicity through a reduction of microglial release of pro-inflammatory factors in a dose-dependent manner. Mechanistically, neuroprotective effects elicited by PGE₂ were mediated by the inhibition of microglial NOX2, a major superoxide-producing enzyme. This conclusion was supported by (1) the close relationship between inhibition of superoxide and PGE₂-induced neuroprotective effects; (2) the mediation of PGE₂-induced reduction of superoxide and neuroprotection via direct inhibition of the catalytic subunit of NOX2, gp91^phox, rather than through the inhibition of conventional prostaglandin E2 receptors; and (3) abolishment of the neuroprotective effect of PGE₂ in NOX2-deficient cultures. In summary, this study revealed a potential physiological role of PGE₂ in maintaining brain immune homeostasis and protecting neurons via an EP receptor-independent mechanism.

Tetramethylpyrazine reverses intracerebroventricular streptozotocin-induced memory deficits by inhibiting GSK-3β

Brain dysfunction, especially cognitive impairment, is one of the main complications in Alzheimer's disease (AD), which threatens the health of 46.8 million people worldwide. At present, the pathogenesis of cognitive dysfunction is only partially understood, and effective therapies for memory loss in AD remain elusive. Tetramethylpyrazine (TMP) is one of the major bioactive compounds purified from Chuanxiong, a Chinese herb used for the treatment of neurovascular and cardiovascular diseases. The neuroprotective properties of TMP are evident in some neurodegenerative diseases, including Parkinson's disease. However, whether TMP plays a neuroprotective role in AD is still unknown. Here, we report that 2-week treatment with TMP rescued both short-term and long-term fear memory impairment induced by intracerebroventricular injection of streptozotocin in a well-known AD rat model. Administration of TMP also restored spatial learning and memory retention abilities in streptozotocin-injected rats. Furthermore, TMP inhibited the activity of GSK-3β, an important kinase that mediates hippocampal synaptic and memory disorders in diabetes mellitus. Finally, we found that TMP treatment restored the function of cholinergic neurons. Our data suggest that dietary uptake of TMP can provide protection against memory loss in AD, and the inhibition of GSK-3β may play an important role in this protective effect.

Antipyretic and anti-inflammatory activities of Thais luteostoma extracts and underlying mechanisms

Thais luteostoma has been utilized as a crude drug whose shell and soft tissue have been widely used for the treatment of heat syndrome in China for thousands of years. The present study was designed to investigate the antipyretic and anti-inflammatory activities of T. luteostoma. T. luteostoma was divided into shell (TLSH) and soft tissue (TLST) samples in the present study. The rat model of yeast-induced fever was used to investigate their antipyretic effects; and the rat model of hind paw edema induced by carrageenan was utilized to study their anti-inflammatory activities, and at the same time, the concentration variations of the central neurotransmitter [prostaglandin E2 (PGE2) and cyclic adenosine monophosphate (cAMP)], inflammatory mediators [tumor necrosis factor (TNFα), interleukin-1β (IL-1), interleukin-2 (IL-2) and interleukin-6 (IL-6)] and ion (Na(+) and Ca(2+)) were also tested. The results showed that TLSH and TLST extracts significantly inhibited yeast-induced pyrexia in rats (P < 0.05), and exhibited more lasting effects as compared to aspirin, and TLSH had the better antipyretic activity than TLST, and that TLSH and TLST could significantly prevent against carrageenan induced paw edema in rats (P < 0.05); and markedly reduced levels of PGE2, cAMP, TNFα, IL-1β, IL-2, IL-6, and Na(+)/Ca(2+). In fever model, TLST could significantly reduce the levels of PGE2 (P < 0.01) in rats' homogenate and TNFα (P < 0.05), IL-1β (P < 0.01) in the plasma than TLSH, whereas TLSH could reduce the content of IL-2 (P < 0.01) and IL-6 (P < 0.01) in plasma and increase the content of Ca(2+) (P < 0.01) in plasma and homogenate more significantly than TLST. In conclusion, T. luteostoma extract has antipyretic and anti-inflammatory activities, which may be mediated through the suppression of production of PGE2, cAMP, Na(+)/Ca(2+), TNFα, IL-1β, IL-2, and IL-6.

The Neuroprotective Effect of Tetramethylpyrazine Against Contusive Spinal Cord Injury by Activating PGC-1α in Rats

Tetramethylpyrazine (TMP) has been suggested to have neuroprotective effects against spinal cord injury (SCI); however, few studies have examined these effects and the corresponding mechanism. Therefore, the present study aimed to investigate the neuroprotective effect and underlying mechanism of TMP against contusive SCI. Adult male Sprague-Dawley rats were randomly divided into Sham, normal saline (NS) and TMP groups. Each group was divided into subgroups according to the time of sacrifice: 1, 3, 7, 14, 21 and 28 days post-injury. Laminectomy was performed in all groups, followed by contusive SCI establishment in the TMP and NS groups. TMP (80 mg/kg) was injected thereafter daily from 3 to 7 days post-injury in the TMP group, which was replaced by equal volume of normal saline in the NS group. The Basso-Beattie-Bresnahan (BBB) Locomotor Rating Scale was measured at different time points post-injury to appraise locomotor functional recovery. Quantitative real-time PCR and immunofluorescence were used to assess the spatio-temporal expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), while western blot was adopted to detect the effect of TMP on PGC-1α. Neural apoptotic changes and neuronal survival were evaluated using the TUNEL method and Nissl staining, respectively. TMP treatment markedly increased PGC-1α expression, neuronal survival and BBB locomotor scores, while also reducing neural apoptosis. These results demonstrate that TMP is neuroprotective against contusive SCI, with the inhibition of neural apoptosis and increase of neuronal survival. The sustained expression of PGC-1α may partially contribute to the TMP-mediated neuroprotective effect.

Attenuation of Streptomycin Ototoxicity by Tetramethylpyrazine in Guinea Pig Cochlea

Objective

Tetramethylpyrazine has been suggested to have a therapeutic effect on impaired hearing that is induced by aminoglycoside antibiotics. However, its effectiveness on streptomycin ototoxicity and its cellular mechanisms are relatively unknown. Here we investigate the protective effect of tetramethylpyrazine on streptomycin-induced ototoxicity in guinea pig cochlea.

Study Design

Prospective randomized laboratory study.

Setting

Hearing Research Laboratory of China Medical University.

Subjects and Methods

Adult guinea pigs were randomized to 4 groups. Hearing sensitivity of guinea pigs was tested by auditory brainstem response measurements before streptomycin exposure and again 10 days later. The cochlear tissues were prepared for electron microscopy and immunohistochemical staining of heat shock protein 70 (HSP70). The effect of tetramethylpyrazine on streptomycin-induced activation of caspase-3 was evaluated by Western blotting.

Results

Co-therapy with tetramethylpyrazine reduced a profound streptomycin-induced auditory threshold shift compared with streptomycin treatment alone ( P = .0002 or P = .00008). Tetramethylpyrazine also attenuated the structural disruption in streptomycin-treated outer hair cells and marginal cells of vascular stria by transmission electronic microscopy and scanning electronic microscopy, respectively. Moreover, tetramethylpyrazine decreased the streptomycin-stimulated expressions of HSP70 and caspase-3. The correlation analysis demonstrated that HSP70 expression had a positive correlation with auditory brainstem response thresholds (|R| = 0.6-0.9, P = .0073 or P = .0169).

Conclusions

Our data suggest that the protective effect of tetramethylpyrazine on hearing function is associated with the reduction of stress response and inhibition of apoptosis. Tetramethylpyrazine may have therapeutic potential for patients with ototoxicity diseases.

Neuroprotective effects of tetramethylpyrazine against dopaminergic neuron injury in a rat model of Parkinson's disease induced by MPTP

Parkinson's disease (PD) is the second most prevalent progressive neurodegenerative disease. Although several hypotheses have been proposed to explain the pathogenesis of PD, apoptotic cell death and oxidative stress are the most prevalent mechanisms. Tetramethylpyrazine (TMP) is a biological component that has been extracted from Ligusticum wallichii Franchat (ChuanXiong), which exhibits anti-apoptotic and antioxidant roles. In the current study, we aimed to investigate the possible protective effect of TMP against dopaminergic neuron injury in a rat model of Parkinson's disease induced by MPTP and to elucidate probable molecular mechanisms. The results showed that TMP could notably prevent MPTP-induced dopaminergic neurons damage, reflected by improvement of motor deficits, enhancement of TH expression and the content of dopamine and its metabolite, DOPAC. We observed MPTP-induced activation of mitochondrial apoptotic death pathway, evidenced by up-regulation of Bax, down-regulation of Bcl-2, release of cytochrome c and cleavage of caspase 3, which was significantly inhibited by TMP. Moreover, TMP could prevent MPTP-increased TBARS level and MPTP-decreased GSH level, indicating the antioxidant role of TMP in PD model. And the antioxidant role of TMP attributes to the prevention of MPTP-induced reduction of Nrf2 and GCLc expression. In conclusion, in MPTP-induced PD model, TMP prevents the down-regulation of Nrf2 and GCLc, maintaining redox balance and inhibiting apoptosis, leading to the attenuation of dopaminergic neuron damage. The effectiveness of TMP in treating PD potentially leads to interesting therapeutic perspectives.

Phytochemical and pharmacological review of da chuanxiong formula: a famous herb pair composed of chuanxiong rhizoma and gastrodiae rhizoma for headache

Chronic headache such as migraine and nervous headache has become one of the most common locations of pain and one of the most difficult diseases to recover due to its numerous causes and inconvenience to keep acesodyne administration for a long time. However, there are a series of treatment theories and herbal formulas for this disease in traditional Chinese medicine (TCM), in which Da Chuanxiong formula (DCXF), a herb pair composed of Chuanxiong Rhizoma (CR), Chuanxiong in Chinese, and Gastrodiae Rhizoma (GR) called as Tianma in China, is a greatly classic representative. This formula has been used for headaches via dispelling wind pathogen and dissipating blood stasis for many years in TCM. In recent years, the efficiency and representativeness of DCXF have garnered many researchers' attention. To reveal the compatibility mechanism and develop innovative Chinese herb, herein ethnopharmacological relevance, chemical characters, and pharmacological actions of DCXF are detailed. It is expected to give a comprehensive interpretation of DCXF, namely, Chuanxiong Tianma herb pair (CTHP), to inherit the essence of herb pair and innovate drug delivery system of this prescription.