Yewei Sun

Antioxidative and thrombolytic TMP nitrone for treatment of ischemic stroke

Ischemic stroke results from brain blood vessel blockage by thrombus, and produces neuronal cell damage and death. While thrombolytic therapy with tPA has achieved some success in clinic, the strategy of using neuroprotective agents to treat ischemic stroke has been disappointing thus far. In the present work, we synthesized TBN, a derivative of the clinically useful stroke drug TMP armed with a powerful free radical-scavenging nitrone moiety. TBN retains the thrombolytic activity of the parent TMP and possesses strong antioxidative properties. TBN demonstrates significant activity in the rat MCAo stroke model. The results suggest that design of molecules possessing both thrombolytic and neuroprotective properties may be a novel strategy for effective stroke therapeutics.

Therapeutic effects of tetramethylpyrazine nitrone in rat ischemic stroke models

Free radical‐mediated neuronal cell damage is an important pathological process in ischemic stroke. We have previously reported a novel dual‐functional agent, 2‐[[(1,1‐dimethylethyl)oxidoimino]‐methyl]‐3,5,6‐trimethylpyrazine (TBN), a derivative of tetramethylpyrazine armed with anitrone moiety. In this report, we further evaluate TBNstherapeutic parameters in a rat middle cerebral artery occlusion (MCAO) model. Its abilities to cross the blood–brain barrier, scavenge free radicals, and inhibitCa2+ influx were also investigated. TBN showed significant activity in both the transient MCAO (t‐MCAO) and permanent MCAO (p‐MCAO) stroke models in the rat. The therapeutic time window is 8 hr in the t‐MCAO model. TBN readily crossed the blood–brain barrier and in vitro had strong activity in neutralizing ·OH, O− 2·, and ONOO− and significantly decreased intracellular Ca2+concentration. TBN is a promising new treatment forischemic stroke, with multiple mechanisms of action. It blocks Ca2+ overload and neutralizes ·OH, O−2·, and ONOO−.

The Novel Tetramethylpyrazine Bis-nitrone (TN-2) Protects Against MPTP/MPP+-Induced Neurotoxicity via Inhibition of Mitochondrial-Dependent Apoptosis

Mitochondrial-dependent apoptosis plays an important role in the degeneration of dopaminergic neurons in Parkinson’s disease (PD). Methyl-4-phenyl-1,2,3,6-tetra- hydropyridine (MPTP), the most widely used neurotoxin to simulate PD, is converted to 1-methyl-4-phenylpyridinium (MPP+) in vivo. MPP+ induces excessive intracellular reactive oxygen species (ROS), leading to mitochondrial-dependent apoptosis via sequentially opening mitochondria permeability transition pore (mPTP) to release cytochrome c from mitochondria into cytoplasm and activate pro-apoptotic caspase proteins. We have previously synthesized 2,5-[[(1,1-dimethylethyl)oxidoimino]methyl]-3,6-trimethylpyrazine (TN-2), a novel derivative of the Chinese herb medicine tetramethylpyrazine (TMP). TN-2 is armed with two powerful free radical-scavenging nitrone moieties. TN-2 significantly reversed the loss of dopaminergic neurons in the substantia nigra and the decrease in dopamine level in the striatum induced by MPTP in mice. TN-2 ameliorated the MPTP-induced decrease of brain superoxide dismutase activity and glutathione concentration and increase of brain malondialdehyde. In addition, TN-2 inhibited MPP+-induced neuronal damage/apoptosis in primary cerebellum granular neurons (CGNs) and SH-SY5Y cells. TN-2 decreased excessive intracellular ROS, prevented the loss of mitochondrial membrane potential, blocked the release of mitochondrial cytochrome c and inhibited the activation of caspase-3 and caspase-9. Moreover, TN-2 treatment increased the mRNA expression of mitochondrial biogenesis factors peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1 (PGC- 1α and β) and mitochondrial transcription factor A (Tfam) in SH-SY5Y cells and CGNs. These results suggest that TN-2 protects dopaminergic neurons against MPTP/MPP+-induced neurotoxicity via the inhibition of mitochondrial-dependent apoptosis and possibly via the activation of mitochondrial biogenesis, indicating that TN-2 is a potential new treatment for PD.

Neuroprotective effects of the andrographolide analogue AL-1 in the MPP⁺/MPTP-induced Parkinson's disease model in vitro and in mice.

The andrographolide-lipoic acid conjugate AL-1 is a newly synthesized molecule by covalently linking andrographolide (Andro) with α-lipoic acid (LA). In the present work, the neuroprotective effect of AL-1 was investigated in vitro and in a mouse model of the Parkinsons disease (PD). We found that AL-1 significantly prevented 1-methyl-4-phenylpyridinium (MPP(+))-induced neurotoxicity in SH-SY5Y cells and primary cerebellar granule neurons. In a mouse model of Parkinsons disease, AL-1 rescued 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced loss of tyrosine hydroxylase (TH)-positive neurons, improved the behavioral impairment, and elevated the striatal levels of dopamine and its metabolites 3,4-dihydroxyphenylacetic acid. Furthermore, AL-1 remarkably lowered the nitric oxide and malondialdehyde levels while increased the superoxide dismutase level in the substantial nigra of MPTP-treated mice. The immunoblotting data showed that AL-1 significantly ameliorated the decreased expression of TH protein in the substantial nigra and inhibited the up-regulation of phosphorylated NF-κB p65 in vitro and in vivo. Taken together, AL-1 exerted neuroprotective effect in vitro and in animal model of PD through anti-oxidation and inhibition of NF-κB activation.

Andrographolide derivative AL-1 improves insulin resistance through down-regulation of NF-κB signalling pathway

Andrographolide is the most active constituent of the medicinal plant Andrographis paniculata. Previously, we synthesized a novel andrographolide derivative AL‐1, conjugating andrographolide with lipoic acid. Although the antioxidative and/or anti‐inflammatory activity of AL‐1 contributes to its cytoprotective effects, whether AL‐1 can improve insulin resistance and the mechanisms responsible for its action have not been elucidated.

A novel tetramethylpyrazine bis-nitrone (TN-2) protects against 6-hydroxyldopamine-induced neurotoxicity via modulation of the NF-κB and the PKCα/PI3-K/Akt pathways

INTRODUCTION The natural product tetramethylpyrazine (TMP) has a variety of biologic activities, including neuroprotection. Nitrones are powerful free radical scavengers. We have designed and synthesized a TMP derivative, TN-2, which is armed with two nitrone moieties. AIMS In this study, we investigated the neuroprotective effect of TN-2 against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in vitro and in zebrafish. METHODS PC12 cells, zebrafish and rats were exposed to 6-OHDA challenge. MTT assay, LDH release, Hoechst staining, DAF-FM staining, luciferase reporter construct transfection, and western blotting were applied to detect cell viability, apoptosis, intracellular nitric oxide (NO), NF-κB transcriptional activity and proteins expression. In zebrafish, whole-mount staining and real-time PCR were performed to quantify dopaminergic neurons and mRNA expression. Hematoxylin and eosin staining and immunohistochemistry for glial fibrillary acidic protein were used to detect the astrocyte activation in the unilateral 6-OHDA rat model. RESULTS TN-2 but not TMP exhibited potent neuroprotective effect against 6-OHDA-induced apoptosis in PC12 cells. Moreover, TN-2 prevented dopaminergic neuron loss and suppressed mRNA expression of pro-inflammatory genes, including IL-1β, TNF-α and COX-2, in 6-OHDA-treated zebrafish. TN-2 remarkably attenuated microglial/astrocyte activation in the unilateral 6-OHDA rat model. The mechanistic study demonstrated that TN-2 inhibited over-production of intracellular NO and protein expression of inducible nitric oxide synthase through down-regulating NF-κB activity. Additionally, the PKCα/PI3-K/Akt pathway was also involved in the neuroprotection of TN-2. CONCLUSION These results suggest that TN-2 protected against 6-OHDA-induced neurotoxicity via modulating the NF-κB-medicated neuroinflammation and PKCα/PI3-K/Akt pathways.

Design, Synthesis, and Preliminary Cardioprotective Effect Evaluation of Danshensu Derivatives

A series of (R)‐3,4‐dihydroxyphenyllactic acid Danshensu (DSS) derivatives were synthesized, and their cardioprotective effects were evaluated in vitro and in vivo. Among the new derivatives, compound 14 showed significant protective effects in cultured myocardial cells and in the rat model of myocardial ischemia. The therapeutic efficacy of compound 14 was significantly higher than that of its parent compound DSS, and amlodipine, a first‐line treatment for angina pain. Compound 14 potently scavenged free radicals, significantly decreased the levels of LDH and MDA, and inhibited the leakage of CK in animal model of ischemia. We had previously found that compound 14 activated PI3K/Akt/GSK‐3β and Nrf2//Keap1/heme oxygenase‐1 (HO‐1) signaling pathways in H9c2 cells. These results suggest that compound 14 has a unique mechanism of action, that is, multifunctional. Compound 14 may be a new potential therapy for ischemic heart diseases.

Andrographolide derivative AL-1 ameliorates TNBS-induced colitis in mice: involvement of NF-кB and PPAR-γ signaling pathways

Andrographolide is a traditional herb medicine, widely used in Asia for conditions involving inflammation. The andrographlide-lipoic acid conjugate, AL-1, has been found being able to alleviate inflammation in our previous reports. Although the anti-inflammatory activity of AL-1 contributes to its cytoprotective effects, whether AL-1 can improve inflammatory bowel disease (IBD) and the underlying mechanisms of its action remain largely unknown. In this study, we investigated the anti-inflammatory effects of AL-1 in C57BL/6 mice with trinitrobenzenesulfonic acid (TNBS)-induced colitis. The body weight loss and length change of colon after TNBS instillation were more severe than those in normal mice. AL-1 treatment led to significant reductions in disease activity index (DAI), macroscopic score and colon mucosa damage index (CMDI) associated with TNBS administration. AL-1 inhibited the inflammatory response via lowering the level of inflammatory cytokines and myeloperoxidase (MPO) activity. AL-1 attenuated the expression of p-p65, p-IκBα and COX-2 in the colitis mice. The alleviation of colon injury by AL-1 treatment was also evidenced by the increased expression of PPAR-γ. These results indicated that AL-1 could protect intestinal tract from the injury induced by TNBS in mice, suggesting that AL-1 may have potential in treatment for IBD.

A Potent Multi-functional Neuroprotective Derivative of Tetramethylpyrazine

Neurodegenerative disorders are one of the leading causes of death among the elderly. Therapeutic approaches with a single target have proven unsuccessful in treating these diseases. Structural combination of multi-functional compounds may lead to a molecule with multiple properties. In this study, we designed and synthesized T-006, a novel analog derived from two multi-functional neuroprotective chemicals, tetramethylpyrazine and J147. The methoxyphenyl group of J147 was replaced by tetramethylpyrazine. Bioactivity evaluation showed that T-006 at very low concentrations had multi-functional neuroprotective effects including rescuing iodoacetic acid-induced neuronal loss, preventing oxidative stress-induced neurotoxicity and reducing glutamate-induced excitotoxicity in vitro. Most importantly, T-006 significantly ameliorated memory impairments in APP/PS1 transgenic mice. These multiple functions of a single molecule suggest that T-006 is a promising novel neuroprotective agent for treating various neurodegenerative disorders, including and in particular Alzheimer’s disease.

Novel multi-functional nitrones for treatment of ischemic stroke.

Ischemic stroke resulting from obstruction of blood vessels is an enormous public health problem with urgent need for effective therapy. The co-administration of thrombolytic/antiplatelet agent and neuroprotective agent improves therapeutic efficacy and agent possessing both thrombolytic/antiplatelet and antiradical activities provides a promising strategy for the treatment of ischemic stroke. We have previously reported a novel compound, namely TBN, possessing both antiplatelet and antiradical activities, showed significant neuroprotective effect in a rat stroke model. We herein report synthesis of a series of new pyrazine derivatives, and evaluation of their biological activities. Their mechanisms of action were also investigated. Among these new derivatives, compound 21, armed with two nitrone moieties, showed the greatest neuroprotective effects in vitro and in vivo. Compound 21 significantly inhibited ADP-induced platelet aggregation. In a cell free antiradical assay, compound 21 was the most effective agent in scavenging the three most damaging radicals, namely (·)OH, O(2)(·-) and ONOO(-).