Sinomenine Administration Research Articles

Simultaneous determination of sinomenine and its metabolites desmethyl-sinomenine and sinomenine N-oxide in rat plasma by liquid chromatography tandem mass spectrometry.

Sinomenine is an active ingredient extracted from herb medicine, which has been prescribed to treat rheumatoid arthritis in clinics. The present work was to develop a simple method to simultaneously determine sinomenine and its metabolites desmethyl sinomenine and sinomenine N-oxide in rat plasma by liquid chromatography tandem mass spectrometry. Precursor-to-product transitions for detection were m/z 330.2 > 239.1 for sinomenine, m/z 316.2 > 239.1 for desmethyl-sinomenine, m/z 346.2 > 314.1 for sinomenine N-oxide and m/z 286.2 > 153.2 for morphine (internal standard), respectively. During the validation and sample quantification, an excellent linear calibration range was observed for all the analytes with correlation coefficients more than 0.999 (r > 0.99). The extraction recovery was more than 85%. No significant matrix effect and carryover were observed. The precision was less than 6.45%, whereas accuracy ranged from -4.10% to 7.23%. The validated method has been successfully applied to the pharmacokinetic study of sinomenine, desmethyl sinomenine, and sinomenine N-oxide in rat plasma after oral administration of sinomenine at a single dose of 5 mg/kg. The results suggested that sinomenine was rapidly metabolized into its metabolite desmethyl sinomenine and sinomenine N-oxide.

Bone protective effect of sinomenine against monosodium iodoacetate induced knee and hip injury in rat model: an inflammatory pathway.

Osteoarthritis (OA) is a degenerative joint disease which is categorized via destruction of joint cartilage and it also affects the various joints, especially knees and hips. Sinomenine active phytoconstituents isolated from the stem of Sinomenium acutum and already proof anti-inflammatory effect against the arthritis model of rodent. In this experimental protocol, we scrutinized the anti-osteoarthritis effect of sinomenine against monosodium iodoacetate (MIA) induced OA in rats. MIA (3 mg/50 μL) was used for inducing the OA in the rats, and rats received the oral administration of sinomenine (2.5, 5 and 7.5 mg/kg body weight) up to the end of the experimental study (four weeks). The body and organs weight were estimated. Aggrecan, C-terminal cross-linked telopeptide of type II collagen (CTX-II), glycosaminoglycans (GCGs), monocyte chemoattractant protein-1 (MCP-1), Interferon gamma (IFN-γ), antioxidant, inflammatory cytokines, inflammatory mediators and matrix metalloproteinases (MMP) were analyzed. Sinomenine significantly (P < 0.001) boosted the body weight and reduced the heart weight, but the weight of spleen and kidney remain unchanged. Sinomenine significantly (P < 0.001) reduced the level of nitric oxide, MCP-1 and improved the level of aggrecan, IFN-γ and GCGs. Sinomenine remarkably upregulated the level of glutathione, superoxide dismutase and suppressed the level of malonaldehyde. It effectually modulated the level of inflammatory cytokines and inflammatory mediators and significantly (P < 0.001) reduced the level of MMPs, like MMP-1, 2, 3, 9 and 13. Sinomenine is a beneficial active agent for the treatment of OA disease.

Sinomenine alleviates lipopolysaccharide-induced acute lung injury via a PPARβ/δ-dependent mechanism

Evidence is mounting that sinomenine and peroxisome proliferator-activated receptor β/δ (PPARβ/δ) are effective against lipopolysaccharide (LPS)-induced acute lung injury (ALI) via anti-inflammatory properties. However, it is unknown whether PPARβ/δ plays a role in the protective effect of sinomenine on ALI. Here, we initially observed that preemptive administration of sinomenine markedly alleviated lung pathological changes, pulmonary edema and neutrophil infiltration, accompanied by inhibition of the expression of the pro-inflammatory cytokines Tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6), which were largely reversed following the addition of a PPARβ/δ antagonist. Subsequently, we also noticed that sinomenine upregulated adenosine A2A receptor expression in a PPARβ/δ-dependent manner in LPS-stimulated bone marrow-derived macrophages (BMDMs). Further investigation indicated that PPARβ/δ directly bound to the functional peroxisome proliferator responsive element (PPRE) in the adenosine A2A receptor gene promoter region to enhance the expression of the adenosine A2A receptor. Sinomenine was identified as a PPARβ/δ agonist. It could bind with PPARβ/δ, and promote the nuclear translocation and transcriptional activity of PPARβ/δ. In addition, combined treatment with sinomenine and an adenosine A2A receptor agonist exhibited synergistic effects and better protective roles than their single use against ALI. Taken together, our results reveal that sinomenine exerts advantageous effects on ALI by activating of PPARβ/δ, with the subsequent upregulation of adenosine A2A receptor expression, and provide a novel and potential therapeutic application for ALI.

Sinomenine alleviates glomerular endothelial permeability by activating the C/EBP-α/claudin-5 signaling pathway.

Diabetic nephropathy (DN) is one of the main complications of diabetes. It is closely associated with the dysfunction of glomerular endothelial cells (GECs) under hyperglycemia. Severe inflammation is an important inducer for the development of GECs dysfunction, and it contributes to the disruption of tight junctions in GECs and the increased endothelial permeability. Sinomenine, an alkaloid monomer extracted from the rhizome of Sinomenium acutum, is recognized for its multiple pharmacological functions, including an anti-DN property. The present study aimed to explore the potential functional mechanism of Sinomenine against DN. Animals were randomly divided into Sham, DN, DN + Sinomenine (20mg/kg), and DN + Sinomenine (40mg/kg) groups. The Sinomenine or vehicle was administered every day for 6weeks, followed by collecting renal tissues for further detection. Increased body weights, elevated blood glucose levels and UAE values, aggravated renal tissue pathology, higher concentrations of IL-18 and IL-1β in renal tissues, and reduced claudin-5 expression were observed in DN rats. However, the administration of Sinomenine significantly alleviated all these DN-related changes. Furthermore, human renal glomerular endothelial cells (HrGECs) were treated with high glucose (HG, 30mM) with or without Sinomenine (50, 100μM) for 24h. We found that Sinomenine treatment ameliorated the elevated production of IL-18 and IL-1β, increased fluorescence intensity of FITC-dextran, declined trans-endothelial electrical resistance (TEER) value, and reduction of claudin-5 and C/EBP-α in HG-treated HrGECs. Moreover, the regulatory effect of Sinomenine on endothelial monolayer permeability in HG-treated HrGECs was abolished by the knockdown of C/EBP-α, indicating C/EBP-α is required for the effect of Sinomenine. We concluded that Sinomenine alleviated diabetic nephropathy-induced renal glomerular endothelial dysfunction via activating the C/EBP-α/claudin-5 axis.

Sinomenine alleviates dorsal root ganglia inflammation to inhibit neuropathic pain via the p38 MAPK/CREB signalling pathway

The objective of study was to investigate the inhibitory effect of sinomenine on neuropathic pain on dorsal root ganglia (DRG). The DRG cell line and spinal nerve ligation (SNL) model were used in this study. The effect of sinomenine on the cell viability was examined by MTT assay. The expression of p38 MAPK, NF-κB, c-fos, SP and TNF-α was detected by using immunofluorescence and immunohistochemistry assay. We also assessed the level of p-CaMKII, COX-2, p-CREB, IL-17A, TLR4 and IL-1β via western blotting and RT-qPCR. Compared to the controls, sinomenine showed a protective effect on TNF-α-induced apoptosis on DRG cells in a dose-dependent manner, with an increase of cell viability and a decrease of reactive oxygen species level as well as LDH release. Parallelly, sinomenine treatment significantly reduced the expression of various factors related to stress and inflammation, including p38 MAPK, NF-κB, c-fos, p-CAMKII, COX-2, p-CREB, TLR4 and IL-17A in DRG cells in vitro. Furthermore, we found that administration of sinomenine significantly reduced mechanical withdrawal threshold and thermal withdrawal latency and inhibited the inflammation and activation of p38 signaling in SNL rats. It is noting that combined therapy of sinomenine and pulsed radiofrequency exhibited higher efficacy of dorsal root ganglia inflammation than single treatment as well as the combination of oxycodone and pulsed radiofrequency. Sinomenine inhibited the apoptosis of DRG cell by regulating p38 MAPK/CREB signalling pathway, which provides evidence to alleviate neuropathic pain in clinic.

Sinomenine Suppress the Vitamin D3 and High Fat Induced Atherosclerosis in Rats via Suppress of Oxidative Stress and Inflammation.

Atherosclerosis (AS) is a cardiovascular disease that arise due to dysfunction of lipid deposition and metabolism. AS is causes the mortality and morbidity worldwide. Sinomenine isolated from the Sinomenium acutum is used extensively against the various cardiac diseases in China. However, the anti-atherosclerosis effect of sinomenine still not explore. In this study, we explore the cardioprotective and anti-atherosclerosis effect of sinomenine against Vitamin D3 and High fat induced atherosclerosis in rats. Sprague Dawley (SD) rats were used in this study. The rats were received the vitamin D (60000) and High fat diet to induce the atherosclerosis and divided into groups and received the oral administration of sinomenine (2.5, 5 and 10 mg/kg) and simvastatin (5 mg/kg). Body weight, organ weight and biochemical parameters were estimated. The mRNA expression of MyD88, TLR4, NF-κB and IκB were estimated. Sinomenine treated rats significantly (p<0.001) suppressed the body weight and modulated the organ weight (hepatic, renal and heart). Sinomenine significantly (p<0.001) decreased the level of triacylglycerols (TG), low density lipoprotein cholesterol (LDL-c), total cholesterol (TC), very low-density lipoprotein cholesterol (VLDL-c) and augmented the level of high-density lipoprotein cholesterol (HDL-c). Sinomenine treatment also reduced the level of atherogenic index (TC/HDL-c and LDL-c/HDL-c). Sinomenine treatment decrease the ratio of HMG CoA/Mevalonate and level of collagen and total protein. Sinomenine significantly (p<0.001) altered the level of heart parameters, antioxidant parameters and inflammatory cytokines. Sinomenine significantly (p<0.001) reduced the expression of MyD88, TLR4, NF-κB and IκB. Taken together, sinomenine exhibited the protective effect against the atherosclerosis via alteration of TLR4/NF-κB signaling pathway.

Sinomenine Alleviates Murine Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis through Inhibiting NLRP3 Inflammasome.

Multiple sclerosis (MS) is known as a chronic neuroinflammatory disorder typified by an immune-mediated demyelination process with ensuing axonal damage and loss. Sinomenine is a natural alkaloid with different therapeutic benefits, including anti-inflammatory and immunosuppressive activities. In this study, possible beneficial effects of sinomenine in an MOG-induced model of MS were determined. Sinomenine was given to MOG35-55-immunized C57BL/6 mice at doses of 25 or 100mg/kg/day after onset of MS clinical signs till day 30 post-immunization. Analyzed data showed that sinomenine reduces severity of the clinical signs and to some extent decreases tissue level of pro-inflammatory cytokines IL-1β, IL-6, IL-18, TNFα, IL-17A, and increases level of anti-inflammatory IL-10. In addition, sinomenine successfully attenuated tissue levels of inflammasome NLRP3, ASC, and caspase 1 besides its reduction of intensity of neuroinflammation, demyelination, and axonal damage and loss in lumbar spinal cord specimens. Furthermore, immunoreactivity for MBP decreased and increased for GFAP and Iba1 after MOG-immunization, which was in part reversed upon sinomenine administration. Overall, sinomenine decreases EAE severity, which is attributed to its alleviation of microglial and astrocytic mobilization, demyelination, and axonal damage along with its suppression of neuroinflammation, and its beneficial effect is also associated with its inhibitory effects on inflammasome and pyroptotic pathways; this may be of potential benefit for the primary progressive phenotype of MS.

Neuroprotective and anticonvulsant effects of sinomenine in kainate rat model of temporal lobe epilepsy: Involvement of oxidative stress, inflammation and pyroptosis

Oxidative stress, inflammation and pyroptosis are three of the most important mechanisms in the pathophysiology of temporal lobe epilepsy (TLE). Most people with TLE are refractory to the existing drugs. Sinomenine has shown neuroprotective effects through counteracting oxidative stress, inflammation and pyroptosis. In this study, we evaluated the effect of sinomenine on seizure behavior, oxidative stress, inflammation and pyroptosis markers in addition to its neuroprotective potential in intrahippocampal kainate-induced rat model of TLE. For this purpose, male rats (n = 60) were randomly divided into five groups, i.e., sham, kainate (lesion) with an intrahippocampal injection of kainate, kainate groups receiving sinomenine at doses of 30 or 50 mg/kg, and kainate group receiving valproic acid at a dose of 200 mg/kg (as the positive control). Our obtained data showed that sinomenine administration at a dose of 50 mg/kg can significantly decreases severity of seizures and incidence of status epilepticus (SE), hippocampal aberrant MFS and DNA fragmentation and prevents reduction of neuronal density. It also significantly restored level of ROS, MDA, HO-1 and SOD but its effect on GSH level was not significant. Additionally, sinomenine at a dose of 50 mg/kg partially counteracted the increase of NF-κB, TLR 4, TNFα, GFAP and caspase 1. These results suggest that sinomenine has anticonvulsant and neuroprotective effects by reducing hippocampal oxidative stress, inflammation, pyroptosis and apoptosis in intrahippocampal kainate model of TLE.

Analgesic Mechanism of Sinomenine against Chronic Pain.

Purified from the roots of the plant Sinomenium acutum, sinomenine is traditionally used in China and Japan for treating rheumatism and arthritis. Previously, we have demonstrated that sinomenine possessed a broad analgesic spectrum in various chronic pain animal models and repeated administration of sinomenine did not generate tolerance. In this review article, we discussed sinomenine's analgesic mechanism with focus on its role on immune regulation and neuroimmune interaction. Sinomenine has distinct immunoregulative properties, in which glutamate, adenosine triphosphate, nitric oxide, and proinflammatory cytokines are thought to be involved. Sinomenine may alter the unbalanced neuroimmune interaction and inhibit neuroinflammation, oxidative stress, and central sensitization in chronic pain states. In conclusion, sinomenine has promising potential for chronic pain management in different clinical settings.

Possible involvement of the μ opioid receptor in the antinociception induced by sinomenine on formalin-induced nociceptive behavior in mice

Sinomenine, an alkaloid originally isolated from the roots and the rhizome of Sinomenium acutum is used as a traditional Chinese herbal medicines for rheumatoid arthritis and neuralgia. The aims of this study were to investigate the effects of oral administration of shinomenine on formalin-induced nociceptive behavior in mice and the opioid receptor subtypes involved in the antinociceptive effects of sinomenine. Our findings showed that a single dose of oral-administrated sinomenine inhibited the formalin induced licking and biting responses in a dose-dependent manner. Intraperitoneal pretreatment with naloxone hydrochloride, an opioid receptor antagonist, and β-funaltrexamine hydrochloride (β-FNA), a selective μ-opioid receptor antagonist, significantly attenuated sinomenine induced antinociception, but not by naltrindole, a nonselective δ-opioid receptor antagonist and nor-binaltorphimine, a selective κ-opioid receptor antagonist. Furthermore, in western blot analysis, oral administration of sinomenine resulted in a significant blockage of spinal extracellular signal-regulated protein kinase (ERK1/2) activation induced by formalin. Naloxone hydrochloride and β-FNA significantly reversed the blockage of spinal ERK1/2 activation induced by sinomenine. These results suggest that sinomenine-induced anti nociceptive effect and blockage of spinal ERK1/2 activation may be triggered by activation of μ-opioid receptors.

Sinomenine Attenuates Traumatic Spinal Cord Injury by Suppressing Oxidative Stress and Inflammation via Nrf2 Pathway.

Traumatic spinal cord injury (SCI) is a devastating condition with few efficacious drugs. Sinomenine, a bioactive alkaloid extracted from medicinal herb, has been used as a treatment of rheumatoid diseases. This present study explored the therapeutic effects of sinomenine on locomotor dysfunction and neuropathology in SCI. Our findings revealed that sinomenine mitigated neurological deficits and enhanced neuronal preservation, paralleled with a reduction of apoptosis. Also, sinomenine significantly reduced inflammatory cytokines and oxidative stress factors. We further examined erythroid-2-related factor 2 (Nrf2) nuclear translocation, which mainly controls the coordinated expression of important antioxidant and detoxification genes. An increase in Nrf2 translocation from cytoplasm to nucleus and Nrf2-mediated transactivation was observed after sinomenine administration. Knocking down Nrf2 by siRNA could counteract sinomenine-mediated anti-oxidant stress and anti-inflammation following H2O2-stimulated and LPS-stimulated PC12 cells. Together, our findings indicated that sinomenine has the potential to be an effective therapeutic agent for SCI by inhibiting inflammation and oxidative stress via Nrf2 activation.

Anti-inflammatory Effects of Sinomenium Acutum Extract On Endotoxin-induced Uveitis in Lewis Rats.

Purpose: Recent studies have reported the anti-inflammatory effect of Sinomenium acutum. We investigated the anti-inflammatory effect of sinomenine on endotoxin-induced uveitis in a rat model.Methods: Endotoxin-induced uveitis was induced in rat by lipopolysaccharide (LPS) immunization. Sinomenine (50mg/kg and 100mg/kg) was administered at 30 minutes before, 6 hours and 12 hours after LPS immunization. Clinical and histological severity was evaluated. Protein concentration and levels of tumor necrosis factor (TNF)-α and prostaglandin (PG)-E2 in aqueous humor were measured. Expression of activated Nuclear factor (NF)-κB p65 in ciliary body was also observed.Results: Clinical and histological severities were significantly milder in sinomenine-treated rat than in controls (P < 0.001). Sinomenine suppressed protein leakage and down-regulated the production of TNF-α and PG-E2 in a dose-dependent manner. Sinomenine treatment suppressed the translocation of the NF-κB p65 subunit into the nuclei.Conclusion: Systemic administration of sinomenine suppressed the inflammation of ocular tissues. These findings suggest that sinomenine could be a novel therapeutic agent for the control of endogenous ocular inflammatory disease.

Sinomenine attenuates cancer-induced bone pain via suppressing microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades in rat models.

Cancer-induced bone pain is one of the most severe types of pathological pain, which often occurs in patients with advanced prostate, breast, and lung cancer. It is of great significance to improve the therapies of cancer-induced bone pain due to the opioids’ side effects including addiction, sedation, pruritus, and vomiting. Sinomenine, a traditional Chinese medicine, showed obvious analgesic effects on a rat model of chronic inflammatory pain, but has never been proven to treat cancer-induced bone pain. In the present study, we investigated the analgesic effect of sinomenine after tumor cell implantation and specific cellular mechanisms in cancer-induced bone pain. Our results indicated that single administration of sinomenine significantly and dose-dependently alleviated mechanical allodynia in rats with cancer-induced bone pain and the effect lasted for 4 h. After tumor cell implantation, the protein levels of phosphorylated-Janus family tyrosine kinase 2 (p-JAK2), phosphorylated-signal transducers and activators of transcription 3 (p-STAT3), phosphorylated-Ca2+/calmodulin-dependent protein kinase II (p-CAMKII), and phosphorylated-cyclic adenosine monophosphate response element-binding protein (p-CREB) were persistently up-regulated in the spinal cord horn. Chronic intraperitoneal treatment with sinomenine markedly suppressed the activation of microglia and effectively inhibited the expression of JAK2/STAT3 and CAMKII/CREB signaling pathways. We are the first to reveal that up-regulation of microglial JAK2/STAT3 pathway are involved in the development and maintenance of cancer-induced bone pain. Moreover, our investigation provides the first evidence that sinomenine alleviates cancer-induced bone pain by inhibiting microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades.

Sinomenine produces peripheral analgesic effects via inhibition of voltage-gated sodium currents

Sinomenium acutum has been used in traditional medicine to treat a painful disease such as rheumatic arthritis and neuralgia. Sinomenine, which is a main bioactive ingredient in Sinomenium acutum, has been reported to have an analgesic effect in diverse pain animal models. However little is known about the detailed mechanisms underlying peripheral analgesic effect of sinomenine. In the present study, we aimed to elucidate its cellular mechanism by using formalin-induced acute inflammatory pain model in mice. We found that intraperitoneal (i.p.) administration of sinomenine (50mg/kg) suppressed formalin-induced paw licking behavior in both the first and the second phase. Formalin-induced c-Fos protein expression was also suppressed by sinomenine (50mg/kg i.p.) in the superficial dorsal horn of spinal cord. Whole-cell patch-clamp recordings from small-sized dorsal root ganglion (DRG) neurons revealed that sinomenine reversibly increased the spike threshold and the threshold current intensity for evoking a single spike and decreased firing frequency of action potentials evoked in response to a long current pulse. Voltage-gated sodium currents (INa) were also significantly reduced by sinomenine in a dose-dependent manner (IC50=2.3±0.2mM). Finally, we confirmed that intraplantar application of sinomenine suppressed formalin-induced pain behavior only in the first phase, but not the second phase. Taken together, our results suggest that sinomenine has a peripheral analgesic effect by inhibiting INa.

Sinomenine Provides Neuroprotection in Model of Traumatic Brain Injury via the Nrf2-ARE Pathway.

The neuroprotective effect of sinomenine (SIN) has been demonstrated in several brain injury models. However, its role and molecular mechanism in traumatic brain injury (TBI) remain unknown. In this study, we investigated the neuroprotective effects of SIN in the weight-drop model of TBI in male ICR mice. Mice were randomly divided into the sham and TBI groups, SIN (10 mg/kg, 30 mg/kg and 50 mg/kg, administered intraperitoneally) or equal volume of vehicle was given at 30 min after TBI. Treatment with 30 mg/kg SIN significantly improved motor performance and alleviated cerebral edema. However, treatment with 10 mg/kg or 50 mg/kg SIN did not exhibit a better outcome. Therefore, we chose 30 mg/kg SIN for our subsequent experiments. SIN significantly increased the expression of Bcl-2 and decreased that of cleaved caspase-3, indicating that SIN is anti-apoptotic. This was confirmed by the observation that SIN-treated animals had fewer apoptotic neurons. Cortical malondialdehyde content, glutathione peroxidase (GPx) activity and superoxide dismutase (SOD) activity were restored in the group that received SIN. Furthermore, Western blot and immunofluorescence experiments showed that SIN enhanced the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) to the nucleus. SIN administration also significantly upregulated the expression of the downstream factors heme oxygenase 1 and NAD(P)H:quinone oxidoreductase 1 at pre- and post-transcriptional levels. Together, these data demonstrate that SIN exerts a neuroprotective effect in a model of TBI, possibly by activating the Nrf2–antioxidant response element (ARE) pathway.

Sinomenine attenuates chronic inflammatory pain in mice.

Sinomenine, an alkaloid originally isolated from the roots of Sinomeniumacutum, is used as a traditional Chinese medicine for rheumatic arthritis. However, little is known about the neuronal mechanisms underlying the analgesic effects of sinomenine in animals with chronic inflammatory pain. In this study, we investigated the persistent inflammatory pain induced by hind paw injection of complete Freund's adjuvant (CFA) in mice, which was reversed by sinomenine administration. In the anterior cingulate cortex (ACC), a region highly associated with chronic pain processing, the upregulation of GluN2B-containing N-methyl-D-aspartate (NMDA) receptors and Ca2+/calmodulin-dependent protein kinase II, total levels of GluA1, and phosphorylation of GluA1 at Ser831 (p-GluA1-Ser831) were reversed by systemically administrating sinomenine. Furthermore, sinomenine treatment downregulated the mammalian target of rapamycin (mTOR) pathway. Increases in p-mTOR, p-p70S6k, p-S6, and p-4EBP, which were induced by chronic inflammation, were all changed. However, sinomenine did not affect the levels of GluN2A-containing NMDA receptors and p-GluA1-Ser845, as well as the total levels of mTOR, p70S6k, S6, and 4EBP. In conclusion, results indicated that sinomenine reduced the chronic inflammatory pain induced by CFA, at least partially by regulating the GluN2B receptors and mTOR signals in the ACC.

Sinomenine enhances microglia M2 polarization and attenuates inflammatory injury in intracerebral hemorrhage

Microglia polarization plays a vital role in brain inflammatory injury following intracerebral hemorrhage (ICH). Previous studies have shown that sinomenine possesses potential immunoregulatory capabilities. However, microglia polarization's exact mechanisms in ICH remain uncertain. Therefore, we examined the role of sinomenine on microglia polarization and brain inflammation following ICH. For the experiment, autologous blood models were constructed in C57/BL6 mice. Markers of classically activated (M1) and alternatively activated (M2) microglia were detected by real-time polymerase chain reaction, immunofluorescence, and flow cytometry. Microglial toxicity was assessed using MTT and FACS assays. In addition, the neurological deficit and cerebral water content of ICH mice were also observed. Sinomenine attenuated M1 markers while promoting M2 markers of microglia. Sinomenine also protected hippocampal neurons from indirect toxicity mediated by ICH-treated microglia. Additionally, administration of sinomenine inhibited matrix metalloproteinase (MMP) 3/9 expression, cerebral water content, and neurological deficit. Therefore, sinomenine protected brain function following ICH, perhaps via M2 microglia phenotype induction and MMP 3/9 inhibition. This result suggests that sinomenine is a promising therapeutical strategy in ICH.

Sinomenine alleviates mechanical hypersensitivity in mice with experimentally induced rheumatoid arthritis

Background and aimsWe have previously reported that sinomenine, an alkaloid isolated from the root of the plant Sinomenium acutum, had antinociceptive effect in rodent models of acute inflammatory or neuropathic pain. As a traditional medicine, sinomenine is used in China to treat rheumatoid arthritis (RA). MethodsIn the present study, we evaluated the potential antinociceptive effect of sinomenine in a mouse model of RA, collagen type II antibody (CII Ab) induced arthritis (CAIA) after acute and chronic administration. ResultsAs single administration, sinomenine at 40 or 80mg/kg significantly reduced mechanical hypersensitivity both at the time of peak joint inflammation (days 11–19 after CII Ab injection) or during the post-inflammatory phase (days 35–54). No tolerance to the effect of 80mg/kg sinomenine was observed during repeated injection twice a day for 5 days from day 11 to day 19 or from day 49 to day 53 after CII Ab injection in CAIA mice. ConclusionsWe have shown that sinomenine is effective in alleviating localized and spread hypersensitivities in CAIA mice both during acute inflammation and in post-inflammatory phase. Further, repeated sinomenine administration has elevated the baseline mechanical threshold without producing tolerance. ImplicationsSinomenine may be clinically useful to treat chronic pain in RA, including wide-spread pain which appears to be a difficult clinical problem despite the improvement in the acute treatment of RA by disease modifying agents.

Repeated sinomenine administration alleviates chronic neuropathic pain-like behaviours in rodents without producing tolerance

Background and aimsWe have previously reported that systemic administration of sinomenine produced antinociception in various experimental pain conditions in rodents, particularly in models of neuropathic pain. In the present study we assessed the effects of repeated administration of sinomenine in two rodent models of neuropathic pain in order to study the development of tolerance. MethodsThe analgesic effect of sinomenine was tested in female Sprague-Dawley rats that exhibited mechanical and cold hypersensitivity following ischaemic injury to the spinal cord and in male C57/BL6 mice that developed mechanical hypersensitivity after ischaemic injury to the sciatic nerve. Briefly, the animals were anaesthetized and injected i.v. with the photosensitizing dye erythrosine B. Vertebral segments T12 to T13 in rats or the sciatic nerve in mice were exposed and irradiated under an argon ion laser for 10min or 45s, respectively. In rats, mechanical hypersensitivity to pressure with von Frey hairs, the response to brushing and decreasing cold temperature were tested in the flanks or upper back areas. In mice, mechanical hypersensitivity on the hind paw to von Frey hairs and response to cold following a drop of acetone were measured. Sinomenine was administered i.p. in rats and p.o. in mice at 10:00 and 16:00, twice a day for 5 days. Response threshold before and 2h after drug administration at 10.00h was recorded. ResultsRepeated administration of sinomenine at 10 or 20mg/kg twice a day, doses that have no analgesic effect as single injection, alleviated mechanical, but not cold allodynia in spinally injured rats and the effect was maintained during the 5 day treatment period with no signs of tolerance. Furthermore, the pre-drug response threshold was significantly elevated during repeated treatment with 20mg/kg sinomenine. Sinomenine administered at 40mg/kg twice a day for 5 days significantly reduced mechanical and cold alldoynia, elevated pre-drug response threshold without tolerance development in spinally injured rats. Similarly, sinomenine at 80mg/kg twice a day for 5 days significantly reduced mechanical allodynia in mice with sciatic nerve injury and increased pre-drug response threshold with no sign of tolerance. The effect of sinomenine on response threshold persisted for days after termination of the 5 day drug administration. ConclusionsThe results suggest that repeated administration of simomenine produced an enhanced anti-allodynic effect without tolerance in rodent models of neuropathic pain. ImplicationsSinomenine may be tested as a novel analgesic in treating some forms of chronic neuropathic pain in patients.

Sinomenine protects against ischaemic brain injury: involvement of co-inhibition of acid-sensing ion channel 1a and L-type calcium channels

Sinomenine (SN), a bioactive alkaloid, has been utilized clinically to treat rheumatoid arthritis in China. Our preliminary experiments indicated that it could protect PC12 cells from oxygen-glucose deprivation-reperfusion (OGD-R), we thus investigated the possible effects of SN on cerebral ischaemia and the related mechanism. Middle cerebral artery occlusion in rats was used as an animal model of ischaemic stroke in vivo. The mechanisms of the effects of SN were investigated in vitro using whole-cell patch-clamp recording, calcium imaging in PC12 cells and rat cortical neurons subjected to OGD-R. Pretreatment with SN (10 and 30 mg·kg(-1) , i.p.) significantly decreased brain infarction and the overactivation of calcium-mediated events in rats subjected to 2 h ischaemia followed by 24 h reperfusion. Extracellular application of SN inhibited the currents mediated by acid-sensing ion channel 1a and L-type voltage-gated calcium channels, in the rat cultured neurons, in a concentration-dependent manner. These inhibitory effects contribute to the neuroprotection of SN against OGD-R and extracellular acidosis-induced cytotoxicity. More importantly, administration of SN (30 mg·kg(-1) , i.p.) at 1 and 2 h after cerebral ischaemia also decreased brain infarction and improved functional recovery. SN exerts potent protective effects against ischaemic brain injury when administered before ischaemia or even after the injury. The inhibitory effects of SN on acid-sensing ion channel 1a and L-type calcium channels are involved in this neuroprotection.