Protective effect of dextromethorphan against endotoxic shock in mice

The N-Methyl-D-Aspartate Receptor Antagonist Dextromethorphan Improves Glucose Homeostasis and Preserves Pancreatic Islets in NOD Mice

For treatment of type 1 diabetes mellitus, a combination of immune-based interventions and medication to promote beta-cell survival and proliferation has been proposed. Dextromethorphan (DXM) is an N-methyl-D-aspartate receptor antagonist with a good safety profile, and to date, preclinical and clinical evidence for blood glucose-lowering and islet-cell-protective effects of DXM have only been provided for animals and individuals with type 2 diabetes mellitus. Here, we assessed the potential anti-diabetic effects of DXM in the non-obese diabetic mouse model of type 1 diabetes. More specifically, we showed that DXM treatment led to five-fold higher numbers of pancreatic islets and more than two-fold larger alpha- and beta-cell areas compared to untreated mice. Further, DXM treatment improved glucose homeostasis and reduced diabetes incidence by 50%. Our data highlight DXM as a novel candidate for adjunct treatment of preclinical or recent-onset type 1 diabetes.

Protection of pancreatic islets from oxidative cell death by a peripherally-active morphinan with increased drug safety

OBJECTIVE

Dextromethorphan (DXM) is a commonly used antitussive medication with positive effects in people with type 2 diabetes mellitus, since it increases glucose tolerance and protects pancreatic islets from cell death. However, its use as an antidiabetic medication is limited due to its central nervous side effects and potential use as a recreational drug. Therefore, we recently modified DXM chemically to reduce its blood-brain barrier (BBB) penetration and central side effects. However, our best compound interacted with the cardiac potassium channel hERG (human ether-à-go-go-related gene product) and the μ-opioid receptor (MOR). Thus, the goal of this study was to reduce the interaction of our compound with these targets, while maintaining its beneficial properties.

METHODS

Receptor and channel binding assays were conducted to evaluate the drug safety of our DXM derivative. Pancreatic islets were used to investigate the effect of the compound on insulin secretion and islet cell survival. Via liquor collection from the brain and a behavioral assay, we analyzed the BBB permeability. By performing intraperitoneal and oral glucose tolerance tests as well as pharmacokinetic analyses, the antidiabetic potential and elimination half-life were investigated, respectively. To analyze the islet cell-protective effect, we used fluorescence microscopy as well as flow cytometric analyses.

RESULTS

Here, we report the design and synthesis of an optimized, orally available BBB-impermeable DXM derivative with lesser binding to hERG and MOR than previous ones. We also show that the new compound substantially enhances glucose-stimulated insulin secretion (GSIS) from mouse and human islets and glucose tolerance in mice as well as protects pancreatic islets from cell death induced by reactive oxygen species and that it amplifies the effects of tirzepatide on GSIS and islet cell viability.

CONCLUSIONS

We succeeded to design and synthesize a novel morphinan derivative that is BBB-impermeable, glucose-lowering and islet cell-protective and has good drug safety despite its morphinan and imidazole structures.

Dextromethorphan Exhibits Anti-Inflammatory and Immunomodulatory Effects in a Murine Model: Therapeutic Implication in Psoriasis

Psoriasis is an immune-mediated skin disease with a worldwide prevalence of 2–4% that causes scaling erythematous skin lesions. It is a chronic relapsing and complex multifactorial disease that often necessitates long-term therapy. Despite various novel therapies, psoriasis remains a treatable but non-curable disease. Because the antitussive medication dextromethorphan (DXM) can inhibit murine bone marrow and human monocytes and slow the progression of arthritis in mice with type II collagen-induced arthritis, we explored whether the oral administration of DXM to mice with imiquimod (IMQ)-induced psoriasis can effectively alleviate psoriasis symptoms and improve immune regulation. Herein, we examined the therapeutic effects of DXM on psoriasis and its potential mechanisms of action in an IMQ-induced psoriasis mice model. We found that an oral dose of DXM (10 mg/kg) could more significantly reduce psoriasis symptoms compared with intraperitoneal injection. Seven days after the oral administration of DXM, the Psoriasis Area and Severity Index (PASI) score was significantly decreased compared with that in the vehicle group. Furthermore, DXM treatment also significantly ameliorated the psoriasis symptoms and the histopathological features of psoriasis, including stratum corneum thickening, desquamation, and immune cell infiltration. Additionally, DXM reduced the mRNA levels of the cytokines TNF-α, IL-6, IL-17A, and IL-22 in skin and the percentage of IL-17A and IL-22 producing T cell receptor γδ T cells (TCRγδT). Taken together, our research demonstrated that DXM could inhibit keratinocyte proliferation and alleviate psoriasis symptoms, which suggests the potential application of DXM in the treatment of chronic inflammation and autoimmune diseases.

Dextromethorphan reduces prenatal lipopolysaccharide exposure-induced dopaminergic neuronal loss and cytokine changes in offspring

Maternal infection during pregnancy may affect fetal brain development and increase the risk of developing neurological and mental disorders later in life in offspring. In this study, we used low-dose lipopolysaccharide (LPS) injection to mimic mild maternal infection at a critical time window for fetal dopamine (DA) and serotonin (5-HT) neuron development. The affected offspring exhibited reduction of dopaminergic and serotonergic neurons and anxiety- and depression-related behaviors in adulthood. In the current study, we evaluated whether dextromethorphan (DM, 30 mg/kg), an over-the-counter antitussive drug with anti-inflammatory and neuroprotective properties, could reduce the adverse effects of maternal infection mimicked by LPS exposure. We discovered that DM application did not change the baseline serum interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) levels in the LPS-exposed offspring. However, DM treatment could reduce the heightened immune responses induced by a postnatal LPS challenge test in prenatal LPS-exposed offspring. The neuroprotective effect of DM was only seen in DA neurons but not in 5-HT neurons. We concluded that DM treatment can partially protect the offspring against the adverse effects of LPS-induced maternal immune activation. The reduction in heightened immune responses and dopaminergic neuronal loss in LPS-exposed offspring could potentially reduce the risk of DA-related neurological and psychiatric disorders later in life.

Gal3 Plays a Deleterious Role in a Mouse Model of Endotoxemia

Lipopolysaccharide (LPS)-induced endotoxemia induces an acute systemic inflammatory response that mimics some important features of sepsis, the disease with the highest mortality rate worldwide. In this work, we have analyzed a murine model of endotoxemia based on a single intraperitoneal injection of 5 mg/kg of LPS. We took advantage of galectin-3 (Gal3) knockout mice and found that the absence of Gal3 decreased the mortality rate oflethal endotoxemia in the first 80 h after the administration of LPS, along with a reduction in the tissular damage in several organs measured by electron microscopy. Using flow cytometry, we demonstrated that, in control conditions, peripheral immune cells, especially monocytes, exhibited high levels of Gal3, which were early depleted in response to LPS injection, thus suggesting Gal3 release under endotoxemia conditions. However, serum levels of Gal3 early decreased in response to LPS challenge (1 h), an indication that Gal3 may be extravasated to peripheral organs. Indeed, analysis of Gal3 in peripheral organs revealed a robust up-regulation of Gal3 36 h after LPS injection. Taken together, these results demonstrate the important role that Gal3 could play in the development of systemic inflammation, a well-established feature of sepsis, thus opening new and promising therapeutic options for these harmful conditions.

Ultralow doses of dextromethorphan protect mice from endotoxin-induced sepsis-like hepatotoxicity

Dextromethorphan, a wildly used over-the-counter antitussive drug, is reported to have anti-inflammatory effects. Previously, we and others have demonstrated that dextromethorphan at micromolar doses displays potent hepatoprotective effects and enhances mice survival in a sepsis model. Moreover, we also observed potent anti-inflammatory and neuroprotective effects of subpicomolar concentrations of dextromethorphan in rodent primary neuron-glial cultures. The purpose of this study was to provide a proof of principle that ultralow dose dextromethorphan displays anti-inflammatory and cytoprotective effects in animal studies. Here, we report that subpico- and micromolar doses of dextromethorphan showed comparable efficacy in protecting mice from lipopolysaccharide/d-galactosamine (LPS/GalN)-induced hepatotoxicity and mortality. Mice were given injections of dextromethorphan from 30 min before and 2, 4 h after an injection of LPS/GalN (20 μg/600 mg/kg). Our results showed that dextromethorphan at subpicomolar doses promoted survival rate in LPS/GalN-injected mice. Ultralow dose dextromethorphan also significantly reduced serum alanine aminotransferase activity, TNF-α level and liver cell damage of endotoxemia mice. Mechanistic studies using primary liver Kupffer cell cultures revealed that subpicomolar concentrations of dextromethorphan reduced the NADPH oxidase-generated superoxide free radicals from Kupffer cells, which in turn reduced the elevation of its downstream reactive oxygen species (iROS) to relieve the oxidative stress and decreased TNF-α production in Kupffer cells. Taken together, these findings suggest a novel therapeutic concept of using ultralow doses of dextromethorphan for the intervention of sepsis or septic shock.

Diarylheptanoid, a constituent isolated from methanol extract of Alpinia officinarum attenuates TNF-α level in Freund's complete adjuvant-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a chronic inflammatory and destructive joint disease that affects the worldwide population. Alpinia officinarum Hance (Zingiberaceae), rhizomes are widely used ethnobotanically as an anti-inflammatory, analgesic, and antioxidant agent in traditional medicine.

AIM

To investigate the efficacy and possible mechanism of isolated phytoconstituent from the methanol extract of A. officinarum (MEAO) rhizomes against Freund's complete adjuvant (FCA)-induced arthritis in rats. Furthermore, molecular docking was performed to study the binding mode of this compound into the active site of TNF-α.

MATERIALS AND METHODS

Diarylheptanoid was isolated from MEAO, well characterized (HPTLC, ¹H NMR, ¹³C NMR, and ESI-MS) and evaluated for its antiarthritic activity in female Wistar rats (170-200 g). Diarylheptanoid (5, 10 and 20 mg/kg, p.o.) was administered starting from day 12. Various behavioral, biochemical, molecular and histopathology parameters were evaluated. Molecular docking study was performed using Glide module integrated into Schrodinger molecular modeling software.

RESULTS

The structure and molecular weight of the isolated compound (diarylheptanoid) were confirmed by 1D and mass spectral data and characterized as 1-phenyl-5-hydroxy-7- (4''-hydroxy-3''-methoxyphenyl) heptane-3-one (i.e., 5-HPH) with molecular formula C₂₀H₂₄O₄. Administration of 5-HPH (10 and 20 mg/kg) significantly inhibited (p < 0.05) FCA induced increases in paw volume, joint diameter, thermal hyperalgesia and tactile allodynia. It also significantly decreased oxido-inflammatory markers (SOD, GSH, MDA, and TNF-α). FCA induced a histological alteration in ankle joint also attenuated by 5-HPH. Its Glide docking score was found to be -9.702 with binding energy (Glide energy) of -37.033 kcal/mol.

CONCLUSION

5-HPH may exhibit its anti-arthritic potential via inhibition of elevated oxido-inflammatory markers thus restoring the elevated hyperalgesia, allodynia and reducing destruction in synovial membrane and cartilage. Therefore, 5-HPH is a potential moiety bearing antioxidant and with anti-inflammatory properties to inhibit FCA-induced arthritis in rats. The results of the present investigation should enable the design of potent small-molecule inhibitors that inactivate TNF-α with high affinity and specificity.

Dextromethorphan Exhibits Anti-inflammatory and Immunomodulatory Effects in a Murine Model of Collagen-Induced Arthritis and in Human Rheumatoid Arthritis

Dextromethorphan (d-3-methoxy-17-methylmorphinan, DXM) is a commonly used antitussive with a favorable safety profile. Previous studies have demonstrated that DXM has anti-inflammatory and immunomodulatory properties; however, the effect of DXM in rheumatoid arthritis (RA) remains unknown. Herein, we found that DXM treatment attenuated arthritis severity and proinflammatory cytokine expression levels, including TNF-α, IL-6, and IL-17A, in paw tissues of CIA mice. DXM treatment also reduced serum TNF-α, IL-6, and IL-17A levels of CIA mice and patients with RA. DXM further decreased the production of anti-CII IgG, IFN-γ, and IL-17A in collagen-reactive CD4⁺ T cells extracted from the lymph nodes of CIA mice. In vitro incubation of bone marrow–derived dendritic cells with DXM limited CD4⁺ T-cell proliferation and inflammatory cytokine secretion. In conclusion, our results showed that DXM attenuated arthritis symptoms in CIA mice and significantly reduced proinflammatory cytokines in patients with RA, suggesting that it can be used as an anti-arthritic agent.

Dextromethorphan: An update on its utility for neurological and neuropsychiatric disorders

Dextromethorphan (DM) is a commonly used antitussive and is currently the only FDA-approved pharmaceutical treatment for pseudobulbar affect. Its safety profile and diverse pharmacologic actions in the central nervous system have stimulated new interest for repurposing it. Numerous preclinical investigations and many open-label or blinded clinical studies have demonstrated its beneficial effects across a variety of neurological and psychiatric disorders. However, the optimal dose and safety of chronic dosing are not fully known. This review summarizes the preclinical and clinical effects of DM and its putative mechanisms of action, focusing on depression, stroke, traumatic brain injury, seizure, pain, methotrexate neurotoxicity, Parkinson's disease and autism. Moreover, we offer suggestions for future research with DM to advance the treatment for these and other neurological and psychiatric disorders.

Umbelliferone β-d-galactopyranoside exerts an anti-inflammatory effect by attenuating COX-1 and COX-2

Umbelliferone β-d-galactopyranoside (UFG) is a coumarin found in many plants. This study examines the anti-inflammatory potential of UFG on chronic inflammation induced by Complete Freund Adjuvant (CFA) in experimental rats.

Determining the neuroprotective effects of dextromethorphan in lipopolysaccharide‑stimulated BV2 microglia

Microglial activation has been recognized as being vital in the pathogenesis of several neurodegenerative disorders. Therefore, the identification of therapeutic drugs to prevent microglial activation and thus protect against inflammation‑mediated neuronal injury, is required. In the present study, dextromethorphan (DM), a compound widely used in antitussive remedies that has been demonstrated to possess neuroprotective effects, was shown to reduce proinflammatory mediator production in lipopolysaccharide (LPS)‑stimulated BV2 mouse microglial cells. Western blot analysis revealed that DM markedly suppressed the activation of nuclear factor‑κB (NFκB), caspase‑3 signaling and the expression of another inflammation‑inducing factor, heat shock protein 60 (HSP60) and heat shock factor‑1, induced by LPS in BV2 cells. Results from ELISA assay demonstrated that DM reduced the release of HSP60, nitric oxide (NO), inducible NO synthase, tumor necrosis factor‑α, interleukin (IL)‑1β and IL‑6 induced by LPS in BV2 microglia. These results were confirmed by immunofluorescence, suggesting that DM may exert a neuroprotective and anti‑inflammatory effect by inhibiting microglial activation through the HSP60‑NFκB signaling pathway. Therefore, DM may offer substantial therapeutic benefits in the treatment of neurodegenerative diseases that are accompanied by microglial activation.

Impairment of autophagy in the central nervous system during lipopolysaccharide-induced inflammatory stress in mice

Background

Current evidence suggests a central role for autophagy in many neurodegenerative diseases including Alzheimer’s disease, Huntington’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Furthermore, it is well admitted that inflammation contributes to the progression of these diseases. Interestingly, crosstalks between autophagy and inflammation have been reported in vitro and at the peripheral level such as in Crohn’s disease. However, the impact of systemic inflammation on autophagic components in the brain remains to be documented. Therefore, this study monitored autophagy markers after acute and chronic lipopolysaccharide (LPS)-induced inflammatory stress in mice.

Results

We showed that acute inflammation, 24 h post-intraperitoneal 10 mg/kg LPS, substantially increased cytokine production (Interleukin(IL)-1β, Tumor necrosis factor (TNF)-α and IL-6), decreased the levels of autophagy markers (Beclin-1, p62 and LC3 II) and reduced p70S6K activation in cortex and hippocampus. In hippocampus, IL-1β levels and LC3 II expression were positively and highly correlated and a negative correlation was noted between TNF-α levels and p70S6K activation. Chronic inflammation by injection of 0.5 mg/kg LPS every three days during three months led to a moderate IL-1β production and decreased TNF-α levels. Interestingly, Beclin-1 and LC3 II levels decreased while those of p62 increased. Cortical IL-1β levels positively correlated with Beclin-1 and LC3 II and on the contrary inversely correlated with p62.

Conclusion

The present study is the first showing links between IL-1β-mediated inflammation and autophagy in the brain. It could open to new therapeutic strategies in brain diseases where regulation impairment of inflammation and autophagy progress with the severity of diseases.

Penetratin derivative-based nanocomplexes for enhanced intestinal insulin delivery

Sufficient mucosal permeability is the bottleneck problem in developing an efficient intestinal delivery system of insulin. Cell-penetrating peptide-based nanocomplexes for the enhanced mucosal permeation of insulin were developed in this study. Penetratin, a cell-penetrating peptide was site-specifically modified with a bis-β-cyclodextrin group. Insulin-loaded nanocomplexes were prepared by self-assembly using penetratin or its bis-β-cyclodextrin modified derivative (P-bis-CD). A stronger intermolecular interaction and higher complex stability were observed for P-bis-CD nanocomplexes than the penetratin nanocomplexes. P-bis-CD nanocomplexes were significantly more efficient for the permeation of insulin as compared to the penetratin nanocomplexes both in vitro and in situ. Interestingly, different cellular internalization mechanisms were observed for the two nanocomplexes. In diabetic rats, intestinal administration of P-bis-CD nanocomplexes resulted in a prominent hypoglycemic effect which lasted for 6 h with maximum inhibitory rate at 60%. The relative pharmacological availability and bioavailability of P-bis-CD nanocomplexes were 10.6% and 7.1%, which were 3.0-fold and 2.3-fold higher than that of penetratin nanocomplexes, respectively. In addition, no sign of toxicity was observed after 7 consecutive days of administration of P-bis-CD nanocomplexes with endotoxin. These results demonstrated that P-bis-CD was a promising epithelium permeation enhancer for insulin and suggested that the chemical modification of cell penetration peptides was a feasible strategy to enhance their potential.

Dextromethorphan attenuates LPS-induced adhesion molecule expression in human endothelial cells

OBJECTIVE

This study examines the effect of Dextromethorphan (d-3-methoxy-17-methylmorphinan; DXM), a commonly used cough-suppressing drug, on the expression of VCAM-1 and ICAM-1 in human umbilical vein endothelial cells (HUVECs) stimulated with lipopolysaccharide (LPS).

METHODS

The effect of DXM on expression of cell adhesion molecules induced by LPS was evaluated by monocyte bindings in vitro and ex vivo and transmigration assays. The signaling pathways involved in the inflammation inhibitory effect of DXM were analyzed by Western blot and immunofluorescent stain.

RESULTS

Pretreatment of HUVECs with DXM inhibited LPS-induced adhesion of THP-1 cells in vitro and ex vivo, and reduced transendothelial migration of these cells. Furthermore, treatment of HUVECs with DXM can significantly decrease LPS-induced expression of ICAM-1 and VCAM-1. DXM abrogated LPS-induced phosphorylation of ERK and Akt. The translocation of early growth response gene-1 (Egr-1), a downstream transcription factor involved in the mitogen-activated kinase (MEK)-ERK signaling pathway, was suppressed by DXM treatment. Furthermore, DXM inhibited LPS-induced IκBα degradation and nuclear translocation of p65.

CONCLUSIONS

Dextromethorphan inhibits the adhesive capacity of HUVECs by reducing the LPS-induced ICAM-1 and VCAM-1 expression via the suppression of the ERK, Akt, and NF-κB signaling pathways. Thus, DXM is a potential anti-inflammatory therapeutic that may modulate atherogenesis.

Dextromethorphan inhibits osteoclast differentiation by suppressing RANKL-induced nuclear factor-κB activation

Dextromethorphan (DXM), a commonly used antitussive, is a dextrorotatory morphinan. Here, we report that DXM inhibits the receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis and bone resorption by abrogating the activation of NF-κB signalling in vitro. Oral administration of DXM ameliorates ovariectomy (OVX)-induced osteoporosis in vivo.

INTRODUCTION

DXM was reported to possess anti-inflammatory properties through inhibition of the release of pro-inflammatory factors. However, the potential role and action mechanism of DXM on osteoclasts and osteoblasts remain unclear. In this study, in vitro and in vivo studies were performed to investigate the potential effects of DXM on osteoclastogenesis and OVX-induced bone loss.

METHODS

Osteoclastogenesis was examined by the TRAP staining, pit resorption, TNF-α release, and CCR2 and CALCR gene expression. Osteoblast differentiation was analyzed by calcium deposition. Osteogenic and adipogenic genes were measured by real-time PCR. Signaling pathways were explored using Western blot. ICR mice were used in an OVX-induced osteoporosis model. Tibiae were measured by µCT and serum markers were examined with ELISA kits.

RESULTS

DXM inhibited RANKL-induced osteoclastogenesis. DXM mainly inhibited osteoclastogenesis via abrogation of IKK-IκBα-NF-κB pathways. However, a higher dosage of DXM antagonized the differentiation of osteoblasts via the inhibition of osteogenic signals and increase of adipogenic signals. Oral administration of DXM (20 mg/kg/day) partially reduced trabecular bone loss in ovariectomized mice.

CONCLUSION

DXM inhibits osteoclast differentiation and activity by affecting NF-κB signaling. Therefore, DXM at suitable doses may have new therapeutic applications for the treatment of diseases associated with excessive osteoclastic activity.

NADPH oxidase and aging drive microglial activation, oxidative stress, and dopaminergic neurodegeneration following systemic LPS administration

Parkinson's disease is characterized by a progressive degeneration of substantia nigra (SN) dopaminergic neurons with age. We previously found that a single systemic lipopolysaccharide (LPS, 5 mg/kg, i.p.) injection caused a slow progressive loss of tyrosine hydroxylase immunoreactive (TH+IR) neurons in SN associated with increasing motor dysfunction. In this study, we investigated the role of NADPH oxidase (NOX) in inflammation-mediated SN neurotoxicity. A comparison of control (NOX2(+/+) ) mice with NOX subunit gp91(phox) -deficient (NOX2(-/-) ) mice 10 months after LPS administration (5 mg/kg, i.p.) resulted in a 39% (P < 0.01) loss of TH+IR neurons in NOX2(+/+) mice, whereas NOX2(-/-) mice did not show a significant decrease. Microglia (Iba1+IR) showed morphological activation in NOX2(+/+) mice, but not in NOX2(-/-) mice at 1 hr. Treatment of NOX2(+/+) mice with LPS resulted in a 12-fold increase in NOX2 mRNA in midbrain and 5.5-6.5-fold increases in NOX2 protein (+IR) in SN compared with the saline controls. Brain reactive oxygen species (ROS), determined using diphenyliodonium histochemistry, was increased by LPS in SN between 1 hr and 20 months. Diphenyliodonium (DPI), an NOX inhibitor, blocked LPS-induced activation of microglia and production of ROS, TNFα, IL-1β, and MCP-1. Although LPS increased microglial activation and ROS at all ages studied, saline control NOX2(+/+) mice showed age-related increases in microglial activation, NOX, and ROS levels at 12 and 22 months of age. Together, these results suggest that NOX contributes to persistent microglial activation, ROS production, and dopaminergic neurodegeneration that persist and continue to increase with age.

Excess soluble CD40L contributes to blood brain barrier permeability in vivo: implications for HIV-associated neurocognitive disorders

Despite the use of anti-retroviral therapies, a majority of HIV-infected individuals still develop HIV-Associated Neurocognitive Disorders (HAND), indicating that host inflammatory mediators, in addition to viral proteins, may be contributing to these disorders. Consistently, we have previously shown that levels of the inflammatory mediator soluble CD40L (sCD40L) are elevated in the circulation of HIV-infected, cognitively impaired individuals as compared to their infected, non-impaired counterparts. Recent studies from our group suggest a role for the CD40/CD40L dyad in blood brain barrier (BBB) permeability and interestingly, sCD40L is thought to regulate BBB permeability in other inflammatory disorders of the CNS. Using complementary multiphoton microscopy and quantitative analyses in wild-type and CD40L deficient mice, we now reveal that the HIV transactivator of transcription (Tat) can induce BBB permeability in a CD40L-dependent manner. This permeability of the BBB was found to be the result of aberrant platelet activation induced by Tat, since depletion of platelets prior to treatment reversed Tat-induced BBB permeability. Furthermore, Tat treatment led to an increase in granulocyte antigen 1 (Gr1) positive monocytes, indicating an expansion of the inflammatory subset of cells in these mice, which were found to adhere more readily to the brain microvasculature in Tat treated animals. Exploring the mechanisms by which the BBB becomes compromised during HIV infection has the potential to reveal novel therapeutic targets, thereby aiding in the development of adjunct therapies for the management of HAND, which are currently lacking.

Mechanism investigation of dioscin against CCl4-induced acute liver damage in mice

The mechanisms of the ameliorating effects of dioscin against CCl(4) induced acute liver damage are investigated in this study. Dioscin significantly inhibited (p<0.01) the increases of serum ALT and AST activities compared with the CCl(4)-treated animals. The hepatic lipid peroxidation formation and, concentrations of TNF-α and IL-6 were also decreased. Liver histopathologic studies and a DNA laddering assay indicated that dioscin protected hepatocytes against CCl(4)-induced apoptosis and necrosis. Furthermore, dioscin decreased the protein expressions of Fas/FasL, increased Bcl-2/Bax ratio, inhibited the release of cytochrome c from mitochondrion to cytosol and attenuated CCl(4)-induced caspase-3 and -8 activities. The expressions of ICAM-1, vimentin, prohibitin, HGF, c-MET and GSTA1 were also regulated by dioscin and iNOS was also involved in the effects of this agent. These protective effects against CCl(4) induced acute liver damage might be through inhibiting lipid peroxidation, inflammatory cytokines, necrosis and apoptosis, and dioscin shows promise for development toward the treatment of acute chemically mediated liver injury.

Reactive oxygen species and inhibitors of inflammatory enzymes, NADPH oxidase, and iNOS in experimental models of Parkinson's disease

Reactive oxygen species (ROSs) are emerging as important players in the etiology of neurodegenerative disorders including Parkinson's disease (PD). Out of several ROS-generating systems, the inflammatory enzymes nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and inducible nitric oxide synthase (iNOS) were believed to play major roles. Mounting evidence suggests that activation of NADPH oxidase and the expression of iNOS are directly linked to the generation of highly reactive ROS which affects various cellular components and preferentially damage midbrain dopaminergic neurons in PD. Therefore, appropriate management or inhibition of ROS generated by these enzymes may represent a therapeutic target to reduce neuronal degeneration seen in PD. Here, we have summarized recently developed agents and patents claimed as inhibitors of NADPH oxidase and iNOS enzymes in experimental models of PD.

pH-responsive nanoparticles shelled with chitosan for oral delivery of insulin: from mechanism to therapeutic applications

Despite advances in drug-delivery technologies, successful oral administration of protein drugs remains an elusive challenge. When protein drugs are administered orally, they can rapidly denature or degrade before they reach their targets. Such drugs also may not absorb adequately within the small intestine. As a protein drug for treating diabetes, insulin is conventionally administered via subcutaneous (SC) injection, yet often fails to achieve the glucose homeostasis observed in nondiabetic subjects. Some of this difference may relate to insulin transport: normally, endogenously secreted insulin moves to the liver via portal circulation. When administered subcutaneously, insulin moves through the body via peripheral circulation, which can produce a peripheral hyperinsulinemia. In addition, because SC treatment requires multiple daily injections of insulin, patients often do not fully comply with treatment. Oral administration of exogenous insulin would deliver the drug directly into the liver through portal circulation, mimicking the physiological fate of endogenously secreted insulin. This characteristic may offer the needed hepatic activation, while avoiding hyperinsulinemia and its associated long-term complications. This Account demonstrates the feasibility of using chitosan nanoparticles for oral insulin delivery. Nanoparticle (NP) delivery systems may provide an alternative means of orally administering protein drugs. In addition to protecting the drugs against a harmful gastric environment, the encapsulation of protein drugs in particulate carriers can avert enzymatic degradation, while controlling the drug release and enhancing their absorption in the small intestine. Our recent study described a pH-responsive NP system composed of chitosan (CS) and poly(γ-glutamic acid) for oral delivery of insulin. As a nontoxic, soft-tissue compatible, cationic polysaccharide, CS also adheres to the mucosal surface and transiently opens the tight junctions (TJs) between contiguous epithelial cells. Therefore, drugs made with CS NPs would have delivery advantages over traditional tablet or powder formulations. This Account focuses on the premise that these CS NPs can adhere to and infiltrate the mucus layer in the small intestine. Subsequently, the infiltrated CS NPs transiently open the TJs between epithelial cells. Because they are pH-sensitive, the nanoparticles become less stable and disintegrate, releasing the loaded insulin. The insulin then permeates through the opened paracellular pathway and moves into the systemic circulation.

Comparative effects of triflusal, S-adenosylmethionine, and dextromethorphan over intestinal ischemia/reperfusion injury

Ischemia/reperfusion (I/R) is a condition that stimulates an intense inflammatory response. No ideal treatment exists. Triflusal is an antiplatelet salicylate derivative with anti-inflammatory effects. S-adenosylmethionine is a metabolic precursor for glutathione, an endogenous antioxidant. Dextromethorphan is a low-affinity N-methyl-D-aspartate receptor inhibitor. There is evidence that these agents modulate some of the pathways involved in I/R physiopathology. Intestinal I/R was induced in rats by clamping the superior mesenteric artery for 60 minutes, followed by 60 minutes of reperfusion. Rats either received saline or the drugs studied. At the end of the procedure, serum concentrations of tumor necrosis factor-alpha (TNF-alpha), malonaldehyde (MDA), and total antioxidant capacity (TAC) were determined and intestinal morphology analyzed. I/R resulted in tissue damage, serum TNF-alpha and MDA elevations, and depletion of TAC. All drugs showed tissue protection. Only triflusal reduced TNF-alpha levels. All drugs lowered MDA levels, but only triflusal and S-adenosylmethionine maintained the serum TAC.

Effects of chitosan-nanoparticle-mediated tight junction opening on the oral absorption of endotoxins

Recently, we reported a pH-responsive nanoparticle (NP) system shelled with chitosan (CS), which could effectively increase the oral absorption of insulin and produce a hypoglycemic effect, presumably due to the CS-mediated tight junction (TJ) opening. It has been often questioned whether CS can also enhance the absorption of endotoxins present in the small intestine. To address this concern, we studied the effect of CS NPs on the absorption of lipopolysaccharide (LPS), the most commonly found toxin in the gastrointestinal tract. To follow their biodistribution by the single-photon emission computed tomography/computed tomography, LPS and insulin were labeled with (99m)Tc-pertechnetate ((99m)Tc-LPS) and (123)iodine ((123)I-insulin), respectively. The (99m)Tc-LPS was ingested 1 h prior to the administration of the (123)I-insulin-loaded NPs to mimic the physiological conditions. The confocal and TEM micrographs show that the orally administered CS NPs were able to adhere and infiltrate through the mucus layer, approach the epithelial cells and mediate to open their TJs. The radioactivity associated with LPS was mainly restricted to the gastrointestinal tract, whereas (123)I-insulin started to appear in the urinary bladder at 3 h post administration. This observation indicates that the insulin-loaded in CS NPs can traverse across the intestinal epithelium and enter the systemic circulation, whereas LPS was unable to do so, probably because of the charge repulsion between the anionic LPS in the form of micelles and the negatively charged mucus layer. Our in vivo toxicity study further confirms that the enhancement of paracellular permeation by CS NPs did not promote the absorption of LPS. These results suggest that CS NPs can be used as a safe carrier for oral delivery of protein drugs.

Dextromethorphan efficiently increases bactericidal activity, attenuates inflammatory responses, and prevents group a streptococcal sepsis

Group A streptococcus (GAS) is an important human pathogen that causes a wide spectrum of diseases, ranging from mild throat and skin infections to severe invasive diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome. Dextromethorphan (DM), a dextrorotatory morphinan and a widely used antitussive drug, has recently been reported to possess anti-inflammatory properties. In this study, we investigated the potential protective effect of DM in GAS infection using an air pouch infection mouse model. Our results showed that DM treatment increased the survival rate of GAS-infected mice. Bacterial numbers in the air pouch were lower in mice treated with DM than in those infected with GAS alone. The bacterial elimination efficacy was associated with increased cell viability and bactericidal activity of air-pouch-infiltrating cells. Moreover, DM treatment prevented bacterial dissemination in the blood and reduced serum levels of the proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-1β and the chemokines monocyte chemotactic protein 1 (MCP-1), macrophage inflammatory protein 2 (MIP-2), and RANTES. In addition, GAS-induced mouse liver injury was reduced by DM treatment. Taken together, DM can increase bacterial killing and reduce inflammatory responses to prevent sepsis in GAS infection. The consideration of DM as an adjunct treatment in combination with antibiotics against bacterial infection warrants further study.

Protective effect of chloral hydrate against lipopolysaccharide/D-galactosamine-induced acute lethal liver injury and zymosan-induced peritonitis in mice

In recent years, certain anesthetics have been shown to have protective effects against acute inflammation in experimental animals, an observation that may yield new options for adjunctive treatment of acute inflammation. In this study, we investigated the effects of chloral hydrate (CH) on the acute inflammatory response in BALB/c mice using lipopolysaccharide/D-galactosamine (LPS/D-GalN)-induced acute lethal liver injury and zymosan A-induced peritonitis models. The survival of mice following LPS/D-GalN treatment was significantly improved by a single injection with chloral hydrate, which could be administered simultaneously or as late as 3h after challenge with LPS/D-GalN; liver injury was also attenuated. A sharp rise in serum levels of MCP-1, IL-6 and TNF-alpha was attenuated or delayed after chloral hydrate treatment. Furthermore, the mechanism by which chlorate hydrate inhibits inflammation was associated with an attenuated increase in nuclear factor kappaappaB (NF-kappaB) activity in NF-kappaB-RE-luc mice upon LPS/D-GalN treatment. In mice with acute peritonitis, leukocyte number and protein concentration in peritoneal exudates peaked with a 16h lag, and serum levels of MCP-1, IL-6 and TNF-alpha were significantly lower at certain time points in the chloral hydrate-treated group compared to those in the normal saline (NS)-treated control group. In addition, chloral hydrate treatment in vitro attenuated the upregulation of TNF-alpha and IL-6 by peritoneal macrophages and NF-kappaB activity in RAW264.7 cells stimulated with LPS, suggesting that monocytes/macrophages may be a target of chloral hydrate. These results indicate that chloral hydrate has a protective effect against LPS/D-GalN-induced acute lethal liver injury in mice, which may be associated with an inhibition of NF-kappaB activity and delays in proinflammatory cytokine production. However, this phenomenon was not associated with levels of serum corticosterone. Chloral hydrate also attenuated the inflammatory response in zymosan A-induced acute peritonitis, a model of mild inflammation. In conclusion, treatment with only a single injection of chloral hydrate could significantly attenuate acute inflammation in mice treated with LPS/D-GalN and zymosan A. These effects are also likely associated with the inhibition of NF-kappaB activity.

Targeting NADPH oxidase and phospholipases A2 in Alzheimer's disease

Alzheimer's disease (AD) is marked by an increase in the production of extracellular beta amyloid plaques and intracellular neurofibrillary tangles associated with a decline in brain function. Increases in oxidative stress are regarded as an early sign of AD pathophysiology, although the source of reactive oxygen species (ROS) and the mechanism(s) whereby beta amyloid peptides (Abeta) impact oxidative stress have not been adequately investigated. Recent studies provide strong evidence for the involvement of NADPH oxidase and its downstream oxidative signaling pathways in the toxic effects elicited by Abeta. ROS produced by NADPH oxidase activate multiple signaling pathways leading to neuronal excitotoxicity and glial cell-mediated inflammation. This review describes recent studies demonstrating the neurotoxic effects of Abeta in conjunction with ROS produced by NADPH oxidase and the downstream pathways leading to activation of cytosolic phospholipase A(2) (PLA(2)) and secretory PLA(2). In addition, this review also describes recent studies using botanical antioxidants to protect against oxidative damage associated with AD. Investigating the metabolic and signaling pathways involving Abeta NADPH oxidase and PLA(2) can help understand the mechanisms underlying the neurodegenerative effects of oxidative stress in AD. This information should provide new therapeutic approaches for prevention of this debilitating disease.

Control protocol for robust in vitro glial scar formation around microwires: essential roles of bFGF and serum in gliosis

Previously, we reported an in vitro cell culture model that recreates many of the hallmarks of glial scarring around electrodes used for recording in the brain; however, the model lacked the reproducibility necessary to establish a useful characterization tool. This methods paper describes a protocol, modeled on protocols typically used to culture neural stem/precursor cells, that generates a predictable positive control of an intense scarring reaction. Six independent cell culture variables (growth media, seeding density, bFGF addition day, serum concentration in treatment media, treatment day, and duration of culture) were varied systematically and the resulting scars were quantified. The following conditions were found to give the highest level of scarring: Neurobasal medium supplemented with B27, 10% fetal bovine serum at treatment, 10 ng/ml b-FGF addition at seeding and at treatment, treatment at least 6 days after seeding and scar growth of at least 5 days. Seeding density did not affect scarring as long as at least 500,000 cells were seeded per well, but appropriate media, bFGF, and serum were essential for significant scar formation-insights that help validate the in vitro-based approach to understanding glial scarring. With the control protocol developed in this study producing a strong, reproducible glial scarring positive control with every dissection, this culture model is suitable for the in vitro study of the mechanisms behind glial scarring and neuroelectrode failure.

Uncoupling protein-2 deficiency provides protection in a murine model of endotoxemic acute liver failure

OBJECTIVE

Liver injury and cell death are prominent features in the pathogenesis of acute liver failure. Mitochondrial uncoupling protein 2 plays a controversial role in liver cell death through its involvement in the production of reactive oxygen species and adenosine triphosphate.

DESIGN

This randomized controlled animal study was designed to investigate the exact role of uncoupling protein 2 in the pathogenesis of endotoxemic acute liver failure.

SETTING

Research laboratory of an academic institution. SUBJECTS, INTERVENTIONS, AND MEASUREMENTS: Uncoupling protein 2+/+ and uncoupling protein 2-/- mice were challenged with D-galactosamine (Gal, 720 mg/kg intraperitoneally) and Escherichia coli lipopolysaccharide (10 microg/kg intraperitoneally) and studied 6 hrs thereafter (n = 5 per group). Control mice received physiologic saline (n = 5 per group). Analysis included in vivo fluorescence microscopy of hepatic microcirculation and hepatocellular apoptosis as well as plasma malondialdehyde concentrations as reactive oxygen species-dependent lipid peroxidation product and hepatic adenosine triphosphate levels.

MAIN RESULTS

Administration of Gal-lipopolysaccharide in uncoupling protein 2+/+ mice caused systemic cytokine release and malondialdehyde production. Further, it provoked marked hepatic damage, characterized by intrahepatic leukocyte recruitment (10.5 +/- 1.3 n/mm2 vs. 3.3 +/- 0.5 n/mm2), microvascular perfusion failure (33.1% +/- 1.6% vs. 2.3% +/- 0.4%), and adenosine triphosphate depletion (3.4 +/- 0.9 micromol/g vs. 6.4 +/- 0.9 micromol/g). Furthermore, uncoupling protein +/+ mice revealed a huge rise in cell apoptosis, given by high numbers of hepatocytes exhibiting nuclear chromatin fragmentation (44.9 +/- 11.5 n/mm2 vs. 0.0 +/- 0.0 n/mm2) and cleaved caspase-3 expression (1.24 +/- 0.24 vs. 0.06 +/- 0.04). Liver injury was coexistent with enzyme release (alanine aminotransferase 442 +/- 126 U/L vs. 57 +/- 12 U/L) and necrotic cell death. Of interest, Gal-lipopolysaccharide-exposed uncoupling protein 2-/- mice exhibited higher rates of hepatocellular apoptosis (135.6 +/- 46.0 n/mm2) as well as cleaved caspase-3 expression (1.75 +/- 0.25), however, preserved hepatic adenosine triphosphate (6.4 +/- 1.7), milder perfusion failure (24.5 +/- 2.4) and decreased leukocyte recruitment (2.7 +/- 0.2), less necrotic injury, lower transaminase levels (340 +/- 91), and finally better survival rates.

CONCLUSION

The higher adenosine triphosphate availability in uncoupling protein 2-deficient mice might allow hepatocytes to undergo apoptosis as an energy-consuming mode of cell death, while at the same time cellular adenosine triphosphate levels seem to increase hepatic resistance against harmful effects upon Gal-lipopolysaccharide exposure. As net result, uncoupling protein 2 deficiency provided protection under endotoxemic stress conditions, underlining the significant role of the bioenergetic status in critical illness.

NADPH oxidase as a therapeutic target in Alzheimer's disease

At present, available treatments for Alzheimer's disease (AD) are largely unable to halt disease progression. Microglia, the resident macrophages in the brain, are strongly implicated in the pathology and progressively degenerative nature of AD. Specifically, microglia are activated in response to both β amyloid (Aβ) and neuronal damage, and can become a chronic source of neurotoxic cytokines and reactive oxygen species (ROS). NADPH oxidase is a multi-subunit enzyme complex responsible for the production of both extracellular and intracellular ROS by microglia. Importantly, NADPH oxidase expression is upregulated in AD and is an essential component of microglia-mediated Aβ neurotoxicity. Activation of microglial NADPH oxidase causes neurotoxicity through two mechanisms: 1) extracellular ROS produced by microglia are directly toxic to neurons; 2) intracellular ROS function as a signaling mechanism in microglia to amplify the production of several pro-inflammatory and neurotoxic cytokines (for example, tumor necrosis factor-α, prostaglandin E2, and interleukin-1β). The following review describes how targeting NADPH oxidase can reduce a broad spectrum of toxic factors (for example, cytokines, ROS, and reactive nitrogen species) to result in inhibition of neuronal damage from two triggers of deleterious microglial activation (Aβ and neuron damage), offering hope in halting the progression of AD.

Treatment with dextromethorphan improves endothelial function, inflammation and oxidative stress in male heavy smokers

BACKGROUND

Dextromethorphan (DM) is reported to reduce the inflammation-mediated degeneration of dopaminergic neurons.

OBJECTIVE

The goal of this study was to test if DM can improve the endothelial dysfunction and inflammatory markers in heavy smokers.

PATIENTS AND METHODS

Forty habitual smoking healthy male volunteers (mean age, 31.5 +/- 1.4 years) were randomly given either DM (120 mg day(-1)) or a placebo for 6 months. We determined endothelial function using the brachial artery diameter changes in flow-mediated dilatation (FMD) and measured their inflammatory and oxidative markers. A sex-and-age matched non-smoking group (n = 20) was compared as normal parameters.

RESULTS

Habitual smokers showed impaired baseline endothelial function in FMD (smoking vs. non-smoking: 6.3 +/- 1.8 vs. 10.2 +/- 2.3% respectively, P < 0.01). Without change in smoking behavior, lipid and metabolic parameters, a significant increase in FMD was found in the DM-treated group (32%), accompanied by a decrease in high-sensitivity C-reactive protein (hs-CRP), phospholipase A(2), matrix metalloproteinase-3, interleukin 6 (IL-6) and tumor necrosis factor-alpha receptor II (TNF-alpha RII) (all P < 0.05), but unchanged in von Willebrand factor (VWF)and plasminogen activator inhibitor-1 (PAI-1). An increase in plasma glutathione peroxidase and a decrease in spot urinary excretion of 8-epi-prostaglandin F(2a) were found in DM-treated smokers.

CONCLUSIONS

Our study suggests that a 6-month treatment with DM can improve endothelial function and attenuate vascular oxidative stress and inflammation markers in habitual smokers.

Prophylactic effect of liposomal N-acetylcysteine against LPS-induced liver injuries

The aim of this study was to evaluate and compare the effectiveness of N-acetylcysteine (NAC) and liposomally-encapsulated NAC (L-NAC) in ameliorating the hepatotoxic effects of lipopolysaccharide (LPS). LPS, a major cell wall molecule of Gram-negative bacteria and the principal initiator of septic shock, causes liver injury in vivo that is dependent on neutrophils, platelets, and several inflammatory mediators, including tumour necrosis factor-alpha (TNF-alpha). Male Sprague-Dawley rats were pretreated intravenously with saline, plain liposomes (dipalmitoylphosphatidylcholine [DPPC]), NAC (25 mg/kg body weight), or L-NAC (25 mg/kg NAC body weight) and 4 h later were challenged intravenously with LPS (Escherichia coli O111:B4, 1.0 mg/kg body weight); animals were killed 20 h post-LPS challenge. Hepatic cell injury was evaluated by measuring the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in plasma. LPS-induced activation of the inflammatory response was evaluated by measuring the levels of myeloperoxidase activity and chloramine concentration in liver homogenates as well as TNF-alpha levels in plasma. The hepatic levels of lipid peroxidation products and non-protein thiols (NPSH) were used to assess the extent of involvement of oxidative stress mechanisms. In general, challenge of animals with LPS resulted in hepatic injuries, activation of the inflammatory response, decreases in NPSH levels and increases in the levels of lipid peroxidation products (malondialdehyde and 4-hydroxyalkenals). Pretreatment of animals with NAC or empty liposomes did not have any significant protective effect against LPS-induced hepatotoxicity. On the other hand, pretreatment of animals with an equivalent dose of L-NAC conferred protection against the liver injuries induced following LPS challenge. These data suggest that NAC when delivered as a liposomal formulation is a potentially more effective prophylactic pharmacological agent in alleviating LPS-induced liver injuries.

Systemic LPS causes chronic neuroinflammation and progressive neurodegeneration

Inflammation is implicated in the progressive nature of neurodegenerative diseases, such as Parkinson's disease, but the mechanisms are poorly understood. A single systemic lipopolysaccharide (LPS, 5 mg/kg, i.p.) or tumor necrosis factor alpha (TNFalpha, 0.25 mg/kg, i.p.) injection was administered in adult wild-type mice and in mice lacking TNFalpha receptors (TNF R1/R2(-/-)) to discern the mechanisms of inflammation transfer from the periphery to the brain and the neurodegenerative consequences. Systemic LPS administration resulted in rapid brain TNFalpha increase that remained elevated for 10 months, while peripheral TNFalpha (serum and liver) had subsided by 9 h (serum) and 1 week (liver). Systemic TNFalpha and LPS administration activated microglia and increased expression of brain pro-inflammatory factors (i.e., TNFalpha, MCP-1, IL-1beta, and NF-kappaB p65) in wild-type mice, but not in TNF R1/R2(-/-) mice. Further, LPS reduced the number of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra (SN) by 23% at 7-months post-treatment, which progressed to 47% at 10 months. Together, these data demonstrate that through TNFalpha, peripheral inflammation in adult animals can: (1) activate brain microglia to produce chronically elevated pro-inflammatory factors; (2) induce delayed and progressive loss of DA neurons in the SN. These findings provide valuable insight into the potential pathogenesis and self-propelling nature of Parkinson's disease.

The Anti-gastropathic and Anti-rheumatic Effect of Niga-ichigoside F1 and 23-Hydroxytormentic Acid Isolated from the Unripe Fruits of Rubus coreanus in a Rat Model

This study was undertaken to produce the clinical merits of two natural antinociceptive anti-inflammatory triterpenoids which synthetic anti-inflammatory drugs do not have. The triterpenoid glycoside niga-ichigoside F1 (NIF1) and its aglycone 23-hydroxytormentic acid (23-HTA), which were isolated from the unripe fruits of Rubus coreanus (Rosaceae), reduced rheumatoid arthritis (RA) factor and C-reactive protein (CRP) factor in Freund's complete adjuvant reagent-induced rats, suggesting that these two triterpenoids had an anti-rheumatic effect. It was also shown that treatment with NIF1 or 23-HTA reduced gastric lesion extent, acidity and total gastric acid output induced by EtOH plus sodium salicylate in a gastric secretion test. Moreover, 23-HTA had a greater effect than the glycoside, NIF1. To clarify the anti-gastropathic mechanism of these two compounds, their free radical scavenging activities in the gastric mucosa were examined in a rat EtOH-sodium salicylate-induced gastropathy model. The two compounds significantly increased superoxide dismutase and glutathione peroxidase activities, indicating that the healing effects of NIF1 and 23-HTA against gastropathy are associated with free radical scavenging enzyme activities. These results support the notion that the long-term administration of NIF1 or 23-HTA should overcome the adverse effects of synthetic anti-inflammatory drugs.