Chrysin attenuates experimental autoimmune neuritis by suppressing immuno-inflammatory responses

Self-Nanoemulsion Intrigues the Gold Phytopharmaceutical Chrysin: In Vitro Assessment and Intrinsic Analgesic Effect

Chrysin is a natural flavonoid with a wide range of bioactivities. Only a few investigations have assessed the analgesic activity of chrysin. The lipophilicity of chrysin reduces its aqueous solubility and bioavailability. Hence, self-nanoemulsifying drug delivery systems (SNEDDS) were designed to overcome this problem. Kollisolv GTA, Tween 80, and Transcutol HP were selected as oil, surfactant, and cosurfactant, respectively. SNEDDS A, B, and C were prepared, loaded with chrysin (0.1%w/w), and extensively evaluated. The optimized formula (B) encompasses 25% Kollisolv GTA, 18.75% Tween 80, and 56.25% Transcutol HP was further assessed. TEM, in vitro release, and biocompatibility towards the normal oral epithelial cell line (OEC) were estimated. Brain targeting and acetic acid-induced writhing in a mouse model were studied. After testing several adsorbents, powdered SNEDDS B was formulated and evaluated. The surfactant/cosurfactant (S/CoS) ratio of 1:3 w/w was appropriate for the preparation of SNEDDS. Formula B exhibited instant self-emulsification, spherical nanoscaled droplets of 155.4 ± 32.02 nm, and a zeta potential of - 12.5 ± 3.40 mV. The in vitro release proved the superiority of formula B over chrysin suspension (56.16 ± 10.23 and 9.26 ± 1.67%, respectively). The biocompatibility of formula B towards OEC was duplicated (5.69 ± 0.03 µg/mL). The nociceptive pain was mitigated by formula B more efficiently than chrysin suspension as the writhing numbers reduced from 8.33 ± 0.96 to 0 after 60 min of oral administration. Aerosil R972 was selected as an adsorbent, and its chemical compatibility was confirmed. In conclusion, our findings prove the therapeutic efficacy of chrysin self-nanoemulsion as a potential targeting platform to combat pain.

An outlook on the target-based molecular mechanism of phytoconstituents as immunomodulators

The immune system is one of the essential defense mechanisms. Immune system inadequacy increases the risk of infections and cancer diseases, whereas over-activation of the immune system causes allergies or autoimmune disorders. Immunomodulators have been used in the treatment of immune-related diseases. There is growing interest in using herbal medicines as multicomponent agents to modulate the complex immune system in immune-related diseases. Many therapeutic phytochemicals showed immunomodulatory effects by various mechanisms. This mechanism includes stimulation of lymphoid cell, phagocytosis, macrophage, and cellular immune function enhancement. In addition increased antigen-specific immunoglobulin production, total white cell count, and inhibition of TNF-α, IFN-γ, NF-kB, IL-2, IL-6, IL-1β, and other cytokines that influenced the immune system. This review aims to overview, widely investigated plant-derived phytoconstituents by targeting cells to modulate cellular and humoral immunity in in vivo and in vitro. However, further high-quality research is needed to confirm the clinical efficacy of plant-based immunomodulators.

Dietary Polyphenols Decrease Chemokine Release by Human Primary Astrocytes Responding to Pro-Inflammatory Cytokines

Astrocytes are considered to be the dominant cell fraction of the central nervous system. They play a supportive and protective role towards neurons, and regulate inflammatory processes; they thus make suitable targets for drugs and supplements, such as polyphenolic compounds. However, due to their wide range, knowledge of their anti-inflammatory potential remains relatively incomplete. The aim of this study was therefore to determine whether myricetin and chrysin are able to decrease chemokine release in reactive astrocytes. To assess the antioxidant and anti-inflammatory potential of polyphenols, human primary astrocytes were cultured in the presence of a reactive and neurotoxic astrocyte-inducing cytokine mixture (TNF-α, IL-1a, C1q), either alone or in the presence of myricetin or chrysin. The examined polyphenols were able to modify the secretion of chemokines by human cortical astrocytes, especially CCL5 (chrysin), CCL1 (myricetin) and CCL2 (both), while cell viability was not affected. Surprisingly, the compounds did not demonstrate any antioxidant properties in the astrocyte cultures.

Chrysin, a 5,7-dihydroxyflavone restrains inflammatory arthritis in rats via subsiding oxidative stress biomarkers and inflammatory cytokines

This study was intended to appraise the anti-inflammatory and anti-arthritic potential of Chrysin (CR), a natural dietary flavone found in several plant genera, including Passiflora and Propalis, and honey. The in vitro anti-arthritic potential was assessed by protein denaturation and membrane stabilization assays. The acute anti-inflammatory action was assessed by Carrageenan and Xylene induced oedema models in Wistar rats. For determining anti-arthritic potential, 0.1 ml Complete Freund's adjuvant was injected into the left hind paw of rats to induce adjuvant-induced arthritis, followed by initiation of treatment with individual CR at 25, 50, 100 mg/kg and in combination with methotrexate (MTX) by oral gavage for 21 days. The standard treatment group was given MTX (1 mg/kg). Treatment with MTX, chrysin and their combination exhibited a notable inhibition of paw oedema and pain, restoration of body weight and immune organ weight as evident by the histology of ankle joints. Treatment with chrysin alone and in combination significantly (p < 0.0001) restored altered blood parameters (CRP, RF, Hb, WBC, and platelets) with notable (p < 0.0001) down-regulation of interleukin (IL)-6,-1β, tumor necrosis factor-α, NF-κβ, and cyclooxygenase-2 and up-regulation (p < 0.0001) of IL-4, 10, and I-κβ in contrast to disease control rats. The treatment with the combination noticeably improved the superoxide dismutase, and catalase activities while reduced the peroxidation level in liver homogenate. It can be concluded from the findings that chrysin especially in combination with MTX ameliorated CFA-induced arthritis owing to its profound anti-oxidant, analgesic and anti-inflammatory actions.

pH-responsive and targeted delivery of chrysin via folic acid-functionalized mesoporous silica nanocarrier for breast cancer therapy

Cancer is a disease of global importance. In order to mitigate conventional chemotherapy-related side effects, phytochemicals with inherent anticancer efficacy have been opted. However, the use of nanotechnology is essential to enhance the bioavailability and therapeutic efficacy of these phytochemicals. Herein, we have formulated folic acid conjugated polyacrylic acid capped mesoporous silica nanoparticles (∼47.6 nm in diameter) for pH-dependent targeted delivery of chrysin to breast cancer (MCF-7) cells. Chrysin loaded mesoporous silica nanoparticles (Chr- mSiO2@PAA/FA) have been noted to induce apoptosis in MCF-7 cells through oxidative insult and mitochondrial dysfunction with subsequent G1 arrest. Further, in tumor bearing mice, intravenous incorporation of Chr-mSiO2@PAA/FA has been noticed to enhance the anti-neoplastic effects of chrysin via tumor site-specific accumulation. Enhanced cytotoxicity of chrysin contributed towards in vivo tumor regression, restoration of normalized tissue architecture and maintenance of healthy body weight. Besides, no serious systemic toxicity was manifested in response to Chr-mSiO2@PAA/FA administration in vivo. Thus, the study evokes about the anticancer potentiality of chrysin and its increased therapeutic activity via incorporation into folic acid conjugated mesoporous silica nanoparticles, which may hold greater impact in field of future biomedical research.

Neurological disorders of COVID-19: insights to applications of natural products from plants and microorganisms

In addition to the typical respiratory manifestations, various disorders including involvement of the nerve system have been detected in COVID-19 ranging from 22 to 36%. Although growing records are focusing on neurological aspects of COVID-19, the pathophysiological mechanisms and related therapeutic methods remain obscure. Considering the increased concerns of SARS-CoV-2 potential for more serious neuroinvasion conditions, the present review attempts to focus on the neuroprotective effects of natural compounds as the principle source of therapeutics inhibiting multiple steps of the SARS-CoV-2 infection cycle. The great majority of the natural products with anti-SARS-CoV-2 activity mainly inhibit the attachment, entry and gene expression rather than the replication, assembly, or release. Although microbial-derived natural products comprise 38.5% of the known natural products with neuroprotective effects following viral infection, the neuroprotective potential of the majority of microorganisms is still undiscovered. Among natural products, chrysin, huperzine A, ginsenoside Rg1, pterostilbene, and terrein have shown potent in vitro neuroprotective activity and can be promising for new or repurpose drugs for neurological complications of SARS-CoV-2.

Potential protective effects of chrysin against immunotoxicity induced by diazinon

Acute intoxication with diazinon (DZN) as a pesticide causes mortality and morbidity annually. This study shows the impact of sub-acute toxicity of DZN 20 mg/kg and the protective activities of chrysin (CH) as a flavone under the flavonoids family (12.5, 25 and 50 mg/kg) were assessed on BALB/c mouse immune system. The changes in morphological and functional properties of the immune system on thymus, spleen and liver histopathology, sub-populations of T lymphocytes, cytokines levels, transcription factors, complement function, phagocytosis, specific and total antibody productions were considered. The histopathological effects of DZN on the spleen and thymus were not significant, but the liver was damaged remarkably. In the presence of CH, the toxic effect of DZN is suppressed. DZN significantly decreased the number of whole blood TCD4⁺, TCD8⁺ and NK cells and suppressed the phagocytosis, delayed-type hypersensitivity (DTH) responses to sheep red blood cell (SRBC). Furthermore, it suppressed specific anti-SRBC-Ab, total IgG and IgM production, T-bet expression, and IFN-γ production. In contrast, DZN did not significantly affect complement function and the number of NK cells, TCD4⁺ and TCD8⁺ splenocytes. However, it potentiated the expression of GATA-3, ROR-γt and FOXP3 gene expression and consequently produced IL-4, IL-10, IL-17 and TGF-β in whole blood. CH not only significantly increased the variables mentioned above at 12.5, 25 and 50 mg/kg but also could overcome the toxic effects of DZN on whole blood lymphocyte sub-populations and specific and total Ab production in 25 and 50 mg/kg concentrations, phagocytosis and DTH responses in 50 mg/kg, and modulation of the transcription factors and cytokine production, mainly in 25 and 50 mg/kg. In conclusion, DZN in sub-acute doses could remarkably deteriorate immune responses. However, CH can overcome the toxic effects of DZN on the immune components and functions of the immune system.

Neonatal Oral Administration of Chrysin Prevents Long-Term Development of Non-Alcoholic Fatty Liver Disease in a Sexually Dimorphic Manner in Fructose Nurtured Sprague Dawley Rats

High-fructose diets are linked with the development of non-alcoholic fatty liver disease (NAFLD), the management of which is a burden to society. Interventions with phytochemicals in the early postnatal period may prevent fructose-induced NAFLD later in adulthood. We investigated the protective potential of chrysin against fructose-induced NAFLD. Four-day-old male and female suckling Sprague Dawley rats (N = 112) were randomly grouped and orally gavaged daily with distilled water (negative Control-Cn + W), chrysin(Chr-100 mg/kg), fructose-solution (Fr-20% w/v), and Chr + Fr between postnatal day (PND) 4 and 21 and then weaned onto normal rat chow and plain drinking water to PND 55. From PND 56 to 130, half of the rats continued on plain water, and the rest had Fr as drinking fluid. Terminally, the liver tissue was collected, and the lipid content was determined and histologically assessed for NAFLD. Dietary Fr induced an increased hepatic lipid content (p = 0.0001 vs. Cn + W) both sexes, and it was only attenuated by neonatal Chr in female rats (p < 0.05). Histologically, there was increased microvesicular steatosis (p = 0.0001 vs. Cn + W) in both sexes, and it was prevented by neonatal Chr (p > 0.05). Fr caused macrovesicular steatosis (p = 0.01 vs. Cn + W) in females only, and chrysin did not prevent it (p > 0.05). Fr induced hepatocellular hypertrophy, and inflammation was observed in females only (p = 0.01 vs. Cn + W), and this was prevented by Chr (p > 0.05). The collagen area fraction was increased by Fr (p = 0.02 (males) and p = 0.04 (females) vs. Cn + W, respectively; however, chrysin did not prevent this (p > 0.05). Neonatal chrysin prevented some of the deleterious effects of the high-fructose diet on the liver, suggesting that chrysin should be further explored as a strategic prophylactic neonatal intervention against high-fructose-diet-induced NAFLD.

Chrysin inhibits hepatocellular carcinoma progression through suppressing programmed death ligand 1 expression

BACKGROUNDS

The aberrant PD-L1 expression on cancer cells was confirmed to participate in immune evasion of hepatocellular carcinoma (HCC). Previous studies had documented that there were anti-tumorigenic effects of chrysin on HCC. However, whether chrysin can act on the over-expressed PD-L1 on HCC cells to exert the therapeutic effectiveness and the involved mechanisms has not yet been deciphered.

PURPOSE

Herein, we aimed to explore the regulatory effects of chrysin on the PD-1/PD-L1 immune checkpoint and investigate its possible mechanisms in vivo and in vitro.

METHODS

H22 xenograft mouse model was used to investigate the effects of chrysin on tumor growth and PD-L1 expression in tumors. In interferon-gamma (IFN-γ)-induced HepG2 cells, the cytotoxicity of chrysin was detected by MTT assay. Flow cytometry, ELISA and RT-PCR were carried out to evaluate the expression of PD-L1, and the expression of proteins in STAT3 and NF-κB pathways was also determined by Western blot. In HepG2 cells and Jurkat T cell co-culture system, ELISA kit was used to detect the level of IL-2, and T cell proliferation was further evaluated by CCK-8 method.

RESULTS

Our data suggested that chrysin could effectively inhibit the progression of tumor, and promote the anti-tumor immunity of mice concomitant with enhanced CD4/CD8-positive T cell proportion in tumor tissues of H22 xenograft mouse model. Additionally, chrysin significantly down-regulated the expression of PD-L1 in vivo and in vitro, which was closely associated with the blockage of STAT3 and NF-κB pathways. Moreover, in the co-culture system, chrysin could increase the proliferation of T cells and the concentration of IL-2.

CONCLUSION

These results indicate that chrysin may have the potential to be an immune checkpoint inhibitor for preventive or as an adjunctive curative agent for HCC.

Role of Phytoconstituents as PPAR Agonists: Implications for Neurodegenerative Disorders

Peroxisome proliferator-activated receptors (PPAR-γ, PPAR-α, and PPAR-β/δ) are ligand-dependent nuclear receptors that play a critical role in the regulation of hundreds of genes through their activation. Their expression and targeted activation play an important role in the treatment of a variety of diseases, including neurodegenerative, cardiovascular, diabetes, and cancer. In recent years, several reviews have been published describing the therapeutic potential of PPAR agonists (natural or synthetic) in the disorders listed above; however, no comprehensive report defining the role of naturally derived phytoconstituents as PPAR agonists targeting neurodegenerative diseases has been published. This review will focus on the role of phytoconstituents as PPAR agonists and the relevant preclinical studies and mechanistic insights into their neuroprotective effects. Exemplary research includes flavonoids, fatty acids, cannabinoids, curcumin, genistein, capsaicin, and piperine, all of which have been shown to be PPAR agonists either directly or indirectly. Additionally, a few studies have demonstrated the use of clinical samples in in vitro investigations. The role of the fruit fly Drosophila melanogaster as a potential model for studying neurodegenerative diseases has also been highlighted.

An updated review on the versatile role of chrysin in neurological diseases: Chemistry, pharmacology, and drug delivery approaches

Neurological diseases are responsible for a large number of morbidities and mortalities in the world. Flavonoids are phytochemicals that possess various health-promoting impacts. Chrysin, a natural flavonoid isolated from diverse fruits, vegetables, and even mushrooms, has several pharmacological activities comprising antioxidant, anti-inflammatory, antiapoptotic, anticancer, and neuroprotective effects. The current study was designed to review the relationship between chrysin administration and neurological complications by discussing the feasible mechanism and signaling pathways. Herein, we mentioned the sources, pharmacological properties, chemistry, and drug delivery systems associated with chrysin pharmacotherapy. The role of chrysin was discussed in depression, anxiety, neuroinflammation, Alzheimer's disease, Parkinson's disease, Huntington's disease, epilepsy, cerebral ischemia, spinal cord injury, neuropathy, Multiple Sclerosis, and Guillain-Barré Syndrome. The findings indicate that chrysin has protective effects against neurological conditions by modulating oxidative stress, inflammation, and apoptosis in animal models. However, more studies should be done to clear the neuroprotective effects of chrysin.

The Immunomodulatory Effects of Honey and Associated Flavonoids in Cancer

Honey has exerted a high impact in the field of alternative medicine over many centuries. In addition to its wound healing, anti-microbial and antioxidant properties, several lines of evidence have highlighted the efficiency of honey and associated bioactive constituents as anti-tumor agents against a range of cancer types. Mechanistically, honey was shown to inhibit cancer cell growth through its pro-apoptotic, anti-proliferative and anti-metastatic effects. However, the potential of honey to regulate anti-tumor immune responses is relatively unexplored. A small number of in vitro and in vivo studies have demonstrated the ability of honey to modulate the immune system by inducing immunostimulatory as well as anti-inflammatory effects. In the present review, we summarize the findings from different studies that aimed to investigate the immunomodulatory properties of honey and its flavonoid components in relation to cancer. While these studies provide promising data, additional research is needed to further elucidate the immunomodulatory properties of honey, and to enable its utilization as an adjuvant therapy in cancer.

Chrysin mitigates bleomycin-induced pulmonary fibrosis in rats through regulating inflammation, oxidative stress, and hypoxia

Pulmonary fibrosis is a chronic condition characterized by fibroblast proliferation, and the infiltration of inflammatory cells that can initiate local tissue hypoxia. In this study the effect of chrysin (50 mg/kg/orally) in a model of bleomycin (BLM)-induced pulmonary fibrosis was studied. Chrysin managed to decrease mortality rate associated with BLM instillation and it managed to improve lung architecture and lung fibrosis by decreasing hydroxyproline content and transforming growth factor-β1 (TGF-β1) protein expression. Chrysin showed anti-inflammatory effect displayed by the decrease in inflammatory cells infiltrates, the decline in permeability of the alveolar/capillary barrier and the reduction in lactate dehydrogenase (LDH) activity. Chrysin demonstrated potent antioxidant effect by decreasing lipid peroxidation, increasing antioxidant defense mechanisms by increasing superoxide dismutase (SOD) activity and reduced glutathione (GSH) content. Additionally, the effect of chrysin on nitric oxide (NOx) content was assessed, where chrysin decreased NOx, increased the protein expression of endothelial nitric oxide synthase (eNOS), and decreased inducible nitric oxide synthase (iNOS) protein expression. Chrysin also succeeded in decreasing thioredoxin-interacting protein (TXNIP), the negative regulator of thioredoxin system, showing potent antioxidant effect. Finally, both tissue and bronchoalveolar lavage fluid contents of hypoxia inducible factor one alpha (HIF1α) were decreased by chrysin indicating that chrysin decreased local tissue hypoxia. In conclusion, this study exposed a possible proof that chrysin could mitigate pulmonary fibrosis induced by BLM through its anti-inflammatory, antioxidant, antifibrotic effects and its effect in alleviating hypoxia.

Therapeutic effects of chrysin in a rat model of traumatic brain injury: A behavioral, biochemical, and histological study

AIMS

Oxidative stress and apoptosis have major roles in the progression of traumatic brain injury (TBI)-associated motor and cognitive deficits. The present study was aimed to elucidate the putative effects of chrysin, a natural flavonoid compound, against TBI-induced motor and cognitive dysfunctions and possible involved mechanisms.

MAIN METHODS

Chrysin (25, 50 or 100 mg/kg) was orally administered to rats starting immediately following TBI induction by Marmarou's weight-drop technique and continuously for 3 or 14 days. Neurological functions, motor coordination, learning and memory performances, histological changes, cell apoptosis, expression of pro- and anti-apoptotic proteins, and oxidative status were assayed at scheduled time points after experimental TBI.

KEY FINDINGS

The results indicated that treatment with chrysin improved learning and memory disabilities in passive avoidance task, and ameliorated motor coordination impairment in rotarod test after TBI. These beneficial effects were accompanied by increased the concentrations of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), decreased malondialdehyde (MDA) content, prevented neuronal loss, diminished apoptotic index, elevated the expression of anti-apoptotic Bcl-2 protein, and reduced the expression of pro-apoptotic Bax protein in the cerebral cortex and hippocampus tissues.

SIGNIFICANCE

Our findings suggest that both anti-oxidative and anti-apoptotic properties of chrysin (especially in the dose of 100 mg/kg) are possible mechanisms that improve cognitive/motor deficits and prevent neuronal cell death after TBI.

Interaction of Chrysin and Its Main Conjugated Metabolites Chrysin-7-Sulfate and Chrysin-7-Glucuronide with Serum Albumin

Chrysin (5,7-dihydroxyflavone) is a flavonoid aglycone, which is found in nature and in several dietary supplements. During the biotransformation of chrysin, its conjugated metabolites chrysin-7-sulfate (C7S) and chrysin-7-glucuronide (C7G) are formed. Despite the fact that these conjugates appear in the circulation at much higher concentrations than chrysin, their interactions with serum albumin have not been reported. In this study, the complex formation of chrysin, C7S, and C7G with human (HSA) and bovine (BSA) serum albumins was investigated employing fluorescence spectroscopic, ultrafiltration, and modeling studies. Our major observations/conclusions are as follows: (1) Compared to chrysin, C7S binds with a threefold higher affinity to HSA, while C7G binds with a threefold lower affinity; (2) the albumin-binding of chrysin, C7S, and C7G did not show any large species differences regarding HSA and BSA; (3) tested flavonoids likely occupy Sudlow’s Site I in HSA; (4) C7S causes significant displacement of Sudlow’s Site I ligands, exerting an even stronger displacing ability than the parent compound chrysin. Considering the above-listed observations, the high intake of chrysin (e.g., through the consumption of dietary supplements with high chrysin contents) may interfere with the albumin-binding of several drugs, mainly due to the strong interaction of C7S with HSA.

Strategies for Targeted Delivery to the Peripheral Nerve

Delivery of compounds to the peripheral nervous system has the potential to be used as a treatment for a broad range of conditions and applications, including neuropathic pain, regional anesthesia, traumatic nerve injury, and inherited and inflammatory neuropathies. However, efficient delivery of therapeutic doses can be difficult to achieve due to peripheral neuroanatomy and the restrictiveness of the blood-nerve barrier. Depending on the underlying integrity of the blood-nerve barrier in the application at hand, several strategies can be employed to navigate the peripheral nerve architecture and facilitate targeted delivery to the peripheral nerve. This review describes different applications where targeted delivery to the peripheral nervous system is desired, the challenges that the blood-nerve barrier poses in each application, and bioengineering strategies that can facilitate delivery in each application.

(E)‑phenethyl 3‑(3,5‑dihydroxy‑4‑isopropylphenyl) acrylate gel improves DNFB-induced allergic contact hypersensitivity via regulating the balance of Th1/Th2/Th17/Treg cell subsets

(E)‑phenethyl 3‑(3,5‑dihydroxy‑4‑isopropylphenyl) acrylate gels (THCA354) is a novel polyphenols acrylic acid derivative. To investigate the immunoregulatory mechanisms of THCA354, we established a mouse model of 2,4‑dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD). Responses of Th1, Th2, Th17 and regulatory T cells (Tregs) were determined by flow cytometry, reverse-transcriptase polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA). Our study found that topical application of THCA354 gel could inhibit ear swelling, reduce inflammatory cell infiltration, down-regulate Th1/Th17 responses and enhance Th2/Treg responses. These findings indicated that THCA354 gel exerted its immunotherapeutic effects by modulating the balance of Th1/Th2/Th17/Treg cell subsets, suggesting that THCA354 gel could be used as a promising drug candidate for intervention of ACD.

Chrysin: Sources, beneficial pharmacological activities, and molecular mechanism of action

In recent years, public and scientific interest in plant flavonoids has tremendously increased because of their postulated health benefits. This review was mainly focuses on the flavone chrysin (5,7-dihydroxyflavone), which occurs naturally in many plants, honey, and propolis. A number of in vitro and in vivo studies have revealed the therapeutic effects of chrysin against various diseases. In general, chrysin exhibits many biological activities and pharmacological effects, including antioxidant, anti-inflammatory, anticancer, and antiviral activities. Moreover, many studies have reported on the bioavailability of chrysin. Because of its compromised bioavailability and enhanced protein stability, chrysin solid lipid nanoparticle (SLN) synthesis avoids proteolytic degradation and sustained release of drug delivery. To clarify the mechanism of action of chrysin, researchers have investigated the structural binding relationship of chrysin through the docking computation method.

Attenuation of experimental autoimmune neuritis with locally administered lovastatin-encapsulating poly(lactic-co-glycolic) acid nanoparticles

Acute inflammatory demyelinating polyneuropathy (AIDP) is an aggressive antibody- and T-cell-mediated variant of Guillain-Barré Syndrome (GBS), a prominent and debilitating autoimmune disorder of the peripheral nervous system. Despite advancements in clinical management, treatment of patients with AIDP/GBS and its chronic variant CIDP remains palliative and relies on the use of non-specific immunemodulating therapies. Our laboratory has previously reported that therapeutic administration of statins safely attenuates the clinical severity of experimental autoimmune neuritis (EAN), a well-characterized animal model of AIDP/GBS, by restricting the migration of autoreactive leukocytes across peripheral nerve microvascular endoneurial endothelial cells that form the blood-nerve barrier. Despite these advancements, the clinical application of systemically administered statins for the management of inflammatory disorders remains controversial as a result of disappointingly inconclusive phase trials. Here, poly(lactic-co-glycolic) acid (PLGA) nanoparticles were evaluated as an alternative strategy by which to locally administer statins for the management of EAN. When tested in vitro, lovastatin-encapsulating PLGA nanoparticles elicited a marked increase in RhoB mRNA content in peripheral nerve microvascular endoneurial endothelial cells, similar to cells treated with activated unencapsulated lovastatin. Unilateral peri-neural administration of lovastatin-encapsulating PLGA nanoparticles, but not empty nanoparticles, to naïve Lewis rats similarly enhanced RhoB mRNA content in adjacent nerve and muscle tissue. When administered in this manner, serum levels of lovastatin were below the level of detection. Bilateral peri-neural administration of lovastatin-encapsulating PLGA nanoparticles to EAN-induced Lewis rats significantly attenuated EAN clinical severity while protecting against EAN-induced peripheral nerve morphological and functional deficits. This study provides the first proof-of-concept approach for the application of a nanoparticle-based local drug delivery platform for the management of inflammatory demyelinating diseases, including AIDP/GBS.

Programmed Death Ligand 1 Plays a Neuroprotective Role in Experimental Autoimmune Neuritis by Controlling Peripheral Nervous System Inflammation of Rats

Programmed death 1 (PD-1; CD279), a member of the CD28 family, is an inhibitory receptor on T cells and is responsible for T cell dysfunction in infectious diseases and cancers. The ligand for PD-1, programmed death ligand 1 (PD-L1; also known as B7-H1, CD274), is a member of the B7 family. The engagement of PD-1 with programmed death ligand can downregulate autoreactive T cells that participate in multiple autoimmune diseases. Experimental autoimmune neuritis (EAN) is an animal model of Guillain-Barré syndrome, and the pathogenesis of EAN is mediated principally through T cells and macrophages. In this study, we investigated the effects of PD-L1 in EAN rats. For preventative and therapeutic management, we administered PD-L1, which successfully decreased the severity of EAN; it alleviated the neurologic course of EAN, as well as inhibited the infiltration of inflammatory cells and demyelination of sciatic nerves. Our data revealed that PD-L1 treatment inhibited lymphocyte proliferation and altered T cell differentiation by inducing decreases in IFN-γ⁺CD4⁺ Th1 cells and IL-17⁺CD4⁺ Th17 cells and increases in IL-4⁺CD4⁺ Th2 cells and Foxp3⁺CD4⁺ regulatory T cells. The expression levels of p-STAT3 and Foxp3 were significantly different in PD-L1-treated groups compared with the control group. Additionally, PD-L1 regulated the expression of Foxp3 and p-STAT3 in EAN, probably by inhibiting PI3K/AKT/mTOR signaling expression. In summary, PD-L1 is a potentially useful agent for the treatment of EAN because of its anti-inflammatory and neuroprotective effects.

Phytochemical-loaded mesoporous silica nanoparticles for nose-to-brain olfactory drug delivery

Central nervous system (CNS) drug delivery is often hampered due to the insidious nature of the blood-brain barrier (BBB). Nose-to-brain delivery via olfactory pathways have become a target of attention for drug delivery due to bypassing of the BBB. The antioxidant properties of phytochemicals make them promising as CNS active agents but possess poor water solubility and limited BBB penetration. The primary aim of this study was the development of mesoporous silica nanoparticles (MSNs) loaded with the poorly water-soluble phytochemicals curcumin and chrysin which could be utilised for nose-to-brain delivery. We formulated spherical MSNP using a templating approach resulting in ∼220nm particles with a high surface porosity. Curcumin and chrysin were successfully loaded into MSNP and confirmed through Fourier transformation infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and HPLC approaches with a loading of 11-14% for curcumin and chrysin. Release was pH dependant with curcumin demonstrating increased chemical stability at a lower pH (5.5) with a release of 53.2%±2.2% over 24h and 9.4±0.6% for chrysin. MSNP were demonstrated to be non-toxic to olfactory neuroblastoma cells OBGF400, with chrysin (100μM) demonstrating a decrease in cell viability to 58.2±8.5% and curcumin an IC₅₀ of 33±0.18μM. Furthermore confocal microscopy demonstrated nanoparticles of <500nm were able to accumulate within cells with FITC-loaded MSNP showing membrane localised and cytoplasmic accumulation following a 2h incubation. MSNP are useful carriers for poorly soluble phytochemicals and provide a novel vehicle to target and deliver drugs into the CNS and bypass the BBB through olfactory drug delivery.

Dimethyl fumarate attenuates experimental autoimmune neuritis through the nuclear factor erythroid-derived 2-related factor 2/hemoxygenase-1 pathway by altering the balance of M1/M2 macrophages

Background

Guillain–Barré syndrome (GBS) is an acute, post-infectious, immune-mediated, demyelinating disease of peripheral nerves and nerve roots. Dimethyl fumarate (DMF), a fumaric acid ester, exhibits various biological activities, including multiple immunomodulatory and neuroprotective effects. However, the potential mechanism underlying the effect of DMF in GBS animal model experimental autoimmune neuritis (EAN) is unclear.

Methods

Using EAN, an established GBS model, we investigated the effect of DMF by assessing clinical score, histological staining and electrophysiological studies. Then, we further explored the potential mechanism by Western blot analysis, flow cytometry, fluorescence immunohistochemistry, PCR, and ELISA analysis. The Mann–Whitney U test was used to compare differences between control group and treatment groups where appropriate.

Results

DMF treatment reduced the neurological deficits by ameliorating inflammatory cell infiltration and demyelination of sciatic nerves. In addition, DMF treatment decreased the level of pro-inflammatory M1 macrophages while increasing the number of anti-inflammatory M2 macrophages in the spleens and sciatic nerves of EAN rats. In RAW 264.7, a shift in macrophage polarization from M1 to M2 phenotype was demonstrated to be depended on DMF application. In sciatic nerves, DMF treatment elevated the level of the antioxidant transcription factor nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and its target gene hemoxygenase-1 (HO-1) which could facilitate macrophage polarization toward M2 type. Moreover, DMF improved the inflammatory milieu in spleens of EAN rats, characterized by downregulation of messenger RNA (mRNA) of IFN-γ, TNF-α, IL-6, and IL-17 and upregulation of mRNA level of IL-4 and IL-10.

Conclusions

Taken together, our data demonstrate that DMF can effectively suppress EAN, and the mechanism involves altering the balance of M1/M2 macrophages and attenuating inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0559-x) contains supplementary material, which is available to authorized users.

Preventive effect of chrysin on experimental autoimmune uveitis triggered by injection of human IRBP peptide 1-20 in mice

Uveitis is a common cause of blindness worldwide. Experimental autoimmune uveitis (EAU) is an animal model of noninfectious uveitis. Chrysin (5,7-dihydroxyflavone) is a member of the flavonoid family and has anti-inflammatory effects. We immunized C57BL/6J mice with human interphotoreceptor retinoid-binding protein peptide 1-20 to induce EAU. Chrysin was administered intragastrically at 25 mg/kg daily to the chrysin-treated mice from 3 days before immunization to 21 days after immunization. Vehicle was administered to the mice in the control group according to the same protocol. Lower clinical and histopathological scores, increased integrity of the blood-retinal barrier (BRB) and higher expression of tight junction proteins were observed in the chrysin-treated mice. Chrysin significantly decreased the proportions of Th1, Th17 and CD4⁺CD3⁺CD62L⁺ Th0 cells, and increased the proportion of Treg cells. Both macrophage infiltration and the expression of inducible nitric oxide synthase in the retina were efficiently inhibited by chrysin treatment. In chrysin-treated mice, the expression of interferon-γ, interleukin (IL)-17A, IL-6, IL-1β and tumor necrosis factor-α was reduced in the retina, whereas higher levels of transforming growth factor-β were detected. Furthermore, NF-κBp65 was downregulated after chrysin treatment. In conclusion, as an anti-inflammatory molecule, chrysin exerts a preventive effect on EAU by modulating the balance among helper T-cell subsets and suppressing ocular inflammation, thereby maintaining the integrity of the BRB.

Proinflammatory Pathways: The Modulation by Flavonoids

Inflammation is a natural, carefully orchestrated response of the organism to tissue damage, involving various signaling systems and the recruitment of inflammatory cells. These cells are stimulated to release a myriad of mediators that amplify the inflammatory response and recruit additional cells. These mediators present numerous redundancies of functions, allowing a broad and effective inflammatory response, but simultaneously make the understanding of inflammation pathways much difficult. The extent of the inflammatory response is usually self-limited, although it depends on the balance between the pro- and anti-inflammatory signals. When that equilibrium is dislocated, a more widespread inflammatory response may take place. Flavonoids have been shown to be possible alternatives to the traditionally molecules used as anti-inflammatory agents. In fact, the biological activities of flavonoids include the modulation of the diverse phases of inflammatory processes, from the gene transcription and expression to the inhibition of the enzymatic activities and the scavenging of the reactive species. In the present review, the inflammatory network is widely revised and the flavonoids' broad spectrum of action in many of the analyzed inflammatory pathways is revised. This kind of integrated revision is original in the field, providing the reader the simultaneous comprehension of the inflammatory process and the potential beneficial activities of flavonoids.