Anti-inflammatory properties of tianeptine on lipopolysaccharide-induced changes in microglial cells involve toll-like receptor-related pathways

Advances in Neuropathic Pain Research: Selected Intracellular Factors as Potential Targets for Multidirectional Analgesics

Neuropathic pain is a complex and debilitating condition that affects millions of people worldwide. Unlike acute pain, which is short-term and starts suddenly in response to an injury, neuropathic pain arises from somatosensory nervous system damage or disease, is usually chronic, and makes every day functioning difficult, substantially reducing quality of life. The main reason for the lack of effective pharmacotherapies for neuropathic pain is its diverse etiology and the complex, still poorly understood, pathophysiological mechanism of its progression. Numerous experimental studies, including ours, conducted over the last several decades have shown that the development of neuropathic pain is based on disturbances in cell activity, imbalances in the production of pronociceptive factors, and changes in signaling pathways such as p38MAPK, ERK, JNK, NF-κB, PI3K, and NRF2, which could become important targets for pharmacotherapy in the future. Despite the availability of many different analgesics, relieving neuropathic pain is still extremely difficult and requires a multidirectional, individual approach. We would like to point out that an increasing amount of data indicates that nonselective compounds directed at more than one molecular target exert promising analgesic effects. In our review, we characterize four substances (minocycline, astaxanthin, fisetin, and peimine) with analgesic properties that result from a wide spectrum of actions, including the modulation of MAPKs and other factors. We would like to draw attention to these selected substances since, in preclinical studies, they show suitable analgesic properties in models of neuropathy of various etiologies, and, importantly, some are already used as dietary supplements; for example, astaxanthin and fisetin protect against oxidative stress and have anti-inflammatory properties. It is worth emphasizing that the results of behavioral tests also indicate their usefulness when combined with opioids, the effectiveness of which decreases when neuropathy develops. Moreover, these substances appear to have additional, beneficial properties for the treatment of diseases that frequently co-occur with neuropathic pain. Therefore, these substances provide hope for the development of modern pharmacological tools to not only treat symptoms but also restore the proper functioning of the human body.

Analysis of differentially expressed microRNAs in bovine mammary epithelial cells treated with lipoteichoic acid

Mastitis is one of the most common diseases of dairy cattle and can be caused by physical stress, chemicals and microbial infection. Staphylococcus aureus is the most common pathogens that induce mastitis in dairy cattle. In this study, bovine mammary epithelial cells (BMECs) were treated either with lipoteichoic acid (LTA, 30 µg/ml) or 1 × phosphate-buffer saline (PBS, control) and RNA-Seq was applied to explore the effect of LTA on the expression microRNAs (miRNAs) in BMECs. Compared to the control group, 43 miRNAs were significantly up-regulated and eight miRNAs were significantly down-regulated. Additionally, 724 genes were significantly up-regulated and 13 genes were significantly down-regulated in LTA group relative to the control group. Bta-miR-196a, bta-miR-2285aj-5p, bta-miR-143, bta-miR-2433, bta-miR-2284f and bta-miR-2368-3p were selected from 51 differentially expressed miRNAs and are discussed in this manuscript. Target gene prediction revealed that the target genes of these six miRNAs were all differentially expressed, including MT1E, SPDYA, FGL1, TLR2, PAPOLG, ZDHHC17 and SMC4. Subsequently, the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the target genes with differentially expressed miRNAs were enriched in mitogen-activated protein kinase (MAPK) signalling pathway, rheumatoid arthritis and cancer. Therefore, the results of this study provided new evidences for the molecular mechanism of LTA-induced mastitis, which may provide new targets for the diagnosis and treatment of mastitis in dairy cattle.

Effect of forsythoside A on the transcriptional profile of bovine mammary epithelial cells challenged with lipoteichoic acid

Mastitis is a common disease of the dairy cattle, which affects the development of the dairy industry and leads to huge economic losses. Forsythoside A (FTA) has anti-inflammatory, antioxidant, antiviral and anti-apoptotic effects. However, the therapeutic effect and molecular mechanism of FTA on dairy cow mastitis remain unclear. In this study, bovine mammary epithelial cells (BMECs) were stimulated with lipoteichoic acid (LTA), a key virulence factor of Staphylococcus aureus (S. aureus), to construct in vitro models, and then treated with FTA. Subsequently, the differentially expressed genes (DEGs) in different groups were determined by RNA sequencing (RNA-Seq) analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyse the possible function of the DEGs, real-time quantitative PCR (RT-qPCR) was used to verify whether the expression levels of these DEGs were consistent with RNA-Seq results. The results showed that cell division cycle 20B (CDC20B), endothelial cell surface expressed chemotaxis and apoptosis regulator (ECSCR), complement factor H-related 5 (CFHR5) and phospholipase A2 group IVA (PLA2G4A) were down-regulated after FTA treatment. In contrast, Kruppel-like factor 15 (KLF15) and Metallothionein 1E (MT1E) were up-regulated. These DEGs are involved in processes such as apoptosis, inflammation and development of cancer. This study provides valuable insights into the transcriptome changes in BMECs after FTA treatment. Further analysis may help identify the underlying molecular mechanisms.

Design, Synthesis, Biological Evaluation, and Computational Studies of Novel Ureidopropanamides as Formyl Peptide Receptor 2 (FPR2) Agonists to Target the Resolution of Inflammation in Central Nervous System Disorders

Formyl peptide receptor 2 (FPR2) agonists can boost the resolution of inflammation and can offer alternative approaches for the treatment of pathologies with underlying chronic neuroinflammation, including neurodegenerative disorders. Starting from the FPR2 agonist 2 previously identified in our laboratory and through fine-tuning of FPR2 potency and metabolic stability, we have identified a new series of ureidopropanamide derivatives endowed with a balanced combination of such properties. Computational studies provided insights into the key interactions of the new compounds for FPR2 activation. In mouse microglial N9 cells and in rat primary microglial cells stimulated with lipopolysaccharide, selected compounds inhibited the production of pro-inflammatory cytokines, counterbalanced the changes in mitochondrial function, and inhibited caspase-3 activity. Among the new agonists, (S)-11l stands out also for the ability to permeate the blood-brain barrier and to accumulate in the mouse brain in vivo, thus representing a valuable pharmacological tool for studies in vivo.

Pathophysiology and Therapeutic Perspectives of Oxidative Stress and Neurodegenerative Diseases: A Narrative Review

Introduction

Neurodegeneration is the term describing the death of neurons both in the central nervous system and periphery. When affecting the central nervous system, it is responsible for diseases like Alzheimer’s disease, Parkinson’s disease, Huntington’s disorders, amyotrophic lateral sclerosis, and other less frequent pathologies. There are several common pathophysiological elements that are shared in the neurodegenerative diseases. The common denominators are oxidative stress (OS) and inflammatory responses. Unluckily, these conditions are difficult to treat. Because of the burden caused by the progression of these diseases and the simultaneous lack of efficacious treatment, therapeutic approaches that could target the interception of development of the neurodegeneration are being widely investigated. This review aims to highlight the most recent proposed novelties, as most of the previous approaches have failed. Therefore, older approaches may currently be used by healthcare professionals and are not being presented.

Methods

This review was based on an electronic search of existing literature, using PubMed as primary source for important review articles, and important randomized clinical trials, published in the last 5 years. Reference lists from the most recent reviews, as well as additional sources of primary literature and references cited by relevant articles, were used.

Results

Eighteen natural pharmaceutical substances and 24 extracted or recombinant products, and artificial agents that can be used against OS, inflammation, and neurodegeneration were identified. After presenting the most common neurodegenerative diseases and mentioning some of the basic mechanisms that lead to neuronal loss, this paper presents up to date information that could encourage the development of better therapeutic strategies.

Conclusions

This review shares the new potential pharmaceutical and not pharmaceutical options that have been recently introduced regarding OS and inflammatory responses in neurodegenerative diseases.

Antidepressant effects of a polysaccharide from okra (Abelmoschus esculentus (L) Moench) by anti-inflammation and rebalancing the gut microbiota

The present study aimed to evaluate the antidepressant-like effect of a polysaccharide (OP), which is isolated from okra (Abelmoschus esculentus (L) Moench), in CUMS-induced mice and its possible mechanisms. OPT, FST and TST were employed to examine the anxiety and depressive behavior in CUMS-induced mice and fecal microbiota transplantation (FMT) CUMS-induced mice, while proinflammatory cytokines, TLR4/NF-κB pathway and MAPKs signaling were detected in both CUMS-induced mice and LPS-induced BV2 cells. The results showed that anxiety- and depressive-like behaviors, gut microbiota dysbiosis and changes of SCFAs, and activation of inflammatory reactions in the colon, serum, and hippocampus of CUMS-induced mice, as well as activation of inflammatory reactions in BV2 cells, could be alleviated by the treatment of OP. The mice that were colonized by OP microbiota showed improved anxiety and depressive behaviors and lower inflammatory response. Furthermore, OP inhibited the expression of TLR4, the nuclear translocation of NF-κB and high levels of proinflammatory cytokines, and enhanced the MAPKs signaling, these effects of OP also observed in LPS-induced BV2 cells. Above all, suggested that the potential mechanism of the antidepressant-like effects of OP was closely correlated with the bidirectional communication of microbiota-gut-brain axis via regulation of inflammation response.

Isorhamnetin alleviates lipopolysaccharide-induced inflammatory responses in BV2 microglia by inactivating NF-κB, blocking the TLR4 pathway and reducing ROS generation

Isorhamnetin, which is a flavonoid predominantly found in fruits and leaves of various plants, including Hippophae rhamnoides L. and Oenanthe javanica (Blume) DC, is known to possess various pharmacological effects. However, the anti‑inflammatory potential of isorhamnetin remains poorly studied. Therefore, the present study aimed to investigate the inhibitory potential of isorhamnetin against inflammatory responses in lipopolysaccharide (LPS)‑stimulated BV2 microglia. To measure the effects of isorhamnetin on inflammatory mediators and cytokines, and reactive oxygen species (ROS) generation, the following methods were used: cell viability assay, griess assay, ELISA, reverse transcriptase‑polymerase chain reaction, flow cytometry, western blotting and immunofluorescence staining. The results revealed that isorhamnetin significantly suppressed LPS‑induced secretion of pro‑inflammatory mediators, including nitric oxide (NO) and prostaglandin E2, without exhibiting significant cytotoxicity. Consistent with these results, isorhamnetin inhibited LPS‑stimulated expression of regulatory enzymes, including inducible NO synthase and cyclooxygenase‑2 in BV2 cells. Isorhamnetin also downregulated LPS‑induced production and expression of pro‑inflammatory cytokines, such as tumor necrosis factor‑α and interleukin‑1β. The mechanism underlying the anti‑inflammatory effects of isorhamnetin was subsequently evaluated; this flavonoid inhibited the nuclear factor (NF)‑κB signaling pathway by disrupting degradation and phosphorylation of inhibitor κB‑α in the cytoplasm and blocking translocation of NF‑κB p65 into the nucleus. In addition, isorhamnetin effectively suppressed LPS‑induced expression of Toll‑like receptor 4 (TLR4) and myeloid differentiation factor 88. It also suppressed the binding of LPS with TLR4 in BV2 cells. Furthermore, isorhamnetin markedly reduced LPS‑induced generation of ROS in BV2 cells, thus indicating a strong antioxidative effect. Collectively, these results suggested that isorhamnetin may suppress LPS‑mediated inflammatory action in BV2 microglia through inactivating the NF‑κB signaling pathway, antagonizing TLR4 and eliminating ROS accumulation. Further studies are required to fully understand the anti‑inflammatory effects associated with the antioxidant capacity of isorhamnetin; however, the findings of the present study suggested that isorhamnetin may have potential benefits in inhibiting the onset and treatment of neuroinflammatory diseases.

Low level laser therapy alters satellite glial cell expression and reverses nociceptive behavior in rats with neuropathic pain

BACKGROUND

Nerve injury often results in persistent or chronic neuropathic pain characterized by spontaneous burning pain accompanied by allodynia and hyperalgesia. Low level laser therapy (LLLT) is a noninvasive method that has proved to be clinically effective in reducing pain sensitivity and consequently in improving the quality of life. Here we examined the effects of LLLT on pain sensitivity induced by chronic constriction injury (CCI) in rats. CCI was performed on adult male rats, subjected thereafter to 10 sessions of LLLT, every other day, and starting 14 days after CCI. Over the treatment period, the animals were evaluated for nociception using behavioral tests, such as allodynia, thermal and mechanical hyperalgesia. Following the sessions, we observed the involvement of satellite glial cells in the dorsal root ganglion (DRG) using immunoblotting and immunofluorescence approaches. In addition we analyzed the expression levels of interleukin 1 (IL-1β) and fractalkine (FKN) after the same stimulus.

RESULTS

LLLT induced an early reduction (starting at the second session; p ≤ 0.001) of the mechanical and thermal hyperalgesia and allodynia in CCI rats, which persisted until the last session. Regarding cellular changes, we observed a decrease of GFAP (50%; p ≤ 0.001) expression after LLLT in the ipsilateral DRG when compared with the naive group. We also observed a significant increase of pro-inflammatory cytokines after CCI, whereas LLLT dramatically inhibited the overexpression of these proteins.

CONCLUSIONS

These data provide evidence that LLLT reverses CCI-induced behavioral hypersensitivity, reduces glial cell activation in the DRG and decreases pro-inflammatory cytokines; we suggest that this involvement of glial cells can be one potential mechanism in such an effect.

Petasites japonicus bakkenolide B inhibits lipopolysaccharide‑induced pro‑inflammatory cytokines via AMPK/Nrf2 induction in microglia

Abnormal neuroinflammatory responses have diverse roles in neuronal death, oxidative stress and neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. Microglia regulate these responses via molecular signaling cascades that involve inflammatory cytokines and complement proteins. Bakkenolide B from Petasites japonicus exhibits significant anti‑inflammatory and anti‑allergic bioactivities. The present study investigated the anti‑neuroinflammatory effects and underlying molecular mechanisms of bakkenolide B on the lipopolysaccharide (LPS)‑mediated neuroinflammatory response in microglia. The results indicated that bakkenolide B pretreatment significantly reduced microglial production of interleukin (IL)‑1β, IL‑6, IL‑12, and tumor necrosis factor (TNF)‑α. Furthermore, this effect was associated with reduced production of reactive oxygen species. The role of bakkenolide B was then evaluated in the upregulation of nuclear factor erythroid 2‑related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. The results suggested that bakkenolide B significantly upregulated Nrf2/ARE pathway‑related downstream factors, such as NADPH dehydrogenase quinone‑1 (NQO‑1) and heme oxygenase‑1 (HO‑1). Silencing of Nrf2, HO‑1 and NQO‑1 diminished the anti‑neuroinflammatory properties of bakkenolide B. AMP‑activated protein kinase (AMPK) activates the Nrf2/ARE signaling pathway, and the results of the present study demonstrated that bakkenolide B increased AMPK phosphorylation in microglia. In addition, an AMPK inhibitor abolished the bakkenolide B‑induced increase in nuclear Nrf2, NQO‑1 and HO‑1 protein expression. Finally, an AMPK inhibitor diminished the bakkenolide B‑mediated inhibition of LPS‑stimulated TNF‑α production. Taken together, the present results demonstrate that bakkenolide B may be an effective and therapeutically relevant AMPK/Nrf2 pathway activator for suppressing abnormal neuro-inflammation in neurodegenerative diseases.

Pharmacokinetic study of tianeptine and its active metabolite MC5 in rats following different routes of administration using a novel liquid chromatography tandem mass spectrometry analytical method

Tianeptine is an atypical antidepressant with a unique mechanism of action and recently it has been also reported that its major metabolite, compound MC5, possesses pharmacological activity similar to that of the parent drug. The current study aims to investigate the pharmacokinetics (PK) of both tianeptine and MC5 after intravenous or intraperitoneal administration of the parent drug as well as the metabolic ratio of MC5 in rats. To achieve these goals an LC-MS/MS method using the small sample volume for the quantitation of tianeptine and its active metabolite MC5 in rat plasma and liver perfusate has been developed and validated. Following an intravenous administration of tianeptine pharmacokinetic parameters were calculated by non-compartmental analysis. The average tianeptine volume of distribution at steady state was 2.03 L/kg and the systemic clearance equaled 1.84 L/h/kg. The mean elimination half-lives of tianeptine and MC5 metabolite were 1.16 and 7.53 h, respectively. The hepatic clearance of tianeptine determined in the isolated rat liver perfusion studies was similar to the perfusate flow rate despite the low metabolic ratio of MC5. Mass spectrometric analysis of rat bile indicated that tianeptine and MC5 metabolite are eliminated with bile as glucuronide and glutamine conjugates. Bioavailability of tianeptine after its intraperitoneal administration was 69%. The PK model with a metabolite compartment developed in this study for both tianeptine and MC5 metabolite after two routes of administration may facilitate tianeptine dosage selection for the prospective pharmacological experiments.

Novel ureidopropanamide based N-formyl peptide receptor 2 (FPR2) agonists with potential application for central nervous system disorders characterized by neuroinflammation

Formyl peptide receptor2 (FPR2) is a G-protein coupled receptor that plays critical roles in inflammatory reactions. FPR2-specific interaction can be possibly used to facilitate the resolution of pathological inflammatory responses by enhancing endogenous anti-inflammation systems. Starting from our lead agonist 5, we designed new ureidopropanamides derivatives able to activate FPR2 in transfected cells and human neutrophils. The new FPR2 agonists showed good stability towards oxidative metabolism in vitro. Moreover, selected compounds showed anti-inflammatory properties in LPS-stimulated rat primary microglial cells. (S)-3-(4-Cyanophenyl)-N-[[1-(3-chloro-4-fluorophenyl)cyclopropyl]methyl]-2-[3-(4-fluorophenyl)ureido]propanamide ((S)-17) emerged as prospective pharmacological tool to study the effects of FPR2 activation in the central nervous system (CNS) being able to reduce IL-1β and TNF-α levels in LPS-stimulated microglial cells and showing good permeation rate in hCMEC/D3 cells, an in vitro model of blood brain barrier. These results are very promising and can open new therapeutic perspectives in the treatment of CNS disorders characterized by neuroinflammation.

Large-conductance Ca2+ -activated K+ channel activation by apical P2Y receptor agonists requires hydrocortisone in differentiated airway epithelium

KEY POINTS

Hydrocortisone (HC) is required for activation of large-conductance Ca²⁺ -activated K⁺ current (BK) by purinergic receptor agonists. HC reduces insertion of the stress-regulated exon (STREX) in the KCNMA1 gene, permitting protein kinase C (PKC)-dependent channel activation. Overlapping and unique purinergic signalling regions exist at the apical border of differentiated surface cells. BK channels localize in the cilia of surface cells.

ABSTRACT

In the present study we investigated the role of hydrocortisone (HC) on uridine-5'-triphosphate (UTP)-stimulated ion transport in differentiated, pseudostratified epithelia derived from normal human bronchial basal cells. The presence of a UTP-stimulated, paxilline-sensitive large-conductance Ca²⁺ -activated K⁺ (BK) current was demonstrated in control epithelia but was not stimulated in epithelia differentiated in the absence of HC (HC0). Addition of the BK channel opener NS11021 directly activated channels in control epithelia; however, under HC0 conditions, activation only occurred when UTP was added after NS11021. The PKC inhibitors GF109203x and Gö6983 blocked BK activation by UTP in control epithelia, suggesting that PKC-mediated phosphorylation plays a permissive role in purinoceptor-stimulated BK activation. Moreover, HC0 epithelia expressed significantly more KCNMA1 containing the stress-regulated exon (STREX), a splice-variant of the α-subunit that displays altered channel regulation by phosphorylation, compared to control epithelia. Furthermore, BK channels as well as purinergic receptors were shown to localize in unique and overlapping domains at the apical membrane of ciliated surface cells. These results establish a previously unrecognized role for glucocorticoids in regulation of BK channels in airway epithelial cells.

Nanocapsules with Polyelectrolyte Shell as a Platform for 1,25-dihydroxyvitamin D3 Neuroprotection: Study in Organotypic Hippocampal Slices

Calcitriol (1,25-dihydroxyvitamin D3), an active metabolite of vitamin D3, besides the role in calcium and phosphorus metabolism, plays a role in maintaining the functions of the brain. Active forms of vitamin D3 stimulate neurotrophic factors’ expression, regulate brain immune processes, and prevent neuronal damage. Therefore, a potential utility of vitamin D3 in a therapy of neurodegenerative disorders should be taken into account. On the other hand, systemic vitamin D3 treatment carries the risk of undesirable effects, e.g., hypercalcemia. Thus, 1,25-dihydroxyvitamin D3 targeting delivery by nanoparticles would be a tremendous advancement in treatment of brain disorders. Calcitriol was enclosed in emulsion-templated nanocapsules with different polymeric shells: PLL (Poly(l-lysine hydrobromide)), PLL/PGA (/Poly(l-glutamic acid)), and PLL/PGA-g-PEG (Poly(l-glutamic acid) grafted with polyethylene glycol). The average size of all synthesized nanocapsules ranged from −80 to −100 nm. Biocompatibilities of synthesized nanocarriers were examined in hippocampal organotypic cultures in basal conditions and after treatment with lipopolysaccharide (LPS) using various biochemical tests. We demonstrated that nanocapsules coated with PLL were toxic, while PLL/PGA- and PLL/PGA-g-PEG-covered ones were nontoxic and used for further experiments. Our study demonstrated that in LPS-treated hippocampal slices, both types of loaded nanoparticles have protective ability. Our findings underlined that the neuroprotective action of vitamin D3 in both free and nanoparticle forms seems to be related to the suppression of LPS-induced nitric oxide release.

Targeting the Microglial Signaling Pathways: New Insights in the Modulation of Neuropathic Pain

The microglia, once thought only to be supporting cells of the central nervous system (CNS), are now recognized to play essential roles in many pathologies. Many studies within the last decades indicated that the neuro-immune interaction underlies the generation and maintenance of neuropathic pain. Through a large number of receptors and signaling pathways, the microglial cells communicate with neurons, astrocytes and other cells, including those of the immune system. A disturbance or loss of CNS homeostasis causes rapid responses of the microglia, which undergo a multistage activation process. The activated microglia change their cell shapes and gene expression profiles, which induce proliferation, migration, and the production of pro- or antinociceptive factors. The cells release a large number of mediators that can act in a manner detrimental or beneficial to the surrounding cells and can indirectly alter the nociceptive signals. This review discusses the most important microglial intracellular signaling cascades (MAPKs, NF-kB, JAK/STAT, PI3K/Akt) that are essential for neuropathic pain development and maintenance. Our objective was to identify new molecular targets that may result in the development of powerful tools to control the signaling associated with neuropathic pain.