Roflumilast Reduces Cerebral Inflammation in a Rat Model of Experimental Subarachnoid Hemorrhage

Roflumilast counteracts high-dose dexamethasone-induced steatohepatitis, metabolic abnormalities and aortic injury via inhibiting TNF-α/NF-κB, NLRP3/IL-1β and ER stress sensors

INTRODUCTION

High-dose dexamethasone (DEX) is used for management of severe conditions. However, the multisystem adverse effects induced by glucocorticoids represent a hindering stone toward the effective clinical use of such agents. Various initiatives have been taken to ameliorate these complications with limited success.

AIM

The present study aims to explore the beneficial effects of roflumilast (ROF), a phosphodiesterase-4 (PDE-4) inhibitor, to combat DEX-induced steatohepatitis, metabolic abnormalities and aortic degeneration.

RESULTS

The application of ROF (2.5 and 5 mg/kg) has reverted the hepatic and aortic histopathological abnormalities as well as the rise in serum liver enzymes induced by DEX. Such palliative effect is probably attributed to PDE-4 inhibition (↑cAMP) that subsequently regulates multiple effectors. The chemotaxis of inflammatory cells (MCP-1) was inhibited by ROF treatments which was linked to inhibition of extracellular ROS production (MDA and NO) as well as restoration of cellular antioxidant defense (GSH). DEX challenge was associated with activation of the inflammatory pathways including TNF-α/NF-κB and NLRP3/IL-1β that were significantly dampened in the ROF groups. The oxidative stress as well as activation of inflammatory pathways exerted by DEX has contributed to the activation of endoplasmic reticulum stress (CHOP and PERK) posing more threats to the insulted cells, however, fortunately, ROF treatments showed inhibited activation of ER stress sensors and thereby abstaining the cells from inevitable damage. The metabolic abnormalities induced by DEX including elevated fasting insulin and heightened AUC of blood glucose level upon application of oral glucose tolerance test were significantly improved by ROF treatment.

CONCLUSION

The findings of our study depicted the hepatoprotective and metabolic regulating potentials of ROF in a rat model of DEX- induced steatohepatitis. Thereby, enhancing the overall efficacy and safety of DEX use in management of various disorders.

Mitigating seizure-induced cognitive deficits in mice induced with pentylenetetrazol by roflumilast through targeting the NLRP3 inflammasome/BDNF/SIRT3 pathway and regulating ferroptosis

AIMS

Comorbidities with epilepsy and antiseizure medications (ASMs) are currently the main challenges in treating epilepsy. The current study evaluates for the first time the neuroprotective effect of roflumilast (ROF) alone or combined with phenytoin (PHT) against pentylenetetrazol (PTZ)-induced kindling in mice. It focuses on the crosstalk between the NOD-like receptor protein 3 (NLRP3)/caspase 1/interleukin 1β (IL-1β) cascade and the brain-derived neurotrophic factor (BDNF)/sirtuin 3 (SIRT3) pathway as possible strategies to treat epilepsy.

MAIN METHODS

The kindled mouse model was induced via fifteen (35 mg/kg) intraperitoneal injections every other day. Roflumilast (0.4 mg/kg) and phenytoin (30 mg/kg) were orally administered daily from the start until the end of the experiment. Following the PTZ injection, the seizure severity score was assessed. The Morris water maze (MWM) test was performed to evaluate cognition. Histopathological examinations of hippocampi were conducted.

KEY FINDINGS

Roflumilast significantly improved neurobehavioral and histological assessments, whereas Racine scores declined. The improvement was confirmed through BDNF upregulation in contrast to NLRP3 and caspase-1 in the hippocampus, as revealed immunohistochemically. In addition, roflumilast induced a prominent elevation in gamma-aminobutyric acid (GABA), sirtuin 3 (SIRT3), and glutathione peroxidase (GPX4), whereas malondialdehyde (MDA), and arachidonic acid 15-lipoxygenase (ALOX15) expressions were downregulated.

SIGNIFICANCE

Our findings demonstrate that roflumilast conferred neuroprotective benefits against PTZ-induced kindling seizures, suggesting its potential as a novel adjuvant therapy for epilepsy-related disorders. This effect might be due to the modification of the NLRP3 inflammasome/BDNF pathway, ferroptosis, and a decrease in oxidative stress and neuroinflammation.

Roflumilast attenuates doxorubicin and cyclophosphamide combination-induced chemobrain in rats through modulation of NLRP3/ASC/caspase-1/GSDMD axis

AIM

The aim of this study is to investigate the neuroprotective effect of roflumilast, a phosphodiesterase-4 (PDE-4) inhibitor on cognitive impairment induced by doxorubicin (DOX)/cyclophosphamide (CP) combination therapy and to elucidate its modulatory effect on the pyroptosis pathway.

MATERIALS AND METHODS

Rats were allocated into five groups: a control group, a DOX/CP-intoxicated group, two groups receiving DOX/CP plus low-dose (0.5 mg/kg/day) or high-dose (1 mg/kg/day) roflumilast, and a roflumilast-only group. Behavioral assessments and brain tissue analyses were conducted, including histopathological staining and the measurement of inflammatory and oxidative stress markers.

FINDINGS

DOX/CP treatment resulted in cognitive impairment, abnormal brain histology. It significantly elevated the levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and malondialdehyde (MDA). Concurrently, superoxide dismutase (SOD) activity was reduced. Pyroptosis-associated markers, including nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), caspase-1, gasdermin-D (GSDMD), and interleukin-18 (IL-18) were upregulated. Apoptotic marker caspase-3 also exhibited increased expression. Conversely, administration of roflumilast (1 mg/kg/day) for four weeks ameliorated these pathological changes. Roflumilast improved cognitive function, reduced oxidative stress, and modulated inflammatory signaling. Additionally, it suppressed pyroptotic and apoptotic pathways within hippocampal tissue.

SIGNIFICANCE

These results suggest that roflumilast exerts neuroprotective effects against chemotherapy-induced cognitive dysfunction and neurodegeneration through inhibition of the NLRP3/ASC/caspase-1/GSDMD pyroptosis pathway.

PDE4 inhibitors: potential protective effects in inflammation and vascular diseases

Phosphodiesterase 4 (PDE4) inhibitors are effective therapeutic agents for various inflammatory diseases. Roflumilast, apremilast, and crisaborole have been developed and approved for the treatment of chronic obstructive pulmonary disease psoriatic arthritis, and atopic dermatitis. Inflammation underlies many vascular diseases, yet the role of PDE4 inhibitors in these diseases remains inadequately explored. This review elucidates the clinical applications and anti-inflammatory mechanisms of PDE4 inhibitors, as well as their potential protective effects on vascular diseases. Additionally, strategies to mitigate the adverse reactions of PDE4 inhibitors are discussed. This article emphasizes the need for further exploration of the therapeutic potential and clinical applications of PDE4 inhibitors in vascular diseases.

A study of roflumilast treatment on functional and structural changes in hippocampus in depressed Adult male Wistar rats

Depression is a common stress disability disorder that affects higher mental functions including emotion, cognition, and behavior. It may be mediated by inflammatory cytokines that interfere with neuroendocrine function, and synaptic plasticity. Therefore, reductions in inflammation might contribute to treatment response. The current study aims to evaluate the role of Protein Kinase (PKA)- cAMP response element-binding protein (CREB)- brain derived neurotropic factor (BDNF) signaling pathway in depression and the effects of roflumilast (PDE4 inhibitor) as potential antidepressant on the activity of the PKA-CREB-BDNF signaling pathway, histology, and pro-inflammatory cytokine production. Forty Adult male Wistar rats were divided into 4 groups: Control group, Positive Control group: similar to the controls but received Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment, Depressed group which were exposed to chronic stress for 6 weeks, and Roflumilast-treated group which were exposed to chronic stress for 6 weeks and treated by Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment. The depressed group showed significant increase in immobility time with significant decrease in swimming and struggling times, significant decrease in hippocampal PKA, CERB, BDNF, Dopamine, Cortisone, and Superoxide dismutase while hippocampal Phosphodiesterase-E4, Interleukin-6, and Malondialdhyde levels were significantly elevated. These findings were significantly reversed upon Roflumilast treatment. Therefore, it could be concluded that depression is a neurodegenerative inflammatory disease and oxidative stress plays a key role in depression. Roflumilast treatment attenuated the depression behavior in rats denoting its neuroprotective, and anti-inflammatory effects.

The Cell Permeant Phosphopetpide mimetic of VASP Alleviates Motor Function Deficits After Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) due to the rupture of an intracranial aneurysm leads to delayed vasospasm and neuroischemia, which can result in profound neurologic deficit and death. Therapeutic options after SAH are currently limited to hemodynamic optimization and nimodipine, which have limited clinical efficacy. Experimental SAH results in cerebral vasospasm have demonstrated the downregulation of nitric oxide (NO)-protein kinase G (PKG) signaling elements. VP3 is a novel cell permeant phosphopeptide mimetic of VASP, a substrate of PKG and an actin-associated protein that modulates vasorelaxation in vascular smooth muscle cells. In this study, we determined that intravenous administration of high doses of VP3 did not induce systemic hypotension in rats except at the maximal soluble dose, implying that VP3 is well-tolerated and has a wide therapeutic window. Using a single cisterna magna injection rat model of SAH, we demonstrated that intravenous administration of low-dose VP3 after SAH improved neurologic deficits for up to 14 days as determined by the rotarod test. These findings suggest that strategies aimed at targeting the cerebral vasculature with VP3 may improve neurologic deficits associated with SAH.

Roflumilast extenuates inflammation and oxidative stress in cadmium-induced hepatic and testicular injury in rats

Roflumilast (ROF), a highly selective phosphodiesterase-4 inhibitor, has proven anti-inflammatory and immunomodulatory effects on the pulmonary system. However, the protective effects of ROF on cadmium (Cd)-induced hepatic and testicular injury has never been investigated. Adult male Sprague Dawley rats were acutely intoxicated with CdCl2 (3 mg/Kg, ip, qd, for 5 days). In treatment groups, ROF was administered in two doses (1.5 & 3 mg/Kg, po, qd, for 5 days) 2 h prior to CdCl2 intoxication. The results demonstrated that the therapeutic potential of ROF can extend beyond the pulmonary system. The histopathological manifestation of Cd in the liver and testes were evidently mitigated by ROF prophylaxis. This study unraveled the multi-faceted ROF protective mechanisms, these comprise (i) reviving normal liver and testicular architecture, (ii) lessen immune cell infiltration in injured tissues (iii) restoration of cellular oxidant status (GSH, SOD, NO and MDA), (iv) shielding pro-inflammatory signaling pathways (NF-κB, NLRP3, IL-1β axis), (v) dampening endoplasmic reticulum stress (IRE-1), (vi) mitigating apoptotic injury (caspase-3), (vii) restoring the integrity of blood testes barrier (Cathepsin-D) and (viii) promoting the regenerative potentials of injured testes (SDF-1). In conclusion, ROF is a promising anti-inflammatory and anti-oxidative candidate in Cd-induced hepatic and testicular injury.

Blood-Brain Barrier Rescue by Roflumilast After Transient Global Cerebral Ischemia in Rats

Phosphodiesterase 4 inhibitors (PDE4-I), which selectively increase cyclic adenosine monophosphate (cAMP) levels, have shown neuroprotective effects after several neurological injuries inducing blood-brain barrier (BBB) damage including local/focal cerebral ischemia. The present investigated whether roflumilast confers BBB neuroprotection in the hippocampus after transient global cerebral ischemia (TGCI) in rats. TGCI resulted in whole BBB disruption as measured by the increase of Evans blue (EB) and IgG extravasation, neurodegeneration, and downregulation of claudin-5 and endothelial nitric oxide synthase (eNOS) levels in the CA1 hippocampal subfield of ischemic rats. Roflumilast attenuated BBB disruption and restored the levels of eNOS in the CA1 hippocampal area. Moreover, roflumilast increased the levels of B2 cell lymphoma (BcL-2) and neuron-glial antigen-2 (NG2) in the CA1 subfield after global ischemia in rats. The protective effects of roflumilast against TGCI-induced BBB breakdown might involve preservation of BBB integrity, vascularization and angiogenesis, and myelin repair.

Differential effects of two phosphodiesterase 4 inhibitors against lipopolysaccharide-induced neuroinflammation in mice

BACKGROUND

Several phosphodiesterase 4 (PDE4) inhibitors have emerged as potential therapeutics for central nervous system (CNS) diseases. This study investigated the pharmacological effects of two selective PDE4 inhibitors, roflumilast and zatolmilast, against lipopolysaccharide-induced neuroinflammation.

RESULTS

In BV-2 cells, the PDE4 inhibitor roflumilast reduced the production of nitric oxide and tumor necrosis factor-α (TNF-α) by inhibiting NF-κB phosphorylation. Moreover, mice administered roflumilast had significantly reduced TNF-α, interleukin-1β (IL-1β), and IL-6 levels in plasma and brain tissues. By contrast, zatolmilast, a PDE4D inhibitor, showed no anti-neuroinflammatory effects in vitro or in vivo. Next, in vitro and in vivo pharmacokinetic studies of these compounds in the brain were performed. The apparent permeability coefficients of 3 µM roflumilast and zatolmilast were high (> 23 × 10^-6 cm/s) and moderate (3.72-7.18 × 10^-6 cm/s), respectively, and increased in a concentration-dependent manner in the MDR1-MDCK monolayer. The efflux ratios were < 1.92, suggesting that these compounds are not P-glycoprotein substrates. Following oral administration, both roflumilast and zatolmilast were slowly absorbed and eliminated, with time-to-peak drug concentrations of 2-2.3 h and terminal half-lives of 7-20 h. Assessment of their brain dispositions revealed the unbound brain-to-plasma partition coefficients of roflumilast and zatolmilast to be 0.17 and 0.18, respectively.

CONCLUSIONS

These findings suggest that roflumilast, but not zatolmilast, has the potential for use as a therapeutic agent against neuroinflammatory diseases.

Roflumilast ameliorates ovariectomy-induced depressive-like behavior in rats via activation of AMPK/mTOR/ULK1-dependent autophagy pathway

AIMS

Roflumilast, a well-known phosphodiesterase-4 (PDE-4) inhibitor, possess an anti-inflammatory activity with approved indications in chronic obstructive pulmonary disease. This study aimed to evaluate the neuroprotective role of roflumilast in ovariectomy (OVX)-induced depressive-like behavior in female rats and to shed light on a potential autophagy enhancing effect.

MAIN METHODS

Rats were randomly divided into four groups: sham, OVX, OVX + roflumilast (1 mg/kg, p.o), and OVX + roflumilast + chloroquine (CQ) (50 mg/kg, i.p). Drugs were administered for 4 weeks starting 2 weeks after OVX.

KEY FINDINGS

Roflumilast improved the depressive-like behaviors observed in OVX rats as evidenced by decreasing both forced swimming and open field immobility times while, increasing % sucrose preference and number of open field crossed squares. Histopathological analysis provides further evidence of roflumilast's beneficial effects, demonstrating that roflumilast ameliorated the neuronal damage caused by OVX. Roflumilast antidepressant potential was mediated via restoring hippocampal cAMP and BDNF levels as well as down-regulating PDE4 expression. Moreover, roflumilast revealed anti-inflammatory and anti-apoptotic effects via hindering TNF-α level and diminishing Bax/Bcl2 ratio. Roflumilast restored the autophagic function via up-regulation of p-AMPK, p-ULK1, Beclin-1 and LC3II/I expression, along with downregulation of P62 level and p-mTOR protein expression. The autophagy inhibitor CQ was used to demonstrate the suggested pathway.

SIGNIFICANCE

The present study revealed that roflumilast showed an anti-depressant activity in OVX female rats via turning on AMPK/mTOR/ULK1-dependent autophagy pathway; and neurotrophic, anti-inflammatory, and anti-apoptotic activities. Roflumilast could offer a more secure alternative to hormone replacement therapy for postmenopausal depression treatment.

Unleashing Spinal Cord Repair: The Role of cAMP-Specific PDE Inhibition in Attenuating Neuroinflammation and Boosting Regeneration after Traumatic Spinal Cord Injury

Traumatic spinal cord injury (SCI) is characterized by severe neuroinflammation and hampered neuroregeneration, which often leads to permanent neurological deficits. Current therapies include decompression surgery, rehabilitation, and in some instances, the use of corticosteroids. However, the golden standard of corticosteroids still achieves minimal improvements in functional outcomes. Therefore, new strategies tackling the initial inflammatory reactions and stimulating endogenous repair in later stages are crucial to achieving functional repair in SCI patients. Cyclic adenosine monophosphate (cAMP) is an important second messenger in the central nervous system (CNS) that modulates these processes. A sustained drop in cAMP levels is observed during SCI, and elevating cAMP is associated with improved functional outcomes in experimental models. cAMP is regulated in a spatiotemporal manner by its hydrolyzing enzyme phosphodiesterase (PDE). Growing evidence suggests that inhibition of cAMP-specific PDEs (PDE4, PDE7, and PDE8) is an important strategy to orchestrate neuroinflammation and regeneration in the CNS. Therefore, this review focuses on the current evidence related to the immunomodulatory and neuroregenerative role of cAMP-specific PDE inhibition in the SCI pathophysiology.

Investigation of apoptotic and autophagic effects of chronic roflumilast use on testicular tissue in rats by immunohistochemical and immunofluorescence methods

Objectives

The present study aims to determine how various dosages of chronic roflumilast affect testicular tissue and testosterone levels in healthy rats.

Materials and Methods

Biochemical tests, along with histopathological, immunohistochemical, and immunofluorescence studies, were carried out.

Results

Loss of tissue in the seminiferous epithelium, degeneration in the interstitial area, a separation between cells, desquamation, interstitial edema, and degenerative alterations in testicular tissue were observed in roflumilast groups when compared with the other groups. While apoptosis and autophagy were statistically negligible in the control and sham groups, the roflumilast groups had significantly higher apoptotic and autophagic alterations, as well as immunopositivity. Serum testosterone levels in the 1 mg/kg roflumilast group were lower than those in the control, sham, and 0.5 mg/kg roflumilast groups.

Conclusion

Analyses of the research findings revealed that continuous usage of the broad-spectrum active component roflumilast exerted unfavorable effects on the testicular tissue and testosterone levels of rats.

Xueshuantong injection alleviates cerebral microcirculation disorder in middle cerebral artery occlusion/reperfusion rats by suppressing inflammation via JNK mediated JAK2/STAT3 and NF-κB signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

In the long history of traditional Chinese medicine, Panax notoginseng has been used as a key herb for the treatment of blood diseases. Brain microvessels support adequate blood circulation to maintain normal physiological function, therefore, brain microcirculation disorder is an important therapeutic target for various brain diseases. However, the role of Xueshuantong (XST) injection composed of saponins from P. Notoginseng (PNS) in the amelioration of cerebral microcirculation disorder is unclear.

AIMS OF THE STUDY

Cerebral microcirculation disorder and inflammation play a vital role in stroke. Capillary endothelial cells and adjacent tight junctions are fundamental to the structure and function of cerebrovascule. XST injection has been used clinically in the treatment of stroke, but no studies have reported its indication in cerebral microcirculation disorder. This study is to explore the action and mechanism of XST injection in the alleviation of cerebral microcirculation disorder in middle cerebral artery occlusion/reperfusion (MCAO/R) rats.

MATERIALS AND METHODS

MCAO/R rats and LPS-induced bEnd.3 cells were employed for the investigation of effect and mechanism of XST injection. Brain damages were evaluated by neurobehavioral assessment, 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, hematoxylin and eosin staining (H&E), and Nissl staining. Morphology and density changes of cerebral microvessels were monitored by immunohistochemistry. Cell permeability was detected by measurement of trans-endothelial electrical resistance (TEER) and sodium fluorescein (NaF) leakage. The mRNA and protein expressions of inflammatory cytokines, tight junction proteins, adhesion molecules, Janus kinase 2 (JAK2), signal transducer and activator of transcription-3 (STAT3), inhibitor of NF-κB (IκB), nuclear factor-κB (NF-κB) and c-jun N-terminal kinase (JNK) in brain microvessels and lipopolysaccharide (LPS)-induced bEnd.3 cells were measured by real-time PCR and Western blot, respectively.

RESULTS

XST injection at 48 mg/kg significantly improved the neurological damage, inflammatory infiltration, and microvessel morphology, and increased microvessel density in brain of MCAO/R rats. The endothelial permeability was significantly mitigated by XST injection in LPS-induced bEnd.3 cells. Meanwhile, the tight junction proteins such as zona occludens 1 (ZO-1) and occludin were elevated remarkably in brain microvessel of MCAO/R rats and LPS-induced bEnd.3 cells. Moreover, the expression of inflammatory mediators including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), cycloocygenases 2 (COX-2), vascular cellular adhesion molecule-1 (VCAM-1), matrix metalloproteinase (MMP)-2, and MMP-9 were inhibited by XST injection. In addition, XST injection suppressed the phosphorylation of JAK2, STAT3, IκB, NF-κB and JNK, which could be abolished by anisomycin, the JNK agonist.

CONCLUSION

XST injection improved cerebral microvescular structure damage and dysfunction in MCAO/R rats through inhibiting inflammation activated by JNK mediated JAK2/STAT3 and NF-κB signaling pathways. The novel findings may provide theoretical basis for the clinical application in the treatment of cerebral microcirculation disorder.

TAT-HSP27 Peptide Improves Neurologic Deficits via Reducing Apoptosis After Experimental Subarachnoid Hemorrhage

Cell apoptosis plays an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Heat shock protein 27 (HSP27), a member of the small heat shock protein (HSP) family, is induced by various stress factors and exerts protective role on cells. However, the role of HSP27 in brain injury after SAH needs to be further clarified. Here, we reported that HSP27 level of cerebrospinal fluid (CSF) is increased obviously at day 1 in patients with aneurysmal SAH (aSAH) and related to the grades of Hunt and Hess (HH), World Federation of Neurological Surgeons (WFNS), and Fisher score. In rat SAH model, HSP27 of CSF is first increased and then obviously declined; overexpression of HSP27, not knockdown of HSP27, attenuates SAH-induced neurological deficit and cell apoptosis in the basal cortex; and overexpression of HSP27 effectively suppresses SAH-elevated activation of mitogen-activated protein Kinase Kinase 4 (MKK4), the c-Jun N-terminal kinase (JNK), c-Jun, and caspase-3. In an in vitro hemolysate-damaged cortical neuron model, HSP2765-90 peptide effectively inhibits hemolysate-induced neuron death. Furthermore, TAT-HSP2765-90 peptide, a fusion peptide consisting of trans-activating regulatory protein (TAT) of HIV and HSP2765-90 peptide, effectively attenuates SAH-induced neurological deficit and cell apoptosis in the basal cortex of rats. Altogether, our results suggest that TAT-HSP27 peptide improves neurologic deficits via reducing apoptosis.

Schisandrin B Inhibits NLRP3 Inflammasome Pathway and Attenuates Early Brain Injury in Rats of Subarachnoid Hemorrhage

OBJECTIVE

To determine whether Schisandrin B (Sch B) attenuates early brain injury (EBI) in rats with subarachnoid hemorrhage (SAH).

METHODS

Sprague-Dawley rats were divided into sham (sham operation), SAH, SAH+vehicle, and SAH+Sch B groups using a random number table. Rats underwent SAH by endovascular perforation and received Sch B (100 mg/kg) or normal saline after 2 and 12 h of SAH. SAH grading, neurological scores, brain water content, Evan's blue extravasation, and terminal transferase-mediated dUTP nick end-labeling (TUNEL) staining were carried out 24 h after SAH. Immunofluorescent staining was performed to detect the expressions of ionized calcium binding adapter molecule 1 (Iba-1) and myeloperoxidase (MPO) in the rat brain, while the expressions of B-cell lymphoma 2 (Bcl-2), Bax, Caspase-3, nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), apoptosis-associated specklike protein containing the caspase-1 activator domain (ASC), Caspase-1, interleukin (IL)-1β, and IL-18 in the rat brains were detected by Western blot.

RESULTS

Compared with the SAH group, Sch B significantly improved the neurological function, reduced brain water content, Evan's blue content, and apoptotic cells number in the brain of rats (P<0.05 or P<0.01). Moreover, Sch B decreased SAH-induced expressions of Iba-1 and MPO (P<0.01). SAH caused the elevated expressions of Bax, Caspase-3, NLRP3, ASC, Caspase-1, IL-1β, and IL-18 in the rat brain (P<0.01), all of which were inhibited by Sch B (P<0.01). In addition, Sch B increased the Bcl-2 expression (P<0.01).

CONCLUSION

Sch B attenuated SAH-induced EBI, which might be associated with the inhibition of neuroinflammation, neuronal apoptosis, and the NLRP3 inflammatory signaling pathway.

Roflumilast ameliorates cognitive deficits in a mouse model of amyloidogenesis and tauopathy: Involvement of nitric oxide status, Aβ extrusion transporter ABCB1, and reversal by PKA inhibitor H89

The biological cascade of second messenger-cyclic adenosine monophosphate (cAMP) -as a molecular mechanism implicated in memory and learning regulation has captured the attention of neuroscientists worldwide. cAMP triggers its foremost effector, protein kinase A (PKA), resulting in the activation of innumerable downstream targets. Roflumilast (ROF), a phosphodiesterase 4 inhibitor, has demonstrated a greater efficiency in enhancing cAMP signaling in various neurological disorders. This study was conducted to identify various downstream targets of PKA as mechanistic tools through which ROF could hinder the progressive cognitive impairment following central streptozotocin (STZ) administration in mice. Animals were injected with STZ (3 mg/kg/i.c.v) once. Five hours later, mice received ROF (0.4 mg/kg) with or without the PKA inhibitor, H89, for 21 days. ROF highly preserved the structure of hippocampal neurons. It improved the ability of mice to develop short-term memories and retrieve spatial memories in Y-maze and Morris water maze tests, respectively. ROF enhanced the gene expression of ABCB1 transporters and pregnane X receptors (PXR), and hampered Aβ accumulation in hippocampus. Simultaneously, it interfered with the processes of tau phosphorylation and nitration. This effect was associated with an upsurge in hippocampal arginase activity as well as a decline in glycogen synthase kinase-3β activity, nitric oxide synthase (NOS) activity, and inducible NOS expression. Contrariwise, ROF's beneficial effects were utterly abolished by co-administration of H89. In conclusion, boosting PKA, by ROF, modulated PXR/ABCB1 expression and arginase/NOS activities to restrict the main post-translational modifications of tau, Aβ deposition and, accordingly, cognitive deterioration of sporadic Alzheimer's disease.

SERS-based immunoassay based on gold nanostars modified with 5,5'-dithiobis-2-nitrobenzoic acid for determination of glial fibrillary acidic protein

A surface-enhanced Raman scattering (SERS)-based immunoassay with gold nanostars (GNSs) is utilized for determination of the subarachnoid hemorrhage (SAH) biomarker glial fibrillary acidic protein (GFAP) at very low concentration levels, which allows for early diagnosis and guides clinical decision-making to treat SAH-induced complications. The Raman reporter 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) modified on GNSs was selected as the SERS tags. The SERS immunoassay was assembled by SERS tag and GFAP probe-immobilized ITO substrate. Therefore, the level of GFAP can be detected by monitoring the characteristic Raman peak intensity of GFAP-conjugated GNSs at 1332 cm^-1 with a very low detection limit. Under optimized conditions, the assay can work in the GFAP concentration range from 1 pg⋅mL^-1 to 1 μg⋅mL^-1, with a detection limit as low as 0.54 fg⋅mL^-1. The performance of the SERS immunoassay proven by the detection of GFAP is equivalent to that of the conventional enzyme-linked immunosorbent assay (ELISA). Scheme 1. Schematic illustration of GNSs SERS immunoassay for ultrasensitive dynamic change detection of GFAP. (SAH: Subarachnoid hemorrhage, SCF: Cerebrospinal fluid; GNSs: gold nanostars; SERS: surface-enhanced Raman scattering; GFAP: glial fibrillary acidic protein).

Novel pharmacological strategies to treat cognitive dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and currently the 3rd largest cause of death in the world, with approximately 3.23 million deaths per year. Globally, the financial burden of COPD is approximately €82 billion per year and causes substantial morbidity and mortality. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and viral and bacterial-induced acute exacerbations (AECOPD). Recent clinical studies have shown that cognitive dysfunction is present in up to 60% of people with COPD, with impairments in executive function, memory, and attention, impacting on important outcomes such as quality of life, hospitalisation and survival. The high prevalence of cognitive dysfunction in COPD may also help explain the insufficient adherence to therapeutic plans and strategies, thus worsening disease progression in people with COPD. However, the mechanisms underlying the impaired neuropathology and cognition in COPD remain largely unknown. In this review, we propose that the observed pulmonary oxidative burden and inflammatory response of people with COPD 'spills over' into the systemic circulation, resulting in damage to the brain and leading to cognitive dysfunction. As such, drugs targeting the lungs and comorbidities concurrently represent an exciting and unique therapeutic opportunity to treat COPD and cognitive impairments, which may lead to the production of novel targets to prevent and reverse the debilitating and life-threatening effects of cognitive dysfunction in COPD.

Host Directed Therapies for Tuberculous Meningitis

A dysregulated host immune response significantly contributes to morbidity and mortality in tuberculous meningitis (TBM). Effective host directed therapies (HDTs) are critical to improve survival and clinical outcomes. Currently only one HDT, dexamethasone, is proven to improve mortality. However, there is no evidence dexamethasone reduces morbidity, how it reduces mortality is uncertain, and it has no proven benefit in HIV co-infected individuals. Further research on these aspects of its use, as well as alternative HDTs such as aspirin, thalidomide and other immunomodulatory drugs is needed. Based on new knowledge from pathogenesis studies, repurposed therapeutics which act upon small molecule drug targets may also have a role in TBM. Here we review existing literature investigating HDTs in TBM, and propose new rationale for the use of novel and repurposed drugs. We also discuss host variable responses and evidence to support a personalised approach to HDTs in TBM.

Interleukin 6 and Aneurysmal Subarachnoid Hemorrhage. A Narrative Review

Interleukin 6 (IL-6) is a prominent proinflammatory cytokine. Neuroinflammation in general, and IL-6 signaling in particular, appear to play a major role in the pathobiology and pathophysiology of aneurysm formation and aneurysmal subarachnoid hemorrhage (SAH). Most importantly, elevated IL-6 CSF (rather than serum) levels appear to correlate with delayed cerebral ischemia (DCI, “vasospasm”) and secondary (“vasospastic”) infarctions. IL-6 CSF levels may also reflect other forms of injury to the brain following SAH, i.e., early brain damage and septic complications of SAH and aneurysm treatment. This would explain why many researchers have found an association between IL-6 levels and patient outcomes. These findings clearly suggest CSF IL-6 as a candidate biomarker in SAH patients. However, at this point, discrepant findings in variable study settings, as well as timing and other issues, e.g., defining proper clinical endpoints (i.e., secondary clinical deterioration vs. angiographic vasospasm vs. secondary vasospastic infarct) do not allow for its routine use. It is also tempting to speculate about potential therapeutic measures targeting elevated IL-6 CSF levels and neuroinflammation in SAH patients. Corticosteroids and anti-platelet drugs are indeed used in many SAH cases (not necessarily with the intention to interfere with detrimental inflammatory signaling), however, no convincing benefit has been demonstrated yet. The lack of a robust clinical perspective against the background of a relatively large body of data linking IL-6 and neuroinflammation with the pathophysiology of SAH is somewhat disappointing. One underlying reason might be that most relevant studies only report correlative data. The specific molecular pathways behind elevated IL-6 levels in SAH patients and their various interactions still remain to be delineated. We are optimistic that future research in this field will result in a better understanding of the role of neuroinflammation in the pathophysiology of SAH, which in turn, will translate into the identification of suitable biomarkers and even potential therapeutic targets.

Medicinal plants and bioactive natural products as inhibitors of NLRP3 inflammasome

The NLR family, pyrin domain-containing 3 (NLRP3) inflammasome is a multiprotein complex that induces caspase-1 activation and the downstream substrates involved with the processing and secretion of the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18 and tumor necrosis factor-α (TNF- α). The NLRP3 inflammasome is activated by a wide range of danger signals that derive from metabolic dysregulation. Activation of this complex often involves the adaptor ASC and upstream sensors including NLRP1, NLRP3, NLRC4, AIM2, and pyrin, which are activated by different stimuli including infectious agents and changes in cell homeostasis. It has been shown that nutraceuticals and medicinal plants have antiinflammatory properties and could be used as complementary therapy in the treatment of several chronic diseases that are related to inflammation, for example, cardiovascular diseases and diabetes mellitus. Herb-based medicine has demonstrated protective effects against NLRP3 inflammasome activation. Therefore, this review focuses on the effects of nutraceuticals and bioactive compounds derived from medicinal plants on NLRP3 inflammasome activation and the possible mechanisms of action of these natural products. Thus, herb-based, natural products/compounds can be considered novel, practical, and accessible agents in chronic inflammatory diseases by inhibiting NLRP3 inflammasome activation.

Neuroprotective effects of roflumilast against quinolinic acid-induced rat model of Huntington's disease through inhibition of NF-κB mediated neuroinflammatory markers and activation of cAMP/CREB/BDNF signaling pathway

Huntington's disease (HD) is a progressive neurodegenerative and hyperkinetic movement disorder. Decreased activity of cAMP-responsive element-binding protein (CREB) is thought to contribute to the death of striatal medium spiny neurons in HD. The present study has been designed to explore the possible role of roflumilast against qunilonic acid (QA) induced neurotoxicity in rats intending to investigate whether it inhibits the neuroinflammatory response through activation of the cAMP/CREB/BDNF signaling pathway. QA was microinjected (200 nmol/2 µl, bilaterally) through the intrastriatal route in the stereotaxic apparatus. Roflumilast (0.5, 1, and 2 mg/kg, orally) once-daily treatment for 21 days significantly improved locomotor activity in actophotometer, motor coordination in rotarod, and impaired gait performance in narrow beam walk test. Moreover, roflumilast treatment significantly attenuated oxidative and nitrosative stress (p < 0.05) through attenuating lipid peroxidation nitrite concentration and enhancing reduced glutathione, superoxide dismutase, and catalase levels. Furthermore, roflumilast also significantly decreased elevated pro-inflammatory cytokines like TNF-α (p < 0.01), IL-6 (p < 0.01), IFN-γ (p < 0.05), NF-κB (p < 0.05) and significantly increased BDNF(p < 0.05) in the striatum and cortex of rat brain. The results further demonstrated that roflumilast effectively increased the gene expression of cAMP(p < 0.05), CREB(p < 0.05) and decreased the gene expression of PDE4 (p < 0.05) in qRT-PCR. These results conclusively depicted that roflumilast could be a potential candidate as an effective therapeutic agent in the management of HD through the cAMP/CREB/BDNF signaling pathway.

Roflumilast Ameliorates Isoflurane-Induced Inflammation in Astrocytes via the CREB/BDNF Signaling Pathway

Background and purpose: Astrocyte-mediated neuroinflammation plays an important role in anesthetic isoflurane-induced cognitive impairment. Roflumilast, a selective inhibitor of phosphodiesterase-4 (PDE-4) used for the treatment of chronic obstructive pulmonary disease (COPD), has displayed a wide range of anti-inflammatory capacity in different types of cells and tissues. In the current study, we aimed to investigate whether roflumilast possesses a protective effect against isoflurane-induced insults in mouse primary astrocytes. Methods: Primary astrocytes were isolated from the cerebral cortices of immature rats. The production of NO was determined using DAF-FM DA staining assay. QRT-PCR and western blot were used to evaluate the expression levels of iNOS, COX-2, and BDNF in the astrocytes treated with different therapies. The gene expressions and concentrations of IL-6 and MCP-1 released by the astrocytes were detected using qRT-PCR and ELISA, respectively. The expression levels of phosphorylated CREB and PGE₂ were determined using western blot and ELISA, respectively. H89 was introduced to evaluate the function of CREB. Recombinant human BDNF and ANA-12 were used to verify the role of BDNF. Results: The upregulated iNOS, excessive production of NO, IL-6, and MCP-1, and activated COX-2/PGE₂ signaling pathways in the astrocytes induced by isoflurane were significantly reversed by the introduction of roflumilast, in a dose-dependent manner. Subsequently, we found that BDNF could be upregulated by roflumilast, which was verified to be related to the activation of CREB and blocked by H89 (a CREB inhibitor). In addition, the COX-2/PGE₂ signaling pathway activated by isoflurane can be inactivated by recombinant human BDNF. Finally, the regulatory effect of roflumilast against the isoflurane-activated COX-2/PGE₂ signaling pathway was significantly blocked by ANA-12, which is a BDNF inhibitor. Conclusion: Roflumilast might ameliorate isoflurane-induced inflammation in astrocytes via the CREB/BDNF signaling pathway.

Host Directed Therapies for Tuberculous Meningitis

A dysregulated host immune response significantly contributes to morbidity and mortality in tuberculous meningitis (TBM). Effective host directed therapies (HDTs) are critical to improve survival and clinical outcomes. Currently only one HDT, dexamethasone, is proven to improve mortality. However, there is no evidence dexamethasone reduces morbidity, how it reduces mortality is uncertain, and it has no proven benefit in HIV co-infected individuals. Further research on these aspects of its use, as well as alternative HDTs such as aspirin, thalidomide and other immunomodulatory drugs is needed. Based on new knowledge from pathogenesis studies, repurposed therapeutics which act upon small molecule drug targets may also have a role in TBM. Here we review existing literature investigating HDTs in TBM, and propose new rationale for the use of novel and repurposed drugs. We also discuss host variable responses and evidence to support a personalised approach to HDTs in TBM.

Paeoniflorin attenuates early brain injury through reducing oxidative stress and neuronal apoptosis after subarachnoid hemorrhage in rats

Paeoniflorin is a natural monoterpene glucoside from Paeoniae Radix with neuroprotective properties. However, it is still unclear whether paeoniflorin has neuroprotective effects on subarachnoid hemorrhage (SAH). This study explores the effect of paeoniflorin on early brain injury (EBI) using rat SAH model. We found that paeoniflorin significantly improves neurological deficits, attenuates brain water content and Evans blue extravasation at 72 h after SAH. Paeoniflorin attenuates the oxidative stress following SAH as evidenced by decrease of reactive oxygen species (ROS), malondialdehyde (MDA), 3-Nitrotyrosine, and 8-Hydroxy-2-deoxy guanosine (8-OHDG) level, increase of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase activity, and up-regulates the nuclear factor erythroid‑related factor 2 (Nrf2)/heme oxygenase‑1 (HO-1) pathway. Inhibition of microglia activation and neuro-inflammatory response both contributed to paeoniflorin's protective effects. Moreover, paeoniflorin treatment significantly reduces the ratio of Bax/Bcl-2, active caspase-3/ neuronal nuclei (NeuN) and TUNEL/DAPI positive cells at 72 h following SAH. Our results indicate that paeoniflorin may attenuate early brain injury after experimental SAH.

Calpastatin peptide attenuates early brain injury following experimental subarachnoid hemorrhage

Calpain activation may have an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). The present study investigated the effects of the calpastatin peptide, a cell-permeable peptide that functions as a potent inhibitor of calpain, on EBI in a rat SAH model. It was revealed that calpastatin peptide treatment significantly reduced SAH-induced body weight loss and neurological deficit at 72 h when compared with untreated SAH controls. Furthermore, the quantification of brain water content and the extravasation of Evans blue dye revealed a significant reduction in SAH-induced brain edema and blood-brain barrier permeability at 72 h due to treatment with the calpastatin peptide when compared with untreated SAH controls. Finally, calpastatin peptide treatment significantly attenuated the protein levels of Bax, cytochrome c, cleaved caspase-9 and cleaved caspase-3, and reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labelling-positive cells in the basal cortex at 72 h after SAH when compared with untreated SAH controls. These results indicated that the calpastatin peptide may ameliorate EBI following SAH in rat models.

The role of haptoglobin and hemopexin in the prevention of delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage: a review of current literature

Delayed cerebral ischaemia (DCI) after aneurysmal subarachnoid haemorrhage (aSAH) is a major cause of mortality and morbidity. The pathophysiology of DCI after aSAH is thought to involve toxic mediators released from lysis of red blood cells within the subarachnoid space, including free haemoglobin and haem. Haptoglobin and hemopexin are endogenously produced acute phase proteins that are involved in the clearance of these toxic mediators. The aim of this review is to investigate the pathophysiological mechanisms involved in DCI and the role of both endogenous as well as exogenously administered haptoglobin and hemopexin in the prevention of DCI.

CPCGI confers neuroprotection by enhancing blood circulation and neurological function in cerebral ischemia/reperfusion rats

The current study used a rat middle cerebral artery occlusion (MCAO) model with the aim to explore the effects of compound porcine cerebroside and ganglioside injection (CPCGI) on brain ischemia/reperfusion injury in rats. Improvement in the infarct‑side microcirculation and the overall recovery of neurological function were detected by triphenyltetrazolium chloride staining, laser speckle blood flow monitoring, latex perfusion, immunofluorescence and immunoblotting. The results revealed that administration of CPCGI for 7 consecutive days following ischemic stroke contributed to the recovery of neurological function and the reduction of cerebral infarct volume in rats. Blood flow monitoring results demonstrated that the administration of CPCGI effectively promoted cerebral blood flow following stroke, and contributed to the protection of the ischemic side blood vessels. In addition, CPCGI treatment increased the numbers of new blood vessels in the peripheral ischemic region, and upregulated the expression levels of vascular endothelial growth factor, angiopoietin 1 and its receptor TEK receptor tyrosine kinase, fibroblast growth factor and Wnt signaling pathway‑associated proteins. Taken together, the present results indicated that CPCGI improved the blood circulation and neurological function following cerebral ischemia/reperfusion in rats.

Astaxanthin mitigates subarachnoid hemorrhage injury primarily by increasing sirtuin 1 and inhibiting the Toll-like receptor 4 signaling pathway

Inflammation plays a key role in the progression of subarachnoid hemorrhage (SAH). Here, we examined the effects of astaxanthin (ATX) on the inflammatory response and secondary damage after SAH and the underlying mechanisms of action. In vivo, a prechiasmatic cistern injection model was established in rats and mice. In addition, neuron-microglia cocultures were exposed to oxyhemoglobin to mimic SAH in vitro. Western blotting revealed that protein expression of TLR4 was markedly increased in microglia at 24 h after SAH, with consequent increases in the downstream molecules myeloid differentiation factor 88 and NF-кB. Treatment with ATX significantly inhibited the TLR4 activation, increased sirtuin 1 expression, and inhibited the subsequent inflammatory response both in vivo and in vitro. ATX also significantly decreased high-mobility group box 1 nuclear translocation and secretion in neurons, an effect that was reversed by the sirtuin 1-specific inhibitor sirtinol. ATX administered 4 h after SAH ameliorated cerebral inflammation, brain edema, and neuronal death and improved neurologic function. ATX reduced neuronal death but did not improve neurologic function in TLR4 knockout mice. These results suggest that ATX reduces the proinflammatory response and secondary brain injury after SAH, primarily by increasing sirtuin 1 levels and inhibiting the TLR4 signaling pathway.-Zhang, X., Lu, Y., Wu, Q., Dai, H., Li, W., Lv, S., Zhou, X., Zhang, X., Hang, C., Wang, J. Astaxanthin mitigates subarachnoid hemorrhage injury primarily by increasing sirtuin 1 and inhibiting the Toll-like receptor 4 signaling pathway.

Cerebroprotection by salvianolic acid B after experimental subarachnoid hemorrhage occurs via Nrf2- and SIRT1-dependent pathways

Salvianolic acid B (SalB), a natural polyphenolic compound extracted from the herb of Salvia miltiorrhiza, possesses antioxidant and neuroprotective properties and has been shown to be beneficial for diseases that affect vasculature and cognitive function. Here we investigated the protective effects of SalB against subarachnoid hemorrhage (SAH)-induced oxidative damage, and the involvement of underlying molecular mechanisms. In a rat model of SAH, SalB inhibited SAH-induced oxidative damage. The reduction in oxidative damage was associated with suppressed reactive oxygen species generation; decreased lipid peroxidation; and increased glutathione peroxidase, glutathione, and superoxide dismutase activities. Concomitant with the suppressed oxidative stress, SalB significantly reduced neurologic impairment, brain edema, and neural cell apoptosis after SAH. Moreover, SalB dramatically induced nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation and increased expression of heme oxygenase-1 and NADPH: quinine oxidoreductase-1. In a mouse model of SAH, Nrf2 knockout significantly reversed the antioxidant effects of SalB against SAH. Additionally, SalB activated sirtuin 1 (SIRT1) expression, whereas SIRT1-specific inhibitor sirtinol pretreatment significantly suppressed SalB-induced SIRT1 activation and Nrf2 expression. Sirtinol pretreatment also reversed the antioxidant and neuroprotective effects of SalB. In primary cultured cortical neurons, SalB suppressed oxidative damage, alleviated neuronal degeneration, and improved cell viability. These beneficial effects were associated with activation of the SIRT1 and Nrf2 signaling pathway and were reversed by sirtinol treatment. Taken together, these in vivo and in vitro findings suggest that SalB provides protection against SAH-triggered oxidative damage by upregulating the Nrf2 antioxidant signaling pathway, which may be modulated by SIRT1 activation.

Dexmedetomidine attenuated early brain injury in rats with subarachnoid haemorrhage by suppressing the inflammatory response: The TLR4/NF-κB pathway and the NLRP3 inflammasome may be involved in the mechanism

Early brain injury (EBI) plays a pivotal role in the prognosis of patients with subarachnoid haemorrhage (SAH). Dexmedetomidine (DEX), a highly selective α₂ receptor agonist, is reported to exert multiple protective effects in many neurological diseases. This study was designed to investigate whether DEX had neuroprotective functions in EBI after SAH, and to explore the possible mechanisms. The SAH model was established by an endovascular perforation in adult male Sprague-Dawley (SD) rats. DEX (25 µg/kg) or vehicle was administered intraperitoneally 2 h after SAH. Neurological deficits, brain oedema, inflammation, BBB damage, and cell apoptosis at 24 h after SAH were evaluated. Additionally, the expression of components of the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway, and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome were also assessed. We demonstrated that DEX treatment improved neurological scores, alleviated brain oedema, reduced the permeability of the blood-brain barrier (BBB), and up-regulated the expression of tight junction proteins. DEX treatment could reduce the neutrophil infiltration, microglial activation, and pro-inflammatory factor release. In addition, DEX alleviated cell apoptosis at 24 h after SAH. Notably, DEX could also suppress the activation of the TLR4/NF-κB pathway and the NLRP3 inflammasome. These findings suggested that treatment with DEX after SAH attenuated SAH-induced EBI, partially through the suppression of the TLR4/NF-κB pathway and the NLRP3 inflammasome.

Interleukin 6-Mediated Endothelial Barrier Disturbances Can Be Attenuated by Blockade of the IL6 Receptor Expressed in Brain Microvascular Endothelial Cells

Compromised blood-brain barrier (BBB) by dysregulation of cellular junctions is a hallmark of many cerebrovascular disorders due to the pro-inflammatory cytokines action. Interleukin 6 (IL6) is implicated in inflammatory processes and in secondary brain injury after subarachnoid hemorrhage (SAH) but its role in the maintenance of cerebral endothelium still requires a precise elucidation. Although IL6 has been shown to exert pro-inflammatory action on brain microvascular endothelial cells (ECs), the expression of one of the IL6 receptors, the IL6R is controversially discussed. In attempt to reach more clarity in this issue, we present here an evident baseline expression of the IL6R in BBB endothelium in vivo and in an in vitro model of the BBB, the cEND cell line. A significantly increased expression of IL6R and its ligand was observed in BBB capillaries 2 days after experimental SAH in mice. In vitro, we saw IL6 administration resulting in an intracellular and extracellular elevation of IL6 protein, which was accompanied by a reduced expression of tight and adherens junctions, claudin-5, occludin, and vascular-endothelial (VE-) cadherin. By functional assays, we could demonstrate IL6-incubated brain ECs to lose their endothelial integrity that can be attenuated by inhibiting the IL6R. Blockade of the IL6R by a neutralizing antibody has reconstituted the intercellular junction expression to the control level and caused a restoration of the transendothelial electrical resistance of the cEND cell monolayer. Our findings add depth to the current understanding of the involvement of the endothelial IL6R in the loss of EC integrity implicating potential therapy options.

Resveratrol Attenuates Early Brain Injury after Experimental Subarachnoid Hemorrhage via Inhibition of NLRP3 Inflammasome Activation

Previous studies have demonstrated resveratrol (RSV) has beneficial effects in early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the beneficial effects of RSV and the underlying mechanisms have not been clearly identified. The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation plays a crucial role in the EBI pathogenesis. The aim of this study was to investigate the role of RSV on the NLRP3 inflammasome signaling pathway and EBI in rats after SAH. A prechiasmatic cistern injection model was established in rats, and the primary cultured cortical neurons were stimulated with oxyhemoglobin (oxyHb) to induce SAH in vitro. It showed that the NLRP3 inflammasome components, including NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, mature interleukin-1β (IL-1β), and interleukin-18 (IL-18) were upregulated after SAH, and the enhanced NLRP3 after SAH was mainly located in microglia. Treatment with 60 or 90 mg/kg RSV after SAH dramatically inhibited the expression of NLRP3, but there was no significant difference in the expression of NLRP3 between the SAH + 60 mg/kg RSV and SAH + 90 mg/kg RSV groups. In addition, treatment with 30 mg/kg RSV did not significantly reduced the expression of NLRP3. We next evaluated the neuroprotective effects of RSV against SAH. We determined that SAH-induced NLRP3 inflammasome activation was significantly inhibited in the SAH + 60 mg/kg RSV group. Meanwhile, 60 mg/kg RSV administration could markedly inhibit microglia activation and neutrophils infiltration after SAH. Concomitant with the decreased cerebral inflammation, RSV evidently reduced cortical apoptosis, brain edema, and neurobehavioral impairment after SAH. In vitro experiments, RSV treatment also clearly protected primary cortical neurons against oxyHb insults, including reduced the proportion of neuronal apoptosis, alleviated neuronal degeneration, and improved cell viabilities. These in vitro data further confirm that RSV has an efficient neuroprotection against SAH. Taken together, these in vivo and in vitro findings suggested RSV could protect against EBI after SAH, at least partially via inhibiting NLRP3 inflammasome signaling pathway.