Linarin Protects the Kidney against Ischemia/Reperfusion Injury via the Inhibition of Bioactive ETS2/IL-12

Linarin attenuates hyperuricemic nephropathy by modulating Nrf2/Keap1 and TLR4/NF-κB signaling pathways: Linarin attenuates hyperuricemic nephropathy

BACKGROUND

Hyperuricemia (HUA) can lead to hyperuricemic nephropathy (HN) as a result of prolonged uric acid (UA) supersaturation, primarily characterized by excessive inflammation and oxidative stress. In clinical practice, the absence of specific drugs for HN treatment necessitates the use of urate-lowering drugs, despite their lack of reno-protective properties. Linarin, the principal pharmacological constituent of Chrysanthemum indicum L. (C. indicum L.), exhibits diverse bioactivities, including anti-inflammatory, antioxidant, and nephroprotective effects. However, there have been no reports on linarin's ability to mitigate HN, and the underlying mechanisms remain unexplored.

PURPOSE

This study aimed to investigate the mechanisms of linarin on ameliorating HN, with a particular emphasis on oxidative stress and inflammatory pathways.

METHODS

A HUA mouse model was developed using male ICR mice treated with hypoxanthine and potassium oxonate. Additionally, an adenosine-induced hyperuricemic cell model was established in NRK-52E cells. Following linarin treatment, serum UA levels and renal function parameters were assessed. The expression of proteins associated with UA production and excretion, oxidative stress, inflammation, and apoptosis was evaluated using western blot, immunohistochemical, and immunofluorescence analyses. Furthermore, Nrf2 knockout mice and Nrf2 inhibitor ML385 were utilized to investigate the mechanism of linarin on improving HN.

RESULTS

Linarin significantly decreased the serum UA levels, inhibited XO activity and regulated UA transporter in the HUA mice. Moreover, linarin reversed the renal index, serum BUN and Cr levels, along with the expression levels of KIM-1, apoptosis-related molecules. Additionally, linarin obviously reduced the levels of TNF-α, IL-1β and IL-6, and alleviated renal inflammatory via suppressing the TLR4, p-NF-κB and p-IκBα levels. Furthermore, linarin was able to reverse the levels of SOD and MDA, and the expression of Nrf2, Keap1, NQO1, and HO-1 to mitigate oxidative stress both in vitro and in vivo. Inhibition of Nrf2 further confirmed that the renoprotective effect of linarin was linked to the activation of Nrf2.

CONCLUSION

This study is the first to propose linarin as a potential natural compound for alleviating HN by modulating the Nrf2/Keap1 and TLR4/NF-κB signaling pathways, providing a promising strategy for HN.

Glycosides as Potential Medicinal Components for Ulcerative Colitis: A Review

Ulcerative colitis (UC) is a chronic, non-specific disease of unknown etiology. The disease develops mainly in the rectum or colon, and the main clinical symptoms include abdominal pain, diarrhea, and purulent bloody stools, with a wide variation in severity. The specific causative factors and pathogenesis of the disease are not yet clear, but most scholars believe that the disease is caused by the interaction of genetic, environmental, infectious, immune, and intestinal flora factors. As for the treatment of UC, medications are commonly used in clinical practice, mainly including aminosalicylates, glucocorticoids, and immunosuppressive drugs. However, due to the many complications associated with conventional drug therapy and the tendency for UC to recur, there is an urgent need to discover new, safer, and more effective drugs. Natural compounds with biodiversity and chemical structure diversity from medicinal plants are the most reliable source for the development of new drug precursors. Evidence suggests that glycosides may reduce the development and progression of UC by modulating anti-inflammatory responses, inhibiting oxidative stress, suppressing abnormal immune responses, and regulating signal transduction. In this manuscript, we provide a review of the epidemiology of UC and the available drugs for disease prevention and treatment. In addition, we demonstrate the protective or therapeutic role of glycosides in UC and describe the possible mechanisms of action to provide a theoretical basis for preclinical studies in drug development.

Relationship of Serum IL-12 to Inflammation, Hematoma Volume, and Prognosis in Patients With Intracerebral Hemorrhage

Objective. Inflammatory cascades and hematomas after intracerebral hemorrhage (ICH) cause brain tissue and neuronal damage. Interleukin-12 (IL-12) promotes brain inflammation, and regulates coagulation mediated by red blood cells and platelets. This study was designed to investigate the relationship of serum IL-12 to inflammation, hematoma volume, and prognosis in ICH patients. Methods. We recruited patients with ICH within 12 hours of symptom onset (n = 209) and measured their serum IL-12 levels. Patients with an increased National Institute of Health stroke scale (NIHSS) score ≥4 were defined as early neurological deterioration, and modified rankin scale (mRS) score >2 at 3 months after intracerebral hemorrhage was defined as poor prognosis. Results. Levels of serum IL-12 was positively correlated with the admission of NIHSS scores (r = 0.535, $P<0.001$ ), hematoma volume (r = 0.608, $P<0.001$ ), serum CRP levels (r = 0.561, $P<0.001$ ), and serum TNF-α levels (r = 0.533, $P<0.001$ ) in 209 cases ICH patients. Levels of IL-12 in ICH patients with early neurological deterioration (median: 82.9 versus 65.8, $P<0.001$ ) or with poor prognosis (median: 79.0 versus 65.3, $P<0.001$ ) were all significantly higher than those in other ICH patients. In addition, serum IL-12 levels could be used to differentiate ICH patients at risk for early neurological deterioration with an AUC of 0.788 (95% CI: 0.717–0.858) or ICH patients at risk for suffering from an unfavorable outcome with an AUC of 0.787 (95% CI: 0.722–0.851). Conclusion. Elevated admission serum IL-12 levels are closely related to the inflammation, hematoma volume, and prognosis in ICH patients. Substantializing serum IL-12 levels is a prognostic biomarker for ICH.

Linarin ameliorates dextran sulfate sodium-induced colitis in C57BL/6J mice via the improvement of intestinal barrier, suppression of inflammatory responses and modulation of gut microbiota

Linarin is a natural flavonoid compound found in Chrysanthemum indicum, Mentha species and other plants with various biological activities. The study aimed to investigate the protective effect of linarin supplementation on dextran sulfate sodium (DSS)-induced colitis in C57BL/6J mice and its potential mechanisms. The results showed that doses of linarin at 25 and 50 mg kg^-1 day^-1 alleviated the DSS-induced histopathological damage, and improved the mucosal layer and intestinal barrier function. Importantly, Linarin significantly suppressed the levels of myeloperoxidase activity and pro-inflammatory cytokines (IL-6, TNF-α, IFN-γ and IL-1β) in the colon, and enhanced the mRNA level of anti-inflammatory cytokine (IL-10). Moreover, 50 mg kg^-1 day^-1 linarin reversed the gut microbiota damaged by DSS, including Alistipes, Rikenella and Clostridia UCG-014_norank. Linarin also partly increased the relative abundance of short-chain fatty acids (SCFAs)-producing bacteria, including Lactobacillus, Roseburia, Parabacteroides and Blautia, and elevated the contents of SCFAs. Collectively, linarin attenuates DSS-induced colitis in mice, suggesting that linarin may be a promising nutritional strategy for reducing inflammatory bowel disease.

A Linarin Derivative Protects against Ischemia-Induced Neuronal Injury in Mice by Promoting Cerebral Blood Flow Recovery via KDELR-Dependent CSPG4 Activation

The cerebral ischemic microvascular response and collateral circulation compensatory capacity are important for the outcome of ischemic stroke. Here, we sought to evaluate the effect of a linarin derivate 4′-benzylapigenin-7-β-rutinoside (BLR) on neurological function and cerebral blood flow restoration in ischemic stroke. A mouse model of middle cerebral artery occlusion (30 min) with reperfusion (24 h) was used to mimic ischemic stroke in vivo, and 2,3,5-triphenyltetrazolium chloride (TTC) staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays, and immunofluorescence microscopy were used to assess the protective effects of BLR on infarct volume, neurological function, neuronal apoptosis, and inflammatory damage. Cerebral blood flow was assayed by laser speckle contrast imaging. Double immunostaining of GFAP-collagen IV and brain lucidification were performed to determine the protective effects of BLR on the disruption of brain vasculature. Differential gene expression was assessed by RNA sequencing. Coimmunoprecipitation and western blotting were used to explore the mechanism of BLR-induced neuroprotection. The results of in vivo experiments showed that BLR administration after reperfusion onset reduced infarct volume, improved neurological function, and decreased the neural cell apoptosis and inflammatory response in the ischemic brain, which was accompanied by increased cerebral blood flow and reduced detachment of astrocyte endfeet from the capillary basement membrane. The RNA sequencing data showed that BLR promoted the upregulation of extracellular matrix and angiogenesis pathway-related genes; in particular, BLR significantly increased the expression of the chondroitin sulfate proteoglycan 4 (CSPG4) gene, enhanced the membrane location of CSPG4, and promoted its downstream signaling protein expression, which is associated with KDEL receptor (KDELR) activation. In addition, activated KDELR further increased the phosphorylation of mitogen-activated protein kinases after BLR treatment. Taken together, our data showed that BLR could protect against ischemic brain injury and may serve as a new promising therapeutic candidate drug for ischemic stroke, and that KDELR might act as both a sensor and effector to activate CSPG4 to increase cerebral blood flow.

Phosphatidylserine-Specific Phospholipase A1 Alleviates Lipopolysaccharide-Induced Macrophage Inflammation by Inhibiting MAPKs Activation

Macrophages are key in innate immune responses and play vital roles in homeostasis and inflammatory diseases. Phosphatidylserine-specific phospholipase A1 (PS-PLA1) is a specific phospholipase which hydrolyzes fatty acid from the sn-1 position of phosphatidylserine (PS) to produce lysophosphatidylserine (lysoPS). Both PS and lysoPS are associated with activation of immune cells including macrophages. However, the effect of PS-PLA1 on macrophage inflammation remains unclear. The purpose of this study is to evaluate the role of PS-PLA1 in lipopolysaccharide (LPS)-induced macrophage inflammation. Alterations of PS-PLA1 expression in LPS-stimulated RAW264.7 macrophages were investigated via Western blot. PS-PLA1 stable knockdown and overexpression RAW264.7 cell lines were generated by infecting cells with appropriate lentiviral vectors, respectively. PS-PLA1 expression was found to be dramatically upregulated in RAW264.7 macrophages after LPS stimulation. PS-PLA1 knockdown promotes while PS-PLA1 overexpression ameliorates the release of TNF-α, IL-1β and nitric oxide from RAW264.7 cells and M1 macrophage polarization. Additionally, PS-PLA1 knockdown facilitates phosphorylation of p38, ERK and JNK, while PS-PLA1 overexpression attenuates their phosphorylation. Moreover, mitogen-activated protein kinase (MAPK) inhibitors blocks the release of TNF-α and IL-1β in PS-PLA1 knockdown RAW264.7 cells after LPS stimulation. These findings suggest PS-PLA1 ameliorates LPS-induced macrophage inflammation by inhibiting MAPKs activation, and PS-PLA1 might be considered as a target for modulating macrophage inflammation.

microRNA-145-5p attenuates acute lung injury via targeting ETS2

The protective effect of microRNA (miR)-145-5p in acute lung injury (ALI) has been discovered previously. Thus, in this study, we attempted to further investigate the mechanism of miR-145-5p in ALI through the downstream E26 transformation-specific proto-oncogene 2 (ETS2)/transforming growth factor β1 (TGF-β1)/Smad pathway. A lipopolysaccharide (LPS)-induced ALI rat model was established. The expression of miR-145-5p in ALI rat lung tissues was up-regulated. Afterward, pathological damage in the lung tissue, the wet/dry (W/D) ratio, apoptosis, and serum inflammatory factor contents were observed. miR-145-5p, ETS2, TGF-β1, Smad2/3, and phosphorylated Smad2/3 levels were measured in rats. miR-145-5p expression was down-regulated, ETS2 expression was up-regulated, and the TGF-β1/Smad pathway was activated in LPS-exposed rats. Overexpression of miR-145-5p inactivated the TGF-β1/Smad pathway and attenuated ALI, as reflected by relieved pathological damage, a decreased W/D ratio, reduced apoptosis, and suppressed inflammatory response. In contrast, loss of miR-145-5p or elevated ETS2 levels worsened ALI and activated the TGF-β1/Smad pathway. Moreover, elevation of ETS2 diminished miR-145-5p-mediated protection against ALI. Evidently, miR-145-5p negatively regulates ETS2 expression and inactivates the TGF-β1/Smad pathway to ameliorate ALI in rats.

Linarin, a Glycosylated Flavonoid, with Potential Therapeutic Attributes: A Comprehensive Review

Many flavonoids, as eminent phenolic compounds, have been commercialized and consumed as dietary supplements due to their incredible human health benefits. In the present study, a bioactive flavone glycoside linarin (LN) was designated to comprehensively overview its phytochemical and biological properties. LN has been characterized abundantly in the Cirsium, Micromeria, and Buddleja species belonging to Asteraceae, Lamiaceae, and Scrophulariaceae families, respectively. Biological assessments exhibited promising activities of LN, particularly, the remedial effects on central nervous system (CNS) disorders, whereas the remarkable sleep enhancing and sedative effects as well as AChE (acetylcholinesterase) inhibitory activity were highlighted. Of note, LN has indicated promising anti osteoblast proliferation and differentiation, thus a bone formation effect. Further biological and pharmacological assessments of LN and its optimized semi-synthetic derivatives, specifically its therapeutic characteristics on osteoarthritis and osteoporosis, might lead to uncovering potential drug candidates.