Methylglyoxal-derived advanced glycation end products induce matrix metalloproteinases through activation of ERK/JNK/NF-κB pathway in kidney proximal epithelial cells

Roles of Matrix Metalloproteinases and Their Natural Inhibitors in Metabolism: Insights into Health and Disease

Matrix metalloproteinases (MMPs) are a family of zinc-activated peptidases that can be classified into six major classes, including gelatinases, collagenases, stromelysins, matrilysins, membrane type metalloproteinases, and other unclassified MMPs. The activity of MMPs is regulated by natural inhibitors called tissue inhibitors of metalloproteinases (TIMPs). MMPs are involved in a wide range of biological processes, both in normal physiological conditions and pathological states. While some of these functions occur during development, others occur in postnatal life. Although the roles of several MMPs have been extensively studied in cancer and inflammation, their function in metabolism and metabolic diseases have only recently begun to be uncovered, particularly over the last two decades. This review aims to summarize the current knowledge regarding the metabolic roles of metalloproteinases in physiology, with a strong emphasis on adipose tissue homeostasis, and to highlight the consequences of impaired or exacerbated MMP actions in the development of metabolic disorders such as obesity, fatty liver disease, and type 2 diabetes.

Azilsartan Modulates HMGB1/NF-κB/p38/ERK1/2/JNK and Apoptosis Pathways during Renal Ischemia Reperfusion Injury

Renal ischemia/reperfusion (IR) injury is characterized by an unexpected impairment of blood flow to the kidney. Azilsartan is an angiotensin receptor blocker that is approved for the management of hypertension. The present study aimed to investigate, on molecular basics, the nephroprotective activity of azilsartan on renal IR injury in rats. Rats were assigned into four groups: (1) Sham group, (2) Azilsartan group, (3) IR group, and (4) IR/Azilsartan-treated group. Histological examination and renal function were evaluated. Levels of KIM-1, HMGB1, caspase 3, GPX, SOD, NF-κB, and p53 proteins were investigated using ELISA. mRNA levels of IL-1β, IL6, IL10, TNF-α, NF-κB, p53, and bax were assessed by qRT-PCR. Expression of p38, JNK, and ERK1/2 proteins was investigated by Western blotting. IR injury resulted in tissue damage, elevation of creatinine, BUN, KIM-1, HMGB1, caspase 3, NF-κB, and p53 levels, decreasing GPX and SOD activities, and up-regulation of NF-κB, IL-1β, IL6, TNF-α, p53, and bax genes. Furthermore, it up-regulated the expression of phosphorylated/total ratio of p38, ERK1/2, and JNK proteins. Interestingly, treatment of the injured rats with azilsartan significantly alleviated IR injury-induced histopathological and biochemical changes. It reduced the creatinine, BUN, KIM-1, HMGB1, caspase-3, NF-κB, and p53 levels, elevated GPX and SOD activities, down-regulated the expression of NF-κB, IL-1β, IL6, TNF-α, p53, and bax genes, and up-regulated IL10 gene expression. Furthermore, it decreased the phosphorylated/total ratio of p38, ERK1/2, and JNK proteins. Azilsartan exhibited nephroprotective activity in IR-injured rats via its antioxidant effect, suppression of inflammation, attenuation of apoptosis, and inhibition of HMGB1/NF-κB/p38/ERK1/2/JNK signaling pathway.

Activation of Nrf2 by Esculetin Mitigates Inflammatory Responses through Suppression of NF-κB Signaling Cascade in RAW 264.7 Cells

Inflammation is a major root of several diseases such as allergy, cancer, Alzheimer’s, and several others, and the present state of existing drugs provoked researchers to search for new treatment strategies. Plants are regarded to be unique sources of active compounds holding pharmacological properties, and they offer novel designs in the development of therapeutic agents. Therefore, this study aimed to explore the anti-inflammatory mechanism of esculetin in lipoteichoic acid (LTA)-induced macrophage cells (RAW 264.7). The relative expression of inducible nitric oxide synthase (iNOS), nitric oxide (NO) production and COX-2 expression were intensified in LTA-induced RAW cells. The phosphorylation status of mitogen-activated protein kinases (extracellular signal-regulated kinase (ERK)1/2, p38 MAPK, and c-Jun N-terminal kinase (JNK)) and nuclear factor kappa B (NF-κB) p65 were detected by using Western blot assay. The nuclear translocation of p65 was assessed by confocal microscopic image analysis. Esculetin significantly and concentration-dependently inhibited LTA-induced NO production and iNOS expression, but not COX-2 expression, in RAW cells. Esculetin was not effective in LTA-induced MAPK molecules (ERK, p38 and JNK). However, esculetin recovered LTA-induced IκBα degradation and NF-κB p65 phosphorylation. Moreover, esculetin at a higher concentration of 20 µM evidently inhibited the nuclear translocation of NF-κB p65. At the same high concentration, esculetin augmented Nrf2 expression and decreased DPPH radical generation in RAW 264.7 cells. This study exhibits the value of esculetin for the treatment of LTA-induced inflammation by targeting NF-κB signaling pathways via its antioxidant properties.

Targeted therapy of cognitive deficits in fragile X syndrome

Breaking an impasse in finding mechanism-based therapies of neuropsychiatric disorders requires a strategic shift towards alleviating individual symptoms. Here we present a symptom and circuit-specific approach to rescue deficits of reward learning in Fmr1 knockout mice, a model of Fragile X syndrome (FXS), the most common monogenetic cause of inherited mental disability and autism. We use high-throughput, ecologically-relevant automated tests of cognition and social behavior to assess effectiveness of the circuit-targeted injections of designer nanoparticles, loaded with TIMP metalloproteinase inhibitor 1 protein (TIMP-1). Further, to investigate the impact of our therapeutic strategy on neuronal plasticity we perform long-term potentiation recordings and high-resolution electron microscopy. We show that central amygdala-targeted delivery of TIMP-1 designer nanoparticles reverses impaired cognition in Fmr1 knockouts, while having no impact on deficits of social behavior, hence corroborating symptom-specificity of the proposed approach. Moreover, we elucidate the neural correlates of the highly specific behavioral rescue by showing that the applied therapeutic intervention restores functional synaptic plasticity and ultrastructure of neurons in the central amygdala. Thus, we present a targeted, symptom-specific and mechanism-based strategy to remedy cognitive deficits in Fragile X syndrome.

Levilactobacillus brevis KU15151 Inhibits Staphylococcus aureus Lipoteichoic Acid-Induced Inflammation in RAW 264.7 Macrophages

Inflammation is a host defense response to harmful agents, such as pathogenic invasion, and is necessary for health. Excessive inflammation may result in the development of inflammatory disorders. Levilactobacillus brevis KU15151 has been reported to exhibit probiotic characteristics and antioxidant activities, but the effect of this strain on inflammatory responses has not been determined. The present study aimed to investigate the anti-inflammatory potential of L. brevis KU15151 in Staphylococcus aureus lipoteichoic acid (aLTA)-induced RAW264.7 macrophages. Treatment with L. brevis KU15151 reduced the production of nitric oxide and prostaglandin E₂ by suppressing the expression of inducible nitric oxide synthase and cyclooxygenase-2. Additionally, the production of proinflammatory cytokines including tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, decreased after treatment with L. brevis KU15151 in aLTA-stimulated RAW 264.7 cells. Furthermore, this strain alleviated the activation of nuclear factor-κB and mitogen-activated protein kinase signaling pathways. Moreover, the generation of reactive oxygen species was downregulated by treatment with L. brevis KU15151. These results demonstrate that L. brevis KU15151 possesses an inhibitory effect against aLTA-mediated inflammation and may be employed as a functional probiotic for preventing inflammatory disorders.

Roles, molecular mechanisms, and signaling pathways of TMEMs in neurological diseases

Transmembrane protein family members (TMEMs) span the entire lipid bilayer and act as channels that allow the transport of specific substances through biofilms. The functions of most TMEMs are unexplored. Numerous studies have shown that TMEMs are involved in the pathophysiological processes of various nervous system diseases, but the specific mechanisms of TMEMs in the pathogenesis of diseases remain unclear. In this review, we discuss the expression, physiological functions, and molecular mechanisms of TMEMs in brain tumors, psychiatric disorders, abnormal motor activity, cobblestone lissencephaly, neuropathic pain, traumatic brain injury, and other disorders of the nervous system. Additionally, we propose that TMEMs may be used as prognostic markers and potential therapeutic targets in patients with various neurological diseases.

Ecklonia cava Extract Exerts Anti-Inflammatory Effect in Human Gingival Fibroblasts and Chronic Periodontitis Animal Model by Suppression of Pro-Inflammatory Cytokines and Chemokines

Periodontitis is one of the most common chronic inflammatory diseases. The anti-inflammatory effect of the extract from brown algae Ecklonia cava was analyzed in lipopolysaccharide (LPS)-stimulated human gingival fibroblasts (HGF-1), the most abundant cells in gingival tissue. The gene expressions of cyclooxygenase-2 and interleukin-6 were decreased by 78 and 50%, respectively, at 100 μg/mL Ecklonia cava extract (ECE) treatment. The gene expressions of matrix metalloproteases (MMP-2 and MMP-8) and chemokines (macrophage inflammatory protein 1-alpha and stromal cell-derived factor 1) were also significantly down-regulated by ECE treatment (p < 0.05). The increased reactive oxygen species (ROS) production in HGF-1 cells by LPS stimulation was decreased by 30% at 100 μg/mL ECE treatment. The mitogen-activated protein kinase pathway and the nuclear factor-kappa B (NF-κB) signal activated by ROS were suppressed by ECE in a dose-dependent manner. ECE treatment (400 mg/kg, 8 weeks) significantly improved alveolar bone resorption in the ligature-induced chronic periodontitis rat model. ECE supplementation also lowered elevated mRNA expression of the receptor activator of nuclear factor-kappa B (RANKL)/osteoprotegerin (OPG) in the gingival tissue (p < 0.05). Therefore, ECE mitigated gingival tissue destruction and bone resorption associated with chronic periodontitis condition.

Dietary polyphenols inhibit plasma protein arabinosylation: Biomolecular interaction of genistein and ellagic acid with serum albumins

The mode of interaction of polyphenolic compounds like genistein (GTN) and ellagic acid (EGA) with human and bovine serum albumin (HSA and BSA, respectively) was found to differ significantly. Stern-Volmer (SV) analysis of the fluorescence quenching data revealed that the binding strength of EGA (1.9 ± 0.09 × 10⁵ M^-1) to HSA is about one order of magnitude higher than GTN (2.24 ± 0.06 × 10⁴ M^-1). While the static quenching of HSA fluorescence was found to proceed through simple Stern-Volmer (SV) mechanism, a quenching sphere-of-action model was indispensable for BSA. Temperature dependent fluorescence along with a series of other biophysical experiments and ensemble docking calculation revealed that EGA and GTN bind to the serum proteins primarily through the entropy driven process. The α-helical content and the microenvironment near Trp residue of HSA and BSA did not show any appreciable change due to the binding of either GTN or EGA. Interestingly, both GTN and EGA were found to inhibit the formation of advanced glycated end (AGE) product of serum proteins up to the extent of 70-90% within 12-24 h. Relatively moderate binding propensity along with the anti-glycation ability of the polyphenols confirmed that GTN and EGA can be used either as an alternative or towards development of suitable drugs in the prevention of many diabetic-related complications.

Methylglyoxal-Derived Advanced Glycation End Product (AGE4)-Induced Apoptosis Leads to Mitochondrial Dysfunction and Endoplasmic Reticulum Stress through the RAGE/JNK Pathway in Kidney Cells

Advanced glycation end products (AGEs) are formed via nonenzymatic reactions between reducing sugars and proteins. Recent studies have shown that methylglyoxal, a potent precursor for AGEs, causes a variety of biological dysfunctions, including diabetes, inflammation, renal failure, and cancer. However, little is known about the function of methylglyoxal-derived AGEs (AGE4) in kidney cells. Therefore, we verified the expression of endoplasmic reticulum (ER) stress-related genes and apoptosis markers to determine the effects of AGE4 on human proximal epithelial cells (HK-2). Moreover, our results showed that AGE4 induced the expression of apoptosis markers, such as Bax, p53, and kidney injury molecule-1, but downregulated Bcl-2 and cyclin D1 levels. AGE4 also promoted the expression of NF-κB, serving as a transcription factor, and the phosphorylation of c-Jun NH₂-terminal kinase (JNK), which induced cell apoptosis and ER stress mediated by the JNK inhibitor. Furthermore, AGE4 induced mitochondrial dysfunction by inducing the permeabilization of the mitochondrial membrane and ATP synthesis. Through in vitro and in vivo experiments, this study provides a new perspective on renal dysfunction with regard to the AGE4-induced RAGE /JNK signaling pathway, which leads to renal cell apoptosis via the imbalance of mitochondrial function and ER stress in kidney damage.

Diabetic nephropathy induced by methylglyoxal: gallic acid regulates kidney microRNAs and glyoxalase1-Nrf2 in male mice

BACKGROUND

Methylglyoxal (MG) has been reported to be a toxic by-product of glycolysis and intracellular stressor compound. This study investigated the effects of gallic acid (GA) against diabetic nephropathy (DN) induced by MG in male mice.

METHODS

DN was induced by methylglyoxal (600 mg/kg/day, p.o.) treated for 28 consecutive days. The animals received GA (30 mg/kg/day, p.o.) and metformin (MT) (150 mg/kg/day, p.o.) for 7 consecutive days after diabetes induction. Biochemical assays, antioxidant evaluation, microRNAs associated with fibrosis, endoplasmic reticulum stress, and histopathological analysis were examined.

RESULTS

MG increased malondialdehyde, albuminuria, Nrf2, miR-192 and miR-204 expression in diabetic groups and GA decreased them. Superoxide dismutase, catalase, glyoxalase1, and miR-29a expression decreased in diabetic groups and increased in treatment with GA.

CONCLUSION

Our results revealed that GA has improved DN induced by MG via amelioration of biochemical indices, histopathological aspects, oxidative stress and microRNAs associated with endoplasmic reticulum stress and fibrosis.

Inhibitory effect of caffeic acid on advanced glycation end product-induced renal fibrosis in vitro: A potential therapeutic target

Advanced glycation end products (AGEs) are formed from amino acids and reducing sugars through nonenzymatic Maillard reaction. AGEs are known to induce oxidative stress, which may cause fibrosis or cancer. In this study, we investigated the protective effect of caffeic acid (CA) on AGE-mediated kidney epithelial to mesenchymal transition (EMT) in human HK-2 cells. Exposure to 100 µg/mL of AGEs by kidney epithelial cells raised the production of reactive oxygen species by 5.2-fold and decreased levels of glutathione. In addition, cardamonin, a β-catenin inhibitor, was used to determine the signaling pathway for β-catenin in which cardamonin inhibited the AGEs-induced translocation of β-catenin into the nucleus, resulting in an inhibition of the EMT process. Similarly, our findings showed that, close to the control level, CA treatment decreased AGE-mediated oxidative stress, loss of E-cadherin expression, and overexpression of α-smooth muscle actin and fibronectin by inactivation of the β-catenin pathway. Furthermore, AGE treatment enhanced the expression of collagen type I (1.99-fold) as well as the activity of metalloproteinases 2 (1.86-fold) and 9 (2.79-fold), but such increase was inhibited by the pretreatment of CA. In conclusion, this study determined the inhibitory effect of CA on AGE-induced β-catenin signaling, which prevented the occurrence of EMT in kidney epithelial cells. This suggests that CA may be a potential target for AGE-induced renal fibrosis. PRACTICAL APPLICATION: Exposure of kidney epithelial cells to advanced glycation end products (AGEs) leads to a rise in reactive oxygen species and a decrease in glutathione, thereby increasing oxidative stress that may cause fibrosis. However, treatment of kidney cells with caffeic acid (CA) prior to their exposure to AGEs lowers oxidative stress and decreases fibrosis. This research reveals the beneficial influence of CA on renal fibrosis in laboratory-cultured kidney cells (in vitro), which makes CA a potential therapeutic target for AGE-induced fibrosis.