Catalpol ameliorates advanced glycation end product-induced dysfunction of glomerular endothelial cells via regulating nitric oxide synthesis by inducible nitric oxide synthase and endothelial nitric oxide synthase

Iridoids modulate inflammation in diabetic kidney disease: A review

In recent years, preclinical research on diabetic kidney disease (DKD) has surged to the forefront of scientific and clinical attention. DKD has become a pervasive complication of type 2 diabetes. Given the complexity of its etiology and pathological mechanisms, current interventions, including drugs, dietary modifications, exercise, hypoglycemic treatments and lipid-lowering methods, often fall short in achieving desired therapeutic outcomes. Iridoids, primarily derived from the potent components of traditional herbs, have been the subject of long-standing research. Preclinical data suggest that iridoids possess notable renal protective properties; however, there has been no summary of the research on their efficacy in the management and treatment of DKD. This article consolidates findings from in vivo and in vitro research on iridoids in the context of DKD and highlights their shared anti-inflammatory activities in treating this condition. Additionally, it explores how certain iridoid components modify their chemical structures through the regulation of intestinal flora, potentially bolstering their therapeutic effects. This review provides a focused examination of the mechanisms through which iridoids may prevent or treat DKD, offering valuable insights for future research endeavors. Please cite this article as: Zhou TY, Tian N, Li L, Yu R. Iridoids modulate inflammation in diabetic kidney disease: A review. J Integr Med. 2024; 22(3): 210-222.

Catalpol Prevents Glomerular Angiogenesis Induced by Advanced Glycation End Products via Inhibiting Galectin-3

OBJECTIVE

The main characteristics of diabetic nephropathy (DN) at the early stage are abnormal angiogenesis of glomerular endothelial cells (GECs) and macrophage infiltration. Galectin-3 plays a pivotal role in the pathogenesis of DN via binding with its ligand, advanced glycation end products (AGEs). Catalpol, an iridoid glucoside extracted from Rehmannia glutinosa, has been found to ameliorate vascular inflammation, reduce endothelial permeability, and protect against endothelial damage in diabetic milieu. However, little is known about whether catalpol could exert an anti-angiogenesis and anti-inflammation effect induced by AGEs.

METHODS

Mouse GECs (mGECs) and RAW 264.7 macrophages were treated with different concentrations of AGEs (0, 50, 100, 200 and 400 µg/mL) for different time (0, 6, 12, 24 and 48 h) to determine the optimal concentration of AGEs and treatment time. Cells were treated with catalpol (10 µmol/L), GB1107 (1 µmol/L, galectin-3 inhibitor), PX-478 (50 µmol/L, HIF-1α inhibitor), adenovirus-green fluorescent protein (Ad-GFP) [3×107 plaque-forming unit (PFU)/mL] or Ad-galectin-3-GFP (2×108 PFU/mL), which was followed by incubation with 50 µg/mL AGEs. The levels of galectin-3, vascular endothelial growth factor A (VEGFA) and pro-angiogenic factors angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), tunica interna endothelial cell kinase-2 (Tie-2) were detected by enzymelinked immunosorbent assay (ELISA). Cell counting kit-8 (CCK-8) assay was used to evaluate the proliferation of these cells. The expression levels of galectin-3, vascular endothelial growth factor receptor 1 (VEGFR1), VEGFR2, and hypoxia-inducible factor-1α (HIF-1α) in mGECs and those of galectin-3 and HIF-1α in RAW 264.7 macrophages were detected by Western blotting and immunofluorescence (IF) staining. The rat DN model was established. Catalpol (100 mg/kg) or GB1107 (10 mg/kg) was administered intragastrically once a day for 12 weeks. Ad-galectin-3-GFP (6×107 PFU/mL, 0.5 mL) or Ad-GFP (6×106 PFU/mL, 0.5 mL) was injected into the tail vein of rats 48 h before the sacrifice of the animals. The expression of galectin-3, VEGFR1, VEGFR2, and HIF-1α in renal cortices was analyzed by Western blotting. The expression of galectin-3, F4/80 (a macrophage biomarker), and CD34 (an endothelium biomarker) in renal cortices was detected by IF staining, and collagen accumulation by Masson staining.

RESULTS

The expression levels of galectin-3 and VEGFA were significantly higher in mGECs and RAW 264.7 macrophages treated with 50 µg/mL AGEs for 48 h than those in untreated cells. Catalpol and GB1107 could block the AGEs-induced proliferation of mGECs and RAW 264.7 macrophages. Over-expression of galectin-3 was found to reduce the inhibitory effect of catalpol on the proliferation of cells. Catalpol could significantly decrease the levels of Ang-1, Ang-2 and Tie-2 released by AGEs-treated mGECs, which could be reversed by over-expression of galectin-3. Catalpol could significantly inhibit AGEs-induced expression of galectin-3, HIF-1α, VEGFR1, and VEGFR2 in mGECs. The inhibitory effect of catalpol on galectin-3 in AGEs-treated mGECs was impaired by PX-478. Moreover, catalpol attenuated the AGEs-activated HIF-1α/galectin-3 pathway in RAW 264.7 macrophages, which was weakened by PX-478. Additionally, catalpol significantly inhibited the expression of galectin-3, macrophage infiltration, collagen accumulation, and angiogenesis in the kidney of diabetic rats. Over-expression of galectin-3 could antagonize these inhibitory effects of catalpol.

CONCLUSION

Catalpol prevented the angiogenesis of mGECs and macrophage proliferation via inhibiting galectin-3. It could prevent the progression of diabetes-induced renal damage.

Natural Monoterpenes as Potential Therapeutic Agents against Atherosclerosis

Traditional herbal medicines based on natural products play a pivotal role in preventing and managing atherosclerotic diseases, which are among the leading causes of death globally. Monoterpenes are a large class of naturally occurring compounds commonly found in many aromatic and medicinal plants. Emerging evidence has shown that monoterpenes have many biological properties, including cardioprotective effects. Remarkably, an increasing number of studies have demonstrated the therapeutic potential of natural monoterpenes to protect against the pathogenesis of atherosclerosis. These findings shed light on developing novel effective antiatherogenic drugs from these compounds. Herein, we provide an overview of natural monoterpenes' effects on atherogenesis and the underlying mechanisms. Monoterpenes have pleiotropic and multitargeted pharmacological properties by interacting with various cell types and intracellular molecular pathways involved in atherogenesis. These properties confer remarkable advantages in managing atherosclerosis, which has been recognized as a multifaceted vascular disease. We also discuss limitations in the potential clinical application of monoterpenes as therapeutic agents against atherosclerosis. We propose perspectives to give new insights into future preclinical research and clinical practice regarding natural monoterpenes.

A systematic review on botany, processing, application, phytochemistry and pharmacological action of Radix Rehmnniae

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Rehmanniae (RR) is the tuber root of Rehmannia glutionsa Libosch, which was firstly recorded in Shennong's Classic of Materia Medica (⟪⟫). RR is a non-toxic and wide used traditional Chinese medicine. RR has the effect of clearing heat, generating essence, cooling blood, stopping bleeding, nourishing yin and blood, and filling marrow. It is used in clinic in the form of processed decoction pieces, including Dry Radix Rehmnniae (DRR) and Rehmanniae Radix Praeparata (RRP). The application of RR in traditional Chinese medicine (TCM) prescriptions can treat various diseases, such as anemia, irregular menstruation, deficiency of liver yin, renal failure and so on.

AIM OF REVIEW

This paper aims to provide a comprehensive and productive review of RR, which mainly contains botanical characteristics, processing methods, traditional application, chemical composition, quality control and pharmacological action.

MATERIALS AND METHODS

Literature search was conducted through the Web of Science, Baidu Scholar, ScienceDirect, PubMed, CNKI, and WanFang DATA using the keywords "Radix Rehmnniae", "Rehmanniae Radix Praeparata", "processing", "clinical application", "chemical composition", "quality control", and "pharmacological action". In addition, information was collected from relevant textbooks, reviews, and documents.

RESULTS

RR is a traditional Chinese herbal medicine with clinical value and rich resources. More than 100 components have been isolated and identified from RR. It has multiple pharmacological actions, such as hemostasis, antioxidation, anti-osteoporosis, lowering blood sugar, improving renal function, anti-inflammation, protecting neuronal function, antidepression and anti-anxiety. DRR and RRP are two different processed products of RR. After processing, there are great changes in property, taste, efficacy, clinical application, chemical composition and pharmacological action. At present, identifying chemical constituents of RR and its medicinal value has been deeply studied. However, there is a lack of research on the reasons for the differences in pharmacological effects between DRR and RRP. The reasons for these differences need to be further verified. Catalpol, the active component of RR, has been studied extensively in the literature, but the pharmacological effects of catalpol cannot represent the pharmacological effects of the whole RR. In the future, effective components such as rehmannioside D, polysaccharide, total glycosides, and effective parts in RR need to be further studied and developed. The pharmacodynamic material basis and mechanism of RR need to be further discussed. The scientific connotation and processing methods of RRP need to be studied and standardized.

The Pathophysiology of H2S in Renal Glomerular Diseases

Renal glomerular diseases such as glomerulosclerosis and diabetic nephropathy often result in the loss of glomerular function and consequently end-stage renal disease. The glomerulus consists of endothelial cells, mesangial cells and glomerular epithelial cells also referred to as podocytes. A fine-tuned crosstalk between glomerular cells warrants control of growth factor synthesis and of matrix production and degradation, preserving glomerular structure and function. Hydrogen sulfide (H2S) belongs together with nitric oxide (NO) and carbon monoxide (CO) to the group of gasotransmitters. During the last three decades, these higher concentration toxic gases have been found to be produced in mammalian cells in a well-coordinated manner. Recently, it became evident that H2S and the other gasotransmitters share common targets as signalling devices that trigger mainly protective pathways. In several animal models, H2S has been demonstrated as a protective factor in the context of kidney disorders, in particular of diabetic nephropathy. Here, we focus on the synthesis and action of H2S in glomerular cells, its beneficial effects in the glomerulus and its action in the context of the other gaseous signalling molecules NO and CO.

AGE/RAGE in diabetic kidney disease and ageing kidney

Diabetic kidney disease (DKD) is the primary cause of chronic kidney disease that inevitably progress to end-stage kidney disease. Intervention strategies such as blood glucose control is effective for preventing DKD, but many patients with DKD still reach end-stage kidney disease. Although comprehensive mechanisms shed light on the progression of DKD, the most compelling evidence has highlighted that hyperglycemia-related advanced glycation end products (AGEs) formation plays a central role in the pathogenesis of DKD. Pathologically, accumulation of AGEs-mediated receptor for AGEs (RAGE) triggers oxidative stress and inflammation, which is the major deleterious effect of AGEs in host and intestinal microenvironment of diabetic and ageing conditions. The activation of AGEs-mediated RAGE could evoke nicotinamide adenine dinucleotide phosphate oxidase-induced reactive oxygen and nitrogen species production and subsequently give rise to oxidative stress in DKD and ageing kidney. Therefore, targeting RAGE with its ligands mediated oxidative stress and chronic inflammation is considered as an additional intervention strategy for DKD and ageing kidney. In this review, we summarize AGEs/RAGE-mediated oxidative stress and inflammation signaling pathways in DKD and ageing kidney, discussing opportunities and challenges of targeting at AGEs/RAGE-induced oxidative stress that could hold the promising potential approach for improving DKD and ageing kidney.

Phytochemicals against anti-diabetic complications: targeting the advanced glycation end product signaling pathway

The role of advanced glycation end products (AGEs) is not limited to diabetes and diabetes-related complications. There are multiple modulators, including the receptor for advanced glycation end products, high mobility group box 1, glyoxalase 1, nuclear factor-kappa B, tumor necrosis factor-α, chronic unpredictable stress, reactive oxygen species, and inflammatory cytokines, which interact with AGE signaling and control diabetes, modulating these interacting modulators. The progression of diabetes, as well as related complications, can be controlled and treated. Natural products rich in bioactive constituents can interact with AGEs and their related mediators through various signaling cascades, thereby controlling and preventing the progression of diabetes. This review provides a deeper assessment of the signaling pathway, interactions between phytochemicals and AGEs, and its mediators, to develop a multifold therapeutic approach to prevent and treat diabetes and its related complications.

Catalpol protects rat ovarian granulosa cells against oxidative stress and apoptosis through modulating the PI3K/Akt/mTOR signaling pathway

Disrupted follicular development may result in increased follicular atresia, which is a crucial mechanism of various ovarian pathologies. It has been demonstrated that oxidative stress is associated with disrupted follicular development. Catalpol is a natural compound that has been found to possess antioxidative stress. However, the effects of catalpol on oxidative stress-induced disrupted follicular development remain unclear. In the present study, we evaluated the protective effect of catalpol on hydrogen peroxide (H₂O₂)-induced oxidative damage in granulosa cells (GCs), which play crucial roles in the follicular development. Our results showed that catalpol significantly improved cell viability, reduced reactive oxygen species (ROS) and malondialdehyde (MDA) production, and elevated superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in H₂O₂-induced GCs. Catalpol treatment caused significant increase in bcl-2 expression, and decreases in bax and caspase-9 expressions. Compared with the H₂O₂-induced GCs, caspase-3 activity in catalpol-treated cells was markedly decreased. Furthermore, catalpol caused significant activation of PI3K/Akt/mTOR pathway in GCs in response to H₂O₂ stimulation. Additionally, inhibition of this pathway reversed the inhibitory effects of catalpol on H₂O₂-induced oxidative injury and apoptosis in GCs. In conclusion, these findings suggested that catalpol protected GCs from H₂O₂-induced oxidative injury and apoptosis via activating PI3K/Akt/mTOR signaling pathway. Thus, catalpol might serve as a therapeutic approach for regulating disrupted follicular development.

Gasotransmitter synthesis and signalling in the renal glomerulus. Implications for glomerular diseases

Glomerular injury is a hallmark of kidney diseases such as diabetic nephropathy, IgA nephropathy or other forms of glomerulonephritis. Glomerular endothelial cells, mesangial cells, glomerular epithelial cells (podocytes) and, in an inflammatory context, infiltrating immune cells crosstalk to mediate signalling processes in the glomerulus. Under physiological conditions, mesangial cells act by the control of extracellular matrix production and degradation, by the synthesis of growth factors and by preserving a well-defined crosstalk with glomerular podocytes and endothelial cells to regulate glomerular structure and function. It is well known that mesangial cells are able to amplify an inflammatory process by the formation of cytokines, reactive oxygen species (ROS) and nitric oxide (NO). This exaggerated reaction may result in a vicious cycle with subsequent damage of neighboured podocytes and endothelial cells, loss of the filtration barrier and, finally destruction of the whole glomerulus. Unfortunately, all efforts to develop new therapies for the treatment of glomerular diseases by controlling unbridled ROS or NO production directly had so far no success. However, on-going research on ROS and NO defined these autacoids more as important signalling molecules than as endogenously produced cytotoxic compounds. New findings on signalling activities of ROS, NO but also hydrogen sulfide (H₂S) and carbon monoxide (CO) supported this paradigm shift. Because of their similar chemical properties and their similar signal transduction capacities, NO, H₂S and CO are meanwhile designated as the group of gasotransmitters. In this review, we describe the current knowledge of the signalling properties of gasotransmitters with a focus on glomerular cells and their role in glomerular diseases.

Lentinan Inhibits AGE-Induced Inflammation and the Expression of Matrix-Degrading Enzymes in Human Chondrocytes

Background

Chondrocyte-mediated inflammation is an important pathological component of osteoarthritis (OA) development. There are currently no therapies that completely reverse the development of OA. Lentinan, a type of polysaccharide derived from Lentinus edodes, has been demonstrated to possess significant anti-viral, anti-cancer, and anti-inflammatory effects, and has been recently used in the treatment of several inflammatory diseases. However, little research has focused on the pharmacological effect of lentinan in human OA.

Materials and Methods

We evaluated the anti-inflammatory and anti-ROS effects of lentinan in SW1353 chondrocytes treated with AGEs using real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and the nitro oxide-specific stain DAF-FM DA. The regulatory effects of lentinan on NF-κB and MAPK p38 signaling were investigated via promoter assay and Western blot analysis.

Results

We found that lentinan inhibits the production of pro-inflammatory cytokines, including IL-1β, TNF-α, IL-8 and the secretion of PGE₂ and NO, by reducing the expression of COX-2 and iNOS in AGE-challenged chondrocytes. Lentinan also reduces AGE-induced increased expression of matrix metalloproteinases-1, −3, and −13 (MMP-1, MMP-3, MMP-13). Furthermore, lentinan has a similar effect on a disintegrin and metalloproteinase with thrombospondin motifs-4 and −5 (ADAMTS-4, ADAMTS-5). Mechanistically, lentinan reduces the activation of NF-κB.

Conclusion

Our findings indicate that lentinan shows a protective effect against AGE-induced inflammatory response in chondrocytes. These findings suggest that lentinan is a promising agent for the treatment of OA that could be used as a dietary supplement for patients with OA.

Protective effects of catalpol on mitochondria of hepatocytes in cholestatic liver injury

Cholestasis, which is caused by the obstruction of bile flow, can lead to rapid organ injury, cell apoptosis and necrosis of hepatocytes, and may eventually develop into fibrosis and cirrhosis. Oxidative stress and mitochondrial dysfunction are the key pathogenic signs of hepatic cholestasis. Catalpol has pharmacological activities, including antioxidative and anti-inflammatory effects, and may relieve mitochondrial damage and restore mitochondrial membrane potential. However, the potential roles and mechanisms of catalpol in cholestasis-induced liver injury are not clear. In the present study, liver function-related indexes were measured in the serum of mice by commercial kits. In addition, levels of serum inflammatory factors were detected by ELISA. Hematoxylin and eosin staining was performed to observe histopathological changes, and mitochondrial membrane potential was detected using JC-1 staining. Mitochondrial adenosine triphosphate (ATP), reactive oxygen species (ROS) and malondialdehyde levels were determined using a luciferase reporter kit, flow cytometry and a thiobarbituric acid reactive substance assay kit, respectively. Western blotting was performed to detect the expression levels of apoptosis-related proteins in liver tissues. The findings revealed that catalpol reduced liver damage caused by cholestasis, improved the mitochondrial membrane potential, and increased the ATP content and glutathione content of cholestasis model mice. Moreover, catalpol also reduced the ROS level, inhibited lipid peroxidation, and regulated oxidative stress and apoptotic protein expression. Thus, the present study preliminarily confirmed that catalpol can reduce liver injury in a mouse model of cholestasis through inhibiting oxidative stress and enhancing mitochondrial membrane potential.

Induction of peroxisome proliferator activated receptor γ (PPARγ) mediated gene expression and inhibition of induced nitric oxide production by Maerua subcordata (Gilg) DeWolf

BACKGROUND

The health benefits of botanicals is linked to their phytochemicals that often exert pleiotropic effects via targeting multiple molecular signaling pathways such as the peroxisome proliferator-activated receptors (PPARs) and the nuclear factor kappaB (NFκB). The PPARs are transcription factors that control metabolic homeostasis and inflammation while the NF-κB is a master regulator of inflammatory genes such as the inducible nitric-oxide synthase that result in nitric oxide (NO) overproduction.

METHODS

Extracts of Maerua subcordata (MS) and selected candidate constituents thereof, identified by liquid chromatography coupled to mass spectroscopy, were tested for their ability to induce PPARγ mediated gene expression in U2OS-PPARγ cells using luciferase reporter gene assay and also for their ability to inhibit lipopolysaccharide (LPS) induced NO production in RAW264.7 macrophages. While measuring the effect of test samples on PPARγ mediated gene expression, a counter assay that used U2OS-Cytotox cells was performed to monitor cytotoxicity or any non-specific changes in luciferase activity.

RESULTS

The results revealed that the fruit, root, and seed extracts were non-cytotoxic up to a concentration of 30 g dry weight per litre (gDW/L) and induced PPARγ mediated gene expression but the leaf extract showed some cytotoxicity and exhibited minimal induction. Instead, all extracts showed concentration (1-15 gDW/L) dependent inhibition of LPS induced NO production. The root extract showed weaker inhibition. Among the candidate constituents, agmatine, stachydrine, trigonelline, indole-3-carboxyaldehyde, plus ethyl-, isobutyl-, isopropyl, and methyl-isothiocyanates showed similar inhibition, and most showed increased inhibition with increasing concentration (1-100 μM) although to a lesser potency than the positive control, aminoguanidine.

CONCLUSION

The present study demonstrated for the first time the induction of PPARγ mediated gene expression by MS fruit, root, and seed extracts and the inhibition of LPS induced NO production by MS fruit, leaf, root, and seed extracts and some candidate constituents thereof.

Endothelial tight junctions and their regulatory signaling pathways in vascular homeostasis and disease

Endothelial tight junctions (TJs) regulate the transport of water, ions, and molecules through the paracellular pathway, serving as an important barrier in blood vessels and maintaining vascular homeostasis. In endothelial cells (ECs), TJs are highly dynamic structures that respond to multiple external stimuli and pathological conditions. Alterations in the expression, distribution, and structure of endothelial TJs may lead to many related vascular diseases and pathologies. In this review, we provide an overview of the assessment methods used to evaluate endothelial TJ barrier function both in vitro and in vivo and describe the composition of endothelial TJs in diverse vascular systems and ECs. More importantly, the direct phosphorylation and dephosphorylation of TJ proteins by intracellular kinases and phosphatases, as well as the signaling pathways involved in the regulation of TJs, including and the protein kinase C (PKC), PKA, PKG, Ras homolog gene family member A (RhoA), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt/β-catenin pathways, are discussed. With great advances in this area, targeting endothelial TJs may provide novel treatment for TJ-related vascular pathologies.

Structural and functional abnormalities of penile cavernous endothelial cells result in erectile dysfunction at experimental autoimmune prostatitis rat

Background

There is growing recognition of the association of CP/CPPS accompany with ED. However, the specific mechanism of action remains unclear. The aim of this study was to investigate structural and functional abnormalities of cavernous endothelial cells in EAP rat, which may result in the ED.

Methods

we use rat prostate protein extract supplemented with immunoadjuvant to induce EAP rat, ICP and MAP were measured and inflammatory factor infiltration, Akt, eNOS, AR, nNOS and iNOS in the corpus cavernosum were tested. Subsequently, the normal rat and EAP rat cavernosum endothelial cells were purified by MACS, and the metabolism, oxidative stress, MMP, Akt, eNOS, AR and iNOS were evaluated.

Results

The EAP rat model was successfully constructed. The ratio of max ICP/MAP in EAP rat was significantly lower and TNF-α infiltration in corpus cavernosum was significantly higher than normal rats. Besides, Akt, eNOS and AR were decreased, iNOS was significantly increased. The growth and metabolism of endothelial cells in the EAP rats corpus cavernosum decreased and inflammatory factor mRNA was increased and intracellular oxidative stress was also increased significantly. The MMP of EAP rats cavernosum endothelial cells decreased and the expression of Akt, eNOS and AR were also significantly decreased, iNOS was significantly increased.

Conclusion

The prostate suffer local inflammatory infiltrate and promotes cytokines infiltrated into corpus cavernosum caused the oxidative stress increases and the metabolism or MMP decreases. In addition, AR, Akt and eNOS expression and phosphorylation are also reduced, thereby inhibiting the diastolic function of the corpus cavernosum, resulting in decreased erectile function.