Caffeic acid attenuates neuroinflammation and cognitive impairment in streptozotocin-induced diabetic rats: Pivotal role of the cholinergic and purinergic signaling pathways

Deciphering the NLRP3 inflammasome in diabetic encephalopathy: Molecular insights and emerging therapeutic targets

Diabetic encephalopathy (DE) is a neurological complication characterized by neuroinflammation, cognitive impairment, and memory decline, with its pathogenesis closely linked to the activation of the NLRP3 inflammasome. As a central regulator of the innate immune system, the NLRP3 inflammasome plays a pivotal role in DE progression by mediating neuroinflammation, pyroptosis, mitochondrial dysfunction, oxidative stress, endoplasmic reticulum (ER) stress, and microglial polarization. This review systematically explores the molecular mechanisms by which the NLRP3 inflammasome contributes to DE, focusing on its role in neuroinflammatory cascades and neuronal damage, as well as the diabetes-associated physiological changes that exacerbate DE pathogenesis. Furthermore, we summarize emerging therapeutic strategies targeting the NLRP3 inflammasome, including small-molecule inhibitors and bioactive compounds derived from traditional herbal medicine, highlighting their potential for DE treatment. These findings not only advance our understanding of DE but also provide a foundation for developing NLRP3-targeted pharmacological interventions.

From the gut to the brain: the long journey of phenolic compounds with neurocognitive effects

The human gut microbiota is a complex community of micro-organisms that play a crucial role in maintaining overall health. Recent research has shown that gut microbes also have a profound impact on brain function and cognition, leading to the concept of the gut-brain axis. One way in which the gut microbiota can influence the brain is through the bioconversion of polyphenols to other bioactive molecules. Phenolic compounds are a group of natural plant metabolites widely available in the human diet, which have anti-inflammatory and other positive effects on health. Recent studies have also suggested that some gut microbiota-derived phenolic metabolites may have neurocognitive effects, such as improving memory and cognitive function. The specific mechanisms involved are still being studied, but it is believed that phenolic metabolites may modulate neurotransmitter signaling, reduce inflammation, and enhance neural plasticity. Therefore, to exert a protective effect on neurocognition, dietary polyphenols or their metabolites must reach the brain, or act indirectly by producing an increase in bioactive molecules such as neurotransmitters. Once ingested, phenolic compounds are subjected to various processes (eg, metabolization by gut microbiota, absorption, distribution) before they cross the blood-brain barrier, perhaps the most challenging stage of their trajectory. Understanding the role of phenolic compounds in the gut-brain axis has important implications for the development of new therapeutic strategies for neurological and psychiatric disorders. By targeting the gut microbiota and its production of phenolic metabolites, it may be possible to improve brain function and prevent cognitive decline. In this article, the current state of knowledge on the endogenous generation of phenolic metabolites by the gut microbiota and how these compounds can reach the brain and exert neurocognitive effects was reviewed.

Blackcurrant (Ribes nigrum L.) improves cholinergic signaling and protects against chronic Scopolamine-induced memory impairment in mice

BACKGROUND

Blackcurrant (Ribes nigrum L.) is a berry rich in anthocyanins, bioactive compounds known for their antioxidant and neuroprotective properties that benefit human health.

AIMS

This study aimed to investigate the effects of blackcurrant and its association with Donepezil on memory impairment, cholinergic neurotransmission, and antioxidant systems in a mouse model of amnesia induced by chronic administration of Scopolamine.

METHODS

Adult male Swiss mice were given saline, blackcurrant (50 mg/kg, orally), and/or Donepezil (5 mg/kg, orally) and/or Scopolamine (1 mg/kg, intraperitoneally).

RESULTS

Behavioral tests revealed that blackcurrant and/or Donepezil prevented the learning and memory deficits induced by Scopolamine. In the cerebral cortex and hippocampus, blackcurrant and/or Donepezil treatments prevented the increase in acetylcholinesterase and butyrylcholinesterase activities induced by Scopolamine. Scopolamine also disrupted the glutathione redox system and increased levels of reactive species; nevertheless, blackcurrant and/or Donepezil treatments were able to prevent oxidative stress. Furthermore, these treatments prevented the increase in gene expression and protein density of acetylcholinesterase and the decrease in gene expression of the choline acetyltransferase enzyme induced by Scopolamine.

CONCLUSIONS

Findings suggest that blackcurrant and Donepezil, either alone or in combination, have anti-amnesic effects by modulating cholinergic system enzymes and improving the redox profile. Therefore, blackcurrant could be used as a natural supplement for the prevention and treatment of memory impairment in neurodegenerative diseases.

Nexus of NFκB/VEGF/MMP9 signaling in diabetic retinopathy-linked dementia: Management by phenolic acid-enabled nanotherapeutics

AIMS

The purpose of this review is to highlight the therapeutic effectiveness of phenolic acids in slowing the progression of diabetic retinopathy (DR)-linked dementia by addressing the nuclear factor kappa B (NFκB)/matrix metalloproteinase-9 (MMP9)/vascular endothelial growth factor (VEGF) interconnected pathway.

MATERIALS AND METHODS

We searched 80 papers published in the last 20 years using terms like DR, dementia, phenolic acids, NFkB/VEFG/MMP9 signaling, and microRNAs (miRs) in databases including Pub-Med, WOS, and Google Scholar. By encasing phenolic acid in nanoparticles and then controlling its release into the targeted tissues, nanotherapeutics can increase their effectiveness. Results were summarized, and compared, and research gaps were identified throughout the data collection and interpretation.

KEY FINDINGS

Amyloid beta (Aβ) deposition in neuronal cells and drusen sites of the eye leads to the activation of NFkB/VEGF/MMP9 signaling and microRNAs (miR146a and miR155), which in turn energizes the accumulation of pro-inflammatory and pro-angiogenic microenvironments in the brain and retina leading to DR-linked dementia. This study demonstrates the potential of phenolic acid-enabled nanotherapeutics as a functional food or supplement for preventing and treating DR-linked dementia, and oxidative stress-related diseases.

SIGNIFICANCE

The retina has mechanisms to clear metabolic waste including Aβ, but the activation of NFkB/ MMP9/ VEGF signaling leads to fatal pathological consequences. Understanding the role of miR146a and miR155 provides potential therapeutic avenues for managing the complex pathology shared between DR and dementia. In particular, phenolic acid nanotherapeutics offer a dual benefit in retinal regeneration and dementia management.

Progress in the Pathogenesis of Diabetic Encephalopathy: The Key Role of Neuroinflammation

Diabetic encephalopathy (DE) is a severe complication that occurs in the central nervous system (CNS) and leads to cognitive impairment. DE involves various pathophysiological processes, and its pathogenesis is still unclear. This review summarised current research on the pathogenesis of diabetic encephalopathy, which involves neuroinflammation, oxidative stress, iron homoeostasis, blood-brain barrier disruption, altered gut microbiota, insulin resistance, etc. Among these pathological mechanisms, neuroinflammation has been focused on. This paper summarises some of the molecular mechanisms involved in neuroinflammation, including the Mammalian Target of Rapamycin (mTOR), Lipocalin-2 (LCN-2), Pyroptosis, Advanced Glycosylation End Products (AGEs), and some common pro-inflammatory factors. In addition, we discuss recent advances in the study of potential therapeutic targets for the treatment of DE against neuroinflammation. The current research on the pathogenesis of DE is progressing slowly, and more research is needed in the future. Further study of neuroinflammation as a mechanism is conducive to the discovery of more effective treatments for DE in the future.

Effects of Ferulic Acid on Cognitive Function: A Systematic Review

SCOPE

Plant (poly) phenolic compounds have been reported to decrease the risk of developing dementia and have been associated with maintenance of cognitive performance in normal ageing. Ferulic acid (FA) is a phenolic acid, present in a wide variety of foods including cereals, fruits, vegetables, and coffee. The aim of this systematic review is to examine the effect of FA on cognitive function in humans and animals.

METHODS AND RESULTS

The search terms "Ferulic acid AND cognit*" and "Ferulic acid OR feruloyl OR ferula AND (memory OR attention OR learning OR recognition)" are used in Web of Science, Scopus, PubMED, OVID (Medline/PsycInfo), and CINAHL through October 2023. No human studies are identified that matched the inclusion criteria. Twenty-six animal studies are identified. A small number (n = 5) of these studies examined FA in healthy animals whilst the remainder examined animal models of dementia. Alzheimer's disease (n = 11) is the most prevalent model.

CONCLUSION

Overall, results from studies employing disease models suggest that FA ameliorates induced cognitive decline in a time and dose-dependent manner. Similarly, studies in healthy animals show a beneficial effect of FA. However, further studies are required to determine the effects of FA on human cognitive function.

Vitamin D3 mitigates type 2 diabetes induced by a high carbohydrate-high fat diet in rats: Role of the purinergic system

This study evaluated the effect of vitamin D3 (VIT D3) supplementation on the enzymatic activities and density of ectonucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-5-nucleotidase (E-5'-NT), adenosine deaminase (ADA), as well as the density of P2 × 7R, P2Y12R, A1R, A2AR receptors, IL-1β, and oxidative parameters in type 2 diabetic rats. Forty male Wistar rats were fed a high carbohydrate-high fat diet (HCHFD) and received an intraperitoneal injection containing a single dose of streptozotocin (STZ, 35 mg/kg). Animals were divided into four groups: 1) control; 2) control/VIT D3 12 µg/kg; 3) diabetic; and 4) diabetic/VIT D3 12 µg/kg. Results show that VIT D3 reduced blood glucose, ATP hydrolysis, ADA activity, P2Y12R density (platelets), as well as ATP, ADP, and AMP hydrolysis and ADA activity (synaptosomes). Moreover, VIT D3 increased insulin levels and AMP hydrolysis (platelets) and improved antioxidant defense. Therefore, we suggest that VIT D3 treatment modulates hyperglycemia-induced changes via purinergic enzymes and receptor expression, consequently attenuating insulin homeostasis dysregulation in the diabetic state.

Caffeic acid alleviates skeletal muscle atrophy in 5/6 nephrectomy rats through the TLR4/MYD88/NF-kB pathway

Skeletal muscle atrophy is a common complication of chronic kidney disease (CKD) that affects the quality of life and prognosis of patients. We aimed to investigate the effects and mechanisms of caffeic acid (CA), a natural phenolic compound, on skeletal muscle atrophy in CKD rats. Male Sprague-Dawley rats underwent 5/6 nephrectomy (NPM) and were treated with CA (20, 40, or 80 mg/kg/day) for 10 weeks. The body and muscle weights, renal function, hemoglobin, and albumin were measured. The histological, molecular, and biochemical changes in skeletal muscles were evaluated using hematoxylin-eosin staining, quantitative real-time PCR, malondialdehyde/catalase/superoxide dismutase/glutathione level detection, and enzyme-linked immunosorbent assay. Western blotting and network pharmacology were applied to identify the potential targets and pathways of CA, CKD, and muscle atrophy. The results showed that CA significantly improved NPM-induced muscle-catabolic effects, reduced the expression of muscle atrophy-related proteins (muscle atrophy F-box and muscle RING finger 1) and proinflammatory cytokines (interleukin [IL]-6, tumor necrosis factor-alpha, and IL-1β), and attenuated muscle oxidative stress. Network pharmacology revealed that CA modulated the response to oxidative stress and nuclear factor kappa B (NF-κB) signaling pathway and that Toll-like receptor 4 (TLR4) was a key target. In vivo experiment confirmed that CA inhibited the TLR4/myeloid differentiation primary response 88 (MYD88)/NF-kB signaling pathway, reduced muscle iron levels, and restored glutathione peroxidase 4 activity, thereby alleviating ferroptosis and inflammation in skeletal muscles. Thus, CA might be a promising therapeutic agent for preventing and treating skeletal muscle atrophy in CKD by modulating the TLR4/MYD88/NF-κB pathway and ferroptosis.

Caffeic acid protects against l-methionine induced reduction in neurogenesis and cognitive impairment in a rat model

l-methionine (L-met) is a substantial non-polar amino acid for normal development. L-met is converted to homocysteine that leads to hyperhomocysteinemia and subsequent excessive homocysteine in serum resulting in stimulating oxidative stress and vascular dementia. Several studies have found that hyperhomocysteine causes neuronal cell damage, which leads to memory impairment. Caffeic acid is a substrate in phenolic compound discovered in plant biosynthesis. Caffeic acid contains biological antioxidant and neuroprotective properties. The neuroprotective reaction of caffeic acid can protect against the brain disruption from hydrogen peroxide produced by oxidative stress. It also enhances GSH and superoxide dismutase activities, which protect against neuron cell loss caused by oxidative stress in the hippocampus. Hence, we investigated the protective role of caffeic acid in hippocampal neurogenesis and cognitive impairment induced by L-met in rats. Six groups of Sprague Dawley rats were assigned including control, L-met (1.7 g/kg/day), caffeic acid (20, 40 mg/kg), and L-met + caffeic acid (20, 40 mg/kg) groups. Spatial and recognition memories were subsequently examined using novel object location (NOL) and novel object recognition (NOR) tests. Moreover, the immunofluorescence technique was performed to detect Ki-67/RECA-1, bromodeoxyuridine (BrdU)/NeuN and p21 markers to represent hippocampal neurogenesis changes. The results revealed decreases in vasculature related cell proliferation and neuronal cell survival. By contrast, cell cycle arrest was increased in the L-met group. These results showed the association of the spatial and recognition memory impairments. However, the deterioration can be restored by co-administration with caffeic acid.

Purinergic signaling influences the neuroinflammatory outcomes of a testosterone-derived synthetic in female rats: Resistance training protective effects on brain health

Physical exercise is recognized as a non-pharmacological approach to treat and protect against several neuroinflammatory conditions and thus to prevent brain disorders. However, the interest in ergogenic resources by athletes and bodybuilding practitioners is widespread and on the rise. These substances shorten the process of performance gain and improve aesthetics, having led to the prominent use and abuse of hormones in the past years. Recent evidence has shown that the purinergic system, composed of adenine nucleotides, nucleosides, enzymes, and receptors, participates in a wide range of processes within the brain, such as neuroinflammation, neuromodulation, and cellular communication. Here, we investigated the effects of the anabolic androgenic steroid (AAS) testosterone (TES) at a dose of 70 mg/kg/week in female rats and the neuroprotective effect of resistance exercise related to the purinergic system and oxidative stress parameters. Our findings showed a decrease in ATP and ADO hydrolysis in treated and trained animals. Furthermore, there was an increase in the density of purinoceptors (P2X7 and A2A) and inflammatory markers (IBA-1, NRLP3, CASP-1, IL-1β, and IL-6) in the cerebral cortex of animals that received AAS. On the other hand, exercise reversed neuroinflammatory parameters such as IBA-1, NLRP3, CASP-1, and IL-1β and improved antioxidant response and anti-inflammatory IL-10 cytokine levels. Overall, this study shows that the use of TES without indication or prescription disrupts brain homeostasis, as demonstrated by the increase in neuroinflammation, and that the practice of exercise can protect brain health.

Aegle marmelos (L.) Leaf Extract Improves Symptoms of Memory Loss Induced by Scopolamine in Rats

Alzheimer's disease (AD) is the most common neurodegenerative disease that results in memory impairment. Aegle marmelos (L.) Correa (AM) is used as a traditional medicine. AM leaves have the potential to inhibit acetylcholinesterase activity. This study used scopolamine to induce AD in rats. The aim of this study was to investigate the effects of AM leaf extract using this model. Motor and memory functions were tested by the motor activity and Morris water maze (MWM) tests, respectively. The density of the synaptophysin and dendritic spines in the CA1 were detected by immunofluorescence and Golgi impregnation, respectively. The hippocampal histology was reviewed by H&E staining. After the treatment, the latency times in the MWM tests of the AD groups reduced, while the motor activities showed no difference. The density of the synaptophysin of the AD groups increased after the treatments, and that of the dendritic spines also increased in all AD groups post-treatment. The hippocampal tissue also recovered. AM leaf extract can improve cognitive impairment in AD models by maintaining the presynaptic vesicle proteins and dendritic spines in a dose-dependent manner.

Caffeic acid modulates intestinal microbiota, alleviates inflammatory response, and enhances barrier function in a piglet model challenged with lipopolysaccharide

Young animals are highly susceptible to intestinal damage due to incomplete intestinal development, making them vulnerable to external stimuli. Weaning stress in piglets, for instance, disrupts the balance of intestinal microbiota and metabolism, triggering intestinal inflammation and resulting in gut damage. Caffeic acid (CA), a plant polyphenol, can potentially improve intestinal health. Here, we evaluated the effects of dietary CA on the intestinal barrier and microbiota using a lipopolysaccharide (LPS)-induced intestinal damage model. Eighteen piglets were divided into three groups: control group (CON), LPS group (LPS), and CA + LPS group (CAL). On the 21st and 28th day, six piglets in each group were administered either LPS (80 μg/kg body weight; Escherichia coli O55:B5) or saline. The results showed that dietary CA improved the intestinal morphology and barrier function, and alleviated the inflammatory response. Moreover, dietary CA also improved the diversity and composition of the intestinal microbiota by increasing Lactobacillus and Terrisporobacter while reducing Romboutsia. Furthermore, the LPS challenge resulted in a decreased abundance of 14 different bile acids and acetate, which were restored to normal levels by dietary CA. Lastly, correlation analysis further revealed the potential relationship between intestinal microbiota, metabolites, and barrier function. These findings suggest that dietary CA could enhance intestinal barrier function and positively influence intestinal microbiota and its metabolites to mitigate intestinal damage in piglets. Consuming foods rich in CA may effectively reduce the incidence of intestinal diseases and promote intestinal health in piglets.

Exploring the phenolic profile, antibacterial, and antioxidant properties of walnut leaves (Juglans regia L.)

The aim of this study was to identify phenolic compounds in walnut leaves from northern Iraq and evaluate their ability to act as antibacterial and antioxidant agents. Phenolic compounds were determined by reversed-phase HPLC. Antibacterial activity was tested against various bacteria. Antioxidant properties were evaluated by various assays, including reducing power and DPPH radical scavenging activity. The HPLC profiles of walnut leaf fractions revealed quercetin, hydroquinone, 4-hydroxybenzoic acid, and caffeic acid in three fractions. The inhibitory activity of DPPH was determined as 47.66, 32.41, and 51.90 μg/mL for fractions I, II, and III, respectively. For ferric reducing power activity, fraction II > fraction III > fraction I and the FRAP activity was observed as 64.43, 73.19, and 68.18 μg/mL for fractions I, II, and III, respectively. All extracted fractions had antibacterial properties against all bacterial strains tested. Observations showed that fraction I was able to produce similar zones of inhibition as streptomycin in most cases. These results suggest that the fractions of this plant extract are plausible natural antioxidants that could be used as prime candidates for the synthesis of antioxidant drugs that can be used for the treatment of many oxidative stress-related diseases.

Caffeic acid supplementation ameliorates intestinal injury by modulating intestinal microbiota in LPS-challenged piglets

During weaning, piglets are susceptible to intestinal injuries caused by a range of infections, which result in serious economic losses for pig producers. Caffeic acid (CA) is a plant-derived phenolic acid that exhibits potential as a dietary supplement for enhancing intestinal health. There is, however, limited information available about the potential benefits of CA supplementation on intestinal injury and growth performance in piglets. A 28-day study was conducted to examine the effectiveness of CA supplementation in protecting against intestinal injury induced by intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS) in piglets. Twenty-four piglets (7.43 ± 0.79 kg body weight; Duroc × Landrace × Large White; barrows) were randomly divided into 4 groups: the control group, the LPS group, the LPS + CA group, and the CA group. Piglets were administered with LPS or saline on d21 and d28 of the experiment. Supplementation with CA improved intestinal barrier function in LPS-challenged piglets by enhancing intestinal morphology and integrity, as well as increasing the expression of Claudin-1 and ZO-1. Meanwhile, CA supplementation improved the systemic and colonic inflammation responses, oxidative stress, and apoptosis induced by LPS. CA supplementation improved the alpha diversity and structure of the intestinal microbiota by increasing the abundance of beneficial microbiota. Additionally, it was found that it improves metabolic disorders of colonic bile acids (BAs) and short-chain fatty acids (SCFAs) in LPS-challenged piglets, including an increase in primary BAs and isovalerate. In conclusion, CA supplementation could enhance intestinal integrity and barrier function by modifying intestinal microbiota and its metabolites, which could lead to a reduction in inflammatory responses and oxidative stress and ultimately enhanced growth performance in piglets.

Caffeic acid recovers ischemia-induced synaptic dysfunction without direct effects on excitatory synaptic transmission and plasticity in mouse hippocampal slices

Caffeic acid is a polyphenolic compound present in a vast array of dietary components. We previously showed that caffeic acid reduces the burden of brain ischemia joining evidence by others that it can attenuate different brain diseases. However, it is unknown if caffeic acid affects information processing in neuronal networks. Thus, we now used electrophysiological recordings in mouse hippocampal slices to test if caffeic acid directly affected synaptic transmission, plasticity and dysfunction caused by oxygen-glucose deprivation (OGD), an in vitro ischemia model. Caffeic acid (1-10 μM) was devoid of effect on synaptic transmission and paired-pulse facilitation in Schaffer collaterals-CA1 pyramidal synapses. Also, the magnitude of either hippocampal long-term potentiation (LTP) or the subsequent depotentiation were not significantly modified by 10 μM caffeic acid. However, caffeic acid (10 μM) increased the recovery of synaptic transmission upon re-oxygenation following 7 minutes of OGD. Furthermore, caffeic acid (10 μM) also recovered plasticity after OGD, as heralded by the increased magnitude of LTP after exposure. These findings show that caffeic acid does not directly affect synaptic transmission and plasticity but can indirectly affect other cellular targets to correct synaptic dysfunction. Unraveling the molecular mechanisms of action of caffeic acid may allow the design of hitherto unrecognized novel neuroprotective strategies.