Protocatechuic Acid Attenuates Lipolysaccharide-Induced Acute Lung Injury

The protective effects of protocatechuic acid against natural and chemical toxicants: cellular and molecular mechanisms

Protocatechuic acid (PCA) is a water-soluble polyphenol compound that is extracted from certain fruits and plants or obtained from glucose fermentation. Several in vivo and in vitro studies have determined that PCA has protective effects against the toxicity of natural and chemical toxicants. We searched these articles in PubMed, Google Scholar, and Scopus with appropriate keywords from inception up to August 2023. Forty-nine studies were found about protective effects of PCA against drug toxicity, metal toxicity, toxins, chemical toxicants, and some other miscellaneous toxicants. PCA indicates these protective effects by suppression of oxidative stress, inflammation, and apoptosis. PCA reduces reactive oxygen/nitrogen species (RONS) and enhances the level of antioxidant parameters mainly through the activation of the Nrf-2 signaling pathway. PCA also decreases the levels of inflammatory mediators via downregulating the TLR-4-mediated IKBKB/NF-κB and MAPK/Erk signaling pathways. In addition, PCA inhibits apoptosis by lowering the expression of Bax, caspase-3, and caspase-9 along with enhancing the level of the antiapoptotic protein Bcl-2. Further evaluation, especially in humans, is necessary to confirm PCA as a potential therapeutic approach to intervene in such toxicities.

Protocatechuic acid and quercetin attenuate ETEC-caused IPEC-1 cell inflammation and injury associated with inhibition of necroptosis and pyroptosis signaling pathways

BACKGROUND

Necroptosis and pyroptosis are newly identified forms of programmed cell death, which play a vital role in development of many gastrointestinal disorders. Although plant polyphenols have been reported to protect intestinal health, it is still unclear whether there is a beneficial role of plant polyphenols in modulating necroptosis and pyroptosis in intestinal porcine epithelial cell line (IPEC-1) infected with enterotoxigenic Escherichia coli (ETEC) K88. This research was conducted to explore whether plant polyphenols including protocatechuic acid (PCA) and quercetin (Que), attenuated inflammation and injury of IPEC-1 caused by ETEC K88 through regulating necroptosis and pyroptosis signaling pathways.

METHODS

IPEC-1 cells were treated with PCA (40 μmol/L) or Que (10 μmol/L) in the presence or absence of ETEC K88.

RESULTS

PCA and Que decreased ETEC K88 adhesion and endotoxin level (P < 0.05) in cell supernatant. PCA and Que increased cell number (P < 0.001) and decreased lactate dehydrogenases (LDH) activity (P < 0.05) in cell supernatant after ETEC infection. PCA and Que improved transepithelial electrical resistance (TEER) (P < 0.001) and reduced fluorescein isothiocyanate-labeled dextran (FD4) flux (P < 0.001), and enhanced membrane protein abundance of occludin, claudin-1 and ZO-1 (P < 0.05), and rescued distribution of these tight junction proteins (P < 0.05) after ETEC infection. PCA and Que also declined cell necrosis ratio (P < 0.05). PCA and Que reduced mRNA abundance and concentration of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-8 (P < 0.001), and down-regulated gene expression of toll-like receptors 4 (TLR4) and its downstream signals (P < 0.001) after ETEC infection. PCA and Que down-regulated protein abundance of total receptor interacting protein kinase 1 (t-RIP1), phosphorylated-RIP1 (p-RIP1), p-RIP1/t-RIP1, t-RIP3, p-RIP3, mixed lineage kinase domain-like protein (MLKL), p-MLKL, dynamin- related protein 1 (DRP1), phosphoglycerate mutase 5 (PGAM5) and high mobility group box 1 (HMGB1) (P < 0.05) after ETEC infection. Moreover, PCA and Que reduced protein abundance of nod-like receptor protein 3 (NLRP3), nod-like receptors family CARD domain-containing protein 4 (NLRC4), apoptosis-associated speck-like protein containing a CARD (ASC), gasdermin D (GSDMD) and caspase-1 (P < 0.05) after ETEC infection.

CONCLUSIONS

In general, our data suggest that PCA and Que are capable of attenuating ETEC-caused intestinal inflammation and damage via inhibiting necroptosis and pyroptosis signaling pathways.

Chronic Gastric Ulcer Healing Actions of the Aqueous Extracts of Staple Plant Foods of the North-West, Adamawa, and West Regions of Cameroon

Aim

This study is aimed at establishing phenolic compound profile and assessing the possible antiulcer activities of aqueous extracts of some staple plant foods from the West and North-West regions of Cameroon against chronic gastric ulcer models in rats.

Materials and Methods

Phenolic constituents of extracts were evaluated using HPLC-DAD. Aqueous extracts of Corchorus olitorius, Solanum nigrum, Vigna unguiculata, Triumfetta pentandra, "nkui" spices, and "yellow soup" spices were tested at two doses (200 and 400 mg/kg). After treatments, animals were sacrificed, healing percentage and antioxidant status (catalase, superoxide dismutase, and glutathione peroxidase) were evaluated, and histological examination of gastric mucosa was realized.

Results

HPLC-DAD revealed that p-hydroxybenzoic and protocatechuic acids were the phenolic compound present in all extracts. Oral administration of extracts (200 and 400 mg/kg) significantly reduced ulcer surface value and significantly increased mucus production compared to the control groups (p < 0.05). Histological study supported the observed healing activity of different extracts characterized by a reduced inflammatory response. Moreover, administration of aqueous extracts increased the activity of antioxidant enzymes.

Conclusion

This study revealed that aqueous extracts of Solanum nigrum, Corchorus olitorius, Vigna unguiculata, Triumfetta pentandra, "yellow soup" spices, and "nkui" spices possess healing antiulcer effects against models of gastric ulcers. The antiulcer mechanisms involved may include increase of gastric mucus production and improvement of the antioxidant activity of gastric tissue. These activities may be due to the phenolic compounds identified in the extracts, especially p-hydroxybenzoic and protocatechuic acids present in all extracts and with known antioxidant, cytoprotective, and healing properties. However, all the diets may promote the healing process of chronic ulcers caused by excessive alcohol consumption/stress.

Protocatechuic acid counteracts oxidative stress and inflammation in carrageenan-induced paw edema in mice

Protocatechuic acid (PCA), a phenolic compound found in teas, fruits, and vegetables, is widely recognized with its antioxidant and anti-inflammatory activities. Here, we verified the protective role of PCA on carrageenan (CGN)-induced paw edema in mice. Forty-five male Swiss albino mice were assigned into five groups: control group, CGN-injected group (1% w/v), PCA (25 mg/kg) + CGN group. PCA (50 mg/kg) + CGN group and diclofenac sodium (20 mg/kg) + CGN group. PCA and diclofenac sodium were administered orally for 5 consecutive days prior to the CGN injection. PCA pretreatment notably decreased the volume of the developed edema and alleviated the histopathological alterations induced by carrageenan. Additionally, PCA administration enhanced the cellular antioxidant capacity as demonstrated by the increased levels of catalase, superoxide dismutase, and reduced glutathione, in addition to the decreased malondialdehyde level in the edematous tissue. Interestingly, PCA administration was able significantly to suppress the developed inflammatory response upon carrageenan injection as indicated by the decreased levels and expression of pro-inflammatory cytokines and mediators including tumor necrosis factor alpha, interleukin-1 beta, interleukin-6, inducible nitric oxide synthase, nitric oxide, cyclooxygenase-II, prostaglandin E2, monocyte chemoattractant protein-1, myeloperoxidase and nuclear factor kappa B. These results collectively confirm the protective effect of PCA against carrageenan-induced paw edema owing to its antioxidant and anti-inflammatory characteristics.

Analysis of Antioxidant Phytochemicals and Anti-Inflammatory Effect from Vitex rotundifolia L.f

An extraction method using 80% EtOH was selected and applied to obtain the total extracts from leaves, flowers, fruits, twigs, and roots of Vitex rotundifolia L.f. based on the antioxidant activity-guided experiments. Subsequently, total extract from each part of V. rotundifolia was successfully partitioned into fractions, which were evaluated for their antioxidant and anti-inflammatory properties via DPPH, ABTS, and NO assays, respectively. Among them, EtOAc (E) and n-butanol (B) fractions showed the potent antioxidant activity and the methylene chloride (MC) fractions of roots, leaves, and fruits that exhibited strong scavenging activity on DPPH and ABTS radicals. In the anti-inflammatory assay, n-hexane (H) and MC fractions of leaves potently inhibited NO production in LPS-stimulated RAW264.7 cells, followed by E fractions derived from fruits, flowers, twigs, and roots, along with B fractions from flowers and twigs. Additionally, a comprehensive HPLC-decoupled MS profiling was established and validated using seven isolated marker compounds (1–7), which were identified by analysis of their UV, NMR, and MS data. The established method was also applied for quantification of these marker compounds in each organ collected from different locations, and to assess their antioxidant capacity by a screening DPPH-HPLC method. Principal component analysis suggested the botanical organs from this plant correlated with the marker compound contents in association with bioactivity. The study results are a prelude to further studies involving the active fractions and provide a comprehensive insight into the functional products of this plant against oxidative diseases.

Protocatechuic acid protects against thioacetamide-induced chronic liver injury and encephalopathy in mice via modulating mTOR, p53 and the IL-6/ IL-17/ IL-23 immunoinflammatory pathway

Protocatechuic acid (PCA), a natural phenolic acid, is known for antioxidant, anti-inflammatory, anti-apoptotic, and anti-fibrotic activities. However, the protective mechanisms of PCA on thioacetamide (TAA)-induced liver/brain injury are not well addressed. Chronic liver injury was induced in mice by intraperitoneal injection of TAA (200 mg/kg, 3 times/week) for 8 weeks. Simultaneously, PCA (100, 150 mg/kg/day, p.o.) was given daily from the 4th week. Protocatechuic acid ameliorated liver and brain damage indicated by the decrease in serum activities of aminotransferases, gamma-glutamyl transferase, alkaline phosphatase, lactate dehydrogenase, levels of bilirubin, and ammonia concomitant with restoration of normal albumin levels. Additionally, PCA treatment ameliorated oxidative stress in liver and brain, confirmed by the decrease in malondialdehyde and nitric oxide levels and the increase in antioxidant activities. Moreover, PCA showed anti-inflammatory actions through downregulation of TNF-α expression in the liver and IL-6/IL-17/IL-23 levels in the brain, which is confirmed by the decrease in CD4⁺ T brain cell numbers. Most importantly, PCA treatment showed a significant decrease in mTOR level and number of LC3 positive cells in both liver and brain tissues. Consequently, PCA could inhibit mTOR-induced apoptosis, as it showed anti-apoptotic actions through downregulation of caspase-3 expression in liver and p53 expression in liver and brain. Furthermore, liver and brain tissues of treated mice showed restoration of normal histology. It can be concluded that, several mechanisms, including: antioxidant, anti-inflammatory, anti-autophagic and anti-apoptotic activities can be implicated in the hepato- and neuroprotective potentials of PCA.

Protocatechuic acid attenuates lipopolysaccharide-induced septic lung injury in mice: The possible role through suppressing oxidative stress, inflammation and apoptosis

Here, we investigated the protective efficacy of protocatechuic acid (PCA) against lipopolysaccharide (LPS)-induced septic lung injury. Eighty-two male Balb/c mice were divided into six groups: control, PCA30 (30 mg/kg), LPS (10 mg/kg), PCA10-LPS, PCA20-LPS, and PCA30-LPS treated with 10, 20 and 30 mg/kg PCA, respectively, for seven days before intraperitoneal LPS injection. PCA pre-treatment, especially at higher dose, significantly reduced LPS-induced lung tissue injury as indicated by increased heat shock protein 70 and antioxidant molecules (reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) accompanied by lower oxidative stress indices (malondialdehyde and nitric oxide). PCA administration decreased inflammatory mediators including myeloperoxidase, nuclear factor kappa B (NF-κB p65), and pro-inflammatory cytokines, and prevented the development of apoptotic events in the lung tissue. At the molecular level, PCA downregulated mRNA expression of nitric oxide synthase 2, C/EBP homologous protein, and high mobility group box1 in the lungs of all PCA-LPS treated mice. Thus, PCA-pre-treatment effectively counteracted sepsis-induced acute lung injury in vivo by promoting and antioxidant status, while inhibiting inflammation and apoptosis. PRACTICAL IMPLICATIONS: Sepsis-mediated organ dysfunction and high mortality is aggravated by acute lung injury (ALI). Therefore, new therapeutic approaches are needed to encounter sepsis-mediated ALI. Protocatechuic acid (PCA) is a naturally occurring phenolic acid with various biological and pharmacological activities. PCA is abundant in edible plants including Allium cepa L., Oryza sativa L., Hibiscus sabdariffa, Prunus domestica L., and Eucommia ulmoides. In this investigation we studied the potential protective role of pure PCA (10, 20 and 30 mg/kg) on LPS-mediated septic lung injury in mice through examining oxidative challenge, inflammatory response, apoptotic events and histopathological changes in addition to evaluating the levels and mRNA expression of heat shock protein 70, C/EBP homologous protein and high mobility group box1 in the lung tissue. The recorded results showed that PCA pre-administration was able to significantly abrogate the damages in the lung tissue associated septic response. This protective effect comes from its strong antioxidant, anti-inflammatory, and anti-apoptotic activities, suggesting that PCA may be applied to alleviate ALI associated with the development of sepsis.

Pediococcus Pentosaceus from the Sweet Potato Fermented Ger-Minated Brown Rice Can Inhibit Type I Hypersensitivity in RBL-2H3 Cell and BALB/c Mice Models

In this study, the effect of GBR fermented with the Pediococcus pentosaceus SP024 strain on IgE/Ag mediated passive cutaneous anaphylaxis (PCA) was investigated. Protocatechuic acid and trans-ferulic acid levels in GBR-SP024 increased more than those in unfermented GBR, respec-tively. The inhibitory activity of GBR-SP024 on β-hexosaminidase release and the level of proin-flammatory cytokine mRNA expression (tumor necrosis factor-α (TNF-α) and interleukin 4 (IL-4)) was observed in IgE/Ag-stimulated RBL-2H3 cells. Western blot analysis showed that GBR-SP024 significantly inhibited the phosphorylation of the linker for activation of T cell (LAT) and nuclear factor-κB (NF-κB) in IgE/Ag-stimulated RBL-2H3 cells. Further, we investigated the anti-allergic effect of GBR-SP024 using PCA murine model. The number of infiltrated immune cells and degranulated mast cells in GBR-SP024 treated dermis was lower than that in the GBR-treated mice. In addition, mRNA expression of 5-lipoxygenase (5-LOX) in the dermis of ear tissue declined in the GBR-SP024–treated group, compared to that in the GBR group. GBR-SP024 was also more effective than GBR at reducing the levels of IL-33 protein expression in IgE/Ag-stimulated BALB/c mice. Our study suggests the potential usage of GBR-SP024 as a dietary supplement or an adjuvant for treating IgE-dependent-allergic diseases.

The protective effect of protocatechuic acid on hepatotoxicity induced by cisplatin in mice

Cisplatin is one of the most potent anti-cancer drugs used for the treatment of various solid tumors, yet it has several side effects that may limit its clinical use. Hepatotoxicity is one of the most serious side effects as it may lead to liver failure. Several mechanisms including oxidative stress, inflammation, and apoptosis have been examined in cisplatin-induced hepatotoxicity. Protocatechuic acid (Proto) which is naturally occurring phenolic acid has shown different biological activity as antioxidant, anti-inflammatory, and anti-apoptotic. In this study, we investigate the protective effect of Proto at two doses 100 and 150 mg/kg on hepatotoxicity induced by a single injection of 10 mg/kg cisplatin in female albino mice. The present study demonstrates for the first time that Proto administration (100 and 150 mg/Kg) significantly attenuates cisplatin-induced changes in liver function [increase serum albumin and decrease liver injury markers ALT, AST, GGT, and bilirubin]. This was associated with marked hepatic antioxidant effects [decrease MDA and NO levels, increase GSH and SOD activity]. Moreover, Proto reduced cisplatin-induced apoptosis in the liver through decreasing caspase-3, annexin-V, and BAX. Both doses suppressed cisplatin-induced expression of iNOS and NF-ᴋB p65 subunit and pro-inflammatory cytokines (IL-6 and TNF-α). Also, Proto improved histopathological examination of the liver. The present findings reveal that the antioxidant, anti-inflammatory, and anti-apoptotic effects of Proto are the main mechanisms by which Proto can ameliorate cisplatin-induced liver injury.

Natural product derived phytochemicals in managing acute lung injury by multiple mechanisms

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS) as common life-threatening lung diseases with high mortality rates are mostly associated with acute and severe inflammation in lungs. With increasing in-depth studies of ALI/ARDS, significant breakthroughs have been made, however, there are still no effective pharmacological therapies for treatment of ALI/ARDS. Especially, the novel coronavirus pneumonia (COVID-19) is ravaging the globe, and causes severe respiratory distress syndrome. Therefore, developing new drugs for therapy of ALI/ARDS is in great demand, which might also be helpful for treatment of COVID-19. Natural compounds have always inspired drug development, and numerous natural products have shown potential therapeutic effects on ALI/ARDS. Therefore, this review focuses on the potential therapeutic effects of natural compounds on ALI and the underlying mechanisms. Overall, the review discusses 159 compounds and summarizes more than 400 references to present the protective effects of natural compounds against ALI and the underlying mechanism.

Peanut skin polyphenols inhibit toxicity induced by advanced glycation end-products in RAW264.7 macrophages

This is the first work to use a polyphenolic fraction derived from peanut skin to attenuate the toxicity induced by advanced glycation-end products (AGEs) in RAW264.7 macrophages. The RAW264.7 cells were stimulated by AGEs using the bovine serum albumin-fructose (BSA-FRU), bovine serum albumin-methylglyoxal (BSA-MGO) and arginine-methylglyoxal (ARG-MGO) models. The AGEs increased considerably the levels of reactive oxygen species and the gene expression of proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nitric oxide. Twenty-eight polyphenols, including catechin, phenolic acids, and resveratrol were annotated in peanut skin extract (PSE) with the use of ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-QTOF/MS^E) and to the UNIFI Scientific Information System. The administration of PSE at 100 and 150 μg/mL significantly inhibited oxidative stress, by suppressing the production of reactive oxygen species up to 70% and reducing the production of nitric oxide, IL-6 and TNF-α up to 1.7-, 10- and 107-fold, respectively.

Protocatechuic acid supplement alleviates allergic airway inflammation by inhibiting the IL-4Rα-STAT6 and Jagged 1/Jagged2-Notch1/Notch2 pathways in allergic asthmatic mice

OBJECTIVE AND DESIGN

To clarify the effects of dietary supplementation of protocatechuic acid (PCA) and in-depth mechanisms on allergic asthma in ovalbumin (OVA)-induced mice.

MATERIALS

Female BALB/c mice were randomly divided into three groups (n = 10 in each group): control group, OVA-induced allergic asthma group, and OVA plus PCA group.

TREATMENT

Dietary supplementation of PCA was achieved by adding 50 mg/kg PCA to AIN 93G diet for 25 days.

METHODS

Peripheral blood cells, pulmonary inflammatory cell infiltration, the levels of IL-4, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), the mRNA levels of Th2-related genes in the lungs, and the protein expressions of the IL-4Rα-STAT6 and the Jagged1/Jagged2-Notch1/Notch2 signaling pathways were measured.

RESULTS

Significantly reduced inflammatory cells infiltration and mucosal hypersecretion in the lung tissues, repaired levels of interleukin IL-4, IL-5, and IL-13 in the BALF, and decreased mRNA expression of IL-4, IL-5, and GATA3 were observed in OVA plus PCA group. Moreover, PCA treatment down-regulated the protein levels of IL-4Rα-STAT6 and Jagged1/Jagged2-Notch1/Notch2 signaling pathways.

CONCLUSIONS

Dietary supplement of PCA alleviated allergic asthma partly through suppressing the IL-4Rα-STAT6 and Jagged1/Jagged2-Notch1/Notch2 signaling pathways in mice. Our study provided the theoretic basis of PCA used as functional food in preventing allergic asthma.

Protocatechuic acid improves functional recovery after spinal cord injury by attenuating blood-spinal cord barrier disruption and hemorrhage in rats

After spinal cord injury (SCI), blood-spinal cord barrier (BSCB) disruption and hemorrhage lead to blood cell infiltration and progressive secondary injuries including inflammation. Inflammatory response is one of the major events resulting in apoptosis, scar formation and neuronal dysfunction after SCI. Here, we investigated whether protocatechuic acid (PCA), a natural phenolic compound, would attenuate BSCB disruption and hemorrhage, leading to functional improvement after SCI. After a moderate contusion injury at T9, PCA (50 mg/kg) was administrated via intraperitoneal injection immediately, 6 h, and 12 h after SCI, and the same dose of PCA once a day until 7 d after injury. Our data show that PCA inhibited apoptotic cell death of neurons and oligodendrocytes and improved functional recovery after injury. PCA also attenuated BSCB disruption and hemorrhage and reduced the infiltration of neutrophils and macrophages compared to vehicle control. Moreover, PCA inhibited the expression and activation of matrix metalloprotease-9, which is well known to disrupt BSCB after SCI. Furthermore, PCA treatment significantly inhibited the expression of sulfonylurea receptor 1 and transient receptor potential melastatin 4, which are known to mediate hemorrhage at an early stage after SCI. Consistent with these findings, the mRNA and protein expression of inflammatory mediators such as tumor necrosis factor alpha, interleukin 1 beta, cyclooxygenase-2, inducible nitric oxide synthase, and chemokines was significantly alleviated by PCA treatment. Thus, our results suggest that PCA improved functional recovery after SCI in part by inhibiting BSCB disruption and hemorrhage through the down-regulation of sulfonylurea receptor 1/transient receptor potential melastatin 4 and matrix metalloprotease-9.

Pro-apoptosis effects of protocatechuic acid in the early stage of infectious bursal disease virus infection

Infectious bursal disease virus (IBDV) is a very important small RNA virus in the family of Birnaviridae, which can cause severe immunosuppressive effects and pathological damages in young chickens. It can replicate in bursal lymphocytes and impede the growth and development of B cells, finally causing bursal lymphocytes apoptosis. Previous results have shown that protocatechuic acid (PCA) as an important phenolic compound could effectively improve the survival rate of chickens infected with IBDV. The current study aimed to explore how PCA influenced the pathogenesis of IBDV, especially lymphocyte apoptosis in the process of IBDV infection. The results showed that PCA could effectively alleviate bursal pathological changes at the early stage of IBDV invasion. Moreover, bursal lymphocyte apoptosis for tissue section samples was largely elevated by PCA by using the terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) method while the bursal lymphocyte apoptosis ratio was also increased by PCA by flow cytometry in the early stage of IBDV infection in vivo. Meanwhile, PCA could promote non-lymphocyte apoptosis in vitro. Further study displayed that the potential mechanisms mainly relied on regulation of the expressions of pro-apoptotic protein Bax and anti-apoptotic Bcl-2, thus speeding up the process of IBDV-infected cell apoptosis and preventing virus infection. Meanwhile, the results displayed that the PI3K/Akt and NF kappa B signal pathways might play an important role in promoting cell apoptosis after IBDV infection. Overall, PCA as a potent antiviral drug precursor is expected to be applied in the poultry industry as a substitute for clinical antiviral application.

Alternative and Natural Therapies for Acute Lung Injury and Acute Respiratory Distress Syndrome

Introduction

Acute respiratory distress syndrome (ARDS) is a complex clinical syndrome characterized by acute inflammation, microvascular damage, and increased pulmonary vascular and epithelial permeability, frequently resulting in acute respiratory failure and death. Current best practice for ARDS involves “lung-protective ventilation,” which entails low tidal volumes and limiting the plateau pressures in mechanically ventilated patients. Although considerable progress has been made in understanding the pathogenesis of ARDS, little progress has been made in the development of specific therapies to combat injury and inflammation.

Areas Covered

In recent years, several natural products have been studied in experimental models and have been shown to inhibit multiple inflammatory pathways associated with acute lung injury and ARDS at a molecular level. Because of the pleiotropic effects of these agents, many of them also activate antioxidant pathways through nuclear factor erythroid-related factor 2, thereby targeting multiple pathways. Several of these agents are prescribed for treatment of inflammatory conditions in the Asian subcontinent and have shown to be relatively safe.

Expert Commentary

Here we review natural remedies shown to attenuate lung injury and inflammation in experimental models. Translational human studies in patients with ARDS may facilitate treatment of this devastating disease.

Protective effect of Tremella fuciformis Berk extract on LPS-induced acute inflammation via inhibition of the NF-κB and MAPK pathways

Tremella fuciformis Berk (TFB) has long been used as a traditional medicine in Asia. Although TFB exhibits antioxidant and anti-inflammatory effects, the mechanisms of action responsible have remained unknown. We confirmed the anti-inflammatory effects of Tremella fuciformis Berk extract (TFE) in RAW 264.7 cells and observed significantly suppressed LPS-induced iNOS/NO and COX-2/PGE2 production. TFE also suppressed LPS-induced IKK, IkB, and p65 phosphorylation, as well as LPS-induced translocation of p65 from the cytosol. Additionally, TFE inhibited LPS-induced phosphorylation of MAPKs. In an acute inflammation study, oral administration of TFE significantly inhibited LPS-induced IL-1β, IL-6 and TNF-α production and iNOS and COX-2 expression. The major bioactive compounds from TFB extract were identified as gentisic acid, protocatechuic acid, 4-hydroxybenzoic acid, and coumaric acid. Among these compounds, protocatechuic acid showed the strongest inhibitory effects on LPS-induced NO production in RAW 264.7 cells. Overall, these results suggest that TFE is a promising anti-inflammatory agent that suppresses iNOS/NO and COX-2/PGE2 expression, as well as the NF-κB and MAPK signaling pathways.

Antihypertensive and antioxidant effects of protocatechuic acid in deoxycorticosterone acetate-salt hypertensive rats

Protocatechuic acid (PCA) is a natural antioxidant with beneficial cardiovascular properties. In this study, the effect of supplementation with PCA was investigated in deoxycorticosterone acetate (DOCA)-salt hypertension. Male Wistar rats received DOCA (25 mg/kg, s.c.) twice weekly and 1% NaCl in drinking water and simultaneously treated with PCA (50, 100 and 200 mg/kg, p.o.) for 4 weeks. Systolic blood pressure (SBP) was detected using tail-cuff method. Electrolytes including Na⁺, K⁺ and chloride, catalase activity, glutathione, total antioxidant capacity, malondialdehyde (MDA) and hydroperoxides concentration were measured in serum samples. Body and organs weight, water intake and, kidney and heart histopathology were also evaluated. Administration of PCA reversed the changes caused by DOCA-salt approximately at all doses. At the lowest dose, PCA significantly decreased SBP (132.5 ± 4.0 vs 152.3 ± 4.5 mmHg, P < .05), serum sodium (138.5  ± 1.52 vs 141 ± 1.50, P < .05) and chloride level (101.6 ± 1.47 vs 110 ± 1.39, P < .01) and raised serum potassium level (3.8 ± 0.09 vs 3.1 ± 0.17, P < .05) compared with DOCA-salt hypertensive rats. PCA increased serum catalase activity, total antioxidant capacity and glutathione concentration and reduced MDA and hydroperoxides levels. PCA also improved organ weight changes, reduced water intake and moderately prevented histopathological changes of kidney and heart upon DOCA-salt administration. The present study indicates the antihypertensive and antioxidant effects of PCA against DOCA-salt hypertension.

Therapeutic Potential of Medicinal Plants and Their Constituents on Lung Inflammatory Disorders

Acute bronchitis and chronic obstructive pulmonary diseases (COPD) are essentially lung inflammatory disorders. Various plant extracts and their constituents showed therapeutic effects on several animal models of lung inflammation. These include coumarins, flavonoids, phenolics, iridoids, monoterpenes, diterpenes and triterpenoids. Some of them exerted inhibitory action mainly by inhibiting the mitogen-activated protein kinase pathway and nuclear transcription factor-κB activation. Especially, many flavonoid derivatives distinctly showed effectiveness on lung inflammation. In this review, the experimental data for plant extracts and their constituents showing therapeutic effectiveness on animal models of lung inflammation are summarized.

The Immunoregulatory Effects of Traditional Chinese Medicine on Treatment of Asthma or Asthmatic Inflammation

Asthma is a chronic respiratory symptoms with variable airflow limitation and airway hyperresponsiveness (AHR), and causes high economic burden. Traditional Chinese medicine (TCM) has a long-lasting history of using herbal medicine in the treatment of various respiratory diseases including asthma. In the last several decades, an increasing number of herbs have been shown to be effective in the treatment of asthma in clinical trials or asthmatic inflammation in animal models. Literature about the effects of TCM on the immune system were searched in electronic databases such as PubMed, Google Scholar and Scopus from 2000 to 2014. 'TCM' and 'asthma' were used as keywords for the searches. Over 400 literatures were searched and the literatures about the immune system were selected and reviewed. We only reviewed literatures published in English. Accumulating evidence suggests that TCM can directly inhibit the activation and migration of inflammatory cells, regulate the balance of Th1/Th2 responses, and suppress allergic hyperreactivity through inducing regulatory T cells or attenuating the function of dendritic cells (DCs). These studies provided useful information to facilitate the use of TCM to treat asthma. This review was conducted to classify the findings based on their possible mechanisms of action reported.

Heat-Processed Scutellariae Radix Enhances Anti-Inflammatory Effect against Lipopolysaccharide-Induced Acute Lung Injury in Mice via NF- κ B Signaling

The present study was conducted to examine whether heat-processed Scutellariae Radix has an ameliorative effect on lipopolysaccharide- (LPS-) induced acute lung injury in mice. The effects of Scutellariae Radix heat-processed at 160°C (HSR) were compared with those of nonheat-processed Scutellariae Radix (NSR). The LPS-treated group displayed a markedly decreased body weight and significantly increased lung weight; however, the administration of NSR or HSR improved both the body and lung weights. The increased oxidative stress and inflammatory biomarker levels in the serum and lung were reduced significantly with HSR. The reduced superoxide dismutase and catalase increased significantly by both NSR and HSR. Also, the dysregulated oxidative stress and inflammation were significantly ameliorated by NSR and HSR. The expression of inflammatory mediators and cytokines by nuclear factor-kappa B activation was modulated through inhibition of a nuclear factor kappa Bα degradation. Also, lung histological change was markedly suppressed by HSR rather than NSR. Overall, the ameliorative effects of HSR were superior to those when being nonheat-processed. The representative flavonoid contents of Scutellariae Radix that include baicalin, baicalein, and wogonin were greater by heat process. These data reveal heat-processed Scutellariae Radix may be a critical factor involved in the improvement of lung disorders caused by LPS.

Flavonoid metabolites reduce tumor necrosis factor-α secretion to a greater extent than their precursor compounds in human THP-1 monocytes

Scope

Flavonoids are generally studied in vitro, in isolation, and as unmetabolized precursor structures. However, in the habitual diet, multiple flavonoids are consumed together and found present in the circulation as complex mixtures of metabolites. Using a unique study design, we investigated the potential for singular or additive anti‐inflammatory effects of flavonoid metabolites relative to their precursor structures.

Methods and results

Six flavonoids, 14 flavonoid metabolites, and 29 combinations of flavonoids and their metabolites (0.1–10 μM) were screened for their ability to reduce LPS‐induced tumor necrosis factor‐α (TNF‐α) secretion in THP‐1 monocytes. One micromolar peonidin‐3‐glucoside, cyanidin‐3‐glucoside, and the metabolites isovanillic acid (IVA), IVA‐glucuronide, vanillic acid‐glucuronide, protocatechuic acid‐3‐sulfate, and benzoic acid‐sulfate significantly reduced TNF‐α secretion when in isolation, while there was no effect on TNF‐α mRNA expression. Four combinations of metabolites that included 4‐hydroxybenzoic acid (4HBA) and/or protocatechuic acid also significantly reduced TNF‐α secretion to a greater extent than the precursors or metabolites alone. The effects on LPS‐induced IL‐1β and IL‐10 secretion and mRNA expression were also examined. 4HBA significantly reduced IL‐1β secretion but none of the flavonoids or metabolites significantly modified IL‐10 secretion.

Conclusion

This study provides novel evidence suggesting flavonoid bioactivity results from cumulative or additive effects of circulating metabolites.

G protein-coupled estrogen receptor-1 is involved in the protective effect of protocatechuic aldehyde against endothelial dysfunction

Protocatechuic aldehyde (PCA), a phenolic aldehyde, has therapeutic potency against atherosclerosis. Although PCA is known to inhibit the migration and proliferation of vascular smooth muscle cells and intravascular thrombosis, the underlying mechanism remains unclear. In this study, we investigated the protective effect of PCA on endothelial cells and injured vessels in vivo in association with G protein-coupled estrogen receptor-1 (GPER-1). With PCA treatment, cAMP production was increased in HUVECs, while GPER-1 expression was increased in both HUVECs and a rat aortic explant. PCA and G1, a GPER-1 agonist, reduced H₂O₂ stimulated ROS production in HUVECs, whereas, G15, a GPER-1 antagonist, increased ROS production further. These elevations were inhibited by co-treatment with PCA or G1. TNFα stimulated the expression of inflammatory markers (VCAM-1, ICAM-1 and CD40), phospho-NF-κB, phospho-p38 and HIF-1α; however, co-treatment with PCA or G1 down-regulated this expression significantly. Likewise, increased expression of inflammatory markers by treatment with G15 was inhibited by co-treatment with PCA. In re-endothelization, aortic ring sprouting and neointima formation assay, rat aortas treated with PCA or G1 showed accelerated re-endothelization of the endothelium and reduced sprouting and neointima formation. However, aortas from G15-treated rats showed decelerated re-endothelization and increased sprouting and neointima formation. The effects of G15 were restored by co-treatment with PCA or G1. Also, in the endothelia of these aortas, PCA and G1 increased CD31 and GPER-1 and decreased VCAM-1 and CD40 expression. In contrast, the opposite effect was observed in G15-treated endothelium. These results suggest that GPER-1 might mediate the protective effect of PCA on the endothelium.

Protocatechuic acid, a novel active substance against avian influenza virus H9N2 infection

Influenza virus H9N2 subtype has triggered co-infection with other infectious agents, resulting in huge economical losses in the poultry industry. Our current study aims to evaluate the antiviral activity of protocatechuic acid (PCA) against a virulent H9N2 strain in a mouse model. 120 BALB/c mice were divided into one control group, one untreated group, one 50 mg/kg amantadine hydrochloride-treated group and three PCA groups treated 12 hours post-inoculation with 40, 20 or 10 mg/kg PCA for 7 days. All the infected animals were inoculated intranasally with 0.2 ml of a A/Chicken/Hebei/4/2008(H9N2) inoculum. A significant body weight loss was found in the 20 mg/kg and 40 mg/kg PCA-treated and amantadine groups as compared to the control group. The 14 day survivals were 94.4%, 100% and 95% in the PCA-treated groups and 94.4% in the amantadine hydrochloride group, compared to less than 60% in the untreated group. Virus loads were less in the PCA-treated groups compared to the amantadine-treated or the untreated groups. Neutrophil cells in BALF were significantly decreased while IFN-γ, IL-2, TNF-α and IL-6 decreased significantly at days 7 in the PCA-treated groups compared to the untreated group. Furthermore, a significantly decreased CD4+/CD8+ ratio and an increased proportion of CD19 cells were observed in the PCA-treated groups and amantadine-treated group compared to the untreated group. Mice administered with PCA exhibited a higher survival rate and greater viral clearance associated with an inhibition of inflammatory cytokines and activation of CD8+ T cell subsets. PCA is a promising novel agent against bird flu infection in the poultry industry.

Methanol extract of Antrodia camphorata protects against lipopolysaccharide-induced acute lung injury by suppressing NF-κB and MAPK pathways in mice

Antrodia camphorata (AC) has been used as a herbal medicine for drug intoxication for the treatment of inflammation syndromes and liver-related diseases in Taiwan. This study demonstrates the protective effect of the methanol extract of AC (MAC) on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Mice were treated with MAC 1 h before the intratracheal (I.T.) instillation of LPS challenge model. Lung injury was evaluated 6 h after LPS induction. Pretreatment with MAC markedly improved LPS-induced histological alterations and edema in lung tissues. Moreover, MAC also inhibited the release of pro-inflammatory mediators such as nitric oxide (NO), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-6 at 6 h in the bronchoalveolar lavage fluid (BALF) during LPS-induced lung injury. Furthermore, MAC reduced total cell number and protein concentrations in the BALF the pulmonary wet/dry weight (W/D) ratio, and myeloperoxidase activity and enhanced superoxide dismutase (SOD) activity in lung tissues. MAC also efficiently blocked protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and phosphorylation of mitogen-activated protein kinases (MAPKs) and inhibited the degradation of nuclear factor-kappa B (NF-κB) and IκBα. This is the first investigation in which MAC inhibited acute lung edema effectively, which may provide a potential target for treating ALI. MAC may utilize the NF-κB and MAPKs pathways and the regulation of SOD activity to attenuate LPS-induced nonspecific pulmonary inflammation.

Protocatechuic acid induces angiogenesis through PI3K-Akt-eNOS-VEGF signalling pathway

In this study, we sought to elucidate whether protocatechuic acid contributes to induce angiogenesis as well as its mechanisms. To this end, we examined the role of protocatechuic acid on human brain microvascular endothelial cell line (HBMEC) proliferation, invasion and tube formation in in vitro. For the study of mechanisms involved, the phosphoinositide 3 kinase (PI3K)-Akt inhibitor LY294002, the endothelial nitric oxide synthase (eNOS) inhibitor L-NAME, vascular endothelial growth factor (VEGF), antagonist sFlt-1 and VEGF receptor blocker SU-1498 were used. Proliferation of HBMEC was tested by MTT. Scratch adhesion test was used to assess the ability of invasion. A Matrigel tube formation assay was performed to test capillary tube formation ability. PI3K-Akt-eNOS-VEGF pathway activation in HBMEC was tested by Western blot. Our data suggested that protocatechuic acid induces angiogenesis in vitro by increasing proliferation, invasion and tube formation. VEGF expression was increasing by protocatechuic acid and counteracted by VEGF antagonist sFlt-1, LY294002 and L-NAME in HBMEC. Tube formation was increased by protocatechuic acid and counteracted by VEGF receptor blocker-SU1498, LY294002 and L-NAME. These data suggest that protocatechuic acid may be a candidate therapy for stroke recovery by promoting angiogenesis via a programmed PI3K/Akt/eNOS/VEGF signalling axis.

Protocatechuic acid suppresses ovalbumin-induced airway inflammation in a mouse allergic asthma model

Protocatechuic acid (PCA) has been isolated from the leaves of ilex chinenses and has numerous pharmacologic effects, including anti-inflammatory and antitumoral activities. This study aims to evaluate the antiasthma activity of PCA and investigate its possible molecular mechanisms. BALB/c mice were sensitized and challenged to ovalbumin (OVA).Then mice were intraperitoneally (i.p.) injected with PCA 1h before OVA challenge. We found that PCA treatment at 15 or 30 mg/kg significantly decreased OVA-induced airway hyper-responsiveness (AHR) to inhaled methacholine. Type 2 helper T cell (Th2) cytokines in bronchoalveolar lavage (BAL) fluid, such as interleukin-4 (IL-4), interleukin 5 (IL-5) and interleukin-13 (IL-13), and serum OVA-specific immunoglobulin E (IgE) levels, were also reduced by PCA. Moreover treatment with PCA markedly decreased the number of inflammatory cells in BALF and attenuated OVA-induced mRNA expression of CCl11, CCR3, Muc5ac, acidic mammalian chitinase (AMCase), chitinase 3-like protein 4 (Ym2) and E-selectin in lung tissues, lung histopathological studies showed that PCA inhibited inflammatory cell infiltration and mucus hypersecretion compared with the OVA-induced mice group. We then investigated the possible molecular mechanisms which might be implicated in PCA activity. Our results suggested that the protective effect of PCA might be mediated by the inhibition of the extracellular signal-regulated protein kinase (ERK), p38 Mitogen-activated protein kinase (MAPK) phosphorylation and the nuclear factor-κB (NF-κB) activation.