Novel non-specific lipid-transfer protein (TdLTP4) isolated from durum wheat: Antimicrobial activities and anti-inflammatory properties in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages

Lipid transfer protein VAS inhibits the hypersensitive response via reactive oxygen species signaling in Nicotiana benthamiana

Lipid transfer proteins (LTPs) are small cysteine-rich soluble proteins that affect flower and seed development, cuticular wax deposition, and biotic and abiotic stress responses. We isolated an LTP-encoding gene homologous to LTPVAS in Nicotiana benthamiana and designated it LTP-VASCULAR TISSUE SIZE (NbLTPVAS). This gene was expressed in seeds, leaves, roots, and stems. Additionally, NbLTPVAS expression was induced by hypersensitive response (HR)-inducing agents. Cell death was accelerated and the phytopathogenic bacterial population decreased significantly in NbLTPVAS-silenced plants infected with the incompatible Ralstonia solanacearum strain 8107. The expression of HR marker gene hin1 in NbLTPVAS-silenced plants was markedly induced by R. solanacearum 8107, indicative of the acceleration of HR. HR cell death in NbLTPVAS-silenced plants was also promoted by the Agrobacterium-mediated expression of HR-inducing proteins including INF1, AvrA, and PopP1. Excessive production of reactive oxygen species (ROS) was detected in NbLTPVAS-silenced plants. The expression of NbrbohB (encoding a ROS-generating enzyme) also increased in NbLTPVAS-silenced plants, but the expression of the antioxidant enzyme-encoding genes NbSOD and NbAPX decreased. The silencing of both NbLTPVAS and NbrbohB adversely affected HR induction. Moreover, NbLTPVAS was secreted into the intercellular washing fluid. The transient expression of the full-length NbLTPVAS induced the expression of antioxidant genes, attenuated ROS production, and suppressed the induction of HR cell death. This is the first functional analysis of LTPVAS in plant-microbe interactions. Our study provides novel insights into the role of NbLTPVAS as a negative regulator of HR via ROS homeostasis in N. benthamiana.

Soybean transcription factor GmNF-YB20 confers resistance to stripe rust in transgenic wheat by regulating nonspecific lipid transfer protein genes

Worldwide food security is severely threatened by the devastating wheat stripe rust disease. The utilization of resistant wheat cultivars represents the most cost-effective and efficient strategy for combating this disease. However, the lack of resistant resources has been a major bottleneck in breeding for wheat disease resistance. Therefore, revealing novel gene resources for combating stripe rust and elucidating the underlying resistance mechanism is of utmost urgency. In this study, we identified that the soybean NF-YB transcription factor GmNF-YB20 in wheat provides resistance to the stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst). Wheat lines with stable overexpression of the GmNF-YB20 enhanced resistance against multiple Pst races. Transcriptome profiling of GmNF-YB20 transgenic wheat under Pst infection unveiled its involvement in the lipid signaling pathway. RT-qPCR assays suggested that GmNF-YB20 increased transcript levels of multiple nonspecific lipid transfer protein (LTP) genes during wheat-Pst interaction, luciferase reporter analysis illustrates that it activates the transcription of TaLTP1.50 in wheat protoplast, and GmNF-YB20 overexpressed wheat plants had higher total LTP content in vivo during Pst infection. Overexpression of TaLTP1.50 in wheat significantly increased resistance to Pst, whereas knockdown of TaLTP1.50 exhibited the opposite trends, indicating that TaLTP1.50 plays a positive role in wheat resistance. Taken together, our findings provide perspective regarding the molecular mechanism of GmNF-YB20 in wheat and highlight the potential use for wheat breeding.

Co-release of nitric oxide and L-arginine from poly (β-amino ester)-based adhesive reprogram macrophages for accelerated wound healing and angiogenesis in vitro and in vivo

Recently, insufficient angiogenesis and prolonged inflammation are crucial challenges of chronic skin wound healing. The sustained release of L-Arginine (L-Arg) and nitric oxide (NO) production can control immune responses, improve angiogenesis, enhance re-epithelialization, and accelerate wound healing. Here, we aim to improve wound healing via the controlled release of NO and L-Arg from poly (β-amino ester) (PβAE). In this regard, PβAE is functionalized with methacrylate poly-L-Arg (PAMA), and the role of PAMA content (50, 66, and 75 wt%) on the adhesive properties, L-Arg, and NO release, as well as collagen deposition, inflammatory responses, and angiogenesis, is investigated in vitro and in vivo. Results show that the PAMA/ PβAE could provide suitable adhesive strength (~25 kPa) for wound healing application. In addition, increasing the PAMA content from 50 to 75 wt% results in an increased release of L-Arg (approximately 1.4-1.7 times) and enhanced NO production (approximately 2 times), promoting skin cell proliferation and migration. The in vitro studies also show that compared to PβAE hydrogel, incorporation of 66 wt% PAMA (PAMA 66 sample) reveals superior collagen I synthesis (~ 3-4 times) of fibroblasts, controlled pro-inflammatory and improved anti-inflammatory cytokines secretion of macrophages, and accelerated angiogenesis (~1.5-2 times). In vivo studies in a rat model with a full-thickness skin defect also demonstrate the PAMA66 sample could accelerate wound healing (~98 %) and angiogenesis, compared to control (untreated wound) and Tegaderm™ commercial wound dressing. In summary, the engineered multifunctional PAMA functionalized PβAE hydrogel with desired NO and L-Arg release, and adhesive properties can potentially reprogram macrophages and accelerate skin healing for chronic wound healing.

Oomycete pathogen pectin acetylesterase targets host lipid transfer protein to reduce salicylic acid signaling

During initial stages of microbial invasion, the extracellular space (apoplast) of plant cells is a vital battleground between plants and pathogens. The oomycete plant pathogens secrete an array of apoplastic carbohydrate active enzymes, which are central molecules for understanding the complex plant-oomycete interactions. Among them, pectin acetylesterase (PAE) plays a critical role in the pathogenesis of plant pathogens including bacteria, fungi, and oomycetes. Here, we demonstrated that Peronophythora litchii (syn. Phytophthora litchii) PlPAE5 suppresses litchi (Litchi chinensis) plant immunity by interacting with litchi lipid transfer protein 1 (LcLTP1). The LcLTP1-binding activity and virulence function of PlPAE5 depend on its PAE domain but not on its PAE activity. The high expression of LcLTP1 enhances plant resistance to oomycete and fungal pathogens, and this disease resistance depends on BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1) and Suppressor of BIR1 (SOBIR1) in Nicotiana benthamiana. LcLTP1 activates the plant salicylic acid (SA) signaling pathway, while PlPAE5 subverts the LcLTP1-mediated SA signaling pathway by destabilizing LcLTP1. Conclusively, this study reports a virulence mechanism of oomycete PAE suppressing plant LTP-mediated SA immune signaling and will be instrumental for boosting plant resistance breeding.

LIPID TRANSFER PROTEIN4 regulates cotton ceramide content and activates fiber cell elongation

Cell elongation is a fundamental process for plant growth and development. Studies have shown lipid metabolism plays important role in cell elongation; however, the related functional mechanisms remain largely unknown. Here, we report that cotton (Gossypium hirsutum) LIPID TRANSFER PROTEIN4 (GhLTP4) promotes fiber cell elongation via elevating ceramides (Cers) content and activating auxin-responsive pathways. GhLTP4 was preferentially expressed in elongating fibers. Over-expression and down-regulation of GhLTP4 led to longer and shorter fiber cells, respectively. Cers were greatly enriched in GhLTP4-overexpressing lines and decreased dramatically in GhLTP4 down-regulating lines. Moreover, auxin content and transcript levels of indole-3-acetic acid (IAA)-responsive genes were significantly increased in GhLTP4-overexpressing cotton fibers. Exogenous application of Cers promoted fiber elongation, while NPA (N-1-naphthalic acid, a polar auxin transport inhibitor) counteracted the promoting effect, suggesting that IAA functions downstream of Cers in regulating fiber elongation. Furthermore, we identified a basic helix-loop-helix transcription factor, GhbHLH105, that binds to the E-box element in the GhLTP4 promoter region and promotes the expression of GhLTP4. Suppression of GhbHLH105 in cotton reduced the transcripts level of GhLTP4, resulting in smaller cotton bolls and decreased fiber length. These results provide insights into the complex interactions between lipids and auxin-signaling pathways to promote plant cell elongation.

The Anti-Inflammatory Effect of Low Molecular Weight Fucoidan from Sargassum siliquastrum in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages via Inhibiting NF-κB/MAPK Signaling Pathways

Brown seaweed is a rich source of fucoidan, which exhibits a variety of biological activities. The present study discloses the protective effect of low molecular weight fucoidan (FSSQ) isolated from an edible brown alga, Sargassum siliquastrum, on lipopolysaccharide (LPS)-stimulated inflammatory responses in RAW 264.7 macrophages. The findings of the study revealed that FSSQ increases cell viability while decreasing intracellular reactive oxygen species production in LPS-stimulated RAW 264.7 macrophages dose-dependently. FSSQ reduced the iNOS and COX-2 expression, inhibiting the NO and prostaglandin E2 production. Furthermore, mRNA expression of IL-1β, IL-6, and TNF-α was downregulated by FSSQ via modulating MAPK and NF-κB signaling. The NLRP3 inflammasome protein complex, including NLRP3, ASC, and caspase-1, as well as the subsequent release of pro-inflammatory cytokines, such as IL-1β and IL-18, release in LPS-stimulated RAW 264.7 macrophages was inhibited by FSSQ. The cytoprotective effect of FSSQ is indicated via Nrf2/HO-1 signaling activation, which is considerably reduced upon suppression of HO-1 activity by ZnPP. Collectively, the study revealed the therapeutic potential of FSSQ against inflammatory responses in LPS-stimulated RAW 264.7 macrophages. Moreover, the study suggests further investigations on commercially viable methods for fucoidan isolation.

A non-specific lipid transfer protein, NtLTPI.38, positively mediates heat tolerance by regulating photosynthetic ability and antioxidant capacity in tobacco

Non-specific lipid transfer proteins (nsLTPs) play an important role in plant growth and stress resistance; however, their function in tobacco remains poorly understood. Therefore, to explore the function of NtLTP in response to high temperature, we identified an NtLTPI.38 from tobacco, obtained its overexpression and knockout transgenic plants, and further studied their response to heat stress (42 °C). The results showed that NtLTPI.38 overexpression in tobacco reduced chlorophyll degradation, alleviated the high temperature damage to photosynthetic organs, and enhanced the photosynthetic capacity of tobacco under heat stress. NtLTPI.38 overexpression in heat-stressed tobacco increased the contents of soluble sugar and protein, proline, and flavonoid substances, reduced the relative conductivity, and decreased H₂O₂, O₂^•-, and MDA accumulation, and increased the enzymatic antioxidant activities, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), compared to wild type (WT) and knockout mutant plants. RT-PCR confirmed that the expression levels of antioxidant enzymes and thermal stress-related genes were significantly upregulated under thermal stress in overexpression plants. Therefore, NtLTPI.38 enhanced heat tolerance in tobacco by mitigating photosynthetic damage and improving osmoregulation and antioxidant capacity. These results provided the theoretical basis and a potential resource for further breeding projects to improve heat tolerance in plants.

Inhibition of Staphylococcus aureus biofilms by poly-L-aspartic acid nanoparticles loaded with Litsea cubeba essential oil

Staphylococcus aureus (S. aureus) biofilms contamination on various food-contacting surfaces is considered a significant threat in the field of food. Poly-L-aspartic acid (PASP) was proven to damage biofilm by affecting bacterial adhesion, metabolic activity, and extracellular polymeric substances in this study. Especially for eDNA, its generation was reduced by 49.4 %. After treatment with 5 mg/mL of PASP, the number of S. aureus in the biofilm at different growth stages decreased by 1.20-1.68 log CFU/mL. The nanoparticles prepared by PASP and hydroxypropyl trimethyl ammonium chloride chitosan were used to embed LC-EO (EO@PASP/HACCNPs). The results indicated that the particle size of the optimized nanoparticles was 209.84 nm with an encapsulation rate of 70.28 %. Compared to LC-EO alone, EO@PASP/HACCNPs had more significant permeation and dispersion effects on biofilms and possessed long-lasting anti-biofilm activity. For the biofilm grown for 72 h, the population of S. aureus in the EO@PASP/HACCNPs-treated biofilm was additionally reduced by 0.63 log CFU/mL compared with the LC-EO-treated group. EO@PASP/HACCNPs were also applied to different food-contacting materials. The lowest inhibition rate of EO@PASP/HACCNPs on S. aureus biofilm still reached 97.35 %. The sensory properties of the chicken breast were not affected by EO@PASP/HACCNPs.

Immunomodulatory effect of Linalool (Lin) against CCl4 -induced hepatotoxicity and oxidative damage in rats

The current study explored the hepatoprotective and immunomodulatory effects of Linalool (Lin) against carbon tetrachloride (CCl₄ )-induced toxicity in mice. Four study groups (n = 8 each) were used: (1) a negative control group and (2) a toxicity control group (single dose of CCl₄ administered on day 14 as 1 mL/kg of CCL₄ in 1% olive oil). Intraperitoneally (i.p.)), and two experimental groups where mice were treated with either (3) Lin (25 mg/kg b.w., orally, daily for 15 days) or (4) pretreated with Lin (25 mg/kg b.w., orally, daily for 14 days) and intoxicated with CCl₄ (1 mL/kg of CCL₄ in 1% olive oil. i.p.) on day 14. The levels of the anti-inflammatory cytokine interleukin 10 (IL-10), the proinflammatory cytokines TNF-α, IL-6, and TGF-1β, and the histopathology of the liver were assessed. According to our findings, IL-10 concentrations were significantly increased in Lin-treated groups, while other cytokine levels were marked by a considerable decrease in the toxicity model group (CCl₄ -treated group). Histopathological examinations of liver tissues showed that the Lin-treated groups had an almost normal structure. The current findings showed that Lin could inhibit CCl₄ -induced liver injury in mice, which warrants further investigation of Lin as a potential protective and therapeutic agent against hepatotoxicity.

Lipid transfer proteins involved in plant-pathogen interactions and their molecular mechanisms

Nonspecific lipid transfer proteins (LTPs) are small, cysteine-rich proteins that play numerous functional roles in plant growth and development, including cutin wax formation, pollen tube adhesion, cell expansion, seed development, germination, and adaptation to changing environmental conditions. LTPs contain eight conserved cysteine residues and a hydrophobic cavity that provides a wide variety of lipid-binding specificities. As members of the pathogenesis-related protein 14 family (PR14), many LTPs inhibit fungal or bacterial growth, and act as positive regulators in plant disease resistance. Over the past decade, these essential immunity-related roles of LTPs in plant immune processes have been documented in a growing body of literature. In this review, we summarize the roles of LTPs in plant-pathogen interactions, emphasizing the underlying molecular mechanisms in plant immune responses and specific LTP functions.

Addition of Natural Extracts with Antioxidant Function to Preserve the Quality of Meat Products

Antioxidants are used to prevent oxidation reactions and inhibit the development of unwanted sensory characteristics that decrease the nutritional quality, acceptance, and shelf-life of processed meat products, improving their stability. Synthetic antioxidants, although efficient, are related to the development of diseases because they present toxic and carcinogenic effects. Thus, researchers and the meat industry are studying natural alternatives to synthetic antioxidants to be used in meat products, thus meeting the demand of consumers who seek foods without additives in their composition. These natural extracts have compounds that exert antioxidant activity in different meat products by different mechanisms. Thus, this review work aimed to gather studies that applied natural extracts derived from different plant sources as possible antioxidants in meat products and their action in preserving the quality of these products.

Potato (Solanum tuberosum L.) non-specific lipid transfer protein StLTP6 promotes viral infection by inhibiting virus-induced RNA silencing

For the first time it is reported that members of the nsLTP protein family could promote viral infection by inhibiting virus-induced RNA silencing. Non-specific lipid transfer proteins (nsLTPs) are a class of soluble proteins with low relative molecular weight and widely present in higher plants. The role of nsLTPs in biotic and abiotic stresses has been studied, but no report has shown that nsLTPs play a role in the process of viral infection. We report the function and mechanism of the classical nsLTP protein StLTP6 in viral infection. We found that StLTP6 expression was remarkably upregulated in potato infected with potato virus Y and potato virus S. The infection efficiency and virus content of StLTP6-overexpressed potato and Nicotiana benthamiana were remarkable increased. Further study found that the overexpression of StLTP6 inhibited the expression of multiple genes in the RNA silencing pathway, thereby inhibiting virus-induced RNA silencing. This result indicated that StLTP6 expression was induced during viral infection to inhibit the resistance of virus-induced RNA silencing and promote viral infection. In summary, we reported the role of StLTP6 in viral infection, broadening the biological function range of the nsLTP family and providing valuable information for the study of viral infection mechanism.

Antioxidant and hepatoprotective effects of novel heteropolysaccharide isolated from Lobularia maritima on CCl4-induced liver injury in rats

The aim of the present study was to investigate the extraction and the characterization of a novel heteropolysaccharide from Tunisian halophyte Lobularia maritima (LmPS). We were also interested in its antioxidant, anti-inflammatory, and hepatoprotective effects on carbon tetrachloride (CCl4)-induced liver injury in rats. LmPS physicochemical properties were evaluated by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and UV absorption. According to TLC and HPLC results, LmPS was a heteropolysaccharide composed of glucose, galactose, and xylose. Its molecular weight was 130.62 kDa. This heteropolysaccharide was characterized by a significant antioxidant potential and was efficient against oxidative stress and CCL4-induced hepatotoxicity in rat Wistar models (n = 8) treated with a single dose of LmPS 250 mg/kg of body weight. This was evidenced by a significant increase in serum marker enzymes specially aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). The cytokines released after stimulation of rats with LmPS showed high anti-inflammatory profiles with an increased rate of interleukine-10 (IL-10) with 0.03 pg/mL compared to animals treated only with CCl4. On the contrary, we noticed a decrease of the other cytokines (tumor necrosis factor α: TNF-α, interleukine-6: IL-6, transforming growth factor beta 1: TGF-β1) with average concentration values of <0.2, 0.1, and 0.04 pg/mL, respectively. Besides, histopathological examinations revealed that CCl4 causes acute liver damage, characterized by extensive hepatocellular necrosis, vacuolization, and inflammatory cell infiltration, as well as DNA fragmentation. LmPS administration at a dose of 250 mg/kg resulted in a significant hepatoprotection, evidenced by a reduction of CCl4-induced oxidative damage for all tested markers. These findings eagerly confirmed that LmPS was effective in the protection against CCl4-induced hepatotoxicity and genotoxicity. It, therefore, suggested a potential therapeutic use of this polysaccharide as an alternative medicine for patients with acute liver diseases.

Thiamine Demonstrates Bio-Preservative and Anti-Microbial Effects in Minced Beef Meat Storage and Lipopolysaccharide (LPS)-Stimulated RAW 264.7 Macrophages

This study assessed the anti-inflammatory effect of thiamine (TA) in lipopolysaccharide-stimulated RAW264.7 cells and also assessed the preservative properties of TA in minced beef. TA demonstrated a concentration-dependent antimicrobial effect on microbial contaminants. Inhibition zones and MIC from the effect of TA on the tested bacterial strains were respectively within the ranges 15−20 mm and 62.5−700 µg/mL. TA significantly (p < 0.05) decreased all the pro-inflammatory factors [(nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α, IL-6, IL-1β, and nuclear factor-κB (NF-κB)] monitored relative to LPS-stimulated RAW264.7 cells. TA inhibited the expression of both iNOS and COX-2. In minced beef flesh, the growth of Listeria monocytogenes was inhibited by TA. TA improved physicochemical and microbiological parameters of stored minced beef meat compared to control. Principal component analyses and heat maps elucidate the quality of the tested meats.

NLRP3 priming due to skin damage precedes LTP allergic sensitization in a mouse model

Allergic sensitization is initiated by protein and epithelia interaction, although the molecular mechanisms leading this encounter toward an allergic phenotype remain unknown. Here, we apply the two-hit hypothesis of inflammatory diseases to the study of food allergy sensitization. First, we studied the effects of long-term depilation in mice by analyzing samples at different time points. Several weeks of depilation were needed until clear immunological changes were evidenced, starting with upregulation of NLRP3 protein levels, which was followed by overexpression of Il1b and Il18 transcripts. Secondly, we assessed the effects of allergen addition (in this case, Pru p 3 in complex with its natural lipid ligand) over depilated skin. Systemic sensitization was evaluated by intraperitoneal provocation with Pru p 3 and measure of body temperature. Anaphylaxis was achieved, but only in mice sensitized with Prup3_complex and not treated with the NLRP3 inhibitor MCC950, thus demonstrating the importance of both hits (depilation + allergen addition) in the consecution of the allergic phenotype. In addition, allergen encounter (but not depilation) promoted skin remodeling, as well as CD45+ infiltration not only in the sensitized area (the skin), but across several mucosal tissues (skin, lungs, and gut), furtherly validating the systemization of the response. Finally, a low-scale study with human ILC2s is reported, where we demonstrate that Prup3_complex can induce their phenotype switch (↑CD86, ↑S1P1) when cultured in vitro, although more data is needed to understand the implications of these changes in food allergy development.

Plant non-specific lipid transfer proteins: An overview

Plant non-specific lipid transfer proteins (nsLTPs) are usually defined as small, basic proteins, with a wide distribution in all orders of higher plants. Structurally, nsLTPs contain a conserved motif of eight cysteines, linked by four disulphide bonds, and a hydrophobic cavity in which the ligand is housed. This structure confers stability and enhances the ability to bind and transport a variety of hydrophobic molecules. Their highly conserved structural resemblance but low sequence identity reflects the wide variety of ligands they can carry, as well as the broad biological functions to which they are linked to, such as membrane stabilization, cell wall organization and signal transduction. In addition, they have also been described as essential in resistance to biotic and abiotic stresses, plant growth and development, seed development, and germination. Hence, there is growing interest in this family of proteins for their critical roles in plant development and for the many unresolved questions that need to be clarified, regarding their subcellular localization, transfer capacity, expression profile, biological function, and evolution.