Piperine blocks interleukin-2-driven cell cycle progression in CTLL-2 T lymphocytes by inhibiting multiple signal transduction pathways

Immunosuppressive effects of triptolide via interleukin-2/receptor signaling

BACKGROUND

Triptolide (TP) has been confirmed to possess many beneficial functions including anti-inflammation and immunosuppression.

OBJECTIVE

The present study aimed to explore the potential involvement of IL-2/IL-2R pathway in the immunosuppressive activities of TP.

METHODS

Cultured CTLL-2 cells were utilized to evaluate the potential benefits of TP. Then cell viability was determined by CCK-8 assay, IFN-γ level by ELISA assay, Annexin V-FITC/PI double-staining and CD25 expression by flow cytometry, and protein expression by western blotting. Additionally, rhIL-2-driven lymphocytes following ConA activation were investigated. The interactions of TP with IL-2 and IL-2Rα were investigated by binding assays and molecular dynamics simulations.

RESULTS

TP treatment attenuated IFN-γ level and cell viability in both rhIL-2-induced CTLL-2 cells and rhIL-2-driven splenic lymphocytes. TP treatment increased cellular apoptosis/necrosis and cleaved PARP-1 level, while suppressed c-Myc level in rhIL-2-induced CTLL-2 cells. Additionally, TP treatment reduced CD25 expression on CTLL-2 cell surface. Notably, the phosphorylation protein levels in IL-2R signaling pathways were inhibited by TP exposure prior to rhIL-2 stimulation. SPR and BLI assays verified TP that directly bound to rhIL-2 and rmIL-2Rα, respectively. Molecular simulations suggested that TP bound at the interface of IL-2 and IL-2Rα near the hydrophobic patch composed of F62, L92 on IL-2 and L23, I46, V139 on IL-2Rα, resulting in decreased binding free energy between IL-2 and IL-2Rα.

CONCLUSIONS

These findings collectively emphasized that TP interfered IL-2/IL-2Rα interactions, down-regulated IL-2Rα expression, and inhibited IL-2R signaling pathways activation, thereby leading to the immune cells being desensitized to rhIL-2 and exhibiting immunosuppressive properties.

Synergistic enhancement: Exploring the potential of piperine in cancer therapeutics through chemosensitization and combination therapies

Despite significant advancements in chemotherapy, effective treatments for advanced cancer stages remain largely elusive due to chemoresistance. Resistance to anticancer agents in cancer cells can arise through various mechanisms, including multi-drug resistance, inhibition of apoptosis, modification of drug targets, and enhancement of DNA repair capabilities. Consequently, there is a critical need for agents that can suppress the molecular signatures responsible for drug resistance. Piperine, an active alkaloid extracted from Piper nigrum L. (black pepper), is one such agent that has been extensively studied for its potential in addressing chronic diseases, including cancer. Piperine's antineoplastic properties are mediated through the regulation of numerous key cellular signaling pathways and the modulation of various biological processes. Its capability to enhance drug bioavailability and counteract mechanisms of drug resistance, such as the inhibition of P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP-1), emphasizes its potential as an adjunct in cancer therapy. Research across various cancer types has demonstrated piperine's role in chemosensitization by targeting P-gp and MRP-1 and altering drug-metabolizing enzymes. This review provides a comprehensive analysis of piperine's pharmacological characteristics and its capacity to modulate several cellular signaling pathways involved in drug resistance. Furthermore, the review emphasizes how piperine, when used in conjunction with other chemotherapeutic agents or natural compounds, can enhance therapeutic effects, leading to improved outcomes in cancer treatment.

Effects of ginger extract and its major component 6-gingerol on anti-tumor property through mitochondrial biogenesis in CD8+ T cells

Ginger extract (GE) and its major component 6-gingerol (6G) have been reported to exert anti-tumor effects in various cancers. The underlying mechanism, however, has not been well demonstrated. Here, we have focused on the relationship between promotion of mitochondrial biogenesis in tumor infiltrating CD8+ T cells induced by GE and 6G and their cytotoxic effect. The results showed that GE induced 56% inhibition of tumor growth in Lewis lung carcinoma (LLC) xenograft mouse model and 6G induced 33% (25 mg/kg) and 37% (50 mg/kg) inhibition. GE increased mitochondrial mass of CD8+ T cells in tumor and draining lymph nodes (DLNs) significantly, while 6G had no significant effect. GE and 6G both had no significant influence on histopathological changes of liver and kidney in mice. In the co-culture system of CTLL-2 cells and LLC cells, GE enhanced the cytotoxicity of CTLL-2 cells against LLC cells by 14% and 19% at concentrations of 2.5 and 5 mg/ml, respectively. 6G did not promote cytotoxicity of CTLL-2 cells. GE increased mitochondrial mass at 5 and 10 mg/ml and mtDNA copy number and ATP production at 2.5, 5, 10 mg/ml in CTLL-2 cells. 6G promoted mtDNA copy number at 50, 100, 150 µM and mitochondrial mass and ATP production at 25, 50, 100, 150 µM in CTLL-2 cells. These results suggest that promotion of mitochondrial biogenesis and function in tumor infiltrating CD8+ T cells may play an essential role in GE-induced inhibition of tumor growth. The current results perfect the mechanism of anti-tumor effect of ginger, which is beneficial for further application in cancer management. PRACTICAL APPLICATION: Ginger, as a worldwide food seasoning and herbal medicine in traditional Chinese medicine, has been reported to possess anti-tumor efficacy. To our knowledge, it is the first time to focus on ginger's ability of promoting mitochondrial biogenesis in tumor infiltrating CD8+ T cells to explore the mechanism of its anti-tumor effect. Our observations demonstrate that ginger inhibits tumor growth via promoting mitochondrial biogenesis and function of T cells. The present study links food to anti-tumor immunity and provides impetus to investigate and design dietary supplements for cancer management.

Black pepper prevents anemia of inflammation by inhibiting hepcidin over-expression through BMP6-SMAD1/ IL6-STAT3 signaling pathway

Hepcidin, a circulatory hepatic peptide hormone, is associated with systemic iron homeostasis. Inflammation leads to an increase in hepcidin expression, which dysregulates body iron level. The related disorder, anemia of inflammation, is the second most prevalent anemia-related disorder worldwide. In the present study, we conducted in vitro and in vivo studies to evaluate the effect of black pepper (BP) and its major bioactive alkaloid, piperine, on anemia of inflammation. The initial in vitro study using human hepatocyte cell line, HepG2, confirmed that among different black pepper extracts: methanol (BPME), ethanol (BPEE) and aqueous (BPAE), BPME to be most effective in downregulating transcription of hepcidin gene. Further, BPME and piperine significantly downregulated hepcidin protein expression at 200 μg/ml and 100 μM concentrations, respectively. In the next phase, BPME and piperine were found to significantly attenuate BMP-6 and IL-6 induced hepcidin overexpression by downregulating the increased level of pSMAD1 and pSTAT3 proteins, respectively. For in vivo study, we first subcutaneously injected male BALB/c mice with oil of turpentine, thrice within a period of two weeks, in order to enhance the expression of hepcidin. After that, the intraperitoneal administration of BPME and piperine at 70 and 25 mg/kg body weight, respectively, on alternate days for a period of another two weeks resulted in downregulation of hepcidin overexpression in diseased mice, as confirmed by RT-PCR and immunoblot analysis. The histopathology of liver tissue confirmed increased iron bioavailability in BPME and piperine treated animals. The molecular docking-based interaction studies demonstrated the binding potential of piperine with SMAD1 and STAT3 proteins. The binding patterns supported the proposed inhibition of hepcidin activating proteins. All together, these findings suggest black pepper as a therapeutic candidate for the treatment of anemia of inflammation.

Long-Acting Human Interleukin 2 Bioconjugate Modified with Fatty Acids by Sortase A

Human Interleukin 2 (IL-2) has already achieved impressive results as a therapeutic agent for cancer and autoimmune diseases. However, one of the limitations associated with the clinical application of IL-2 is its short half-life owing to rapid clearance by the kidneys. Modification with fatty acids, as an albumin noncovalent ligand with the advantage of deep penetration into tissues and high activity-to-mass ratio, is a commonly used approach to improve the half-life of native peptides and proteins. In this investigation, we attempted to extend the half-life of IL-2 through conjugation with a fatty acid using sortase A (srtA). We initially designed and optimized three IL-2 analogues with different peptide linkers between the C-terminus of IL-2 and srtA recognition sequence (LPETG). Among these, analogue A3 was validated as the optimal IL-2 analogue for further modification. Next, six fatty acid moieties with the same fatty acid and different hydrophilic spacers were conjugated to A3 through srtA. The six bioconjugates generated were screened for in vitro biological activity, among which bioconjugate B6 was identified as near-optimal to IL-2. Additionally, B6 could effectively bind albumin through the conjugated fatty acid, which contributed to a significant improvement in its pharmacokinetic properties in vivo. In summary, we have developed a novel IL-2 bioconjugate, B6, modified with fatty acids using srtA, which may effectively serve as a new-generation long-acting IL-2 immunotherapeutic agent.

Intravitreal Interleukin-2 modifies retinal excitatory circuits and retinocollicular innervation

Interleukin-2 is a classical immune cytokine whose neural functions have received little attention. Its levels have been found to be increased in some neuropathologies, such as Alzheimer's disease, multiple sclerosis and uveitis. Mechanistically, it has been demonstrated the role of IL-2 in regulating glutamate and acetylcholine transmission, thus being relevant for CNS physiology. In fact, our previous work showed that an acute intravitreal IL-2 injection during retinotectal development promoted contralateral eye axonal plasticity in the superior colliculus, but the involved mechanisms were not explored. So, our present study aimed to investigate the effect of increased intravitreal IL-2 levels on the retinal glutamatergic and cholinergic signalling required for retinotectal normal development. We showed through HRP neuronal tracing that intravitreal IL-2 also induces ipsilateral eye axonal sprouting. Protein level and/or immunolocalization analysis in the retina confirmed IL-2 pathway activation by increased expression of phospho-STAT-3, coupled to transient (24h) reduced levels of Egr1, PSD-95 and nicotinic acetylcholine receptor β2 subunit, suggesting reduced neural activity and synaptic sites. Also, AChE activity and GluN2B and GluA2 contents were reduced within 96h after IL-2 treatment. Therefore, IL-2-induced retinotectal plasticity might be driven by changes in cholinergic and glutamatergic pathways of the retina.

Piperine: A review of its biological effects

Medicinal plants have been used for years as a source of food, spices, and, in traditional medicine, as a remedy to numerous diseases. Piper nigrum, belonging to the family Piperaceae is one of the most widely used spices all over the world. It has a distinct sharp flavor attributed to the presence of the phytochemical, piperine. Apart from its use as a spice, P. nigrum is frequently used for medicinal, preservation, and perfumery purposes. Black pepper contains 2-7.4% of piperine, varying in content is associated with the pepper plant. Piperine displays numerous pharmacological effects such as antiproliferative, antitumor, antiangiogenesis, antioxidant, antidiabetic, anti-obesity, cardioprotective, antimicrobial, antiaging, and immunomodulatory effects in various in vitro and in vivo experimental trials. Furthermore, piperine has also been documented for its hepatoprotective, anti-allergic, anti-inflammatory, and neuroprotective properties. This review highlights and discusses the medicinal and health-promoting effects of piperine, along with possible mechanisms of its action in health promotion and disease prevention. In addition, the present review summarizes the recent literature related to piperine as a therapeutic agent against several diseases.

Piperine-A Major Principle of Black Pepper: A Review of Its Bioactivity and Studies

Piperine is the main compound present in black pepper, and is the carrier of its specific pungent taste, which is responsible for centuries of human dietary utilization and worldwide popularity as a food ingredient. Along with the application as a food ingredient and food preservative, it is used in traditional medicine for many purposes, which has in most cases been justified by modern scientific studies on its biological effects. It has been confirmed that piperine has many bioactive effects, such as antimicrobial action, as well as many physiological effects that can contribute to general human health, including immunomodulatory, hepatoprotective, antioxidant, antimetastatic, antitumor, and many other activities. Clinical studies demonstrated remarkable antioxidant, antitumor, and drug availability-enhancing characteristics of this compound, together with immunomodulatory potential. All these facts point to the therapeutic potential of piperine and the need to incorporate this compound into general health-enhancing medical formulations, as well as into those that would be used as adjunctive therapy in order to enhance the bioavailability of various (chemo)therapeutic drugs.

Gelatinase B/matrix metalloproteinase-9 and other neutrophil proteases switch off interleukin-2 activity

Interleukin 2 (IL-2) is critical for T cell development and homeostasis, being a key regulator of adaptive immune responses in autoimmunity, hypersensitivity reactions and cancer. Therefore, its abundance in serum and peripheral tissues needs tight control. Here, we described a new mechanism contributing to the immunobiology of IL-2. We demonstrated, both in biochemical and cell-based assays, that IL-2 is subject to proteolytic processing by neutrophil matrix metalloproteinase-9 (MMP-9). IL-2 fragments produced after cleavage by MMP-9 remained linked by a disulfide bond and displayed a reduced affinity for all IL-2 receptor subunits and a distinct pattern and timing of signal transduction. Stimulation of IL-2-dependent cells, including murine CTLL-2 and primary human regulatory T cells, with cleaved IL-2 resulted in significantly decreased proliferation. The concerted action of neutrophil proteases destroyed IL-2. Our data suggest that in neutrophil-rich inflammatory conditions in vivo, neutrophil MMP-9 may reduce the abundance of signaling-competent IL-2 and generate a fragment that competes with IL-2 for receptor binding, whereas the combined activity of granulocyte proteases has the potential to degrade and thus eliminate bioavailable IL-2.

Black pepper and its bioactive constituent piperine: promising therapeutic strategies for oral lichen planus

Oral lichen planus (OLP) is a common T cell-mediated chronic inflammatory disease with malignant potential and unclear etiology. The present study suggests that antigen-specific mechanisms in which dentritic cells, T lymphocytes and NF-κB signaling pathway play critical roles, are involved in the pathogenesis of OLP. Additionally, it has been indicated that altered expression of cyclooxygenase 2 (COX-2) and imbalanced oxidant-antioxidant status as well as psychological issue may act as promoters to the development of OLP. Therapies for OLP are primarily aimed to control symptoms and a specific cure is not yet available. Black pepper and its principle bioactive compound piperine have been reported to possess remarkable pharmacological activities. Not only has piperine been evidenced to exhibit repressive effects on the maturation of dentritic cells, the proliferation, activation and function of T lymphocytes as well as the NF-κB signaling pathway, but also to suppress the overproduction of COX-2 and weaken the oxidative stress. Furthermore, piperine might be a possible agent for alleviating psychological disorders and preventing carcinogenesis. Given all these into consideration, piperine may be a novel and effective therapeutic strategy for OLP.

Piperine depresses the migration progression via downregulating the Akt/mTOR/MMP‑9 signaling pathway in DU145 cells

Piperine, an alkaloid derived from natural products, has been demonstrated to exert antitumor activities in vivo and in vitro. However, its anti-tumor effect has not yet been illustrated in the prostate cancer (PCa) metastatic process. Thus, the present study explored the influence of piperine on PCa and the underlying molecular mechanism. Cell migration was detected via the Transwell chamber model. Total protein was identified by western blot analysis. The data revealed that piperine markedly repressed cell proliferation and migration, and induced apoptosis in PCa DU145. In addition, LY294002, an protein kinase B (Akt) inhibitor, greatly suppressed the expression level of phospho (p)-Akt, matrix metalloproteinase (MMP)-9 and p-mammalian target of rapamycin (mTOR), suggesting that the activation of the Akt/mTOR/MMP-9 signaling pathway may participate in regulating cell migration in PCa. Furthermore, piperine reduced the expression of p-Akt, MMP-9 and p-mTOR. Together, these data indicated that piperine may serve as a promising novel therapeutic agent to better overcome PCa metastasis.

Structure-activity relationship of piperine and its synthetic amide analogs for therapeutic potential to prevent experimentally induced ER stress in vitro

Endoplasmic reticulum (ER) is the key organelle involved in protein folding and maturation. Emerging studies implicate the role of ER stress in the development of chronic kidney disease. Thus, there is an urgent need for compounds that could ameliorate ER stress and prevent CKD. Piperine and its analogs have been reported to exhibit multiple pharmacological activities; however, their efficacy against ER stress in kidney cells has not been studied yet. Hence, the goal of this study was to synthesize amide-substituted piperine analogs and screen them for pharmacological activity to relieve ER stress using an in vitro model of tunicamycin-induced ER stress using normal rat kidney (NRK-52E) cells. Five amide-substituted piperine analogs were synthesized and their chemical structures were elucidated by pertinent spectroscopic techniques. An in vitro model of ER stress was developed using tunicamycin, and the compounds of interest were screened for their effect on cell viability, and the expression of ER chaperone GRP78, the pro-apoptotic ER stress marker CHOP, and apoptotic caspases 3 and 12 (via western blotting). Our findings indicate that exposure to tunicamycin (0.5 μg/mL) for 2 h induces the expression of GRP78 and CHOP, and apoptotic markers (caspase-3 and caspase-12) and causes a significant reduction in renal cell viability. Pre-treatment of cells with piperine and its cyclohexylamino analog decreased the tunicamycin-induced upregulation of GRP78 and CHOP and cell death. Taken together, our findings demonstrate that piperine and its analogs differentially regulate ER stress, and thus represent potential therapeutic agents to treat ER stress-related renal disorders. Graphical Abstract Piperine (PIP) reduces the expression of ER stress markers (GRP78 and CHOP) induced by pathologic stimuli and consequently decreases the activation of apoptotic caspase-12 and caspase-3; all of which contributes to its chemical chaperone and cytoprotective properties to protect renal cells against ER stress and ER stress-induced cell death, and would ultimately prevent the development of chronic kidney disease.

Piperine, a Pungent Alkaloid from Black Pepper, Inhibits B Lymphocyte Activation and Effector Functions

Piperine has several well-documented anti-inflammatory properties; however, little is known regarding its effect on humoral immunity. In this study, we describe the immunosuppressive effect of piperine on B lymphocytes, which are integral to the humoral immune response. Mouse B cells were cultured in the absence or presence of non-cytotoxic concentrations (25, 50, and 100 μM) of piperine during T-dependent or T-independent stimulation. Piperine inhibited B cell proliferation by causing G0/G1 phase cell cycle arrest in association with reduced expression of cyclin D2 and D3. The inhibitory effect of piperine was not mediated through transient receptor potential vanilloid-1 ion channel (TRPV1) because piperine also inhibited the proliferation of B cells from TRPV1-deficient mice. Expression of class II major histocompatibility complex molecules and costimulatory CD40 and CD86 on B lymphocytes was reduced in the presence of piperine, as was B cell-mediated antigen presentation to syngeneic T cells. In addition, piperine inhibited B cell synthesis of interleukin (IL)-6 and IL-10 cytokines, as well as IgM, IgG2b, and IgG3 immunoglobulins. The inhibitory effect of piperine on B lymphocyte activation and effector function warrants further investigation for possible application in the treatment of pathologies related to inappropriate humoral immune responses. Copyright © 2017 John Wiley & Sons, Ltd.

Identifying novel protein phenotype annotations by hybridizing protein-protein interactions and protein sequence similarities

Studies of protein phenotypes represent a central challenge of modern genetics in the post-genome era because effective and accurate investigation of protein phenotypes is one of the most critical procedures to identify functional biological processes in microscale, which involves the analysis of multifactorial traits and has greatly contributed to the development of modern biology in the post genome era. Therefore, we have developed a novel computational method that identifies novel proteins associated with certain phenotypes in yeast based on the protein-protein interaction network. Unlike some existing network-based computational methods that identify the phenotype of a query protein based on its direct neighbors in the local network, the proposed method identifies novel candidate proteins for a certain phenotype by considering all annotated proteins with this phenotype on the global network using a shortest path (SP) algorithm. The identified proteins are further filtered using both a permutation test and their interactions and sequence similarities to annotated proteins. We compared our method with another widely used method called random walk with restart (RWR). The biological functions of proteins for each phenotype identified by our SP method and the RWR method were analyzed and compared. The results confirmed a large proportion of our novel protein phenotype annotation, and the RWR method showed a higher false positive rate than the SP method. Our method is equally effective for the prediction of proteins involving in all the eleven clustered yeast phenotypes with a quite low false positive rate. Considering the universality and generalizability of our supporting materials and computing strategies, our method can further be applied to study other organisms and the new functions we predicted can provide pertinent instructions for the further experimental verifications.

Piperine impairs the migration and T cell-activating function of dendritic cells

Piperine, a major alkaloid found in the fruits of black and long pepper plants, has anti-inflammatory properties; however, piperine's effect on dendritic cell (DC) migration and T cell-activating function has not been investigated. Bone marrow-derived mouse DCs that were matured in the presence of 100 μM piperine showed reduced in vitro migration in response to CCL21, as well as reduced in vivo migration to lymph nodes. In addition, piperine-treated DCs had reduced CCR7 expression and elevated CCR5 expression, as well as reduced expression of CD40 and class II major histocompatibility complex molecules and decreased nuclear accumulation of RelB. DC production of interleukin (IL)-6, tumor necrosis factor α, and monocyte chemoattractant protein-1 in response to lipopolysaccharide stimulation was also reduced following piperine treatment. Exposure to piperine during maturation therefore caused DCs to retain an immature phenotype, which was associated with a reduced capacity to promote T cell activation since co-culture of ovalbumin (OVA323-339)-specific T cells with OVA323-339-pulsed DCs that were previously matured in the presence of piperine showed reduced interferon-γ and IL-2 expression. OVA323-339-specific T cell proliferation was also reduced in vivo in the presence of piperine-treated DCs. Inhibition of DC migration and function by piperine may therefore be a useful strategy to down-regulate potentially harmful DC-driven T cell responses to self-antigens and transplantation antigens.