Immunomodulatory Functions of the Human Cathelicidin LL-37 (aa 13-31)-Derived Peptides are Associated with Predicted α-Helical Propensity and Hydrophobic Index

Cathelicidin (LL-37) causes expression of inflammatory factors in coronary artery endothelial cells of Kawasaki disease by activating TLR4-NF-κB-NLRP3 signaling

BACKGROUND

Kawasaki disease (KD) is a type of vasculitis with an unidentified etiology. Cathelicidin (LL-37) may be involved in the development of the KD process; therefore, further research to investigate the molecular mechanism of LL-37 involvement in KD is warranted.

METHODS

Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, NLRP3, and LL-37 in the sera of healthy subjects, children with KD, and children with pneumonia. Subsequently, human recombinant LL-37 or/and toll-like receptors 4 (TLR4)-specific inhibitor TAK-242 stimulated human coronary artery endothelial cells (HCAECs), CCK-8 was used to detect cell proliferation, flow cytometry to detect apoptosis, transmission electron microscopy to observe cytoskeletal changes, Transwell to measure cell migration ability, ELISA to detect inflammatory factor levels, Western blot analysis to analyze protein levels of toll-like receptors 4 (TLR4) and NF-κB p-65, and quantitative real-time polymerase chain reaction (qRT-PCR) to determine LL-37, NLRP3 mRNA levels.

RESULTS

In this study, we found that the level of LL-37 was highly expressed in the serum of children with KD, and after LL-37 stimulation, apoptosis was significantly increased in HCAECs, and the expression levels of TLR4, NLRP3 and inflammatory factors in cells were significantly enhanced. Intervention with the TLR4-specific inhibitor TAK-242 significantly alleviated the LL-37 effects on cellular inflammation, TLR4, NLRP3 promotion effect.

CONCLUSIONS

Our data suggest that LL-37 induces an inflammatory response in KD coronary endothelial cells via TLR4-NF-κB-NLRP3, providing a potential target for the treatment of KD.

Role of Anti-Cancer Peptides as Immunomodulatory Agents: Potential and Design Strategy

The usage of peptide-based drugs to combat cancer is gaining significance in the pharmaceutical industry. The collateral damage caused to normal cells due to the use of chemotherapy, radiotherapy, etc. has given an impetus to the search for alternative methods of cancer treatment. For a long time, antimicrobial peptides (AMPs) have been shown to display anticancer activity. However, the immunomodulatory activity of anti-cancer peptides has not been researched very extensively. The interconnection of cancer and immune responses is well-known. Hence, a search and design of molecules that can show anti-cancer and immunomodulatory activity can be lead molecules in this field. A large number of anti-cancer peptides show good immunomodulatory activity by inhibiting the pro-inflammatory responses that assist cancer progression. Here, we thoroughly review both the naturally occurring and synthetic anti-cancer peptides that are reported to possess both anti-cancer and immunomodulatory activity. We also assess the structural and biophysical parameters that can be utilized to improve the activity. Both activities are mostly reported by different groups, however, we discuss them together to highlight their interconnection, which can be used in the future to design peptide drugs in the field of cancer therapeutics.

Potential Pathogenetic Role of Antimicrobial Peptides Carried by Extracellular Vesicles in an in vitro Psoriatic Model

Purpose

Extracellular Vesicles (EVs) are a heterogeneous group of cell-derived membranous nanoparticles involved in several physiopathological processes. EVs play a crucial role in the definition of the extracellular microenvironment through the transfer of their cargo. Psoriasis is a prototypical chronic inflammatory disease characterized by several secreted mediators, among which antimicrobial peptides (AMPs) are considered pivotal in the development of the psoriatic inflammatory microenvironment. The role of EVs in the pathogenesis of psoriasis has not been elucidated yet, even if emerging evidence demonstrated that interleukin-17A (IL-17A), the psoriasis-related principal cytokine, modifies EVs release and cargo content. The aim of this work was to analyze whether, besides IL-17A, other psoriasis-related cytokines (ie, IFN-γ, TNF-α, IL-22 and IL-23) could affect EVs release and their AMPs mRNAs cargo as well as to analyze the potential biological effect due to EVs internalization by different acceptor cells.

Methods

Nanoparticle tracking analysis (NTA) was performed on supernatants of HaCaT cells stimulated with IL-17A, IFN-γ, TNF-α, IL-22 or IL-23 to enumerate EVs. Real-Time RT-PCR was used for gene expression analysis in cells and EVs. Confocal microscopy and Flow cytometry were used to, respectively, study Netosis and EVs internalization.

Results

IL-17A and IFN-γ increased EVs release by HaCaT cells. All the tested cytokines modulated AMPs mRNA expression in parental cells and in their respective EVs. S100A12 and hBD2 mRNAs were upregulated following IL-17A and IL-22 treatments. Interestingly, EVs derived from cytokine treated HaCaT cells induced Netosis in freshly isolated neutrophils. Upregulation of S100A12 and hBD2 mRNA was also detectable in acceptor cells incubated with EVs derived from cells treated with psoriasis-related cytokines.

Conclusion

The obtained results highlighted the role of EVs in the composition of psoriasis-associated secretome and microenvironment also suggesting the EV involvement in the spreading of the disease mediators and in the possible associated comorbidities.

Antimicrobial Peptides in Early-Life Host Defense, Perinatal Infections, and Necrotizing Enterocolitis—An Update

Host defense against early-life infections such as chorioamnionitis, neonatal sepsis, or necrotizing enterocolitis (NEC) relies primarily on innate immunity, in which antimicrobial peptides (AMPs) play a major role. AMPs that are important for the fetus and neonate include α and β defensins, cathelicidin LL-37, antiproteases (elafin, SLPI), and hepcidin. They can be produced by the fetus or neonate, the placenta, chorioamniotic membranes, recruited neutrophils, and milk-protein ingestion or proteolysis. They possess antimicrobial, immunomodulating, inflammation-regulating, and tissue-repairing properties. AMPs are expressed as early as the 13th week and increase progressively through gestation. Limited studies are available on AMP expression and levels in the fetus and neonate. Nevertheless, existing evidence supports the role of AMPs in pathogenesis of chorioamnionitis, neonatal sepsis, and NEC, and their association with disease severity. This suggests a potential role of AMPs in diagnosis, prevention, prognosis, and treatment of sepsis and NEC. Herein, we present an overview of the antimicrobial and immunomodulating properties of human AMPs, their sources in the intrauterine environment, fetus, and neonate, and their changes during pre- and post-natal infections and NEC. We also discuss emerging data regarding the potential utility of AMPs in early-life infections, as diagnostic or predictive biomarkers and as therapeutic alternatives or adjuncts to antibiotic therapy considering the increase of antibiotic resistance in neonatal intensive care units.

Identification and characterization of immunomodulatory peptides from pepsin-soy protein hydrolysates

To obtain immunomodulatory peptides from isolated soy protein (ISP), pepsin was selected to prepare hydrolysates and 4-h treatment (Pepsin-ISPH4h) showed the highest yield and immunomodulatory activities. The Pepsin-ISPH4h was sequentially fractionated by 30, 10 and 1-kDa molecular weight cut-off (MWCO) membranes, in which 1-kDa MWCO permeate (1P) exhibited the most significant enhancement of phagocytosis activity without causing excessive inflammation as compared with Pepsin-ISPH4h. To further purify and enhance the immunomodulatory activity, 1P was distinct by high-performance liquid chromatography equipped with a reverse-phase column and in vivo immunomodulatory activity of fractions was examined in mice. Fraction 1 (F1) significantly elevated phagocytosis activity of mice spleen macrophages and neutrophils. However, increase of phagocytosis activity did not result from the induction of macrophages M1 or M2 polarization. The immunomodulatory peptide sequence, EKPQQQSSRRGS, from F1 was identified by LC-MS/MS. Phagocytosis activity and macrophage M1 polarization were elevated by synthetic peptide treatment. Hence, our results indicated that isolated soy protein hydrolysates prepared by pepsin could provide a source of peptides with immunomodulatory effects.

Cytokine and LL-37 gene expression levels in Bartonella spp. seropositive and seronegative patients of a rheumatology clinic

PURPOSE

The variation in the immune response to Bartonella spp. infection in humans remains unclear. The present study compares the expression of selected interleukins, cytokines and cathelicidin (LL-37) in rheumatology clinic patients suffering from musculoskeletal symptoms with healthy blood donors. The patients had previously been tested for the presence of Bartonella henselae antibodies.

METHODS

Gene expression of LL-37, interleukin (IL)-2, IL-4, IL-6, IL-12, interferon-(IFN)-γ, and tumor necrosis factor (TNF-α)-α was determined in blood samples using quantitative Polymerase Chain Reaction (qPCR). Statistical analysis was prepared with STATISTICA.

RESULTS

Statistically significant differences in the mRNA levels of the tested cytokines (IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-12; p<0.0001) were observed between the healthy controls and patients; however, no difference was observed for LL37 mRNA (p ​= ​0.1974). No significant differences in mRNA expression were observed between IgG in anti-Bartonella seropositive and seronegative individuals (p>0.05). The only significant differences between the Bartonella spp. DNA positive and negative patients, indicated by PCR, were observed for TNF-α and IL-12 mRNA (p ​= ​0.0045 and p ​= ​0.0255, respectively).

CONCLUSION

A broadly similar immune response to the tested cytokines was observed among the participants irrespective of anti-Bartonella spp. IgG seropositivity. However, the Bartonella DNA-positive participants demonstrated significantly lower expression of IL-12 and TNF-α mRNA; this may indicate that these bacteria have a suppressive influence on the immune system.

Cathelicidin and Calprotectin Are Disparately Altered in Murine Models of Inflammatory Arthritis and Airway Inflammation

Cationic host defense peptides (CHDP) are immunomodulatory molecules that control infections and contribute to immune homeostasis. CHDP such as cathelicidin and calprotectin expression is altered in the arthritic synovium, and in the lungs of asthma and COPD patients. Recent studies suggest a link between airway inflammation and the immunopathology of arthritis. Therefore, in this study we compared the abundance of mouse cathelicidin (CRAMP), defensins, and calprotectin subunits (S100A8 and S100A9) in murine models of collagen-induced arthritis (CIA) and allergen house dust mite (HDM)-challenged airway inflammation. CRAMP, S100A8, and S100A9 abundance were significantly elevated in the joint tissues of CIA mice, whereas these were decreased in the lung tissues of HDM-challenged mice, compared to naïve. We further compared the effects of administration of two different synthetic immunomodulatory peptides, IG-19 and IDR-1002, on cathelicidin and calprotectin abundance in the two models. Administration of IG-19, which controls disease progression and inflammation in CIA mice, significantly decreased CRAMP, S100A8, and S100A9 levels to baseline in the joints of the CIA mice, which correlated with the decrease in cellular influx in the joints. However, administration of IDR-1002, which suppresses HDM-induced airway inflammation, did not prevent the decrease in the levels of cathelicidin and calprotectin in the lungs of HDM-challenged mice. Cathelicidin and calprotectin levels did not correlate with leukocyte accumulation in the lungs of the HDM-challenged mice. Results of this study suggest that endogenous cathelicidin and calprotectin abundance are disparately altered, and may be differentially regulated, within local tissues in airway inflammation compared to arthritis.

The Human Host-Defense Peptide Cathelicidin LL-37 is a Nanomolar Inhibitor of Amyloid Self-Assembly of Islet Amyloid Polypeptide (IAPP)

Amyloid self-assembly of islet amyloid polypeptide (IAPP) is linked to pancreatic inflammation, β-cell degeneration, and the pathogenesis of type 2 diabetes (T2D). The multifunctional host-defence peptides (HDPs) cathelicidins play crucial roles in inflammation. Here, we show that the antimicrobial and immunomodulatory polypeptide human cathelicidin LL-37 binds IAPP with nanomolar affinity and effectively suppresses its amyloid self-assembly and related pancreatic β-cell damage in vitro. In addition, we identify key LL-37 segments that mediate its interaction with IAPP. Our results suggest a possible protective role for LL-37 in T2D pathogenesis and offer a molecular basis for the design of LL-37-derived peptides that combine antimicrobial, immunomodulatory, and T2D-related anti-amyloid functions as promising candidates for multifunctional drugs.