Lactoferricin B-derived peptides with inhibitory effects on ECE-dependent vasoconstriction

Lactoferrin ameliorated obesity-induced endothelial dysfunction by inhibiting the Tak1/IL-18/eNOS pathway between PVAT and vascular endothelium

Vascular endothelial dysfunction (ED) is one of the mechanisms underlying obesity-related hypertension. Perivascular adipose tissue (PVAT) surrounds blood vessels and influences the vascular endothelium function. Previous studies have demonstrated the antihypertensive effects of lactoferrin (LF) and its hydrolysates through various mechanisms. However, the effect of LF on ED and PVAT has not yet been investigated. In this study, we examined the influence of LF on ED and PVAT using high-fat diet mice as well as MAEC cells and 3T3-L1 adipocytes. Finally, LF supplementation decreases the systolic blood pressure (SBP), serum adhesion molecule (ICAM-1 and VCAM-1), and aorta ROS levels, and improves endothelium-dependent relaxation function in high-fat diet mice. Moreover, LF supplementation down-regulates the Tak1/IL-18/eNOS pathway between PVAT and aorta and enhances the NO generation in high-fat diet mice. In addition, we observe that LF decreases the expression levels of IL-18 and p-Tak1 in 3T3-L1 adipocytes, but fails to influence the eNOS and p-eNOS expression levels in MAEC cells. Finally, the significant associations between LF and IL-18 and SBP and hypertension risk are also observed in obesity children only. These findings provide evidence that the Tak1/IL-18/eNOS pathway between the aorta and PVAT is important in obesity-related ED, and LF may improve ED or even hypertension by down-regulating this pathway.

Lactoferrin, Osteopontin and Lactoferrin–Osteopontin Complex: A Critical Look on Their Role in Perinatal Period and Cardiometabolic Disorders

Milk-derived bioactive proteins have increasingly gained attention and consideration throughout the world due to their high-quality amino acids and multiple health-promoting attributes. Apparently, being at the forefront of functional foods, these bioactive proteins are also suggested as potential alternatives for the management of various complex diseases. In this review, we will focus on lactoferrin (LF) and osteopontin (OPN), two multifunctional dairy proteins, as well as to their naturally occurring bioactive LF–OPN complex. While describing their wide variety of physiological, biochemical, and nutritional functionalities, we will emphasize their specific roles in the perinatal period. Afterwards, we will evaluate their ability to control oxidative stress, inflammation, gut mucosal barrier, and intestinal microbiota in link with cardiometabolic disorders (CMD) (obesity, insulin resistance, dyslipidemia, and hypertension) and associated complications (diabetes and atherosclerosis). This review will not only attempt to highlight the mechanisms of action, but it will critically discuss the potential therapeutic applications of the underlined bioactive proteins in CMD.

A Flounder Fish Peptide Shows Anti-Hypertensive Effects by Suppressing the Renin-Angiotensin-Aldosterone System and Endothelin-1

BACKGROUND

Many fishes have been known for their good nutritional effects especially in the cardiovascular aspect. Some specific fish peptides have anti-hypertensive effects.

OBJECTIVE

In the present study, we hypothesized that the hexapeptide (MEVFVP) from flounder fish muscle can be a potent antihypertensive peptide, therefore, decided to perform this experiment.

METHODS

The peptide MEVFVP from flounder fish muscle (40 mg/kg) and vehicle were administered per os to spontaneously hypertensive rats (SHRs) (SHR-M and SHR-C, respectively). Additionally, plasma MEVFVP was measured serially before and after its oral administration to Sprague Dawley rats.

RESULTS

Blood pressures (BPs), especially systolic BP, in SHR rats were decreased around 3-6 hours after MEVFVP administration. Compared with SHR-C rats, endothelin-1 (ET-1) mRNA expression in multiple tissues, and plasma levels of ET-1, angiotensin II, and aldosterone were lower in SHR-M rats, whereas the phosphorylation of AMP-activated protein kinase (AMPK) was increased in the kidney of SHR-M rats. The administered peptide was not detected in rat plasma, while ex vivo incubation of the peptide in rat plasma caused its rapid degradation within minutes.

CONCLUSION

Our results show that the MEVFVP has an antihypertensive effect by regulating renin-angiotensin-aldosterone system, ET-1 and AMPK despite its limited bioavailability.

Peptides with Potential Cardioprotective Effects Derived from Dry-Cured Ham Byproducts

The interest in using food byproducts as a source of bioactive peptides has increased significantly in the recent years. The goal of this work was to determine the presence and stability of peptides showing angiotensin I-converting enzyme (ACE-I), endothelin-converting enzyme (ECE), dipeptidyl peptidase-IV (DPP-IV), and platelet-activating factor-acetylhydrolase (PAF-AH) inhibitory activity derived from dry-cured ham bones, which could exert cardiovascular health benefits. ACE-I and DPP-IV inhibitory peptides were stable against heating typically used in Mediterranean household cooking methods and also to in vitro digestion. PAF-AH inhibitory activity significantly increased following simulated gastrointestinal digestion whereas ECE inhibitory significantly decreased ( P < 0.05). The mass spectrometry analysis revealed a notable degradation of hemoglobin-derived peptides after simulated digestion, and the release of a large number of dipeptides that may have contributed to the observed bioactivities. These results suggest that natural peptides from Spanish dry-cured ham bones could contribute to a positive impact on cardiovascular health.

Evidence that Nitric Oxide is Involved in the Blood Pressure Lowering Effect of the Peptide AVFQHNCQE in Spontaneously Hypertensive Rats

AVFQHNCQE is an antihypertensive nonapeptide obtained from a chicken foot protein hydrolysate. The present study aims to investigate the mechanisms involved in its blood pressure (BP)-lowering effect. Male (17⁻20 weeks old) spontaneously hypertensive rats (SHR) were used in this study. Rats were divided into two groups and orally administered water or 10 mg/kg body weight (bw) AVFQHNCQE. One hour post-administration, animals of both groups were intra-peritoneally treated with 1 mL of saline or with 1 mL of saline containing 30 mg/kg bw Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis, or with 1 mL of saline containing 5 mg/kg bw indomethacin, which is an inhibitor of prostacyclin synthesis (n = 6 per group). Systolic BP was recorded before oral administration and six hours after oral administration. In an additional experiment, SHR were administered water or 10 mg/kg bw AVFQHNCQE (n = 6 per group) and sacrificed six hours post-administration to study the mechanisms underlying the peptide anti-hypertensive effect. Moreover, the relaxation caused by AVFQHNCQE in isolated aortic rings from Sprague-Dawley rats was evaluated. The BP-lowering effect of the peptide was not changed after indomethacin administration but was completely abolished by L-NAME, which demonstrates that its anti-hypertensive effect is mediated by changes in endothelium-derived NO availability. In addition, AVFQHNCQE administration downregulated aortic gene expression of the vasoconstrictor factor endothelin-1 and the endothelial major free radical producer NADPH. Moreover, while no changes in plasma ACE activity were observed after its administration, liver GSH levels were higher in the peptide-treated group than in the water group, which demonstrates that AVFQHNCQE presents antioxidant properties.

The lactoferricin B-derived peptide, LfB17-34, induces melanogenesis in B16F10 cells

Lactoferricin B (LfcinB), a peptide of bovine lactoferrin (LfB), exhibits multiple biological functions, including antimicrobial, antiviral, antioxidant and immuno-modulatory activities. However, the role of LfcinB-related peptides in melanogenesis remains unclear. In this study, a set of five LfcinB-related peptides was examined. We found that LfB17-34, an 18-mer LfcinB-derived peptide, increased melanogenesis in B16F10 melanoma cells without significantly affecting cell viability. LfB17-34 increased in vitro tyrosinase activity and melanin content in a dose-dependent manner. The results of RT-qPCR and western blot analyses showed that LfB17-34 increased the mRNA and protein expression of tyrosinase and tyrosinase-related protein 1 (Trp1). Moreover, LfB17-34 inhibited the phosphorylation of MAPK/Erk, but not p38 and Akt, and constitutively active MEK was able to reverse the LfB17-34-enhanced pigmentation, melanin content, and tyrosinase activity, suggesting a role of Erk signaling in the process of LfB17-34-mediated pigmentation. Taken together, these results suggest that LfB17-34 induces melanogenesis in B16F10 cells primarily through increased tyrosinase expression and activity and that LfB17-34 could be further developed for the treatment of hypopigmentation disorders.

Cytoprotective and antioxidant effects of human lactoferrin against H2O2-induced oxidative stress in human umbilical vein endothelial cells

Background:

Lactoferrin (LF) is an iron-binding glycoprotein with antioxidant, anti-inflammatory and nitric oxide-dependent vasodilatory properties. In the present study, we investigated the protective and antioxidant effects of LF on H₂O₂-induced oxidative stress in human umbilical vein endothelial cells (HUVECs).

Materials and Methods:

HUVECs were pretreated by (6.25–100 μg/ml) LF for 24 h and then exposed to 0.5 mM H₂O₂ for 2 h. Cell viability was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The intra- and extra-cellular hydroperoxides concentration and ferric reducing antioxidant power (FRAP) were determined in pretreated cells.

Results:

Pretreatment of HUVECs with LF at the concentrations of 25–100 μg/ml significantly reduced the cytotoxicity of H₂O₂ in a concentration-dependent manner using MTT assay. LF pretreatment at different concentration ranges also decreased the hydroperoxides level and augmented the FRAP value in both intra-and extra-cellular assay.

Conclusion:

These findings revealed antioxidant and cytoprotective effects of LF against H₂O₂-induced oxidative stress in HUVECs. With regard to the beneficial vascular activity of LF, further investigations are suggested for understanding its clinical value in human endothelial dysfunction and prevention and/or treatment of CVDs.

Unraveling the mechanisms of action of lactoferrin-derived antihypertensive peptides: ACE inhibition and beyond

The characterization of lactoferrin-derived antihypertensive peptides shows that they might act on several molecular targets.

Molecular targets of antihypertensive peptides: understanding the mechanisms of action based on the pathophysiology of hypertension

There is growing interest in using functional foods or nutraceuticals for the prevention and treatment of hypertension or high blood pressure. Although numerous preventive and therapeutic pharmacological interventions are available on the market, unfortunately, many patients still suffer from poorly controlled hypertension. Furthermore, most pharmacological drugs, such as inhibitors of angiotensin-I converting enzyme (ACE), are often associated with significant adverse effects. Many bioactive food compounds have been characterized over the past decades that may contribute to the management of hypertension; for example, bioactive peptides derived from various food proteins with antihypertensive properties have gained a great deal of attention. Some of these peptides have exhibited potent in vivo antihypertensive activity in both animal models and human clinical trials. This review provides an overview about the complex pathophysiology of hypertension and demonstrates the potential roles of food derived bioactive peptides as viable interventions targeting specific pathways involved in this disease process. This review offers a comprehensive guide for understanding and utilizing the molecular mechanisms of antihypertensive actions of food protein derived peptides.

Novel antihypertensive lactoferrin-derived peptides produced by Kluyveromyces marxianus: gastrointestinal stability profile and in vivo angiotensin I-converting enzyme (ACE) inhibition

Novel antihypertensive peptides released by Kluyveromyces marxianus from bovine lactoferrin (LF) have been identified. K. marxianus LF permeate was fractionated by semipreparative high performance liquid chromatography and 35 peptides contained in the angiotensin I-converting enzyme (ACE)-inhibitory fractions were identified by using an ion trap mass spectrometer. On the basis of peptide abundance and common structural features, six peptides were chemically synthesized. Four of them (DPYKLRP, PYKLRP, YKLRP, and GILRP) exerted in vitro inhibitory effects on ACE activity and effectively decreased systolic blood pressure after oral administration to spontaneously hypertensive rats (SHRs). Stability against gastrointestinal enzymes suggested that the sequence LRP could contribute to the in vivo effects of parental peptides. Finally, there were reductions in circulating ACE activity and angiotensin II level in SHRs after either DPYKLRP or LRP intake, thus confirming ACE inhibition as the in vivo mechanism for their antihypertensive effect.

Antioxidant effects of bovine lactoferrin on dexamethasone-induced hypertension in rat

Dexamethasone- (Dex-) induced hypertension is associated with enhanced oxidative stress. Lactoferrin (LF) is an iron-binding glycoprotein with antihypertensive properties. In this study, we investigated the effect of chronic administration of LF on oxidative stress and hypertension upon Dex administration. Male Wistar rats were treated by Dex (30 μg/kg/day subcutaneously) or saline for 14 days. Oral bovine LF (30, 100, 300 mg/kg) was given from day 8 to 14 in a reversal study. In a prevention study, rats received 4 days of LF treatment followed by Dex and continued during the test period. Systolic blood pressure (SBP) was measured using tail-cuff method. Thymus weight was used as a marker of glucocorticoid activity. Plasma hydrogen peroxide (H₂O₂) concentration and ferric reducing antioxidant power (FRAP) value were determined. Dexamethasone significantly increased SBP and plasma H₂O₂ level and decreased thymus and body weights. LF lowered (P < 0.01) and dose dependently prevented (P < 0.001) Dex-induced hypertension. LF prevented body weight loss and significantly reduced the elevated plasma H₂O₂ and increased FRAP values. Chronic administration of LF strongly reduced the blood pressure and production of ROS and improved antioxidant capacity in Dex-induced hypertension, suggesting the role of inhibition of oxidative stress as another mechanism of antihypertensive action of LF.

Antihypertensive mechanism of lactoferrin-derived peptides: angiotensin receptor blocking effect

Looking for antihypertensive mechanisms beyond ACE inhibition, we assessed whether lactoferrin (LF)-derived peptides can act as receptor blockers to inhibit vasoconstriction induced by angiotensin II or endothelin-1. The lactoferricin B (LfcinB)-derived peptide LfcinB20-25 (RRWQWR), the low molecular weight LF hydrolysate (LFH < 3 kDa), and two peptides identified in LFH < 3 kDa (LIWKL and RPYL) were tested in ex vivo assays of vasoactive responses. The peptide RPYL was tested in radioligand receptor binding assays. Both LFH < 3 kDa and individual peptides inhibited angiotensin II-induced vasoconstriction. RPYL showed the highest ex vivo inhibitory effect and also inhibited binding of [(125)I]-(Sar(1),Ile(8))-angiotensin II to AT1 receptors. By contrast, neither LFH < 3 kDa nor RPYL inhibited endothelin-1 and depolarization-induced vasoconstrictions. In conclusion, LF-derived peptides selectively inhibit angiotensin II-induced vasoconstriction by blocking angiotensin AT1 receptors. Therefore, inhibition of angiotensin II-induced vasocontriction is suggested as a mechanism contributing along with ACE inhibition to the antihypertensive effect of some LF-derived peptides.

Antihypertensive effects of lactoferrin hydrolyzates: Inhibition of angiotensin- and endothelin-converting enzymes

The potential of bovine lactoferrin (LF) as a source of antihypertensive peptides acting on the renin-angiotensin system (RAS) and the endothelin (ET) system as dual vasopeptidase inhibitors has been examined. For this purpose enzymatic LF hydrolyzates (LFHs) were generated by trypsin and proteinase K digestions. Permeate fractions with molecular masses lower than 3 kDa (LFH <3 kDa) were orally administered to spontaneously hypertensive rats (SHRs). Although both LFHs <3 kDa showed in vitro angiotensin I-converting enzyme (ACE)-inhibitory activity, only proteinase K LFH <3 kDa exerted an in vivo antihypertensive effect. The proteinase K LFH <3 kDa and a previously characterized pepsin LFH <3 kDa with ACE-inhibitory and antihypertensive effects were tested in ex vivo functional assays as inhibitors of ACE-dependent vasoconstriction. Pepsin LFH <3 kDa but not proteinase K LFH <3 kDa inhibited ACE-dependent vasoconstriction. When tested as inhibitors towards endothelin-converting enzyme (ECE), both LFHs <3 kDa exerted in vitro inhibitory effects on ECE activity and inhibited ECE-dependent vasoconstriction. Most abundant peptides in proteinase K LFH <3 kDa were identified by using an ion trap mass spectrometer. Based on peptide abundance, two peptides (GILRPY and REPYFGY) were chemically synthesized and their ECE-inhibitory activity was tested. Both exerted in vitro inhibitory effects on ECE activity. In conclusion, orally effective antihypertensive LFHs <3 kDa may act as dual vasopeptidase (ACE/ECE) or as single ECE inhibitors with different antivasoconstrictor effects depending on the protease used to release bioactive peptide sequences.