Cyclic angiotensin-(1-7) contributes to rehabilitation of animal performance in a rat model of cerebral stroke

LP2, a stable lanthipeptide derived from cAng-(1-7), exerts myeloprotective action in mice

OBJECTIVES

Linear unstable angiotensins stimulate hematopoiesis. Here we address: (1) Is cyclic angiotensin-(1-7) myeloprotective in mice? (2) Is cyclic angiotensin-(1-7) stable in rat? (3) Does LP2, a cyclic angiotensin-(1-7) with an N-terminal d-lysine, exert myeloprotective action in tumor-bearing mice?

MATERIALS AND METHODS

Cyclic angiotensin-(1-7)'s capacity to restore levels of blood platelets and white blood cells was studied in gemcitabine-treated mice. The stability of cyclic angiotensin-(1-7) in rat was measured in blood samples taken after injection or infusion. The capacity of LP2 to restore total bone marrow cell levels in mice after treatment with 5-fluoruracil was measured. In addition, the capacity of LP2 to counter anemia in tumor-bearing mice treated with erlotinib was measured.

RESULTS

Cyclic angiotensin-(1-7) dose-dependently restored blood platelet levels in gemcitabine-treated mice, whereas its capacity to restore levels of white blood cells was less. In vivo aminoterminal breakdown of cyclic angiotensin-(1-7) yielded cyclic angiotensin-(2-7) and cyclic angiotensin-(3-7). LP2 significantly (p < .0001 at 100 μg/kg/day) restored bone marrow cell counts in mice after treatment with 5-fluoruracil. LP2 also significantly (p < .05) countered anemia in tumor-bearing mice treated with erlotinib.

CONCLUSIONS

LP2 exerts myeloprotective action with perspectives for continuation of its clinical development.

Inhibition of the postsynaptic density protein 95 on the protective effect of Ang-(1-7)-Mas on cerebral ischaemia injury

BACKGROUND

Postsynaptic density protein-95 (PSD95) plays an important role in cerebral ischaemia injury, but its mechanism needs further research. This study aimed to explore the role of PSD95 in (Ang-(1-7))-Mas-mediated cerebral ischaemia protection and its regulatory mechanism.

METHODS

Oxygen-glucose deprivation (OGD) neuron and rat middle cerebral artery occlusion (MCAO) models were used as in vitro and in vivo models, respectively. TAT-MAS9C was used to disrupt the interaction between PSD95 and Mas. The recombinant PSD95 adenovirus (Ad-PSD95) was used to overexpress PSD95 in neurons.

RESULTS

Results showed that in OGD neurons, Ang-(1-7) could promote cell viability; reduce cell apoptosis; reduce the cell membrane localisation of Mas; upregulate the expression levels of pAKT, bcl-2 and I-κB; and downregulate the expression levels of Bax, pI-κB, tumour necrosis factor alpha and interleukin-1β. TAT-MAS9C could enhance the aforementioned effects of Ang-(1-7). However, the PSD95 overexpression inhibited the aforementioned effects of Ang-(1-7). In the MCAO rat model, the 2,3,5-triphenyltetrazolium chloride (TTC) staining showed that Ang-(1-7) reduced the infarct volume. The Morris water maze test showed that the number of crossings over the platform area in the Ang-(1-7) group was significantly increased. TAT-MAS9C could promote the protective effect of Ang-(1-7).

CONCLUSIONS

Results suggested that PSD95 alleviated the activation of AKT and the inhibition of nuclear factor kappa B signalling pathway mediated by the Ang-(1-7)-Mas complex, thereby reducing neuronal activity, increasing apoptosis and inhibiting the Ang-(1-7)-Mas-mediated cerebral ischaemia protection.

Neuroinflammation and COVID-19 Ischemic Stroke Recovery—Evolving Evidence for the Mediating Roles of the ACE2/Angiotensin-(1–7)/Mas Receptor Axis and NLRP3 Inflammasome

Cerebrovascular events, notably acute ischemic strokes (AIS), have been reported in the setting of novel coronavirus disease (COVID-19) infection. Commonly regarded as cryptogenic, to date, the etiology is thought to be multifactorial and remains obscure; it is linked either to a direct viral invasion or to an indirect virus-induced prothrombotic state, with or without the presence of conventional cerebrovascular risk factors. In addition, patients are at a greater risk of developing long-term negative sequelae, i.e., long-COVID-related neurological problems, when compared to non-COVID-19 stroke patients. Central to the underlying neurobiology of stroke recovery in the context of COVID-19 infection is reduced angiotensin-converting enzyme 2 (ACE2) expression, which is known to lead to thrombo-inflammation and ACE2/angiotensin-(1–7)/mitochondrial assembly receptor (MasR) (ACE2/Ang-(1-7)/MasR) axis inhibition. Moreover, after AIS, the activated nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome may heighten the production of numerous proinflammatory cytokines, mediating neuro-glial cell dysfunction, ultimately leading to nerve-cell death. Therefore, potential neuroprotective therapies targeting the molecular mechanisms of the aforementioned mediators may help to inform rehabilitation strategies to improve brain reorganization (i.e., neuro-gliogenesis and synaptogenesis) and secondary prevention among AIS patients with or without COVID-19. Therefore, this narrative review aims to evaluate the mediating role of the ACE2/Ang- (1-7)/MasR axis and NLRP3 inflammasome in COVID-19-mediated AIS, as well as the prospects of these neuroinflammation mediators for brain repair and in secondary prevention strategies against AIS in stroke rehabilitation.

A non-peptidic MAS1 agonist AVE0991 alleviates hippocampal synaptic degeneration in rats with chronic cerebral hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a contributing factor for neurodegenerative diseases. As a recently identified heptapeptide of the brain renin-angiotensin system, angiotensin-(1-7) was revealed to activate its receptor MAS1 and thus ameliorated cognitive impairments in rats with CCH. Since hippocampal synaptic degeneration represents an important pathological basis of cognitive deficits, we hypothesize that activation of MAS1-mediated signaling may alleviate CCH-induced synaptic degeneration in the hippocampus.

METHODS

In this study, we tested this hypothesis and uncovered the underlying mechanisms in a rat model of CCH induced by bilateral common carotid artery ligation surgery. At 1 week after the surgery, rats received a daily intraperitoneal injection of vehicle or a non-peptidic MAS1 agonist AVE0991 for 8 weeks. During this procedure, cerebral blood flow (CBF) was recorded. The levels of MAS1, amyloid-β (Aβ), neuroinflammatory cytokines, glial cell markers and synaptophysin in the hippocampus were assessed at the end of the treatment period.

RESULTS

We showed that AVE0991 significantly alleviated hippocampal synaptic degeneration in rats with CCH. This protection might be achieved by facilitating CBF recovery, reducing hippocampal Aβ levels and suppressing neuroinflammatory responses.

CONCLUSIONS

These findings indicate that MAS1-mediated signaling may represent a novel therapeutic target for CCH-related neurodegenerative diseases.

Intranasal Delivery of a Methyllanthionine-Stabilized Galanin Receptor-2-Selective Agonist Reduces Acute Food Intake

The regulatory (neuro)peptide galanin is widely distributed in the central and peripheral nervous systems, where it mediates its effects via three G protein-coupled receptors (GAL1-3R). Galanin has a vast diversity of biological functions, including modulation of feeding behavior. However, the clinical application of natural galanin is not practicable due to its rapid in vivo breakdown by peptidases and lack of receptor subtype specificity. Much effort has been put into the development of receptor-selective agonists and antagonists, and while receptor selectivity has been attained to some degree, most ligands show overlapping affinity. Therefore, we aimed to develop a novel ligand with specificity to a single galanin receptor subtype and increased stability. To achieve this, a lanthionine amino acid was enzymatically introduced into a galanin-related peptide. The residue's subsequent cyclization created a conformational constraint which increased the peptide's receptor specificity and proteolytic resistance. Further exchange of certain other amino acids resulted in a novel methyllanthionine-stabilized galanin receptor agonist, a G1pE-T3N-S6A-G12A-methyllanthionine[13-16]-galanin-(1-17) variant, termed M89b. M89b has exclusive specificity for GAL2R and a prolonged half-life in serum. Intranasal application of M89b to unfasted rats significantly reduced acute 24 h food intake inducing a drop in body weight. Combined administration of M89b and M871, a selective GAL2R antagonist, abolished the anorexigenic effect of M89b, indicating that the effect of M89b on food intake is indeed mediated by GAL2R. This is the first demonstration of in vivo activity of an intranasally administered lanthipeptide. Consequently, M89b is a promising candidate for clinical application as a galanin-related peptide-based therapeutic.

Therapeutic Application of Lantibiotics and Other Lanthipeptides: Old and New Findings

Lanthipeptides are ribosomally synthesized and posttranslationally modified peptides, with modifications that are incorporated during biosynthesis by dedicated enzymes. Various modifications of the peptides are possible, resulting in a highly diverse group of bioactive peptides that offer a potential reservoir for use in the fight against a plethora of diseases. Their activities range from the antimicrobial properties of lantibiotics, especially against antibiotic-resistant strains, to antiviral activity, immunomodulatory properties, antiallodynic effects, and the potential to alleviate cystic fibrosis symptoms. Lanthipeptide biosynthetic genes are widespread within bacterial genomes, providing a substantial repository for novel bioactive peptides. Using genome mining tools, novel bioactive lanthipeptides can be identified, and coupled with rapid screening and heterologous expression technologies, the lanthipeptide drug discovery pipeline can be significantly sped up. Lanthipeptides represent a group of bioactive peptides that hold great potential as biotherapeutics, especially at a time when novel and more effective therapies are required. With this review, we provide insight into the latest developments made toward the therapeutic applications and production of lanthipeptides, specifically looking at heterologous expression systems.

Exploring structural signatures of the lanthipeptide prochlorosin 2.8 using tandem mass spectrometry and trapped ion mobility-mass spectrometry

Lanthipeptides are a family of ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by intramolecular thioether cross-links formed between a dehydrated serine/threonine (dSer/dThr) and a cysteine residue. Prochlorosin 2.8 (Pcn2.8) is a class II lanthipeptide that exhibits a non-overlapping thioether ring pattern, for which no biological activity has been reported yet. The variant Pcn2.8[16RGD] has been shown to bind tightly to the αvβ3 integrin receptor. In the present work, tandem mass spectrometry, using collision-induced dissociation (CID) and electron capture dissociation (ECD), and trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) were used to investigate structural signatures for the non-overlapping thioether ring pattern of Pcn2.8. CID experiments on Pcn2.8 yielded b_i and y_j fragments between the thioether cross-links, evidencing the presence of a non-overlapping thioether ring pattern. ECD experiments of Pcn2.8 showed a significant increase of hydrogen migration events near the residues involved in the thioether rings with a more pronounced effect at the dehydrated residues as compared to the cysteine residues. The high-resolution mobility analysis, aided by site-directed mutagenesis ([P8A], [P11A], [P12A], [P8A/P11A], [P8A/P12A], [P11A/P12A], and [P8A/P11A/P12A] variants), demonstrated that Pcn2.8 adopts cis/trans-conformations at Pro8, Pro11, and Pro12 residues. These observations were complementary to recent NMR findings, for which only the Pro8 residue was evidenced to adopt cis/trans-orientations. This study highlights the analytical power of the TIMS-MS/MS workflow for the structural characterization of lanthipeptides and could be a useful tool in our understanding of the biologically important structural elements that drive the thioether cyclization process.

LP2, the first lanthipeptide GPCR agonist in a human pharmacokinetics and safety study

Introduction of a lanthionine into a peptide may enhance target affinity, target specificity and proteolytic resistance. This manuscript reports preclinical safety studies and the first-in-human study with the lanthipeptide AT₂R agonist LP2, a structural analog of cAng-(1-7), whose N-terminus was protected against aminopeptidases by the presence of a d-lysine. None of the preclinical studies, including an in vitro multitarget panel, behavioral, respiratory and cardiovascular measurements, genotoxicity and toxicity studies in rat and dog, posed any safety concern. Due to lack of toxicity the maximum tolerated dose was not reached neither in rat nor in dog. In the human dose escalation study, healthy male volunteers received a single 1 mL subcutaneous injection (0.001 mg, 0.01 mg or 0.1 mg) of LP2 or matching placebo. In contrast to angiotensin II which has a T_1/2 in plasma of < 1 min, LP2 has a T_1/2 of approximately 2.1-2.6 hours. The fraction of the dose excreted unchanged in urine ranged from 84.73 ± 10.4 % at a dose of 0.001 mg to 66.4 ± 3.9 % at 0.1 mg. There were no deaths, serious adverse events or subject withdrawals as a result of an adverse event. The incidence of adverse events was 16.7 %; each was mild in severity. One adverse event, peripheral coldness, was considered to be possibly related to LP2 at 0.001 mg LP2. None of the results was considered to pose a clinically relevant safety concern. This study supports the potential for the therapeutic use of lanthipeptides.

Biosynthesis of lanthionine-constrained agonists of G protein-coupled receptors

The conformation with which natural agonistic peptides interact with G protein-coupled receptor(s) (GPCR(s)) partly results from intramolecular interactions such as hydrogen bridges or is induced by ligand–receptor interactions. The conformational freedom of a peptide can be constrained by intramolecular cross-links. Conformational constraints enhance the receptor specificity, may lead to biased activity and confer proteolytic resistance to peptidic GPCR agonists. Chemical synthesis allows to introduce a variety of cross-links into a peptide and is suitable for bulk production of relatively simple lead peptides. Lanthionines are thioether bridged alanines of which the two alanines can be introduced at different distances in chosen positions in a peptide. Thioether bridges are much more stable than disulfide bridges. Biosynthesis of lanthionine-constrained peptides exploiting engineered Gram-positive or Gram-negative bacteria that contain lanthionine-introducing enzymes constitutes a convenient method for discovery of lanthionine-stabilized GPCR agonists. The presence of an N-terminal leader peptide enables dehydratases to dehydrate serines and threonines in the peptide of interest after which a cyclase can couple the formed dehydroamino acids to cysteines forming (methyl)lanthionines. The leader peptide also guides the export of the formed lanthionine-containing precursor peptide out of Gram-positive bacteria via a lanthipeptide transporter. An engineered cleavage site in the C-terminus of the leader peptide allows to cleave off the leader peptide yielding the modified peptide of interest. Lanthipeptide GPCR agonists are an emerging class of therapeutics of which a few examples have demonstrated high efficacy in animal models of a variety of diseases. One lanthipeptide GPCR agonist has successfully passed clinical Phase Ia.