Ac-Endothelin-1 (16-21), Human Mechanisms, Clinical Value, a

Ac-Endothelin-1 (16-21), Human: Mechanisms, Clinical Value, and Research Perspectives

Introduction
Ac-Endothelin-1 (16-21), human, is a synthetic peptide fragment corresponding to amino acids 16 to 21 of the human endothelin-1 (ET-1) sequence. Endothelin-1 is a potent vasoconstrictor peptide produced by vascular endothelial cells, playing a critical role in vascular homeostasis, cell proliferation, inflammation, and fibrosis (Yanagisawa et al., 1988, Nature). The truncated peptide Ac-Endothelin-1 (16-21) is acetylated at the N-terminus, conferring enhanced stability and unique biological properties compared to the full-length peptide.

Mechanistically, Ac-Endothelin-1 (16-21) interacts with endothelin receptors, particularly the ETA and ETB subtypes, but with distinct binding affinities and functional outcomes compared to the parent ET-1 molecule (Khimji & Rockey, 2010, Gastroenterology). This peptide fragment has been shown to modulate vascular tone, influence cell signaling pathways, and participate in the regulation of endothelial and smooth muscle cell function. Its unique sequence and structure allow for selective investigation of endothelin receptor-mediated processes, making it a valuable research tool in cardiovascular, renal, and neurovascular studies.

[Related: bleomyacin] Clinical Value and Applications
The clinical value of Ac-Endothelin-1 (16-21), human, lies primarily in its utility as a research reagent for dissecting the complex roles of endothelin signaling in health and disease. Endothelin-1 and its receptors are implicated in a range of pathophysiological conditions, including hypertension, pulmonary arterial hypertension (PAH), heart failure, chronic kidney disease, and certain cancers (Davenport et al., 2016, Pharmacol Rev). By selectively mimicking or antagonizing specific ET-1 receptor interactions, Ac-Endothelin-1 (16-21) enables researchers to delineate the contributions of distinct receptor subtypes and downstream signaling cascades.

In preclinical models, Ac-Endothelin-1 (16-21) has been employed to study vasoconstriction, endothelial dysfunction, and the molecular mechanisms underlying vascular remodeling. Its application extends to the investigation of neurovascular coupling, blood-brain barrier integrity, and the modulation of inflammatory responses in various organ systems (Khimji & Rockey, 2010). Furthermore, the peptide serves as a reference compound for the development and validation of endothelin receptor antagonists, which are clinically approved for the treatment of PAH and are under investigation for other indications.

[Related: MLM341] Key Challenges and Pain Points Addressed
Current therapeutic strategies targeting the endothelin system, such as ETA and ETB receptor antagonists, are limited by issues of selectivity, off-target effects, and adverse reactions including hepatotoxicity and fluid retention (Rubin et al., 2002, N Engl J Med). Moreover, the redundancy and complexity of endothelin signaling complicate the interpretation of pharmacological interventions in vivo.

Ac-Endothelin-1 (16-21), human, addresses several key challenges in endothelin research:
1. **Receptor Selectivity**: The truncated peptide allows for the selective activation or inhibition of specific endothelin receptor subtypes, facilitating mechanistic studies that are difficult to achieve with full-length ET-1 or non-selective antagonists.
2. **Reduced Systemic Effects**: Due to its smaller size and modified structure, Ac-Endothelin-1 (16-21) exhibits altered pharmacokinetics and tissue distribution, potentially reducing systemic side effects in experimental models.
3. **Tool for Drug Development**: It serves as a benchmark for screening novel endothelin receptor modulators, enabling the identification of compounds with improved efficacy and safety profiles.
4. **Dissection of Downstream Pathways**: The peptide’s selective activity aids in mapping downstream signaling events, such as calcium mobilization, MAPK activation, and nitric oxide production, which are critical for understanding disease mechanisms.

[Related: ruxolitinib phosphate] Literature Review
A growing body of literature supports the utility of Ac-Endothelin-1 (16-21) and related peptide fragments in endothelin research:

1. **Yanagisawa et al. (1988, Nature)**: This seminal study identified and characterized endothelin-1 as a potent vasoconstrictor, laying the foundation for subsequent research into its structure-function relationships and the development of peptide fragments for mechanistic studies.

2. **Davenport et al. (2016, Pharmacol Rev)**: This comprehensive review details the pharmacology of endothelin receptors, highlighting the therapeutic potential and challenges associated with targeting the endothelin system. The authors emphasize the need for selective tools, such as peptide fragments, to unravel receptor-specific effects.

3. **Khimji & Rockey (2010, Gastroenterology)**: The authors discuss the role of endothelin signaling in hepatic and vascular pathophysiology, noting the importance of receptor subtype-selective ligands in experimental models. They reference the use of truncated peptides in dissecting ET-1-mediated effects.

4. **Kedzierski & Yanagisawa (2001, J Cardiovasc Pharmacol)**: This review explores the molecular biology of endothelin receptors and the development of peptide and non-peptide ligands, including the use of ET-1 fragments to study receptor binding and activation.

5. **Kuc et al. (2006, Peptides)**: The authors investigated the biological activity of ET-1 fragments, including Ac-Endothelin-1 (16-21), demonstrating their ability to modulate vascular tone and receptor signaling in vitro and in vivo.

6. **Rubin et al. (2002, N Engl J Med)**: This clinical trial evaluated the efficacy of bosentan, a dual endothelin receptor antagonist, in PAH patients. The study underscores the clinical relevance of endothelin signaling and the need for improved research tools to guide therapeutic development.

7. **Kobayashi et al. (2000, Br J Pharmacol)**: The authors characterized the binding and functional properties of ET-1 fragments, including the (16-21) sequence, in vascular smooth muscle cells, providing insights into their receptor interactions and biological effects.

Experimental Data and Results
Experimental studies utilizing Ac-Endothelin-1 (16-21), human, have elucidated its functional properties and potential applications:

- **Vascular Reactivity**: Kuc et al. (2006) demonstrated that Ac-Endothelin-1 (16-21) induces concentration-dependent vasoconstriction in isolated rat aortic rings, albeit with lower potency compared to full-length ET-1. The peptide’s effects were attenuated by selective ETA and ETB receptor antagonists, confirming receptor-mediated activity.

- **Receptor Binding**: Kobayashi et al. (2000) reported that the (16-21) fragment binds to both ETA and ETB receptors, but with reduced affinity relative to ET-1. This property allows for the selective modulation of receptor subtypes in competitive binding assays.

- **Cell Signaling**: In cultured endothelial and smooth muscle cells, Ac-Endothelin-1 (16-21) was shown to activate intracellular calcium signaling and MAPK pathways, supporting its role as a functional ligand for endothelin receptors (Kuc et al., 2006).

- **In Vivo Models**: Animal studies have utilized Ac-Endothelin-1 (16-21) to probe the contribution of endothelin signaling to blood pressure regulation, vascular remodeling, and organ fibrosis. The peptide’s effects are dose-dependent and can be modulated by co-administration of receptor antagonists (Khimji & Rockey, 2010).

These findings validate the use of Ac-Endothelin-1 (16-21) as a research tool for dissecting endothelin receptor function and for preclinical evaluation of novel therapeutics targeting the endothelin system.

Usage Guidelines and Best Practices
To maximize the utility and reproducibility of experiments involving Ac-Endothelin-1 (16-21), human, the following guidelines are recommended:

1. **Preparation and Storage**: The peptide should be reconstituted in sterile water or appropriate buffer to the desired concentration. Aliquots should be stored at -20°C to -80°C to prevent degradation. Avoid repeated freeze-thaw cycles.

2. **Concentration Selection**: Optimal concentrations depend on the experimental model and endpoint. Typical in vitro studies employ concentrations ranging from 10 nM to 10 μM, while in vivo dosing should be guided by pilot studies and published protocols (Kuc et al., 2006).

3. **Controls**: Include vehicle controls and, where applicable, full-length ET-1 and selective receptor antagonists to validate specificity of observed effects.

4. Additional Resources:
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Research Article: PMC11565735