Myristolated Serotonin 2A Receptor Peptide Promotes Long-Lasting Blood Pressure-Lowering and Reno protection in Hypertensive Rat Species

Abstract

Aim: The aim of the present study was to test whether conjugation of a synthetic peptide corresponding to a fragment of the second extracellular domain of the human serotonin 2A receptor substantially alters the in vivo pharmacodynamic blood pressure-lowering profile of the peptide in different hypertensive rat strains.

Methods: Sertuercept (SCLLADDN) was synthesized and modified using pegylation or myristolation. The two different peptide conjugates were tested in male Zucker diabetic fatty rats for acute and long-lasting blood pressure-lowering effects following single intraperitoneal administration. The myristolated Sertuercept was administered intraperitoneally to female Zucker fatty and male spontaneously hypertensive rats (SHR) and blood pressure was monitored either using tail cuff measurement (female Zucker) or by telemetry (SHR) rats. Plasma immunoglobulin G obtained by Protein G affinity chromatography in 25-week-old female Zucker or male spontaneously hypertensive rats was tested for binding to a linear synthetic peptide corresponding to the second extracellular loop of the serotonin 2A receptor. A cohort of male Zucker diabetic fatty rats was randomized to seven weeks of once-weekly myristolated Sertuercept or scrambled peptide (injections) and the kidneys were examined histologically for differences in total kidney lesions or fibrosis.

Results: Pegylated Sertuercept promoted substantial blood pressure-lowering lasting approximately 30-48 hours in male Zucker diabetic fatty rats. Blood pressure-lowering following a single injection of Myristolated Sertuercept was much longer-lasting (6-11 days) and it was effective in male Zucker diabetic fatty rats, male spontaneously hypertensive rats and in a subset of hypertensive female Zucker fatty rats. Seven weeks' treatment with once-weekly Myristolated Sertuercept (2mg/kg) was associated with significantly fewer kidney lesions and less interstitial fibrosis compared to scrambled peptide in 25-week-old male Zucker diabetic fatty rats. Male spontaneously hypertensive rats (4 of 4 tested) harbored plasma IgG which bound significantly to serotonin 2A receptor peptide, and a subset of female Zucker fatty rats harboring IgG were responsive to blood pressure-lowering from the myristolated Sertuercept peptide.

Summary: Myristolated-Sertuercept, an epitope-specific peptide comprised of a portion of second extracellular loop of the human serotonin 2A receptor was safe, well-tolerated and effectively lowered blood pressure for one week or longer in two different strains of male hypertensive rats. These data provide proof-of-concept that once-weekly systemic drug administration is feasible to achieve not only long-lasting hypertension control, but also substantial renoprotection.

Figure 1:

Single intraperitoneal dose of Pegsertuercept (1 mg/kg) (arrow) caused significantly greater systolic (A) and diastolic blood pressure-lowering (B) vs scrambled peptide (2 mg/kg) IP in 12-week-old male ZDF rats (n=4 per group). Each point is the mean ± SD.

Figure 2:

Rapid- onset and sustained blood pressure-lowering effect of low dose Myr-Sertuercept peptide following IP injection in 13-week-old male ZDF rats. Results are mean ± SEM of multiple determinations at each timepoint in each of two male ZDF rats that received either 1 mg/kg Myr-peptide or Scrambled peptide; *P<0.05 compared to baseline MAP. *P<0.05 compared to baseline mean arterial pressure

Figure 3:

Dose-dependence and sustained blood pressure- lowering effect of Myr-Sertuercept in twenty-week old male SHR rats. Each (time)point represents the mean of five-ten telemetric determinations (Stellar implant, TSE Systems Inc) having standard error of approximately 1%. Mean MAP-lowering (%) at the indicated timepoint compared to baseline MAP

Figure 4:

‘Mean arterial blood pressure-lowering following a single 2 mg/kg IP dose of Myr-Sertuercept in three representative ‘responder’ and ‘non-responder’ 20-week-old female Zucker fatty rats. Results are the mean of three or more determinations which varied by < 15%. Each point is the average of three of more determinations which varied by <15%

Figure 5:

Level and titer of Rat IgG binding to synthetic peptide QN.18 identical to the second extracellular loop of the serotonin 2A receptor. *P<0.05, mean OD in IgG from two male SHR rats vs. two female Zucker fatty rats Dashed line is the background optical density (0.032 absorbance units).

Figure 6:

Chronic (7-week) once weekly IP administration of Myr-Sertuercept (2 mg/kg) significantly reduced A) renal interstitial collagen score and B) total lesions compared to identical dose and course of scrambled peptide in 16–23-week-old male ZDF rats. Results are mean ± SD.

Figure 7:

Representative Masson’s trichome-stained kidney section from male ZDF rat treated with either (A) Myr-Sertuercept or (B) scrambled peptide (2 mg/kg) for seven weeks.