Hypertension research in the 21st century

Antihypertensive activity of transgenic rice seed containing an 18-repeat novokinin peptide localized in the nucleolus of endosperm cells

Novokinin (Arg-Pro-Leu-Lys-Pro-Trp, RPLKPW) is a new potent antihypertensive peptide based on the sequence of ovokinin (2-7) derived from ovalbumin. We previously generated transgenic rice seeds in which eight novokinin were fused to storage protein glutelins (GluA2 and GluC) for expression. Oral administration of these seeds to spontaneously hypertensive rats (SHRs) reduced systolic blood pressures at a dose of 1 g seed/kg of SHR. Here, 10- or 18-tandem repeats of novokinin with an endoplasmic reticulum (ER) retention signal (Lys-Asp-Glu-Leu, KDEL) at the C terminus were directly expressed in rice under the control of the glutelin promoter containing its signal peptide. Only small amounts of the 18-repeat novokinin accumulated, and it was unexpectedly deposited in the nucleolus. This abnormal intracellular localization was explained by an endogenous signal for nuclear localization. The GFP reporter protein fused to this sequence targeted to nuclei by a transient assay using onion epidermal cells. Transgenic seed expressing the 18-repeat novokinin exhibited significantly higher antihypertensive activity after a single oral dose to SHR even at one-quarter the amount (0.25 g/kg) of the transgenic rice seed expressing the fusion construct; though, its novokinin content was much lower (1/5). Furthermore, in a long-term administration for 5 weeks, even a smaller dose (0.0625 g/kg) of transgenic seeds could confer antihypertensive activity. This high antihypertensive activity may be attributed to differences in digestibility of expressed products by gastrointestinal enzymes and the unique intracellular localization. These results indicate that accumulation of novokinin as a tandemly repeated structure in transgenic rice is more effective than as a fusion-type structure.

Novel use of Kaplan-Meier methods to explain age and gender differences in hypertension control rates

Despite 40 years of research demonstrating the efficacy of antihypertensive medications for lowering blood pressure and decreasing cardiovascular disease, hypertension control rates worldwide remain low. We explored here how both medication efficacy rates and patient/physician decision-making (discontinuation rates) affect overall hypertension control rates. To do this we introduced the use of Kaplan-Meier methodology to predict hypertension control rates separately within age strata. An important aspect of our analysis is the use of a "treatment intensity score," including both the number of agent(s) and the percentage of maximal dose of agent(s). We investigated how blood pressure control rates vary with age, gender, and treatment intensity. Our analysis found that both efficacy and discontinuation rates at different treatment intensities vary with age and gender, so that for each increase in age by 1 decade, the log hazard of achieving controlled blood pressure at any given intensity decreases by 0.10 in men and 0.20 in women. Overall hypertension control rates ranged from 80.8% for persons age 15 to 39 years to only 42.1% for persons age >/=80 years. Our analysis more accurately represents achievable hypertension control rates, with differences by gender, than previous work, because we investigated the contributions of efficacy and treatment aggressiveness in the control of hypertension.

A transgenic rice seed accumulating an anti-hypertensive peptide reduces the blood pressure of spontaneously hypertensive rats

RPLKPW is a potent anti-hypertensive peptide designed according to the structure of ovokinin(2-7) (RADHPF). In this study, we generated transgenic rice plants that accumulate the RPLKPW peptide as a fusion protein with the rice storage protein glutelin. The engineered peptide is expressed under the control of endosperm-specific glutelin promoters and specifically accumulates in seeds. Oral administration of either the RPLKPW-glutelin fraction or transgenic rice seeds to spontaneously hypertensive rats (SHRs) significantly reduced systolic blood pressures. These results suggest the possible application of transgenic rice seed as a nutraceutical delivery system and specifically for administration of active peptides in hypertension.