Nutr Res Pract.  2023 Apr;17(2):192-205. 10.4162/nrp.2023.17.2.192.

The effect of curcumin on blood pressure and cognitive impairment in spontaneously hypertensive rats

• Lim JY
• Kim W
• Ha AW

• KMID: 2541358
• DOI: http://doi.org/10.4162/nrp.2023.17.2.192

Abstract

BACKGROUND/OBJECTIVES
It is known that the renin-angiotensin system (RAS) in the brain could regulate cognitive functions as well as blood pressure. Inhibition of RAS for the improvement of cognitive function may be a new strategy, but studies so far have mostly reported on the effects of RAS inhibition by drugs, and there is no research on cognitive improvement through RAS inhibition of food ingredients. Therefore, this study investigated the effect of curcumin on blood pressure and cognitive function and its related mechanism in spontaneously hypertensive rat/Izm (SHR/Izm).
MATERIALS/METHODS
Six-week-old SHR/Izm rats were divided into 5 groups: control group (CON), scopolamine group (SCO, drug for inducing cognitive deficits), positive control (SCO and tacrine [TAC]), curcumin 100 group (CUR100, SCO + Cur 100 mg/kg), and curcumin 200 group (CUR200, SCO + Cur 200 mg/kg). Changes in blood pressure, RAS, cholinergic system, and cognitive function were compared before and after cognitive impairment.
RESULTS
The SCO group showed increased blood pressure and significantly reduced cognitive function based on the y-maze and passive avoidance test. Curcumin treatments significantly improved blood pressure and cognitive function compared with the SCO group. In both the CUR100 and CUR200 groups, the mRNA expressions of angiotensin-converting enzyme (ACE) and angiotensin II receptor type1 (AT1), as well as the concentrations of angiotensin II (Ang II) in brain tissue were significantly decreased. The mRNA expression of the muscarinic acetylcholine receptors (mAChRs) and acetylcholine (ACh) content was significantly increased, compared with the SCO group.
CONCLUSIONS
The administration of curcumin improved blood pressure and cognitive function in SCO-induced hypertensive mice, indicating that the cholinergic system was improved by suppressing RAS and AT1 receptor expression and increasing the mAChR expression.

Keyword

Curcumin; y-maze test; blood pressure; renin-angiotensin-system; cognitive function

Figure

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  Fig. 1 Effect of curcumin on systolic (left) and diastolic blood pressure (right) in spontaneously hypertensive rat. The data showed mean systolic and diastolic blood pressure measured on days 0, 15, and 29 of the experiment. Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg); NS, not significant.

• 

  Fig. 2 Effect of curcumin on alternation behavior (left) and the total number of arm entries (right) of Y-maze test in spontaneously hypertensive rat. Alternation behavior (%) (right) was calculated as follows: Alternation behavior (%) = total number of alternations/(total number of arm entries – 2) × 100. Total number of arm entries (left) under the same experimental condition. Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg); NS, not significant.

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  Fig. 3 Effect of curcumin on latency time of passive avoidance test in spontaneously hypertensive rat. The data represent mean latency time(s). Total number of arm entries under the same experimental condition. Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg).

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  Fig. 4 Effect of curcumin on Angiotensin II content (left) and on the mRNA expression of angiotensin II receptor (right) in brain. Angiotensin II content was determined by using an assay kit (left). The total RNA was isolated and real-time polymerase chain reaction was performed (right) and GADPH level was used as the loading control Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg).

• 

  Fig. 5 Effect of curcumin on the mRNA expression of angiotensin-converting enzyme in the brain. Total RNA was isolated and real-time polymerase chain reaction was performed. GADPH levels were used as the loading control. Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg).

• 

  Fig. 6 Effect of curcumin on acetylcholine content in brain.Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg).

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  Fig. 7 Effect of curcumin on the mRNA expression of muscarinic acetylcholine receptor type I (left) and muscarinic acetylcholine receptor type II (right) in the brain. Total RNA was isolated and real-time polymerase chain reaction was performed. GADPH levels served as the loading control. Different letters above each bar indicate significant differences among groups as determined by Duncan’s multiple range test (P < 0.05).CON, control; SCO, scopolamine (1 mg/kg); TAC, scopolamine (1 mg/kg) + tacrine (10 mg/kg); CUR100, scopolamine (1 mg/kg) + curcumin (100 mg/kg); CUR200, scopolamine (1 mg/kg) + curcumin (200 mg/kg).

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