Effects of 2-hydroxyoleic acid on the structural properties of biological and model plasma membranes

Figures & data

Figure 1.  Electron micrographs of plasma membranes isolated from SHR control rats (SHR-c), SHR rats treated with 2OHOA (SHR-t) and WKY rats treated with 2OHOA (WKY-t). No differences between control and treated WKY membranes were observed. Several bile canaliculi (BC) and regions of higher opacity (indicated by arrows) are shown.

Figure 2.  Effects of 2OHOA treatment on Na⁺/K⁺ ATPase and G protein αq/11 levels in liver plasma membranes from SHR and WKY rats. The upper panel shows a representative immunoblot of 3 animals per group (around 10 µg total protein). Columns show the levels of liver plasma membrane Na⁺/K⁺ ATPase and G protein αq/11 quantified against standard curves and normalized to the protein content of vehicle-treated rats (taken as 100%). ***p < 0.001 and *p < 0.05 vs. vehicle-treated rats.

Table I.  Effect of 2-hydroxyoleic acid (2OHOA) treatment on systolic blood pressure in spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats.

Day of treatment	SHR-c	SHR-t	WKY-c	WKY-t
0	192±3	193±6	132±4	133±4
7	205±8	136±14**	124±6	134±4

Systolic blood pressure values were measured at the beginning (day 0) and end of treatment (7 days) with vehicle (SHR-c and WKY-c) or 2OHOA (600 mg/kg every 12 h) (SHR-t and WKY-t). Values are expressed in mm Hg and represent means±SEM of 6 animals per group. **p<0.01 vs. vehicle-treated (SHR-c).

Table II.  Lipid composition of liver plasma membrane from SHR and WKY rats treated with 2-hydroxyoleic acid or vehicle.

Lipid profile (mol%)	SHR-c	SHR-t	WKY-c	WKY-t
PC	26.43±0.36	28.16**±0.25	29.21±0.08	26.27***±0.17
PE	16.74±2.88	16.43±1.02	15.33±0.06	7.13***±0.01
PS-PI	30.98±1.91	17.31***±0.46	27.36±2.45	27.57±0.01
SM	22.33±2.20	27.45*±1.33	25.35±3.07	32.12*±0.18
CHO	3.53±0.05	10.65***	2.75±1.03	6.91*±2.23
CHO/PL	0.04	0.12	0.03	0.07

The abbreviations represent: SHR-c and WKY-c, vehicle-treated SHR and WKY; SHR-t and WKY-t, 2OHOA-treated SHR and WKY; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PS-PI, phosphatidylserine plus phosphatidylinositol; SM, sphingomyelin; CHO, cholesterol; CHO/PL, cholesterol to total phospholipid ratio. Data are the mean values±SEM from three independent analyses. *p<0.05; **p<0.01, ***p<0.001, groups that are significantly different from the corresponding control.

Table III.  Fatty acid composition of liver plasma membrane from SHR and WKY rats treated with 2-hydroxyoleic acid or vehicle.

Fatty acid profile (mol%)	SHR-c	SHR-t	WKY-c	WKY-t
14:1 (n-5)	–	0.11±0.01	0.20±0.00	0.32±0.05
16:0	21.42±1.31	17.47*±0.59	19.52±0.43	19.27±0.80
16:1 (n-9)	0.59±0.03	0.23***±0.03	0.26±0.03	0.32±0.08
16:1 (n-7)	1.81±0.08	1.11*±0.13	0.76±0.04	0.51**±0.00
16:1 (n-5)	0.40±0.06	0.15*±0.06	0.47±0.01	0.47±0.07
18:0	18.23±0.21	12.50*±1.30	19.22±0.09	22.01***±0.05
18:1 (n-9)	7.31±0.16	22.15***±0.23	5.58±0.32	5.41±0.04
18:1 (n-7)	4.13±0.03	3.99±0.29	3.87±0.00	3.01***±0.01
18:2 (n-6)	14.45±0.05	23.06*±2.02	11.99±0.00	15.09***±0.03
20:2 (n-6)	0.63±0.17	0.28±0.07	0.53±0.01	0.47±0.00
20:4 (n-6)	25.96±0.20	14.58***±0.69	30.03±0.12	23.72***±0.08
22:5 (n-6)	0.63±0.08	0.68±0.18	0.97±0.05	1.41**±0.13
22:6 (n-6)	0.44±0.09	0.45±0.14	0.60±0.07	1.44**±0.14
22:5 (n-3)	1.11±0.12	0.85±0.26	1.46±0.09	1.88±0.20
22:6 (n-3)	2.88±0.41	2.41±0.47	4.53±0.18	4.67±0.32
SFA	39.65±1.53	29.97*±1.89	38.74±0.52	41.29±0.85
MUFA	14.24±0.36	27.73***±0.74	11.15±0.41	10.03±0.25
PUFA	46.11±1.12	42.30±3.84	50.11±0.53	48.68±0.90
UFA/SFA	1.51	2.32	1.58	1.42

The abbreviations represent: SHR-c and WKY-c, vehicle-treated SHR and WKY; SHR-t and WKY-t, 2OHOA-treated SHR and WKY; SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; UFA/SFA, unsaturated to total saturated fatty acids molar ratio. Data are the mean values±SEM from three independent analyses. *p<0.05; **p<0.01, ***p<0.001, groups that are significantly different from the corresponding control.

Figure 3.  Temperature dependency of the polarity of the DPH probe in reconstituted membranes with total lipid extract from SHR-c (□), SHR-t (▪), WKY-c (○) and WKY-t (•) liver plasma membranes. Fluorescence polarization data are mean values from three independent experiments.

Figure 4.  Sequence of X-ray diffraction scattering patterns from reconstituted membranes of total lipid extracts from SHR-c (A, F), SHR-t (B, G), SHR-t plus extra added 2OHOA (C, H), WKY-c (D, I) and WKY-t liver plasma membranes (E, J). The sequence of patterns were acquired in kinetic conditions (A–E) with a scan rate of 1°C/min and quasi-equilibrium conditions (F–J) after equilibrating the sample for 15 min at each temperature. Successive diffraction patterns were collected for 15 s each min. The H_II phase was identified by 3–4 diffraction peaks indicated (panels F–J). The L_α phase was identified by the first order reflection peak on the SAXS and the absence of peak on the WAXS region.

Figure 5.  Dependency of the repeat distance with temperature for the reconstituted membranes from total lipid extract from SHR-c (□), SHR-t (▪), SHR-t plus extra added 2OHOA (♦), WKY-c (○) and WKY-t (•) liver plasma membranes. Phases represented are L_α (dotted lines) and H_II (continuous lines). Non-identified phases have been omitted. The heating sequence is only shown.