Serum amyloid A-induced blood-brain barrier dysfunction associated with decreased claudin-5 expression in rat brain endothelial cells and its inhibition by high-density lipoprotein in vitro

The blood-brain barrier (BBB) is the multicellular interface located between the peripheral circulation and the brain parenchyma. BBB dysfunction is reported in many CNS diseases, such cognitive impairment, depression, Alzheimer's disease (AD), and multiple sclerosis (MS). Emerging evidence indicates that liver-derived inflammatory mediators are upregulated in neurological diseases with BBB dysfunction. Serum amyloid A (SAA), an acute phase protein secreted by hepatocytes, could be a candidate inflammatory signaling molecule transmitted from the liver to the brain; however, its contribution to BBB dysfunction is poorly understood. The present study aimed to elucidate the involvement of SAA in BBB impairment in an in vitro BBB model using rat brain microvascular endothelial cells (RBECs). We demonstrated that Apo-SAA significantly decreased transendothelial electrical resistance (TEER) and increased sodium fluorescein (Na-F) permeability in RBEC monolayers. Apo-SAA also decreased claudin-5 expression levels in RBECs. Furthermore, the Apo-SAA-mediated impairment of the BBB with decreased claudin-5 expression was inhibited by the addition of a high-density lipoprotein (HDL) related to SAA in plasma. These findings suggest that HDL counteracts the effects of SAA on BBB function. Therefore, the functional imbalance between SAA and HDL may induce BBB impairment, thereby triggering development of neuroinflammation. SAA could be a significant endogenous mediator in the liver-to-brain inflammation axis.

Obesity and lipid profiles in middle aged men and women in Tanzania

OBJECTIVE

To examine the relationship between obesity and lipid profiles and to compare the effects of total obesity and central adiposity on lipids in three locations in Tanzania.

DESIGN

Cross-sectional epidemiological study.

SETTING

Three areas in Tanzania: Dar es Salaam (urban), Handeni (rural) and Monduli (pastoralists), in August 1998.

SUBJECTS

Five hundred and forty five men and women from a random sample of 600 people aged 46-58 years.

MAIN OUTCOME MEASURES

Mean BMI, waist circumference, WHR, TC, HDL-C, LDL-C, TG and LDL/HDL ratio. Prevalence rates of overweight,obesity, central obesity and dyslipidaemia.

RESULTS

As compared to men, women had higher BMI (24.7 versus 22.5 kg/m2, p<0.0001), waist circumference (92.4 versus 89.1 cm, p<0.05), TC (4.9 versus 4.2 mmol/L, p<0.0001) and LDL-C (3.3 versus 2.6 mmol/L, p<0.0001). The urban population demonstrated higher levels of lipid factors than the rural population (TC, men 4.8 mmol/L; women 5.3 mmol/L, p<0.0001; TG, men 3.6 mmol/L; women 3.7 mmol/L, p<0.0001, LDL-C, men 2.8 mmol/L, p<0.0001). BMI and waist circumference correlated positively with serum TC, TG, and LDL-C in both genders. Stepwise regression analysis showed that BMI predicted triglyceride concentration in men (p<0.05) and women (p<0.0001). Waist circumference predicted levels of TC in women only (p<0.0001) and of LDL-C in both genders (men p<0.05, women p<0.0001). The prevalence of overweight, obesity and central obesity were significantly higher in urban than in rural areas in both men and women. Compared to lean subjects, obese men and women had significantly higher mean serum TC, TG, LDL-C and a higher prevalence of dyslipidaemia. The mean levels of TC, TG and LDL cholesterol increased across successive increases in BMI and waist circumference quintiles in both genders.

CONCLUSION

Subjects from the urban area had greater lipid abnormalities related to obesity than those from the rural area and that, central adiposity had a greater effect on total cholesterol and LDL cholesterol among women than was BMI.

Cardiovascular risk factors in Tanzania: a revisit

In this assessment of cardiovascular risk factors, we examined the prevalence of selected risk factors according to the World Health Organisation (WHO) CARDIAC Study protocol and compared them with a similar study conducted more than a decade ago. The survey was carried out in Dar es Salaam (D, urban), Handeni (H, rural) and Monduli (Mo, semi-nomadic area). Subjects aged 47-57 were recruited randomly for blood pressure and anthropometrical measurements, 24 h urine collection and blood sampling. A structured questionnaire was used to obtain dietary information. The 1998 survey studied 446 subjects, while the 1987 survey included 496 men and women. The measured weight, body mass index (BMI) and prevalence of obesity (BMI > or = 30 kg/m(2)) increased significantly among women in the 1998 survey in rural Handeni and urban Dar. The overall prevalence of obesity was higher for women in the most recent survey (22.8%, P < 0.0001). Diastolic blood pressure (DBP) was higher in the most recent survey for women in Handeni. The overall prevalence of hypertension (blood pressure > 160/95 mmHg, or antihypertensive drug use), rose to 41.1% in 1998, (P < 0.001) for men and to 38.7% (P < 0.05) for women. The mean total serum cholesterol and prevalence of hypercholesterolaemia increased significantly in the most recent survey in the three studied areas. The overall prevalence of hypercholestrolaemia (serum cholesterol > 5.2 mmol/l) was higher in the 1998 survey for both men (21.8%, P < 0.0001) and women (54.0%, P < 0.0001). The mean HDL cholesterol increased significantly in the most recent survey, with a significant reduction in the mean atherogenic index, though these were still at higher levels (men 5.8, P < 0.0001; women 5.1, P < 0.0001 vs. 1987). A strong positive correlation was observed between blood pressure (SBP and DBP) and body mass index, total serum cholesterol and sodium to potassium ratio. These data suggest that for the past decade there has been an increase in the mean levels and prevalence of selected cardiovascular risk factors in Tanzania.

Expression of plasma membrane Ca(2+)-ATPase in lenses from normal and hereditary cataract UPL rats

PURPOSE

The regulation of calcium concentration in lens cells is important in the mechanisms of cataractogenesis. The Ca( 2+) level in cells is controlled by plasma membrane Ca(2+)-ATPase (PMCA). PMCA has several isoforms that are distributed in various cell types in the body. In this study, we investigated the PMCA mRNA expression in normal lenses and in lenses from rats with newly developed hereditary cataracts.

METHODS

The rats used were the UPL strain of Sprague-Dawley rats, with (UPL) and without (normal) the dominant gene for cataracts. PMCA mRNA expression in the lens, brain, liver and kidney in the normal and UPL rats was detected by reverse transcription-PCR using isoform specific primers. Partial cDNA sequences of the lens PMCA were also determined.

RESULTS

PMCA1, 2, 3 and 4 were expressed in the brain and kidney. Distinct from the brain, liver and kidney, only one isoform of PMCA, PMCA1b, was expressed in both normal and UPL rat lenses. Sequences of PMCA in normal and UPL rat lenses were not different.

CONCLUSIONS

The present study demonstrated that PMCA1b is the only form of PMCA present in both normal and UPL rat lenses.

Nitric oxide participates in cataract development in selenite-treated rats

PURPOSE

The role of nitric oxide in the development of selenite-induced cataracts in rats was examined using nitric oxide synthase (NOS) inhibitors.

METHODS

Subcutaneous injection of sodium selenite was used to induce cataracts in rats, with or without pretreatment with NOS inhibitors. The anterior eye segment analysis system (EAS-1000, Nidek) was used to measure lens opacity. The glutathione content of the lenses was determined by an HPLC method and the Ca2+ content by atomic absorption spectrometry. Nitrite, a stable metabolite of nitric oxide, was determined fluorometrically. NADPH-diaphorase activity staining and Western blot analysis were used to determine NOS levels.

RESULTS

Administration of the NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), inhibited lens opacification in selenite-treated rats. NG-nitro-d-arginine methyl ester, an inactive enantiomer of l-NAME, had no effect. Aminoguanidine, another NOS inhibitor, also inhibited the development of cataracts in a dose-dependent manner. On the other hand, L-arginine, a substrate of NOS, accelerated the development of cataracts. Although the opacification of the lenses was apparent approximately 3 days after selenite injection, the nitrite level was increased within one day. In addition, NOS was induced in the eye within one day of selenite injection.

CONCLUSIONS

The present study demonstrated that NOS inhibitors prevented the development of cataracts in selenite-treated rats. The results also suggest that nitric oxide had an important role in the development of selenite-induced cataracts.

Preventive effect of diethyldithiocarbamate on selenite-induced opacity in cultured rat lenses

Increasing evidence suggests the involvement of reactive oxygen species in the development of cataracts. In this study, we investigated the preventive effect of diethyldithiocarbamate (DDC) on the selenite-induced opacification of cultured rat lenses. Lens opacity was produced by incubation with 0.2 mM selenite for 24 h, which resulted in an increase in selenium content in the cultured lenses. The increase in selenium content and the onset of opacification and lens membrane damage were inhibited by preincubation with DDC. It is reasonable to assume that DDC contributed to anticataract ability. In addition, selenite resulted in a significant decrease in glutathione and protein thiol content and an increase in lipid peroxidation levels in the lenses. These alterations were also depressed by DDC, suggesting a contribution of an antioxidative effect by DDC in the inhibition of lens opacification. At the same lens selenium content, DDC treatment inhibited opacification and lipid peroxide. In conclusion, we propose that the antioxidative properties of DDC play a major role in its contribution to the anticataract effect.

Comparative study of superoxide dismutase in normal and hereditary cataract (UPL) rats

In the present study, the levels of SOD activity and Cu, Zn-SOD mRNA in the brain, kidney, liver and eye of normal and Upjohn Pharmaceutics Limited (UPL) rats, a new hereditary cataract model derived from Sprague-Dawley rats, were measured. Although the levels of SOD activity in the eye and brain of UPL rats were significantly decreased compared with those of normal rats 3 and 5 weeks after birth, the levels of SOD activities in the kidney and liver were the same in both groups. The levels of Cu, Zn-SOD mRNA in kidney and liver of UPL rats were the same as those of normal controls. The level of Cu, Zn-SOD mRNA in the brain of normal rats 5 weeks after birth was about twofold greater than that of UPL, and that in the eye of UPL rats 3 weeks after birth was significantly decreased compared with that of normal controls. The sequences of cDNA encoding Cu, Zn-SOD and the sequences of the regulatory region of the Cu, Zn-SOD gene were confirmed to be the same in normal and UPL rats. These results indicated that the decreases in levels of SOD activity and Cu, Zn-SOD mRNA in the brain and eye of UPL rat were not due to mutation of the genomic Cu, Zn-SOD gene in UPL rats or differences in the sequence of the regulatory region of the Cu, Zn-SOD gene between normal and UPL rats.

Effects of lipid composition on the transcorneal penetration of liposomes containing disulfiram, a potential anti-cataract agent, in the rabbit

We previously demonstrated that topical treatment with disulfiram (DSF) prevented the development of cataracts in sodium selenite-injected rat pups. In biological systems, DSF is rapidly reduced to diethyldithiocarbamate (DDC), a potent antioxidant. In this study, we investigated the effect of altering the lipid composition of liposomes containing DSF on the transcorneal transit of DDC. Liposomes containing DSF were prepared with various molar ratios of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and cetylpyridinum chloride (CPC) by reverse-phase evaporation. Liposomes with a DMPC to DPPC molar ratio of 5:5, examined by differential scanning calorimetry, had the highest enthalpy of transition and the presence of one molar ratio of CPC further enhanced the enthalpy value. The addition of bovine serum albumin or a homogenate of rabbit cornea to the incubation buffer resulted in the release of DDC, but not DSF from the liposomes. The amount of DDC present in the aqueous humor of rabbit eyes following topical administration increased with increase in DMPC to DPPC ratios and was also enhanced by the addition of CPC to the liposomes. The results of this study suggest that liposome formulations are effective for transcorneal drug delivery of anticataract agents such as DSF. DSF in liposomes consisting of DMPC, DPPC, and CPC with a molar ratio of 8:2:1 may be a potential drug formulation for the prevention and/or treatment of cataracts.

Morphological behavior of acidic and neutral liposomes induced by basic amphiphilic alpha-helical peptides with systematically varied hydrophobic-hydrophilic balance

Lipid-peptide interaction has been investigated using cationic amphiphilic alpha-helical peptides and systematically varying their hydrophobic-hydrophilic balance (HHB). The influence of the peptides on neutral and acidic liposomes was examined by 1) Trp fluorescence quenched by brominated phospholipid, 2) membrane-clearing ability, 3) size determination of liposomes by dynamic light scattering, 4) morphological observation by electron microscopy, and 5) ability to form planar lipid bilayers from channels. The peptides examined consist of hydrophobic Leu and hydrophilic Lys residues with ratios 13:5, 11:7, 9:9, 7:11, and 5:13 (abbreviated as Hels 13-5, 11-7, 9-9, 7-11, and 5-13, respectively; Kiyota, T., S. Lee, and G. Sugihara. 1996. Biochemistry. 35:13196-13204). The most hydrophobic peptide (Hel 13-5) induced a twisted ribbon-like fibril structure for egg PC liposomes. In a 3/1 (egg PC/egg PG) lipid mixture, Hel 13-5 addition caused fusion of the liposomes. Hel 13-5 formed ion channels in neutral lipid bilayer (egg PE/egg PC = 7/3) at low peptide concentrations, but not in an acidic bilayer (egg PE/brain PS = 7/3). The peptides with hydrophobicity less than Hel 13-5 (Hels 11-7 and Hel 9-9) were able to partially immerse their hydrophobic part of the amphiphilic helix in lipid bilayers and fragment liposome to small bicelles or micelles, and then the bicelles aggregated to form a larger assembly. Peptides Hel 11-7 and Hel 9-9 each formed strong ion channels. Peptides (Hel 7-11 and Hel 5-13) with a more hydrophilic HHB interacted with an acidic lipid bilayer by charge interaction, in which the former immerses the hydrophobic part in lipid bilayer, and the latter did not immerse, and formed large assemblies by aggregation of original liposomes. The present study clearly showed that hydrophobic-hydrophilic balance of a peptide is a crucial factor in understanding lipid-peptide interactions.

Immunohistochemical study of calpain-mediated alpha-crystallin proteolysis in the UPL rat hereditary cataract

The UPL (Upjohn Pharmaceutical Limited) rat is a dominant hereditary cataract model that develops early-onset cataracts (E-type) in rats homozygous for the trait, and late-onset cataracts (L-type) in heterozygous rats. Using antibodies specific to the calpain-proteolyzed forms of alpha-crystallin, we determined their immunohistochemical localization of the L- and E-rat lenses. Immunoreactivity indicating the proteolyzed forms was detected and found restricted to degenerated lens fibers of the mature stage of the L-rat cataract. Lenses from E-rats, which have abnormally elongated lens fibers during the fetal period, had proteolyzed alpha-crystallin forms at 1 week of age. The results of this present study indicate that calpain-mediated proteolysis of alpha-crystallin occurred in the UPL rat lenses during cataract formation and that calpain may be an important factor in the development of complete lens opacification.