MiR-644a Disrupts Oncogenic Transformation and Warburg Effect by Direct Modulation of Multiple Genes of Tumor-Promoting Pathways

Castration-resistant prostate cancer (CRPC) is defined by tumor microenvironment heterogeneity affecting intrinsic cellular mechanisms including dysregulated androgen signaling, aerobic glycolysis (Warburg effect), and aberrant activation of transcription factors including androgen receptor (AR) and c-Myc. Using in vitro, in vivo, and animal models, we find a direct correlation between miR-644a downregulation and dysregulation of essential cellular processes. MiR-644a downregulated expression of diverse tumor microenvironment drivers including c-Myc, AR coregulators, and antiapoptosis factors Bcl-xl and Bcl2. Moreover, miR-644a modulates epithelial-mesenchymal transition (EMT) by directly targeting EMT-promoting factors ZEB1, cdk6, and Snail. Finally, miR-644a expression suppresses the Warburg effect by direct targeting of c-Myc, Akt, IGF1R, and GAPDH expression. RNA sequencing analysis revealed an analogous downregulation of these factors in animal tumor xenografts. These data demonstrate miR-644a mediated fine-tuning of oncogenesis, stimulating pathways and resultant potentiation of enzalutamide therapy in CRPC patients. SIGNIFICANCE: This study demonstrates that miR-644a therapeutically influences the CRPC tumor microenvironment by suppressing androgen signaling and additional genes involved in metabolism, proliferation, Warburg effect, and EMT, to potentiate the enzalutamide therapy.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/8/1844/F1.large.jpg.

U6atac snRNA stem-loop interacts with U12 p65 RNA binding protein and is functionally interchangeable with the U12 apical stem-loop III

Formation of catalytic core of the U12-dependent spliceosome involves U6atac and U12 interaction with the 5′ splice site and branch site regions of a U12-dependent intron, respectively. Beyond the formation of intermolecular helix I region between U6atac and U12 snRNAs, several other regions within these RNA molecules are predicted to form stem-loop structures. Our previous work demonstrated that the 3′ stem-loop region of U6atac snRNA contains a U12-dependent spliceosome-specific targeting activity. Here, we show a detailed structure-function analysis and requirement of a substructure of U6atac 3′ stem-loop in U12-dependent in vivo splicing. We show that the C-terminal RNA recognition motif of p65, a U12 snRNA binding protein, also binds to the distal 3′ stem-loop of U6atac. By using a binary splice site mutation suppressor assay we demonstrate that p65 protein-binding apical stem-loop of U12 snRNA can be replaced by this U6atac distal 3′ stem-loop. Furthermore, we tested the compatibility of the U6atac 3′ end from phylogenetically distant species in a human U6atac background, to establish the evolutionary relatedness of these structures and in vivo function. In summary, we demonstrate that RNA-RNA and RNA-protein interactions in the minor spliceosome are highly plastic as compared to the major spliceosome.

Abstract 1119: Tumor suppressing dual-action miRNA: Targeting Warburg effect and androgen receptor function in CRPC

The ability of prostate cancer cells to alter their metabolism in a manner distinct from benign cells and energy reprogramming is a major concern in treatment of castration resistant prostate cancer (CRPC). On the other hand, development of resistance to next-generation drugs directed against the AR signaling axis (Abiraterone acetate and Enzalutamide) confers a grim prognosis. Hence, targeting aerobic glycolysis of tumor cells as well as AR signaling axis in CRPC is highly desirable. Here, we report the role of a dual-action miRNA which targets the Androgen Receptor function as well as action of key factors involved in tumor energy metabolism. In addition, the miRNA also targets the key anti-apoptotic factors and enhance the apoptosis in cultured cells. Furthermore, together with Enzalutamide, the miRNA shows a potent synergistic anti-tumor activity in 22RV1 mouse xenografts. We will present the detailed results showing the therapeutic potential of dual-action miRNA in the treatment of CRPC.

Citation Format: Jey Sabith Ebron, Jagjit Singh, Kavleen Sikand, Eswar Shankar, Sanjay Gupta, Girish C. Shukla. Tumor suppressing dual-action miRNA: Targeting Warburg effect and androgen receptor function in CRPC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1119.

Deep sequencing of small RNA libraries from human prostate epithelial and stromal cells reveal distinct pattern of microRNAs primarily predicted to target growth factors

Complex epithelial and stromal cell interactions are required during the development and progression of prostate cancer. Regulatory small non-coding microRNAs (miRNAs) participate in the spatiotemporal regulation of messenger RNA (mRNA) and regulation of translation affecting a large number of genes involved in prostate carcinogenesis. In this study, through deep-sequencing of size fractionated small RNA libraries we profiled the miRNAs of prostate epithelial (PrEC) and stromal (PrSC) cells. Over 50 million reads were obtained for PrEC in which 860,468 were unique sequences. Similarly, nearly 76 million reads for PrSC were obtained in which over 1 million were unique reads. Expression of many miRNAs of broadly conserved and poorly conserved miRNA families were identified. Sixteen highly expressed miRNAs with significant change in expression in PrSC than PrEC were further analyzed in silico. ConsensusPathDB showed the target genes of these miRNAs were significantly involved in adherence junction, cell adhesion, EGRF, TGF-β and androgen signaling. Let-7 family of tumor-suppressor miRNAs expression was highly pervasive in both, PrEC and PrSC cells. In addition, we have also identified several miRNAs that are unique to PrEC or PrSC cells and their predicted putative targets are a group of transcription factors. This study provides perspective on the miRNA expression in PrEC and PrSC, and reveals a global trend in miRNA interactome. We conclude that the most abundant miRNAs are potential regulators of development and differentiation of the prostate gland by targeting a set of growth factors. Additionally, high level expression of the most members of let-7 family miRNAs suggests their role in the fine tuning of the growth and proliferation of prostate epithelial and stromal cells.

Abstract 5212: Regulation of androgen receptor expression by andro-miRs in prostate cancer

Androgen receptor (AR) is a member of the steroid receptor family which plays a significant role in the regulation of both prostate cell proliferation and growth suppression. The targeting of androgen- and AR- signaling axis remains the primary therapeutic option for prostate cancer (PCa) treatment. AR mRNA has a long 3′UTR of 6.8 kb length and is predicted to be a target of many miRNAs. The existence of long 3′UTR proposes a complex mechanism of regulation of AR gene expression through miRNAs and other factors including RNA binding proteins and polyadenylation signals. Differential expression of various miRNAs has been reported to be associated with the progression of the disease to harmone-independence and castration-resistant prostact cancer (CRPC). However, the direct regulation of AR transcriptional activity through miRNAs is not clearly understood. Our lab has discovered that AR is a target of andro-miRs (miR-488*, miR-644, miR-149, miR-512-5p). These andro-miRs bind to target sequences in the 3′UTR of AR and downregulates luciferase expression in the target-validation validation experiments as well as endogeneous AR expression. Our ongoing study of andro-miRs also indicates that, in addition to downregulation of AR gene expression by the action of andro-miRs alone and synergistically, these miRNAs can regulate AR signaling leading to androgen-independence and resistance. This post transcriptional regulation of AR gene expression through andro-miRs makes them an interesting candidate for miR-based adjunctive treatment in CRPC treatment.

Note: This abstract was not presented at the meeting.

Citation Format: Jey Sabith Ebron, Kavleen Sikand, Jagjit Singh, Girish C. Shukla. Regulation of androgen receptor expression by andro-miRs in prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5212. doi:10.1158/1538-7445.AM2014-5212

Abstract 3196: Androgen receptor 3’ untranslated region (UTR): a conundrum and a significant therapeutic opportunity

Master transcriptional regulator Androgen Receptor (AR) remained a fascinating and an enigmatic molecule, particularly in Prostate cancer biology. Major impetus in PCa research is currently focused on the development of new generation of therapeutics to target AR expression, especially in castration-resistant stage of the disease. 920 amino acid coding AR gene encompasses over 180 kilobase (kb) of X-chromosome containing eight exons that produces a nearly 10.7 kb AR mRNA. The fully processed mature AR mRNA account for only 26% of total coding capacity and most of the transcript codes for noncoding regions that includes 5’ and 3’ UTRs. However, functional roles of UTRs in AR gene expression, principally its regulatory involvement in development of CRPC remained indefinable. Our research is focusing on understanding the functional roles of 6.8 kb long AR 3’ UTR in AR gene expression and especially the molecular mechanism that revitalizes AR expression in CRPC. We have shown that a number of regulatory noncoding miRNAs play a critical 3’ UTR targeting role in AR gene expression and has potential therapeutic implications. Here we show a synergistic approach of targeting AR expression mediated via its 3’ UTR, using a miRNA cocktail combinatorial approach. In addition, we are investigating the potential functional association of 3’ UTR in AR gene expression and implication in PCa.

Citation Format: Girish C. Shukla, Kavleen Sikand, Jey S. Ebron. Androgen receptor 3’ untranslated region (UTR): a conundrum and a significant therapeutic opportunity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3196. doi:10.1158/1538-7445.AM2013-3196

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Classification of and cytoreductive surgery for low-grade appendiceal mucinous neoplasms

BACKGROUND

Low-grade appendiceal mucinous neoplasm (LAMN) is a precursor lesion for pseudomyxoma peritonei (PMP), which, if treated suboptimally, may later disseminate throughout the abdominal cavity. The role of cytoreductive surgery for these relatively early lesions is unclear.

METHODS

Clinicopathological details and treatment outcomes of patients with a LAMN and disease limited to the appendix or immediate periappendiceal tissues, referred to a national treatment centre between 2002 and 2009, were evaluated prospectively.

RESULTS

Of 379 patients with a diagnosis of PMP, 43 (median age 49 years) had LAMNs localized to the appendix and periappendiceal tissue. Thirty-two patients initially presented with symptoms of acute appendicitis or right iliac fossa pain. Two distinct lesions were identified: type I (disease confined to the appendiceal lumen) and type II (mucin and/or neoplastic epithelium in the appendiceal submucosa, wall and/or periappendiceal tissue, with or without perforation). Type I lesions were managed by a watch-and-wait surveillance policy with serial measurement of tumour markers and computed tomography in 14 of 16 patients. Seventeen of 27 patients with type II lesions underwent risk-reducing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy with low morbidity. After a median follow-up of 40 months, there was no disease progression in either treatment pathway.

CONCLUSION

This study identified two LAMN subtypes. Type II lesions have pathological features of increased risk for dissemination and should be considered for risk-reducing cytoreductive surgery.

miR 488* inhibits androgen receptor expression in prostate carcinoma cells

Androgen receptor (AR) is a ligand-dependent transcription factor, which plays a significant role in prostate carcinogenesis. Blockade of AR and its ligand, androgen is the basis for the treatment of prostate cancer (PCa). Nevertheless, a modest increase in the critical levels of AR mRNA and corresponding protein is sufficient for the development of resistance to antiandrogen therapy. A strategy to further downregulate AR mRNA and protein expression in combination with antiandrogen therapy may prevent or delay the development of androgen-independent PCa. Recent studies show that microRNAs (miRNAs) perform tumor suppressor functions in various cancers. In this study, we demonstrate that the overexpression of miR 488* downregulates the transcriptional activity of AR and inhibits the endogenous AR protein production in both androgen-dependent and androgen-independent PCa cells. In addition, miR 488* blocks the proliferation and enhances the apoptosis of PCa cells. Our data indicate that miR 488* targets AR and is a potential modulator of AR mediated signaling. Our findings provide insight for utilizing miRNAs as novel therapeutics to target AR in PCa.

Functionally important structural elements of U12 snRNA

U12 snRNA is analogous to U2 snRNA of the U2-dependent spliceosome and is essential for the splicing of U12-dependent introns in metazoan cells. The essential region of U12 snRNA, which base pairs to the branch site of minor class introns is well characterized. However, other regions which are outside of the branch site base pairing region are not yet characterized and the requirement of these structures in U12-dependent splicing is not clear. U12 snRNA is predicted to form an intricate secondary structure containing several stem-loops and single-stranded regions. Using a previously characterized branch site genetic suppression assay, we generated second-site mutations in the suppressor U12 snRNA to investigate the in vivo requirement of structural elements in U12-dependent splicing. Our results show that stem-loop IIa is essential and required for in vivo splicing. Interestingly, an evolutionarily conserved stem-loop IIb is dispensable for splicing. We also show that stem-loop III, which binds to a p65 RNA binding protein of the U11-U12 di.snRNP complex, is essential for in vivo splicing. The data validate the existence of proposed stem-loops of U12 snRNA and provide experimental support for individual secondary structures.

MicroRNAs and Androgen Receptor 3' Untranslated Region: A Missing Link in Castration-resistant Prostate Cancer?

The ligand-activated transcription factor, androgen receptor (AR) plays a central role in the development and progression of prostate cancer. Prostate cancer initiates as an androgen-dependent disease and further accumulation of multiple sequential genetic and epigenetic alterations transform it into an aggressive, castration-resistant prostate cancer (CRPC). The molecular basis of the transition from androgen-dependent prostate cancer to CRPC remains unclear. However, it is apparent that AR plays a pivotal role in this alteration. The recent discovery that microRNAs (miRNAs) can target the function of AR suggests a functional role of these non-coding RNAs in the pathogenesis of prostate cancer. miRNAs usually function by targeting the 3' untranslated region (UTR) of a mRNA by base-pairing interactions and modulate translation either by destabilizing the message or by repression of protein synthesis in actively translating ribosomes. Here, we discuss the potential molecular pathways through which AR targeting miRNAs may promote CRPC. Modulation of AR expression by miRNAs presents a novel therapeutic option for prostate cancer, albeit it will likely be used in combination with the existing therapies.

Intrinsic expression of host genes and intronic miRNAs in prostate carcinoma cells

Background

Recent data show aberrant and altered expression of regulatory noncoding micro (mi) RNAs in prostate cancer (PCa). A large number of miRNAs are encoded in organized intronic clusters within many protein coding genes. While expression profiling studies of miRNAs are common place, little is known about the host gene and their resident miRNAs coordinated expression in PCa cells. Furthermore, whether expression of a subset of miRNAs is distinct in androgen-responsive and androgen-independent cells is not clear. Here we have examined the expression of mature miRNAs of miR 17–92, miR 106b-25 and miR 23b-24 clusters along with their host genes C13orf25, MCM7 and AMPO respectively in PCa cell lines.

Results

The expression profiling of miRNAs and host genes was performed in androgen-sensitive MDA PCa 2b and LNCaP as well as in androgen-refractory PC-3 and DU 145 cell culture models of PCa. No significant correlation between the miRNA expression and the intrinsic hormone-responsive property of PCa cells was observed. Androgen-sensitive MDA PCa 2b cells exhibited the highest level of expression of most miRNAs studied in this report. We found significant expression variations between host genes and their resident miRNAs. The expressions of C13orf25 and miR 17–92 cluster as well as MCM7 and miR 106b-25 cluster did not reveal statistically significant correlation, thus suggesting that host genes and resident miRNAs may be expressed independent of each other.

Conclusion

Our results suggest that miRNA expression profiles may not predict intrinsic hormone-sensitive environment of PCa cells. More importantly, our data indicate the possibility of additional novel mechanisms for intronic miRNA processing in PCa cells.

Importance of LXR-alpha transcriptome in the modulation of innate immunity

Liver-X-Receptor alpha (LXR-alpha) that belongs to nuclear receptor/transcriptional factor family has been recognized to play crucial role in the regulation of lipid metabolism and inflammation. Consequently, the present study was addressed to explore the functional genomics of LXR-alpha within human blood immunomodulatory cells. The results of such a study, which involved LXR-alpha gene silencing through siRNA approach, revealed that: (a) the mRNA expression of genes coding for IL-8, IL-4, CX3CR1, LDLR, hTERT and c-myc was significantly elevated in response to LXR-alpha gene silencing whereas mRNA expression of genes coding for PPARs(alpha, gamma), CD36 and Dicer could not be detected; (b) the expression of Receptor C( k ) protein remained unaffected; (c) the mRNA expression of IFN-gamma gene was down regulated in LXR-alpha knockdown cells. Based upon these results we propose that LXR-alpha gene plays a crucial role in the regulation of innate immunity at the genomic level.

Effect of herbal polyphenols on atherogenic transcriptome

The ancient Indian system of medicine supports the antiatherogenic properties of some herbs. The crosstalk amongst the genes coding for LDLR, LXRalpha, PPARs (alpha,gamma), CD-36 and c-myc may be important in atherogenesis because these genes control lipid metabolism, cytokine production and cellular activity within the arterial wall. Hence, we attempted for the first time to explore whether or not the polyphenols extracted from medicinal herbs had any effect on the transcription of these genes. Normal human mononuclear cells were cultured in the presence of polyphenols (and their HPLC purified sub-fractions) extracted from Green tea (Camellia sinensis), Neem (Azadirachta indica) and Tulsi (Ocimum sanctum). Transcriptional expression of these genes was measured by using RT-PCR and SCION IMAGE analysis software. These polyphenolic extracts were found to have the inherent capacity to inhibit the transcriptional expression of genes having direct involvement in atherogenic process. On the basis of these results, we propose for the first time that HPLC purified polyphenolic fraction IV of Tulsi may have a profound antiatherogenic effect.

Receptor Ck-dependent signaling regulates hTERT gene transcription

Background

Available evidence suggests that the regulation of telomerase activity primarily depends on the transcriptional control of the human telomerase reverse transcriptase (hTERT) gene. Although several activators and repressors of hTERT gene transcription have been identified, the exact mechanism by which hTERT transcription is repressed in normal cells and activated in cancer cells remains largely unknown. In an attempt to identify possible novel mechanisms involved in the regulation of hTERT transcription, the present study examined the role of Receptor C_k, a cell surface receptor specific for cholesterol, in the transcription of hTERT gene in normal human peripheral blood mononuclear cells.

Results

Activated Receptor C_k was found to down-regulate hTERT mRNA expression by repressing the transcription of c-myc gene. Receptor C_k-dependent signaling was also found to down-regulate the mRNA expression of the gene coding for the ligand inducible transcription factor, peroxisome proliferator-activated receptor γ (PPARγ). The ligand activation of PPARγ resulted in the down-regulation of c-myc and hTERT mRNA expression. By using specific activator and inhibitor of protein kinase C (PKC), it was demonstrated that Receptor C_k dependent down-regulation of hTERT gene transcription involved inhibition of PKC. In addition, 25-hydroxycholesterol was found to contribute to the transcriptional regulation of hTERT gene.

Conclusion

Taken together, the findings of this study present evidence for a molecular link between cholesterol-activated Receptor C_k and hTERT transcription, and provide new insights into the regulation of hTERT expression in normal human peripheral blood mononuclear cells.

Sections of the nipple and quadrants in mastectomy specimens for carcinoma are of limited value

AIM

To assess the value of nipple and quadrant sections in mastectomy specimens for carcinoma in detecting Paget's disease and multifocal carcinoma.

METHODS

Two hundred and forty eight consecutive mastectomies performed for carcinoma were reviewed. The presence of Paget's disease of the nipple and mode of identification of any multifocal carcinoma was recorded.

RESULTS

Nipple sections showed Paget's disease in eight specimens: in five the diagnosis had been made on previous biopsy and in three (1%) this was a new diagnosis. In the 220 specimens in which all four quadrants were sampled, multifocal disease was identified more often in specimens with invasive carcinoma (39 of 186; 21%) than in those with only ductal carcinoma in situ (0 of 34). In specimens with invasive carcinoma, multifocality was identified macroscopically in 20: on microscopy of tumour sections in four, on microscopic examination of quadrant sections in 11, in the nipple in three, and in both quadrant and nipple sections in one. Overall, multifocality was found on microscopic examination of quadrant or nipple sections in 15 of 220 specimens (7%).

CONCLUSIONS

The low frequency of detection of multifocality or Paget's disease in nipple and quadrant sections from mastectomy specimens, combined with the fact that such findings do not affect patient management, suggest that nipple and quadrant sections should only be taken if resources permit.

Effect of green tea polyphenols on the genes with atherosclerotic potential

The genomics of atherosclerosis can arise as a result of cross-talk between the genes coding for the LDL-receptor (LDL-R), LXR-alpha, PPARs (alpha, gamma), CD36 and C-myc because these genes control lipid metabolism, cytokine production and cellular activity within the arterial wall. The effect of green tea polyphenols (GTPs) upon such genomics revealed their ability to down-regulate genes coding for PPAR-gamma, CD36, LXR-alpha, C-myc coupled with up-regulation of genes coding for LDL-R and PPAR-alpha at the transcriptional level. Based upon these results, it is proposed that GTPs have the inherent capacity to inhibit the development of atherosclerotic lesions.

Defective RNA-mediated c-myc gene silencing pathway in Burkitt's lymphoma

Keeping in view the fact that molecular basis of Burkitt's lymphoma (BL) is poorly understood, we attempted to explore the small interfering RNA (siRNA) mediated c-myc gene regulation using BL-derived EB-3 cell line as archetype cellular model. Such a study revealed that EB-3 cells possess 4-fold higher expression of Dicer gene coupled with 2-fold higher activity of RNA polymerase III than that observed in normal human lymphocytes. siRNAs derived from EB-3 cells had the inherent capacity to suppress c-myc gene expression in normal cells but not in native cells. Based on these findings we have proposed a novel RNA-mediated c-myc gene regulation pathway that may be responsible for BL.

Effect of pneumolysin on rat brain ciliary function: comparison of brain slices with cultured ependymal cells

This study compares two models for examining ependymal ciliary function: rat brain slices cut from the fourth ventricle and primary ependymal cells in culture. The cilia from both preparations were very reproducible; each preparation had cilia beating at a constant frequency of between 38 and 44 Hz. With the brain slices, ciliary stasis occurred after 5 d in culture. However, ependymal cells had fully functional cilia for up to 48 d in culture. The pneumococcal toxin, pneumolysin, caused a dose-dependent inhibition of cilia beat frequency within 15 min in both models. There were no significant differences in the mean log 50% inhibitory concentration (pIC50) slice = 0.65 +/- 0.05, equivalent to 4.4 hemolytic units (HU)/mL; cells = 0.57 +/- 0.14, equivalent to 3.7 HU/mL. There were also no significant differences in the mean Hill slope factors for the curves (slice = 1.4 +/- 0.05; cells = 1.6 +/- 0.4). These data demonstrate that both models can be used to examine the acute (15-min) effects of pneumolysin on cilia beat frequency. The main advantage of the primary ependymal culture model is that considerably more cultured ependymal cells (approximately 70%) are available, compared with the number of ependymal cells on the brain slices (approximately 2%), thus reducing the number of animals used. A pure ependymal culture was not achieved (approximately 30% of the cells were not ciliated). The increased survival time of the ependymal cells compared with the brain slices make cultured ependymal cells more useful for examining long-term ciliary function, whereas brain slices may be more useful for examining the interactions between ependymal and other nearby cells.

Respiratory and brain ependymal ciliary function

The aims of this study were to compare beat frequencies of tracheal and ependymal cilia and the beat frequencies of ependymal cilia from infant and adult rats. The length of respiratory and ependymal cilia of infant and adult rats was also compared. We have developed an ex vivo model that allows ependymal and respiratory ciliary beat frequency to be measured with a high-speed video system. The beat frequencies of cilia, incubated at 37 degrees C, were measured after an incubation period of 30 min. Ependymal cilia beat at a similar frequency in 10- to 15-d-old rats (mean 38.8 Hz: 95% confidence intervals 37.1-40.6) as in adult animals (mean 40.7 Hz: 95% confidence intervals 38.5-42.9). However, respiratory cilia from adult animals beat (mean 20.9 Hz: 95% confidence intervals 14-27) at a significantly (p = 0.003) lower frequency than ependymal cilia. Ependymal cilia (mean length +/- SD: 8.2 +/- 0.3 microm) measured by scanning electron microscopy were significantly (p = 0.001) longer than respiratory cilia (5.5 +/- 0.6 microm) from the trachea of 9- to 15-d-old rats. Cilia did not grow longer between the time the rats were 9-15 d old and adulthood. Adult respiratory and ependymal ciliary length (mean +/- SD) were 5.6 +/- 0.5 microm and 8.1 +/- 0.2 microm, respectively. In summary, ependymal cilia beat at approximately twice the rate of respiratory cilia and are significantly longer.

Raised affinity for extracellular sodium of the sodium-lithium countertransporter is associated with a family history of hypertension and uraemia in patients with renal disease

1. Increased affinity for sodium (Km) at an external site of the sodium-lithium countertransporter and altered membrane microviscosity in the surface regions of the lipid bilayer identifies a group of essential hypertensive patients with a genetic predisposition to hypertension. The present study investigated the kinetic properties of the sodium-lithium countertransporter and membrane microviscosity in patients with hypertension, renal disease and impaired renal function. 2. Sixty patients with renal disease (28 chronic renal failure, 30 hypertensive, 23 family history of hypertension) were investigated. Standard erythrocyte sodium-lithium countertransport activity, sodium affinity constant (Km), maximum reaction velocity (Vmax) and membrane microviscosity were measured. 3. Patients with renal disease and a family history of hypertension had significantly lower Km (P < 0.05) values and raised membrane microviscosity measured by 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene anisotropy (P < 0.05) compared with patients without a family history of hypertension. 4. Uraemic subjects had low K(m) values compared with patients with renal disease and normal renal function (P < 0.05). However, there was no significant difference in membrane microviscosity between uraemic and non-uraemic subjects. 5. In patients with a family history of hypertension, sodium-lithium countertransport activity and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene anisotropy are important markers of cellular changes in essential hypertension, independent of renal disease. Uraemia, independently of hypertension, produces an alteration in the function of the sodium-lithium countertransporter which has previously been associated with a genetic predisposition to hypertension and cardiovascular disease.

Altered membrane microviscosity in essential hypertension: relationship with family history of hypertension and sodium-lithium countertransport activity

OBJECTIVE

To investigate the alterations in erythrocyte ghost membrane microviscosity in essential hypertensive patients and to determine the relationship between these changes and the sodium-lithium countertransport activity as a sensitive marker of membrane function.

SUBJECTS

Forty-three normolipidaemic essential hypertensive patients (23 treated, 20 untreated) and 27 normotensive controls were studied. Patients were attending the hospital hypertension clinic or a local general practitioner's surgery.

METHODS

Erythrocyte sodium-lithium countertransport activity was measured. The Michaelis constant (Km) for extracellular sodium and maximal reaction velocity for sodium-lithium countertransport were measured in a subgroup consisting of 22 essential hypertensive patients and 11 normotensive controls. Erythrocyte membrane microviscosity was measured using fluorescence polarization anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-trimethylammoniumphenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH).

RESULTS

There was no significant difference in the fluorescence polarization anisotropy of DPH or TMA-DPH between normotensive and essential hypertensive patients. However, the fluorescence polarization anisotropy of TMA-DPH was increased significantly (reflecting increased membrane microviscosity) in hypertensive patients with a family history of hypertension compared with in patients without a family history of hypertension. The standard sodium-lithium countertransport activity was elevated in essential hypertensive patients compared with normotensive controls, and the Km for sodium was significantly lower in patients with a family history of hypertension than in patients without a family history of hypertension. Patients with a family history of hypertension were clustered, with significantly lower Km for sodium and higher TMA-DPH anisotropies than either hypertensive patients without a family history of hypertension or normotensive controls.

CONCLUSIONS

These findings suggest that a high membrane microviscosity affecting the outer region of the lipid bilayer is associated with altered sodium-lithium countertransport kinetics in a subgroup of essential hypertensive patients consisting of those with a family history of hypertension.