Essential hypertension is the leading contributor to premature death worldwide. Endoplasmic reticulum (ER) stress has recently been implicated in diseased blood vessels and hypertension. It is unclear whether ER stress is a cause or a consequence of hypertension. We hypothesized that ER stress inhibition would prevent the development of hypertension in the young spontaneously hypertensive rat (SHR) by improving vascular structure and function. The SHR was used as a genetic model of human essential hypertension, and the Wistar Kyoto (WKY) rat as its normotensive control. The first study conducted involved assessing the levels of ER stress in young SHRs, before they developed hypertension. The second study conducted involved treating rats with 1g/kg/day of the sodium salt of 4-phenylbutyric acid (4-PBA) orally for 8 weeks from 5 weeks of age. Blood pressure was measured weekly, noninvasively via radiotelemetry. Mesenteric arteries were collected at sacrifice. Finally, the third study conducted involved treating rats with 1g/kg/day 4-PBA orally for eight weeks from five weeks of age, and then withdrawing the drug for four weeks to determine if drug treatment created a sustained lowering of blood pressure. In the first study, ER stress markers were observed to be significantly increased in the young SHR when compared to the WKY. In the second study, blood pressure was observed to be significantly lower in the 4-PBA-treated SHR groups than in the untreated SHRs. In addition, mesenteric arteries from the 4-PBA treated SHRs had a significant decrease in media/lumen ratio, ER stress marker expressions, as well as improved vasodilatory response to carbachol and reduced contractile responses to phenylephrine. In the third study, 4-PBA was able to keep the blood pressure low for one week after withdrawal, however, blood pressure returned to similar levels as untreated SHRs by the end of three weeks. Overall, ER stress inhibition, via 4-PBA, blunted the development of hypertension in the SHR. / Thesis / Master of Science (MSc)

Introduction The genetic skin disease epidermolytic ichtyosis is caused by mutations in either keratin gene 1 or 10 and leads to blisters and hyperkeratosis of the epidermis. At cellular level the disease is seen as aggregates in the keratin filaments. Since medicines are hard to investigate and produce mainly due to lack of reproducible model systems, there is no good treatment available for this disease today. In this article we describe how an in vitro model consisting of cells from a stable cell line transfected with expression plasmids to mimic patient cells, may be a possible alternative for screening compounds for therapies. The first step was to generate an expression plasmid required to complete the in vitro model. The model was tested by a preliminary experiment with 4-phenylbuturate (4-PBA) to see if the substance had an effect on the amount of cells with keratin aggregates. Methods PCR and primers containing the desired mutation were used to incorporate a deletion in wild type keratin gene1 plasmid to generate the expression plasmid. HaCaT cells were transfected with the plasmid for expression of keratin. The percentage of cells with keratin aggregates was assessed by fluorescence microscopy. Results/Conclusion Cells containing mutated plasmid had a higher percentage of keratin aggregates compared to cells transfected with wild type plasmid. 4-PBA was found not to affect the amount of cells with keratin aggregates. According to this project the model might be a useful tool for screening compounds, but it needs to be more developed and tested.

Epidermolysis bullosa simplex (EBS) and epidermolytic ichthyosis (EI) are rare skin fragility diseases characterized by intra-epidermal blistering due to autosomal dominant-negative mutations in basal (KRT5 or KRT14) and suprabasal (KRT1 or KRT10) keratin genes,  respectively. Despite vast knowledge in the disease pathogenesis, the pathomechanisms are not fully understood, and no effective remedies exist. The purpose of this work was to search for keratin gene mutations in EBS patients, to develop in vitro models for studying EBS and EI, and to investigate novel pharmacological approaches for both diseases. We identified both novel and recurrent KRT5 mutations in all studied EBS patients but one which did not show any pathogenic keratin mutations. Using cultured primary keratinocytes from EBS patients, we reproduced a correlation between clinical severity and cytoskeletal instability in vitro. Immortalized keratinocyte cell lines were established from three EBS and three EI patients with different phenotypes using HPV16-E6E7. Only cell lines derived from severely affected patients exhibited spontaneous keratin aggregates under normal culture conditions. However, heat stress significantly induced keratin aggregates in all patient cell lines. This effect was more dramatic in cells from patients with a severe phenotype. In organotypic cultures, the immortalized cells were able to differentiate and form a multilayered epidermis reminiscent of those observed in vivo. Addition of two molecular chaperones, trimethylamine N-oxide dihydrate (TMAO) and sodium 4-phenylbutyrate (4-PBA), reduced the keratin aggregates in both stressed and unstressed EBS and EI keratinocytes, respectively. The mechanism of action of TMAO and 4-PBA was shown to involve the endogenous chaperone system (Heat shock proteins e.g. Hsp70). Besides, MAPK signaling pathways also seemed to be incriminated in the pathogenesis of EBS. Furthermore, depending on which type of keratin is mutated, 4-PBA up-regulated Hsp70 and KRT4 (possibly compensating for mutated KRT1/5), and down-regulated KRT1 and KRT10, which could further assist in protecting EBS and EI cells against stress. In conclusion, novel and recurrent pathogenic keratin mutations have been identified in EBS. Immortalized EBS and EI cell lines that functionally reflect the disease phenotype were established. Two pharmacologic agents, TMAO and 4-PBA, were shown to be promising candidates as novel treatment of heritable keratinopathies in this in vitro model.

Indiana University-Purdue University Indianapolis (IUPUI) / Sequestration at the aggresome and degradation through autophagy are two approaches by which a cell can counteract the toxic effect of misfolded proteins. Tuberous sclerosis (TS) and cancer cells can become dependent on autophagy for survival due to the high demand for protein synthesis, thus making protein clearance a potential therapeutic target. Because of its histone deacetylase (HDAC) inhibitory activity, we hypothesized that 4-phenylbutyrate (4-PBA) inhibits HDAC6 and aggresome formation to induce TS cell death. We found that 4-PBA treatment increases cell death and reduces bortezomib-induced aggresome formation. To link these results with HDAC inhibition we used two other HDAC inhibitors, trichostatin A (TSA) and tubastatin, and found that they also reduce bortezomib-induced protein aggregation. Because tubulin is a target of HDAC6, we next measured the effect of the HDAC inhibitors and 4-PBA treatment on tubulin acetylation. As expected, tubastatin increased tubulin acetylation but surprisingly TSA and 4-PBA did not. Because 4-PBA did not significantly inhibit HDAC6, we next hypothesized that 4-PBA was alternatively inducing autophagy and increasing aggresome clearance. Surprisingly, autophagy inhibition did not prevent the 4-PBA-induced reduction in protein aggregation. In conclusion, we found 4-PBA to induce cell death and reduce aggresome levels in TS cells, but we found no link between these phenomena. We next hypothesized that loss of the Ral guanine nucleotide exchange factor Rgl2 induces cell death via autophagy inhibition in pancreatic adenocarcinoma (PDAC) cells. KRas is mutationally activated in over 90% of PDACs and directly activates Rgl2. Rgl2 activates RalB, a known regulator of autophagy, and Rgl2 has been shown to promote PDAC cell survival. We first confirmed that loss of Rgl2 does increase cell death in PDAC cells. Initial experiments using doubly tagged fluorescent p62 and LC3 (autophagy markers) suggested that loss of Rgl2 inhibited autophagosome accumulation, but after developing a more sophisticated quantitation method we found loss of Rgl2 to have no effect. We also measured endogenous LC3 levels, and these experiments confirmed loss of Rgl2 to have no effect on autophagy levels. Therefore, loss of Rgl2 increases cell death in PDAC cells, but does not have a significant effect on autophagy.