Cezary Wójcik

Proteasome Inhibition Potentiates Antitumor Effects of Photodynamic Therapy in Mice through Induction of Endoplasmic Reticulum Stress and Unfolded Protein Response

Photodynamic therapy (PDT) is an approved therapeutic procedure that exerts cytotoxic activity toward tumor cells by inducing production of reactive oxygen species such as singlet oxygen. PDT leads to oxidative damage of cellular macromolecules, including proteins that undergo multiple modifications such as fragmentation, cross-linking, and carbonylation that result in protein unfolding and aggregation. Because the major mechanism for elimination of carbonylated proteins is their degradation by proteasomes, we hypothesized that a combination of PDT with proteasome inhibitors might lead to accumulation of carbonylated proteins in endoplasmic reticulum (ER), aggravated ER stress, and potentiated cytotoxicity toward tumor cells. We observed that Photofrin-mediated PDT leads to robust carbonylation of cellular proteins and induction of unfolded protein response. Pretreatment of tumor cells with three different proteasome inhibitors, including bortezomib, MG132, and PSI, gave increased accumulation of carbonylated and ubiquitinated proteins in PDT-treated cells. Proteasome inhibitors effectively sensitized tumor cells of murine (EMT6 and C-26) as well as human (HeLa) origin to PDT-mediated cytotoxicity. Significant retardation of tumor growth with 60% to 100% complete responses was observed in vivo in two different murine tumor models (EMT6 and C-26) when PDT was combined with either bortezomib or PSI. Altogether, these observations indicate that combination of PDT with proteasome inhibitors leads to potentiated antitumor effects. The results of these studies are of immediate clinical application because bortezomib is a clinically approved drug that undergoes extensive clinical evaluations for the treatment of solid tumors.

Cardiotoxicity of the Anticancer Therapeutic Agent Bortezomib

Recent case reports provided alarming signals that treatment with bortezomib might be associated with cardiac events. In all reported cases, patients experiencing cardiac problems were previously or concomitantly treated with other chemotherapeutics including cardiotoxic anthracyclines. Therefore, it is difficult to distinguish which components of the therapeutic regimens contribute to cardiotoxicity. Here, we addressed the influence of bortezomib on cardiac function in rats that were not treated with other drugs. Rats were treated with bortezomib at a dose of 0.2 mg/kg thrice weekly. Echocardiography, histopathology, and electron microscopy were used to evaluate cardiac function and structural changes. Respiration of the rat heart mitochondria was measured polarographically. Cell culture experiments were used to determine the influence of bortezomib on cardiomyocyte survival, contractility, Ca(2+) fluxes, induction of endoplasmic reticulum stress, and autophagy. Our findings indicate that bortezomib treatment leads to left ventricular contractile dysfunction manifested by a significant drop in left ventricle ejection fraction. Dramatic ultrastructural abnormalities of cardiomyocytes, especially within mitochondria, were accompanied by decreased ATP synthesis and decreased cardiomyocyte contractility. Monitoring of cardiac function in bortezomib-treated patients should be implemented to evaluate how frequently cardiotoxicity develops especially in patients with pre-existing cardiac conditions, as well as when using additional cardiotoxic drugs.

Activated prothrombin complex concentrate factor VIII inhibitor bypassing activity (FEIBA) for the reversal of warfarin-induced coagulopathy

AimsThe purpose of this study was to evaluate the effectiveness of a new, fixed, yet individualized dosing regimen of activated prothrombin complex concentrate factor VIII inhibitor bypassing activity (FEIBA) for warfarin reversal in the setting of a life-threatening bleeding in a secondary care center.MethodsIn this report we present a retrospective chart review of 72 patients who received FEIBA and 69 patients who received fresh-frozen plasma (FFP) to reverse the effects of warfarin in a setting of a life-threatening bleeding. In the FEIBA cohort, patients received 500 units of FEIBA when the initial INR was <5 or 1,000 units of FEIBA when initial INR was ≥5.ResultsFEIBA administration resulted in lower subsequent INR when compared with FFP and shorter time elapsed from drug administration to an INR ≤1.4 when compared with FFP. No significant differences in survival or in the length of hospital stay were observed. A higher FEIBA dose induced a bigger decrease in INR than the lower dose. We observed five adverse events (7%) that could potentially be related to FEIBA administration.ConclusionsThe presented dosing regimen results in safe reversal of warfarin-induced coagulopathy, which appears to be faster and more profound than following FFP. Moreover, the use of activated PCC (FEIBA) does not appear to carry an increased risk of thrombotic events when compared to the rate reported for several non-activated PCC preparations.

TNF potentiates anticancer activity of bortezomib (Velcade®) through reduced expression of proteasome subunits and dysregulation of unfolded protein response

Bortezomib (Velcade®) exploits proteasome inhibition as a unique mechanism of anticancer activity. The effectiveness of bortezomib is, however, limited, therefore, the search for therapeutic regimens combining bortezomib with other agents. In the present work we demonstrate enhanced anticancer activity of bortezomib by its combination with tumor necrosis factor (TNF) in the experimental model of C‐26 colon carcinoma in mice. This interaction likely relies on the induction of a dysregulated response to ER stress, leading to apoptosis of cancer cells, evidenced by caspase‐3 cleavage, p53 accumulation as well as increased SAPK/JNK phosphorylation. ER stress induced by the combination of TNF and bortezomib is corroborated by upregulation of BiP, PDI and calnexin as well as cleavage of caspase‐12; however, in contrast to the classic pathway, it is also associated with decreased phosphorylation of eIF2α and prevention of XBP‐1 splicing. TNF prevented the upregulation of Hsp27 induced by bortezomib, which may contribute to enhanced ER stress. Moreover, TNF interfered with bortezomib‐induced upregulation of distinct subunits of the 26S proteasome. Bortezomib concentration used in this study was not sufficient to prevent TNF from inducing nuclear translocation of p65/RelA; however, the combination of both agents reduced total p65/RelA levels. Combined treatment of tumor‐bearing mice with bortezomib and TNF not only inhibited tumor growth but also significantly prolonged animal survival. Therefore, combination of bortezomib with TNF is an attractive option for further clinical studies.

Decreased ER-associated degradation of α-TCR induced by Grp78 depletion with the SubAB cytotoxin

HeLa cells stably expressing the alpha chain of T-cell receptor (alphaTCR), a model substrate of ER-associated degradation (ERAD), were used to analyze the effects of BiP/Grp78 depletion by the SubAB cytotoxin. SubAB induced XBP1 splicing, followed by JNK phosphorylation, eIF2alpha phosphorylation, upregulation of ATF3/4 and partial ATF6 cleavage. Other markers of ER stress, including elements of ERAD pathway, as well as markers of cytoplasmic stress, were not induced. SubAB treatment decreased absolute levels of alphaTCR, which was caused by inhibition of protein synthesis. At the same time, the half-life of alphaTCR was extended almost fourfold from 70 min to 210 min, suggesting that BiP normally facilitates ERAD. Depletion of p97/VCP partially rescued SubAB-induced depletion of alphaTCR, confirming the role of VCP in ERAD of alphaTCR. It therefore appears that ERAD of alphaTCR is driven by at least two different ATP-ase systems located at two sides of the ER membrane, BiP located on the lumenal side, while p97/VCP on the cytoplasmic side. While SubAB altered cell morphology by inducing cytoplasm vacuolization and accumulation of lipid droplets, caspase activation was partial and subsided after prolonged incubation. Expression of CHOP/GADD153 occurred only after prolonged incubation and was not associated with apoptosis.

Modulation of adipocyte differentiation by omega-3 polyunsaturated fatty acids involves the ubiquitin-proteasome system

We have evaluated the effects of three different omega‐3 polyunsaturated fatty acids (ω‐3 PUFAs) – docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) on fat accumulation and expression of adipogenic and inflammatory markers using both 3T3‐L1 pre‐adipocytes and differentiated 3T3‐L1 adipocytes. Our results indicate that ω‐3 PUFAs induce the degradation of fatty acid synthase through the ubiquitin‐proteasome system, which is likely to have beneficial metabolic effect on adipose cells. Omega‐3 PUFAs also increase overall levels of polyubiquitinated proteins, at least in part through decreasing the expression of proteasome subunits. Moreover, adipocytes are resistant to proteasome inhibition, which induces adipophilin while decreasing perilipin expression. On the other hand, ω‐3 PUFAs decrease expression of SREBP1 while inducing expression of adipophilin and GLUT4. Moreover, all three ω‐3 PUFAs appear to induce tumour necrosis factor‐α without affecting NFκB levels. All three ω‐3 PUFAs appear to have overall similar effects. Further research is needed to elucidate their mechanism of action.

Rubinstein–Taybi syndrome associated with Chiari type I malformation caused by a large 16p13.3 microdeletion: A contiguous gene syndrome?†

Rubinstein–Taybi Syndrome (RSTS, OMIM 180849) is a rare condition, which in 65% of cases is caused by haploinsufficiency of CREBBP (cAMP response element binding protein binding protein) localized to 16p13.3. A small subset of RSTS cases caused by 16p13.3 microdeletions involving neighboring genes have been recently suggested to be a true contiguous gene syndrome called severe RSTS or 16p13.3 deletion syndrome (OMIM 610543). In the present report, we describe a case of a 2‐year‐old female with RSTS who, besides most of the typical features of RSTS has corpus callosum dysgenesis and a Chiari type I malformation which required neurosurgical decompression. CGH microarray showed a ∼520.7u2009kb microdeletion on 16p13.3 involving CREBBP, ADCY9, and SRL genes. We hypothesize that the manifestations in this patient might be influenced by the haploinsufficiency for ADCY9 and SRL.

Functional differences between two major ubiquitin receptors in the proteasome; S5a and hRpn13

It is well known that S5a and hRpn13 are two major ubiquitin (Ub) receptors in the proteasome but little is known about their functional difference in recruiting ubiquitinated substrates. In this study using siRNA-mediated knockdown of S5a or hRpn13, we found that two Ub receptors had different substrate specificity although similar level of accumulation of high molecular weight Ub-conjugates was observed. Interesting enough, depletion of S5a, but not hRpn13, resulted in the Ub-containing aggregates and induced ER chaperones such as Grp78 and Grp94. ERAD substrates such as alpha-TCR and alpha1-antitrypsin were also stabilized by the depletion of S5a but not hRpn13. Our results suggest that there is different substrate specificity between S5a and hRpn13 at the level of delivery and S5a may be the major docking site for ERAD substrates.

Analysis of Npl4 deletion mutants in mammalian cells unravels new Ufd1-interacting motifs and suggests a regulatory role of Npl4 in ERAD

Npl4 is a 67 kDa protein forming a stable heterodimer with Ufd1, which in turn binds the ubiquitous p97/VCP ATPase. According to a widely accepted model, VCP(Ufd1-Npl4) promotes the retrotranslocation of emerging ER proteins, their ubiquitination by associated ligases, and handling to the 26S proteasome for degradation in a process known as ERAD (ER-associated degradation). Using a series of Npl4 deletion mutants we have revealed that the binding of Ufd1 to Npl4 is mediated by two regions: a conserved stretch of amino acids from 113 to 255 within the zf-Npl4 domain and by the Npl4 homology domain between amino acids 263 and 344. Within the first region, we have identified two discrete subdomains: one involved in Ufd1 binding and one regulating VCP binding. Expression of any one of the mutants failed to induce any changes in the morphology of the ER or Golgi compartments. Moreover, we have observed that overexpression of all the analyzed mutants induced mild ER stress, as evidenced by increased Grp74/BiP expression without associated XBP1 splicing or induction of apoptosis. Surprisingly, we have not observed any accumulation of the typical ERAD substrate alphaTCR. This favors the model where the Ufd1-Npl4 dimer forms a regulatory gate at the exit from the retrotranslocone, rather than actively promoting retrotranslocation like the p97VCP ATPase.

Mucosal delivery systems of antihypertensive drugs: A practical approach in general practice

Patients who are unable to receive oral medication (p.o.) are a major problem in outpatient settings, especially in home health care systems. Mucosal administration of drugs offers an alternative to the oral route, especially when the parenteral mode cannot be used. There are three main pathways of mucosal administration: sublingual/buccal, intranasal and rectal. We discuss the possibility of mucosal delivery of antihypertensive drugs. Perindopril arginine and Amlodipine besylate are registered in the EU as orodispersible tablets for oromucosal delivery, however, they are not available in all countries. For this reason, we describe other drugs suitable for mucosal delivery: Captopril and Nitrendipine in the sublingual system and Metoprolol tartrate, Propranolol and Furosemide by the transrectal route. Based on the published data and common clinical practice we discuss the use of mucosal delivery systems of all these antihypertensive drugs with special attention to their pharmacokinetics. We illustrate this mini-review with a case report of the prolonged-term use of mucosal delivery of sublingual Captopril and Nitrendipine combined with rectal Metoprolol tartrate and Furosemide in a patient with severe hypertension unable to receive medication p.o. This is also a report on the first human use of Furosemide-containing suppositories as well as prolonged-term transmucosal administration of these four drugs, describing a practical approach leading to successful control of severe hypertension with four antihypertensive drugs delivered via the mucosal route. The treatment was effective and without side effects; however, the long-term safety and efficacy of such therapy must be confirmed by randomized clinical trials.