15d-PGJ 2 as an endoplasmic reticulum stress manipulator in multiple myeloma in vitro and in vivo

The role of some lipids and their metabolites in programmed cell death (lipoapoptosis)

In recent years, the understanding of the mechanisms involved in the regulation of lipoapoptosis signaling pathways has expanded considerably. However, many mechanisms of apoptosis induction by lipids as well as molecules mediating intracellular and systemic signals belonging to AOS/enzyme-dependent phospholipid metabolites are not completely clear.

This review summarizes the current understanding of the mechanisms of apoptotic cell death induction by some lipid molecules. Literature search was performed in the database “PubMed”, “eLIBRARY” using key words: “apoptosis”, “lipids”, “fatty acids”, “eicosanoids”, “reactive oxygen species”.

A brief characterization of the signaling pathways of apoptosis is given. The role of reactive oxygen species and their dependent products of lipid peroxidation in the regulation of the main signaling pathways of apoptosis are shown. Particular attention is paid to the product of phospholipid metabolism – 4-hydroxynonenal.

Pro- and anti-apoptotic effects of some prostaglandins are demonstrated. Arguments are presented that prostaglandins of series J and D are pro-apoptotic in most cells, and this effect depends on activation of the prostanoid receptor DP2 and on reduction of AKT kinase activity. In contrast, the E-series prostaglandins and hydroxyecosatetraenoic acid act opposite to the J-series and D-series prostaglandins, reducing apoptosis by activating AKT and increasing Bcl-2 protein expression.

The role of individual fatty acids involved in the initiation and transduction of pro-apoptotic and anti-apoptotic signals is assessed. It was shown that saturated fatty acids have the maximum damaging potential than their unsaturated counterparts. An in-depth understanding and deciphering of the mechanisms by which lipids and their metabolites modulate the activation of signaling pathways of programmed cell death can help to develop therapeutic strategies to prevent a number of diseases associated with impaired regulation of apoptosis.

TFEB, a master regulator of autophagy and biogenesis, unexpectedly promotes apoptosis in response to the cyclopentenone prostaglandin 15d-PGJ2

Transcriptional factor EB (TFEB), a master regulator of autophagy and lysosomal biogenesis, is generally regarded as a pro-survival factor. Here, we identify that besides its effect on autophagy induction, TFEB exerts a pro-apoptotic effect in response to the cyclopentenone prostaglandin 15-deoxy-∆-^12,14-prostaglandin J2 (15d-PGJ2). Specifically, 15d-PGJ2 promotes TFEB translocation from the cytoplasm into the nucleus to induce autophagy and lysosome biogenesis via reactive oxygen species (ROS) production rather than mTORC1 inactivation. Surprisingly, TFEB promotes rather than inhibits apoptosis in response to 15d-PGJ2. Mechanistically, ROS-mediated TFEB translocation into the nucleus transcriptionally upregulates the expression of ATF4, which is required for apoptosis elicited by 15d-PGJ2. Additionally, inhibition of TFEB activation by ROS scavenger N-acetyl cysteine or inhibition of protein synthesis by cycloheximide effectively compromises ATF4 upregulation and apoptosis in response to 15d-PGJ2. Collectively, these results indicate that ROS-induced TFEB activation exerts a novel role in promoting apoptosis besides its role in regulating autophagy in response to 15d-PGJ2. This work not only evidences how TFEB is activated by 15d-PGJ2, but also unveils a previously unexplored role of ROS-dependent activation of TFEB in modulating cell apoptosis in response to 15d-PGJ2.

Modulation of Cellular Redox Parameters for Improving Therapeutic Responses in Multiple Myeloma

Raised oxidative stress and abnormal redox status are typical features of multiple myeloma cells, and the identification of the intimate mechanisms that regulate the relationships between neoplastic cells and redox homeostasis may reveal possible new anti-myeloma therapeutic targets to increase the effectiveness of anti-myeloma drugs synergistically or to eradicate drug-resistant clones while reducing toxicity toward normal cells. An alteration of the oxidative state is not only responsible for the onset of multiple myeloma and its progression, but it also appears essential for the therapeutic response and for developing any chemoresistance. Our review aimed to evaluate the literature’s current data on the effects of oxidative stress on the response to drugs generally employed in the therapy of multiple myeloma, such as proteasome inhibitors, immunomodulators, and autologous transplantation. In the second part of the review, we analyzed the possibility of using other substances, often of natural origin, to modulate the oxidative stress to interfere with the progression of myelomatous disease.

STAT3 as a Potential Target for Tumor Suppressive Effects of 15-Deoxy-Δ12,14-prostaglandin J2 in Triple Negative Breast Cancer

STAT3 plays a prominent role in proliferation and survival of tumor cells. Thus, STAT3 has been considered to be a prime target for development of anti-cancer therapeutics. The electrophilic cyclopentenone prostaglandin,15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has been well recognized for its capability to modulate intracellular signaling pathways involved in cancer cell growth and progression. We previously reported that 15d-PGJ₂ had potent cytotoxicity against harvey-ras transformed human mammary epithelial cells through direct interaction with STAT3. In this study, we have attempted to verify the inhibitory effects of 15d-PGJ₂ on STAT3 signaling in human breast tumor cells. The triple negative breast cancer cell lines, MDA-MB-231 and MDA-MB-468 displaying constitutive phosphorylation of STAT3 on the tyrosine 705 (Tyr705) residue, underwent apoptosis upon inhibition of STAT3 by 15d-PGJ₂. In contrast, estrogen receptor positive MCF-7 breast cancer cells that do not exhibit elevated STAT3 phosphorylation were much less susceptible to 15d-PGJ₂-induced apoptosis as assessed by PARP cleavage. Furthermore, 15d-PGJ₂ inhibited interleukin-6-induced tyrosine phosphorylation of STAT3 in LNCaP cells. According to molecular docking studies, 15d-PGJ₂ may preferentially bind to the cysteine 259 residue (Cys259) present in the coiled-coil domain of STAT3. Site-directed mutagenesis of STAT3 identified Cys259 to be the critical amino acid for the 15d-PGJ₂-induced apoptosis as well as epithelial-to-mesenchymal transition. Taken together, these findings suggest STAT3 inactivation through direct chemical modification of its Cys259 as a potential therapeutic approach for treatment of triple negative breast cancer treatment.

Autophagy upregulation may explain inhibition of oral carcinoma in situ by photobiomodulation in vitro

There is currently no clear understanding on the pathways involved in the process of cell inhibition by photobiomodulation (PBM). The present study evaluated the influence of PBM on the expression of autophagy markers in vitro in an in situ model of oral carcinoma. Oral squamous cell carcinoma (Cal27) and stromal fibroblasts (FG) cultures were used. The independent variables were 'cell type' (FG and CAL27) 'culture condition' (monocultures or co-cultures) and PBM (placebo and 36 J/cm²). The cultures were irradiated from a red LED source for mRNA expression and protein expression analyses. The autophagy markers evaluated were Beclin-1, LC3B and p62 as well as adjuvant markers (BAX Bcl-2, VEGF, CD105, CD34, PRDX1, PRDX4 and GRP78). The Cal27 cells upregulated the autophagy markers upon exposure to PBM both at the mRNA and protein expression levels, providing evidence to explain malignant cell inhibition by PBM.

The Role of Prostaglandins in Different Types of Cancer

The prostaglandins constitute a family of lipids of 20 carbon atoms that derive from polyunsaturated fatty acids such as arachidonic acid. Traditionally, prostaglandins have been linked to inflammation, female reproductive cycle, vasodilation, or bronchodilator/bronchoconstriction. Recent studies have highlighted the involvement of these lipids in cancer. In this review, existing information on the prostaglandins associated with different types of cancer and the advances related to the potential use of them in neoplasm therapies have been analyzed. We can conclude that the effect of prostaglandins depends on multiple factors, such as the target tissue, their plasma concentration, and the prostaglandin subtype, among others. Prostaglandin D2 (PGD₂) seems to hinder tumor progression, while prostaglandin E2 (PGE₂) and prostaglandin F2 alpha (PGF_2α) seem to provide greater tumor progression and aggressiveness. However, more studies are needed to determine the role of prostaglandin I2 (PGI₂) and prostaglandin J2 (PGJ₂) in cancer due to the conflicting data obtained. On the other hand, the use of different NSAIDs (non-steroidal anti-inflammatory drugs), especially those selective of COX-2 (cyclooxygenase 2), could have a crucial role in the fight against different neoplasms, either as prophylaxis or as an adjuvant treatment. In addition, multiple targets, related to the action of prostaglandins on the intracellular signaling pathways that are involved in cancer, have been discovered. Thus, in depth research about the prostaglandins involved in different cancer and the different targets modulated by them, as well as their role in the tumor microenvironment and the immune response, is necessary to obtain better therapeutic tools to fight cancer.

15-Deoxy-Δ12,14-prostaglandin J2 Induces Apoptosis in Ha-ras-transformed Human Breast Epithelial Cells by Targeting IκB kinase-NF-κB Signaling

15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), an endogenous ligand for PPARγ, has differential effects on cancer cell proliferation and survival depending on the dose and the type of cells. In the present study, we have investigated the effects of 15d-PGJ₂ on apoptosis of the Ha-ras transformed human breast epithelial (MCF10A-ras) cells. When MCF10A-ras cells were treated with 15d-PGJ₂ (10 μM) for 24 hours, they underwent apoptosis as evidenced by characteristic morphological features, an increased proportion of sub-G₀/G₁ cell population, a typical pattern of annexin V/propidium iodide staining, perturbation of mitochondrial transmembrane potential (Δψ_m), and cleavage of caspase-3 and its substrate PARP. A pan-caspase inhibitor, Z-Val-Ala-Asp (OCH₃)-fluoromethyl ketone attenuated cytotoxicity and proteolytic cleavage of caspase-3 induced by 15d-PGJ₂. The 15d-PGJ₂-induced apoptosis was accompanied by enhanced intracellular accumulation of reactive oxygen species (ROS), which was abolished by the antioxidant N-acetyl-L-cysteine (NAC). 15d-PGJ₂ inhibited the DNA binding activity of NF-κB which was associated with inhibition of expression and catalytic activity of IκB kinase β (IKKβ). 15d-PGJ₂-mediated inhibition of IKKβ and nuclear translocation of phospho-p65 was blocked by NAC treatment. 9,10-Dihydro-PGJ₂, a non-electrophilic analogue of 15d-PGJ₂, failed to produce ROS, to inhibit NF-κB DNA binding, and to induce apoptosis, suggesting that the electrophilic α,β-unsaturated carbonyl group of 15d-PGJ₂ is essential for its pro-apoptotic activity. 15d-PGJ₂-induced inactivation of IKKβ was also attributable to its covalent thiol modification at the cysteine 179 residue of IKKβ. Based on these findings, we propose that 15d-PGJ₂ inactivates IKKβ–ΝF-κB signaling through oxidative or covalent modification of IKKβ, thereby inducing apoptosis in Ha-ras transformed human breast epithelial cells.

Involvement of Metabolic Lipid Mediators in the Regulation of Apoptosis

Apoptosis is the physiological mechanism of cell death and can be modulated by endogenous and exogenous factors, including stress and metabolic alterations. Reactive oxygen species (ROS), as well as ROS-dependent lipid peroxidation products (including isoprostanes and reactive aldehydes including 4-hydroxynonenal) are proapoptotic factors. These mediators can activate apoptosis via mitochondrial-, receptor-, or ER stress-dependent pathways. Phospholipid metabolism is also an essential regulator of apoptosis, producing the proapoptotic prostaglandins of the PGD and PGJ series, as well as the antiapoptotic prostaglandins of the PGE series, but also 12-HETE and 20-HETE. The effect of endocannabinoids and phytocannabinoids on apoptosis depends on cell type-specific differences. Cells where cannabinoid receptor type 1 (CB1) is the dominant cannabinoid receptor, as well as cells with high cyclooxygenase (COX) activity, undergo apoptosis after the administration of cannabinoids. In contrast, in cells where CB2 receptors dominate, and cells with low COX activity, cannabinoids act in a cytoprotective manner. Therefore, cell type-specific differences in the pro- and antiapoptotic effects of lipids and their (oxidative) products might reveal new options for differential bioanalysis between normal, functional, and degenerating or malignant cells, and better integrative biomedical treatments of major stress-associated diseases.

The function of the oxylipin 12-oxophytodienoic acid in cell signaling, stress acclimation, and development

Forty years ago, 12-oxophytodienoic acid (12-OPDA) was reported as a prostaglandin (PG)-like metabolite of linolenic acid found in extracts of flaxseed. Since then, numerous studies have determined the role of 12-OPDA in regulating plant immunity, seed dormancy, and germination. This review summarizes our current knowledge of the regulation of 12-OPDA synthesis in the chloroplast and 12-OPDA-dependent signaling in gene expression and targeting protein functions. We describe the properties of OPDA that are linked to the activities of PGs, which are derived from arachidonic acid and act as tissue hormones in animals, including humans. The similarity of OPDA with bioactive PGs is particularly evident for the most-studied cyclopentenone, PG 15-dPGJ2. In addition to chemical approaches towards 12-OPDA synthesis, bio-organic synthesis strategies for 12-OPDA and analogous substances have recently been established. The resulting availability of OPDA will aid the identification of additional effector proteins, help in elucidating the mechanisms of OPDA sensing and transmission, and will foster the analysis of the physiological responses to OPDA in plants. There is a need to determine the compartmentation and transport of 12-OPDA and its conjugates, over long distances as well as short. It will be important to further study OPDA in animal and human cells, for example with respect to beneficial anti-inflammatory and anti-cancer activities.