Retinoic acid, mitochondrial Cyt c, and cancer.

Retinoic acid and vitamin A play roles within the mitochondria. Retinoic acid may increase reduced Cyt c which is found elevated in cancer. In vitro study.

Research on the role of reduced (loss of an oxygen) Cyt c enzyme of mitochondria in human brain and breast cancers found a link to vitamin A and Retinoic Acid. The spectroscopy Raman imaging method that was used may be able to be used as a preventive screening to detect mitochondrial dysfunction before a symptomatic cancer is detectable. [“The oxidized form of cytochrome c is easily digested by proteinases in contrast to the reduced form which resists the action of them.” (6)]

Highlights: “Mitochondrial dysfunction might be detected by Raman imaging

• Reduced cytochrome c becomes abnormally high in human brain and breast cancers

• Incubation in-vitro with retinoic acid increases amount of reduced cytochrome c.” (1), via @heniek_htw (2)

Raman spectroscopy measures light signatures to assess chemical type.

“Our results prove that Raman spectroscopy can indeed probe the reduction of cytochromes in situ in human brain and breast cells and tissues, and are consistent with earlier observation [[2], [3], [4], [5],9,[25], [26], [27],38].” (1)

Abstract excerpt: Here we show that the amount of reduced cytochrome becomes abnormally high in human brain tumors and breast cancers. In contrast, the amount of reduced cytochrome c is lower in cancer cells when compared to the normal one at in vitro conditions when the effect of microenvironment is eliminated. Mitochondrial dysfunction and alterations in the chemical composition of the nucleus, mitochondria, lipid droplets, cytoplasm in single cells have been detected by Raman imaging. Incubation in vitro with retinoic acid increases the amount of reduced cytochrome c. (1)

The CYP 26 enzyme regulates the level of retinoic acid within cells.

“The coupling between Cyt c and retinoic acid support previous reports that CYP 26 enzyme, which belongs to the cytochrome family, regulates the cellular level of retinoic acid which is involved in regulation of gene expression. [37]

One can see from Fig. 5 that the intensity of the band at 1584 cm−1 corresponding to the reduced Cyt c increases drastically upon incubation with RA for all organelles, but the effect is the strongest for lipid droplets.” (1)

The reduced Cyt c enzyme was found to react with retinoic acid within lipid droplets when it has been thought to be found only within the inner membranes of mitochondria where the Citric Acid Cycle takes place.

“The results in Fig. 5 shows the significant effect of cytochrome activity on lipid droplets (Fig. 5B) and mitochondria (Fig. 5C) where Cyt c is widely believed to be localized solely in the mitochondrial intermembrane space under normal physiological conditions. [41]” (1)

From [37]

“Colorectal cancer is one of the most common types of cancer with over fifty percent of patients presenting at an advanced stage. Retinoic acid is a metabolite of vitamin A and is essential for normal cell growth and aberrant retinoic acid metabolism is implicated in tumourigenesis.” (3)

Vitamin A is essential because it plays many roles besides for vision. When the retinoic acid activation becomes dysfunctional, then many ill effects can result. CYP 26 enzymes help regulate levels of retinoic acid.

“Functionally, CYP26 enzymes are membrane anchored P450 proteins that require NADPH and P450 reductase for their function.” (4, quote at 4.1)

Viral infection can lead to genetic changes in the enzymes that activate or remove active retinoic acid.

“Abstract: Lytic Epstein-Barr virus (EBV) replication occurs in differentiated, but not undifferentiated, epithelial cells. Retinoic acid (RA) induces epithelial cell differentiation. The conversion of retinol into its active form, retinoic acid, requires retinol dehydrogenase enzymes. Here we show that AGS gastric carcinoma cells containing the lytic form of EBV infection have enhanced expression of a gene (DHRS9) encoding an enzyme that mediates conversion of retinol into RA. DHRS9 expression is also increased following induction of lytic viral infection in EBV-positive Burkitt lymphoma cells. We demonstrate that the EBV immediate-early protein, BZLF1, activates the DHRS9 promoter through a direct DNA binding mechanism. Furthermore, BZLF1 expression in AGS cells is sufficient to activate DHRS9 gene expression and increases the ability of retinol to induce the RA-responsive gene, CYP26A1.” (57/5 in list below)

CYP26A1 - code for the enzyme and gene that transcribes it. It is a protein found in the endoplasmic reticulum that regulates the level of retinoic acid. In the case of the EBV infection more activation of retinoic acid (RA) is being induced because it leads to more formation of a cell type that the virus can infect. Then Chronic Fatigue Syndrome may be diagnosed instead of over conversion of retinoids to active Retinoic Acid.

This is all complex, the good news may be a noninvasive screening method to observe mitochondrial dysfunction in earlier stages. Using less vitamin A foods may be helpful if there is an overactivation of retinol (called pre-formed vitamin A, (7)) or carotenoids to active retinoic acid.

“Retinol can be converted by the body to retinal, which can be in turn be oxidized to retinoic acid, the form of vitamin A known to regulate gene transcription. Retinol, retinal, retinoic acid, and related compounds are known as retinoids. β-Carotene and other food carotenoids that can be converted by the body into retinol are referred to as provitamin A carotenoids (see the article on Carotenoids). Hundreds of different carotenoids are synthesized by plants, but only about 10% of them are capable of being converted to retinol (1).” (7)

Avoiding peaches, kale, and sweet potatoes is not fun, nor avoiding animal products, however getting Alzheimer’s dementia or brain cancer would not be fun either. Knowledge provides the power to make changes.

Photo by Kamala Bright on Unsplash

There are many delicious fruits besides peaches, plums, berries, figs, and pears would all be lower in carotenoids than peaches, nectarines, apricots, papaya, mango, cantaloupe, or watermelon. Knowledge provides the ability to make different choices.

More research is needed into whether viral or vaccine immune challenges are leading to an ongoing overactivation of retinol or other retinoids into the active retinoic acid form. Carrots normally are protective against cancer - but for some people maybe they would be adding to cancer or inflammatory risks due to an unexpected over conversion of the carotenoids to retinoic acid.

Niacin - high dose protocol - may be protective against excess Retinoic Acid.

Additionally - NADPH is used in the enzyme that breaks down retinoic acid (8) which suggests high dose niacin therapy may help by supporting NADPH levels. See post: Niacin and Early Treatment… for How-to’s and Cautions for the high dose niacin protocol - which may also be preventive or treatment for schizophrenia. (transcendingsquare.com)

NAD+ is made from tryptophan or niacin and NADPH is a phosphorphylated form of NAD+. (9) Therefore adequate niacin and mitochondrial cofactors and nutrients may be helpful if excessive retinoic acid is a problem - or other steroid or drug overdoses possibly.

“NADPH-cytochrome P450 oxidoreductase (POR) is a membrane-bound enzyme required for electron transfer to cytochrome P450 (CYP), vital in the processes of the metabolism of drugs and steroid production in humans.” (8)

The NADPH-cytochrome P450 oxidoreductase (POR) enzyme and POR gene are regulated by the level of active vitamin A (all-trans Retinoic Acid - ATRA or atRA) and active vitamin D (1, 25 D). The NADPH containing POR enzyme was found in mitochondria in addition to the endoplasmic reticulum. Active vitamin A and D can cause cell differentiation which may contribute to some types of cancer, or add to a viral infection risk. (57/5 in list below)

“In this study we have shown for the first time that POR gene and POR protein content are regulated in AML cells by ATRA and by 1,25D. We have also observed that POR protein is present not only in the membrane fraction which contains endoplasmic reticulum, but also in the mitochondria, where it could participate in 1,25D catabolism. These observations suggest that POR might be important for maintaining local intracellular levels of ATRA and 1,25D. Since these two compounds are important for myeloid cell differentiation, the disturbances in POR activity or expression levels might contribute to the cancer phenotype of myeloid cells.” (8)

The CYP enzymes are involved in activation and breakdown of many types of steroids. Vitamin D is a seco-steroid hormone unlike other vitamins. Vitamin A is not chemically considered a steroid but is fat soluble. Steroid hormones are fat soluble and are derived from cholesterol. People who don’t need high dose vitamin D supplements will have the excess break down to cholesterol in their body. In normal metabolism the level of active vitamin A and D will directly lead to less being activated.

In the case of the EBV example - that was no longer true because of the viral effect on a gene “activate DHRS9 gene expression” involved in vitamin A activation, “increases the ability of retinol to induce the RA-responsive gene, CYP26A1.” (57/5 in list below)

- So the regulatory setting for how much active Retinoic Acid is enough versus too much would be increased - more active (ATRA) Retinoic Acid could be present before the breakdown would start.

And therefore extra niacin might help, but less vitamin A in the diet would have a more direct impact on over-activation of carotenoids to the active form.

“The network of various CYP enzymes is very important for activation and degradation of multiple steroids. These enzymes are heme-binding monooxygenases responsible for oxidative conversions of steroid hormones.

• The major enzyme responsible for ATRA activation is lecithin:retinol acyltransferase (LRAT), which does not belong to the CYP superfamily [4], but the major catabolizing enzymes are members of CYP26 subfamily, where different isoforms of CYP26 have different preferences for RA isomers [6].

• In the case of vitamin D, the activation and degradation enzymes belong to the CYP superfamily. The two steps of activation are maintained primarily by CYP27A1 or CYP2R1 (25-hydroxylation) and subsequently by CYP27B1 (1α-hydroxylation), while all steps of catabolism from 1,25D to calcitrioic acid are executed by CYP24A1 [24].

• The homeostasis of 1,25D and RA is maintained by negative feedback loops, since expressions of CYP26A1 and CYP24A1 are strictly regulated by ATRA and 1,25D respectively.” (8)

“…since expressions of CYP26A1 and CYP24A1 are strictly regulated by ATRA [activated Retinoic Acid form of vitamin A] and 1,25D [active hormone form of vitamin D] respectively.” (8) - Ideally our level of active vitamin A and D will not become elevated because their presence should lead to less being activated. However various infectious pathogens have evolved ways to affect their metabolism.

Disclaimer: This information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.

Reference List

1. Abramczyk H, Surmacki JM, Brozek-Pluska B, Redox state changes of mitochondrial cytochromes in brain and breast cancers by Raman spectroscopy and imaging, J Molecular Structure, 1252;2022, 132134, ISSN 0022-2860, https://doi.org/10.1016/j.molstruc.2021.132134. https://www.sciencedirect.com/science/article/pii/S0022286021022547

2. via @heniek_htw, https://twitter.com/heniek_htw/status/1470824029573500938?s=20

3. [37] G.T. Brown, B.G. Cash, D. Blihoghe, P. Johansson, A. Alnabulsi, G.I. Murray. The expression and prognostic significance of retinoic acid metabolising enzymes in colorectal cancer. PLoS ONE, 9 (2014), p. e90776, 10.1371/journal.pone.0090776 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0090776

4. Stevison F, Jing J, Tripathy S, Isoherranen N. Role of Retinoic Acid-Metabolizing Cytochrome P450s, CYP26, in Inflammation and Cancer. Adv Pharmacol. 2015;74:373-412. doi: 10.1016/bs.apha.2015.04.006. Epub 2015 May 27. PMID: 26233912; PMCID: PMC4859867. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4859867/ quote viewable at Cytochrome P450 Family 26, ScienceDirect.com, 4.1 https://www.sciencedirect.com/topics/medicine-and-dentistry/cytochrome-p450-family-26

5. (57 in my Misfolded Proteins, H1 & NMDARs document) Jones RJ, Dickerson S, Bhende PM, Delecluse HJ, Kenney SC. Epstein-Barr virus lytic infection induces retinoic acid-responsive genes through induction of a retinol-metabolizing enzyme, DHRS9. J Biol Chem. 2007 Mar 16;282(11):8317-24. doi: 10.1074/jbc.M608667200. Epub 2007 Jan 22. PMID: 17244623. https://www.jbc.org/content/282/11/8317.long

6. Structure and Function of Oxidation–Reduction Enzymes, Editors: Å. Åkeson, A. Ehrenberg, Papers presented at the Wenner-Gren Symposium held at the Wenner-Gren Center, Stockholm on August 23-27, 1970. https://www.sciencedirect.com/book/9780080168746/structure-and-function-of-oxidation-reduction-enzymes

7. Vitamin A, Linus Pauling Institute, https://lpi.oregonstate.edu/mic/vitamins/vitamin-A

8. Gocek E, Marchwicka A, Bujko K, Marcinkowska E. NADPH-cytochrome P450 reductase is regulated by all-trans retinoic acid and by 1,25-dihydroxyvitamin D3 in human acute myeloid leukemia cells. Plos one. 2014 ;9(3):e91752. DOI: 10.1371/journal.pone.0091752. PMID: 24642534; PMCID: PMC3958372. https://europepmc.org/article/PMC/3958372

9. Xiao W, Wang RS, Handy DE, Loscalzo J. NAD(H) and NADP(H) Redox Couples and Cellular Energy Metabolism. Antioxid Redox Signal. 2018 Jan 20;28(3):251-272. doi: 10.1089/ars.2017.7216. Epub 2017 Jul 28. PMID: 28648096; PMCID: PMC5737637. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5737637/ (9)