Thymoquinone and Melatonin Boost Both Sirt1 and Nrf2 Activities in a Complementary Way – A Strategy for Controlling Oxidative Stress and Inflammation

Thymoquinone and Melatonin Boost Both Sirt1 and Nrf2 Activities in a Complementary Way – A Strategy for Controlling Oxidative Stress and Inflammation

Simon Bernard Iloki Assanga^1*, Lidianys María Lewis Lujan², Mark F. McCarty³, J. J. DiNicolantonio⁴

¹Departamento de Ciencias Químico Biológicas, Universidad de Sonora Hermosillo, Sonora, México
²Departamento de Investigación y Posgrado en Alimento, Universidad de Sonora, Hermosillo, Sonora, México
³Catalytic Longevity, San Diego, CA 92109, USA
⁴Department of Preventive Cardiology, Saint Luke’s Mid America Heart Institute, Kansas, USA

Received Date: July 05, 2022; Accepted Date: July 15, 2022; Published Date: July 27, 2022
^*Corresponding author: Simon Bernard Iloki Assanga, Departamento de Ciencias Químico Biológicas, Universidad de Sonora Hermosillo, Sonora, México. Email: ilokiassanga@gmail.com

Citation: Iloki -Assanga SB, Lewis Lujan LM, McCarty MF, DiNicolantonio JJ (2022) Thymoquinone and Melatonin Boost Both Sirt1 and Nrf2 Activities in a Complementary Way – A Strategy for Controlling Oxidative Stress and Inflammation. Adv in Nutri and Food Sci: ANAFS-235.

DOI: 10.37722/ANAFS.2022302

Abstract
The oil of black cumin seed (Nigella sativa) has been employed therapeutically in Asian traditional medicine, and rodent studies with it or its most prominent and intriguing component, thymoquinone, suggest that it may indeed have the potential to provide benefit in a wide range of pathologies. There is reason to suspect that thymoquinone’s versatile utility may reflect, in large part, its ability to boost the activity of the sirtuin 1 (Sirt1) deacetylase while concurrently activating the Nrf2 transcription factor. Increased Sirt1 activity promotes autophagy, mitochondrial biogenesis, and FOXO-mediated expression of antioxidant enzymes, while suppressing NF-kappaB-mediated inflammatory signaling; Nrf2 promotes expression of a wide range of antioxidant enzymes, as well as the enzyme rate limiting for glutathione synthesis. Thymoquinone is a substrate for NAD(P)H quinone oxidoreductase 1 (NQO1); this reaction gives rise to NAD⁺ - obligate substrate for Sirt1 activity – while generating thymohydroquinone, a potent scavenging antioxidant. Thymoquinone, which is electrophilic, promotes Nrf2 activation through covalent reaction with its functional inhibitor Keap1. We suggest that supplemental melatonin may be an ideal complement to thymoquinone, as it can promote increased expression of both Sirt1and Nrf2 – likely via activation of the “clock” transcription factor Bmal1 – whereas thymoquinone boosts the biological activities of the pre-formed proteins.

Keywords: Thymoquinone; Sirt1, NAD(P)H quinone oxidoreductase 1; nrf2; Melatonin; NF-kappa B

Thymoquinone – Sirt1 Activation via NQO1-Mediated NAD⁺ Generation

Thymoquinone is believed to be the chief bioactive agent in the oil of Nigella sativa (black cumin), an agent which has been employed therapeutically in Ayurvedic or Islamic traditional medicine. Black cumin seed oil and thymoquinone are now attracting increased research attention, and have been the subject of many recent reviews. In rodent or cell culture studies, thymoquinone or black cumin seed oil are reported to exert a wide range of protective effects; benefits have been reported in models of diabetes, atherosclerosis, hypertension, renal and pulmonary disorders, neurodegenerative disorders, rheumatoid arthritis, and wound healing, among others [1-14].

A case can be made that these benefits are primarily reflective of thymoquinone-mediated activation of the sirtuin 1(Sirt1) deacetylase – increased activity of which has been linked to enhanced healthspan [15-17]– and of the transcription factor Nrf2, which enhances expression of a number of antioxidant enzymes and of the rate-limiting enzyme for glutathione synthesis [18]. Sirt1 is a particularly intriguing for its wide-ranging modulatory activities – enhancing autophagy, mitophagy, mitochondrial biogenesis, DNA repair, antioxidant enzyme expression, osteoblast generation, and endothelial nitric oxide synthase expression and activity, while inhibiting apoptosis, senescence, de novo lipogenesis, and – via suppression of canonical NF-kappaB activity – inflammation [19-23]. In aggregate, these effects may account for the favorable impact of Sirt1 on health span.

Sirt1 activity is absolutely dependent on NAD⁺ as a substrate. In high redox circumstances, in which the ratio of NAD⁺/NADH is low, or when NAD⁺ is degraded, as when PARP is activated by DNA damage or C38 activity is high, a paucity of NAD⁺ can compromise Sirt1 activity [24,25]. Conversely, Sirt1 activity can be boosted by: fasting or calorie restriction – which tends to enhance the NAD⁺/NADH ratio owing to a paucity of oxidizable substrate;²⁶ an increase in NAD⁺ synthesis owing to AMPK activation – which boosts expression of nicotinamide phosphoribosyltransferase (NAMPT), rate-limiting for conversion of free nicotinamide (a Sirt1 inhibitor) to NAD⁺; [27-29] or administration of NAD+ precursors, such as nicotinamide riboside or nicotinamide mononucleotide[30]. (Nicotinamide per se, while promoting NAD+ synthesis, directly inhibits Sirt1 activity – which is another reason why NAMPT induction aids Sirt1 activity [31]. And high intakes of nicotinic acid are problematic owing to flushing/itching side effects.)

NAD⁺ availability can also be enhanced by enzymatic activities which oxidize NADH. In this regard, NAD(P)H quinone oxidoreductase 1 (NQO1) is of particular pertinence. This enzyme, inducible via Nrf2, can reduce a number of endogenous or exogenous quinones with NADH or NADPH – generating NAD⁺ (or NADP⁺) in the process [32-34]. Recent evidence indicates that NQO1 associates tightly with enzymatically active Sirt1 within cells; this association hence appears to be a homeostatic mechanism whereby NQO1 can generate NAD⁺ within the microenvironment of Sirt1[35-36].A corollary is that administration of quinone substrates for NQO1 may have potential for boosting Sirt1 activity, particularly when cellular NAD⁺ levels are relatively low. Indeed, this effect has been demonstrated with the phytochemical β- lapachinone [37, 38]. And the ability of the phytochemical pyrroloquinoline quinone (PQQ) to promote mitochondrial biogenesis has been traced to Sirt1 activation mediated by an increase in NAD⁺ [39,40].PQQ has been found to bind to lactate dehydrogenase with high affinity; this bound form of PQQ readily oxidizes NADH to NAD+, and the resulting increase of NAD+ in the vicinity of lactate dehydrogenase tends to drive oxidation of lactate to pyruvate, which becomes available for mitochondrial oxidation [41]. (This mechanism may explain why dietary PQQ has been found to have a quasi-vitamin status in rodent studies [42]).

There is now evidence that thymoquinone can act in a comparable way – a finding which rationalizes several reports that thymoquinone is a Sirt1 activator [43-48]. Nonetheless, several of these studies also find a thymoquinone-mediated increase in Sirt1 expression, suggesting an additional and complementary mechanism for thymoquinone’s positive effect on Sirt1 activity. Thymoquinone can act either as an antioxidant or a pro-oxidant in cells. When it interacts with NQO1, the thymohydroquinone that is generated can act as a potent scavenging antioxidant [43, 49, 50]. In circumstances of high cellular ROS production, the donation of electrons from this agent in quenching of radicals can return it to its oxidized form thymoquinone, which can then catalyze generation of another molecule of NAD⁺ via interaction with NQO1. On the other hand, there are several enzymatic activities known to induce one-electron reductions of thymoquinone, converting it to a semi-quinone, while concurrently donating an electron to molecular oxygen, generating superoxide [43]. This latter effect appears to explain how thymoquinone can exert cytotoxic effects in certain tumor cell lines in which NQO1 activity is very deficient or absent [43, 51]. Fortunately, the low toxicity of thymoquinone in rodent studies (acute oral LD50 of about 800 mg/kg), and the apparent good tolerance of black cumin seeds as a component of diet or as a traditional herbal medicine, suggests that its net effect is antioxidant in most circumstances, at least when intake is moderate [52].

Thymoquinone Activates Nrf2 via Interaction with Keap1

Moreover, thymoquinone can act as a Nrf2 activator, inasmuch as it is electrophilic and can interact covalently with the free acidic sulfhydryl groups in Keap1 [53-57]. Keap1 is a protein which binds to Nrf2 in the cytoplasm, preventing it from migrating to the nucleus where it can promote transcription; Keap1 also promotes the ubiquitination and proteasomal degradation of Nrf2 [58, 59].The interaction of thymoquinone with Keap1 inhibits its binding to Nrf2, enabling the latter to modulate protein transcription [53]. Nrf2 activation would be expected to complement the direct oxidant-scavenging activity of thymohydroquinone. And thymoquinone-mediated Sirt1 activity also can exert antioxidant activity; Sirt1 alleviates mitochondrially generated oxidant production by promoting mitophagy and mitochondrial biogenesis via PGC-1α activation [60]. Also, via deacetylation of FOXO transcription factors, Sirt1 promotes expression of various antioxidant enzymes – notably catalase and the mitochondrial superoxide dismutase -at the transcriptional level [61-63]. Hence, any direct pro-oxidant activity of thymoquinone induced by its conversion to a semi-quinone appears likely to be counterbalanced by the direct scavenging activity of thymohydroquinone and the consequences of Nrf2 and Sirt1activation.Also of interest is the fact that, as noted about, Nrf2 promotes expression of NQO1; in this way, thymoquinone’s ability to activate Nrf2 may amplify its ability to activate Sirt1.

Owing to the fact that Sirt1 can deacetylate the p65 component of the NF-kappaB transcription factor in a way that suppresses its ability to drive transcription, thymoquinone has anti-inflammatory potential that complements its antioxidant effects [64]. This suggests that adequate doses may have particular therapeutic potential in inflammatory pathologies associated with oxidative stress. The vast range of benefits conferred by thymoquinone in rodent studies may reflect the fact that inflammation and oxidative stress play a role in the pathogenesis of a great number of health disorders.

Melatonin May be an Ideal Complement to Thymoquinone

Another natural compound with antioxidant and anti-inflammatory activity – the neurohormone melatonin, now commonly used as a nutraceutical – may have important clinical potential as a complement to thymoquinone, owing to the fact that it can promote the synthesis and protein expression of both Sirt1 and Nrf2 [65-69]. Melatonin’s induction of Sirt1 and Nrf2 may be attributable to activation of the melatonin-regulated clock transcription factor Bmal1; this been shown to drive the transcription of the genes coding for Sirt1 and Nrf2 [70-74]. Bmal1 also supports Sirt1 activity by inducing nicotinamide phosphoribosyltransferase [75]. In at least certain tissues, melatonin signaling through its plasma membrane receptor MT1 up-regulates Bmal1 mRNA [76-78]. Hence, whereas thymoquinone can boost the biological activities of both Sirt1 and Nrf2, melatonin acts to increase their protein expression.

With respect to dosage considerations, mouse studies reporting protective effects of oral thymoquinone typically employ daily intakes in the range of 20-50 mg/kg. 20 mg/kg in a 25 g mouse amounts to 0.5 mg. If you extrapolate this to a 60 kg human, using the 2/3 power of relative body mass (i.e. ratio of body surface areas [79] as the correction factor, that equates to about 180, or an absolute dose of 90 mg thymoquinone daily. (Extrapolation by ¾ power would yield a value of about 170 mg thymoquinone.) Nigella sativa oil preparations for nutraceutical use are now widely available, as gel caps or oil, standardized at 2% thymoquinone content. A teaspoon (5 ml/ 5 g) of 2% oil would provide 100 mg. So, a teaspoon or two of high-quality Nigella sativa oil daily might be a worthwhile and a practical dose for assessing the potential clinical benefits of thymoquinone. With respect to the limited clinical literature already availability, several controlled clinical studies from Iran have found that 2.5 g of Nigella sativa oil twice daily, or 3 g of the oil once daily, lowered systolic and diastolic and diastolic blood pressure in healthy volunteers, and, in patients who were overweight with metabolic syndrome, decreased LDL cholesterol, fasting blood sugar, and serum levels of C-reactive protein and tumor necrosis factor-α, while potentiating the weight loss achieved with a reduced-calorie diet [80-83]. As to melatonin, bedtime doses of 3-20 mg have typically been employed clinically for effective treatment of sleep disorders, post-surgical pain, and cancer [84].

Conflicts: The authors have no conflicts of interest to declare.

References