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INFLAMM-AGING

  • NF-κB the major regulator of inflammation,

  • p53, the major tumor suppressor.

http://www.anti-agingfirewalls.com/2016/11/05/inflammation-part-2-the-tale-of-three-stress-sensors-and-their-interactions-1inflammation-2genomic-instability-p53-and-3oxidative-stress-nrf2/

Inflammation is an important natural biological defensive response to many threatening agents such as pathological microorganisms, parasites, fungi, viruses, toxic compounds and pollutants.  It is also a body response to of numerous deleterious health conditions including infections, wounding, and disease processes. 

Inflammation is a critical mechanism of the body’s innate immunity system, which seeks to eliminate the cause of irritation or injury, clear dead and necrotic cells, and is an essential initial stage of healing injured tissues.  Inflammation is also induced by reactions of the immune system (hypersensitivity) in the body, which causes a disruption of tissue homeostasis.

So, inflammation is a very good thing.  We could not be alive without it. 

 

Chronic inflammation, however, can be quite a different matter.  In healthy circumstances, the inflammation response vanishes through a normal sequence of healing processes when no longer needed, after a few hours or a few days.  However, in the presence of several disease processes and in the presence of aging, the inflammatory process may not progress through the final healing stages and the inflammation may become chronic.  Chronic inflammation also results when the body’s defense system inappropriately triggers inflammation against its own cells.  Chronic inflammation is both a causal factor and a consequence of most chronic diseases of aging, including rheumatoid arthritis, asthma, atherosclerosis, Alzheimer’s disease and cancer.

Chronic inflammation, can persist over an extended period of weeks to months and even years.  It is often associated with the presence of macrophages and lymphocytes, fibrosis, vascular proliferation, and tissue destruction.  Moreover, chronic inflammation plays critical roles in many disease processes including cancers, dementias, diabetes, pulmonary diseases, cardiovascular diseases, atherosclorsis, sarcopenia, and anaemia.  Chronic inflammation occurs in the case of incurable autoimmune diseases such as arthritis, lupus, scleroderma, asthma and chronic obstructive pulmonary disease (COPD).

NFKb - the Master Activator of Inflammation

The biological mechanisms of chronic inflammation can be very complex,  Nuclear factor- B (NF-κB) is activated by more than 200 different stimuli has for good reason been thought of as the master activator of inflammation.  For example, during inflammation immune system macrophage cells could be activated by Toll-like receptors (TLRs), through the recognition of a pathogen endotoxin such as lipopolysaccharide (LPS).

  • This event initiates a signaling pathway that releases NF-κB into the cell nucleus, activating genes associated with the transcription of proteins related to the inflammatory process, such as iNOS, responsible for NO synthesis, COXs, which synthetize prostaglandins, and other pro-inflammatory cytokines like IL-6. The generation of ROS is also triggered by the TLR signaling pathway.

Inflammation and aging

Since chronic inflammation plays central roles in numerous deleterious health processes and in aging, it is often referred to as “inflammaging” and is the subject of much ongoing research. 

 

From the 2014 publication Chronic inflammation (inflammaging) and its potential contribution to age-associated diseases

  • “Human aging is characterized by a chronic, low-grade inflammation, and this phenomenon has been termed as “inflammaging.”

 

Inflammaging is a highly significant risk factor for both morbidity and mortality in the elderly people, as most if not all age-related diseases share an inflammatory pathogenesis.  Nevertheless, the precise etiology of inflammaging and its potential causal role in contributing to adverse health outcomes remain largely unknown.  The identification of pathways that control age-related inflammation across multiple systems is therefore important in order to understand whether treatments that modulate inflammaging may be beneficial in old people.”

The 2016 publication Inflammaging and Anti-Inflammaging: The Role of Cytokines in Extreme Longevity points out the central linkages between inflammation and aging.  “Longevity and aging are two sides of the same coin, as they both derive from the interaction between genetic and environmental factors.  Aging is a complex, dynamic biological process characterized by continuous remodeling.

  • One of the most recent theories on aging focuses on immune response, and takes into consideration the activation of subclinical, chronic low-grade inflammation which occurs with aging, named “inflammaging.”  

  • Long-lived people, especially centenarians, seem to cope with chronic subclinical inflammation through an anti-inflammatory response, called therefore “anti-inflammaging.”  In the present review, we have focused our attention on the contrast between inflammaging and anti-inflammaging systems, by evaluating the role of cytokines and their impact on extreme longevity.  

 

Cytokines are the expression of a network involving genes, polymorphisms and environment, and are involved both in inflammation and anti-inflammation.  We have described the role of IL-1, IL-2, IL-6, IL-12, IL-15, IL-18, IL-22, IL-23, TNF-α, IFN-γ as pro-inflammatory cytokines, of IL-1Ra, IL-4, IL-10, TGF-β1 as anti-inflammatory cytokines, and of lipoxin A4 and heat shock proteins as mediators of cytokines.  

 

We believe that if inflammaging is a key to understand aging, anti-inflammaging may be one of the secrets of longevity.”  

NF-κB – a key driver of aging

This blog entry centers around the role of the transcription factor NF-κB , long known to be a master regulator of constituitive inflammation. But, NF-κB expression is also correlated with and appears to drive many aspects of aging. 

 

From the 2007 publication Motif module map reveals enforcement of aging by continual NF-κB activity 

  • ”Aging is characterized by specific alterations in gene expression, but their underlying mechanisms and functional consequences are not well understood.  

  • Here we develop a systematic approach to identify combinatorial cis-regulatory motifs that drive age-dependent gene expression across different tissues and organisms.  Integrated analysis of 365 microarrays spanning nine tissue types predicted fourteen motifs as major regulators of age-dependent gene expression in human and mouse.  

  • The motif most strongly associated with aging was that of the transcription factor NF-κB.   

  • Inducible genetic blockade of NF-κB for 2 weeks in the epidermis of chronologically aged mice reverted the tissue characteristics and global gene expression programs to those of young mice.  Age-specific NF-κB blockade and orthogonal cell cycle interventions revealed that NF-κB controls cell cycle exit and gene expression signature of aging in parallel but not sequential pathways.  These results identify a conserved network of regulatory pathways underlying mammalian aging and show that NF-κB is continually required to enforce many features of aging in a tissue-specific manner.”

 

What is NF- kB?

NF-kappaB is not a single molecular substance but is “a collective name for inducible dimeric transcription factors composed of members of the Rel family of DNA-binding proteins that recognize a common sequence motif”(ref).  

What these proteins share in common is a motif, e.g. a characteristic DNA binding sequence. 

In simple language NF-kappaB is a collection of proteins that can profoundly affect the transcription of DNA, that is the production of messenger RNA and the subsequent productions of proteins encoded by DNA.  

  • NF-κB can target over 200 human genes in different kinds of cells.   It has positive roles in maintaining health and also can create disease conditions and accelerate aging.

 

The gene sequence motif most closely associated with aging is that of NF-KappaB.

  • “NF-kappaB is found in essentially all cell types and is involved in activation of an exceptionally large number of genes in response to infections, inflammation, and other stressful situations requiring rapid reprogramming of gene expression(ref).  It is a very rapidly-acting substance, a “first responder” to harmful cellular stimuli.  NF-kappB tends to be plentiful in cells of older people.

 

Normally, NF-kB lives in the cytoplasm of cells where it is bound up and kept out of the nucleus by a family of substances called IkB (inhibitor of kappaB).  When a harmful extracellular stimulus is perceived, the IkB inhibitor molecules are modified by a process called ubiquitination and destroyed by cellular processes known as proteolysis

  • The result is that the NF-kappaB is freed to translocate into the nucleus where it can bind to a variety of genes, activate them and produce a variety of impacts including vicious pro-inflammatory ones.  These processes are in fact quite complex involving many proteins, adapter, promoter and co-activator factors.

 

 

The illustration below suggest that NF-κB is the “master regulator of aging”.

The role of hypoxia in inflammatory disease (Review)

INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE  35:  859-869,  2015

Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH;

Cross-Talk

There is also a very strong link between negative regulation of NF-κB , inflammation and cancer and numerous autoimmune related disorders.

There are numerous inflammatory biological pathways and these are affected differentialy by different anti-inflamatory drugs or natural substances.  Among these pathways are ones involving arachidonic acid, prostaglandins, leukotrienes and thromboxanes, microglial activation, cyclooxygenase COX enzymes, and nitric oxide synthase (iNOS), TNF-alpha, NLRP/NALP inflammasomes, P65, STAT3, and cytokines including IL-6 and IL-1beta. 

  • Proinflammatory cytokines can serve as chemoattractant for neutrophils and facilitate them sticking to the endothelial cells for migration. They also stimulate white cell phagocytosis and the production of inflammatory lipid prostaglandin E2 (PGE2).

 

In case of some medical conditions such as rheumatoid or osteo atheritis, inflammation can generate a great deal of persistent pain and discomfort.  So substances and treatments for the control of chronic inflammation and associated pain are very important. 

Reference: 2011 Inflammation and p53 A Tale of Two Stresses 

“Numerous observations indicate a strong link between chronic inflammation and cancer.  This link is supported by substantial experimental evidence indicating mutual negative regulation of NF-κB the major regulator of inflammation, and p53, the major tumor suppressor.  

This antagonistic relationship reflects the opposite principles of the physiological responses driven by these transcription factors, which act as sensors and mediators of intrinsic and extrinsic cell stresses, respectively.

  • Constitutive activation of NF-κB , the underlying cause of chronic inflammation, is a common acquired characteristic of tumors.  A variety of experimental methods have been used to demonstrate that constitutive activation of NF-κB reduces the tumor suppressor activity of p53, thereby creating permissive conditions for dominant oncogene-mediated transformation.  

  • Loss of p53 activity is also a characteristic of the majority of tumors and results in unleashed inflammatory responses due to loss of p53-mediated NF-κB suppression.

 

On the other hand, in natural or pharmacological situations of enforced p53 activation, NF-κB activity, inflammation, and immune responses are reduced, resulting in different pathologies.  It is likely that the chronic inflammation that is commonly acquired in various tissues of older mammals leads to general suppression of p53 function, which would explain the increased risk of cancer observed in aging animals and humans.  Although the molecular mechanisms underlying reciprocal negative regulation of p53 and NF-κB remain to be deciphered, this phenomenon has important implications for pharmacological prevention of cancer and aging and for new approaches to control inflammation.”

  • Transcriptional activity of NF-κB is increased in a variety of tissues with aging and is associated with numerous age-related degenerative diseases including Alzheimer’s, diabetes and osteoporosis.

 

In mouse models, inhibition of NF-κB leads to delayed onset of age-related symptoms and pathologies.  

  • “Inflammaging“ - at least 4 cytokines can trigger these pathways (IL-6, TNF-a, IL-1A, and IL-1Beta).

Conclusion: there is ample evidence that the NF-kB pathway gets left in the “on position” as we age (also referred to as “constitutive activation”). 

  • Exactly why this pathway is “left on” could be due to a combination of cytokine signaling (IL-6, TNF-alpha, IL-1a, IL-1b), activation of the Insulin/IGF pathway, dysregulated microRNA, overactive mTOR signaling, or other reasons described below. 

 

Whatever the cause, this fact makes a strong case for the use of NF-κB inhibitors for the treatment of aging and age-related diseases. 

 

As we have discussed in previous blog entries, many strategies have been proposed to accomplish this including consumption of natural products (curcumin, etc.)  

NF-κB reduces p53 activity – the inflammation-cancer link

Now the molecular mechanisms of how inflammation causes cancer is coming to light! 

P53, of course is the master tumor suppressor, but when NF-κB is constitutively activated, the tumor suppressor activity of p53 is reduced. 

  • This explains why chronic inflammation and aging both are linked to an increase in cancer risk.

With any cell stressor such as excessive DNA damage, shortened telomeres, or oncogenic stress, both the p53 pathway and the NF-κB pathway are activated by ATM.  p53 then “drives” cell senescence, whereas the NF-κB pathway promotes senescent cell clearance via STAT3 mediated production of over 100 genes called the “SASP,” aka the “senescent associated secretory phenotype”.  

  • The main cytokine secreted with the SASP is IL-6. 

  • IL-6 signaling degrades p53 and reduces the production of more senescent cells.  

References:  2013 Modulation of immune responses by the tumor suppressor p53

From the 2011 publication Inflammation and p53  “Numerous observations indicate a strong link between chronic inflammation and cancer.  

  • This link is supported by substantial experimental evidence indicating mutual negative regulation of NF-κB , the major regulator of inflammation, and p53, the major tumor suppressor.  

  • This antagonistic relationship reflects the opposite principles of the physiological responses driven by these transcription factors, which act as sensors and mediators of intrinsic and extrinsic cell stresses, respectively.  

  • Constitutive activation of NF-κB , the underlying cause of chronic inflammation, is a common acquired characteristic of tumors.  

  • A variety of experimental methods have been used to demonstrate that constitutive activation of NF-κB reduces the tumor suppressor activity of p53, thereby creating permissive conditions for dominant oncogene-mediated transformation.  

  • Loss of p53 activity is also a characteristic of the majority of tumors and results in unleashed inflammatory responses due to loss of p53-mediated NF-κB suppression.  

  • On the other hand, in natural or pharmacological situations of enforced p53 activation, NF-κB activity, inflammation, and immune responses are reduced, resulting in different pathologies.  It is likely that the chronic inflammation that is commonly acquired in various tissues of older mammals leads to general suppression of p53 function, which would explain the increased risk of cancer observed in aging animals and humans.  Although the molecular mechanisms underlying reciprocal negative regulation of p53 and NF-κB remain to be deciphered, this phenomenon has important implications for pharmacological prevention of cancer and aging and for new approaches to control inflammation.”

P53 activates NF-κB – the cancer-inflammation link

In cells where there is DNA damage due to excessive mitochondrial ROS, UV light, X-ray/gamma-ray radiation, or oncogenic stress, p53 is activated and activates NF-kB.

  • Sesquiterpine lactones like Arglabin can inhibit this activation of NF-κB .  

  • This is how constitutive activation of p53 results in constitutive activation of NF- B!  Unfortunately, activating NF-κB actually promotes cancer cell survival!  This is the “double edged sword”. For this reason, many cancer researchers have advocated the simultaneous targeting of p53 and NF-κB (I.e. Activating p53 and inhibiting NF-κB simultaneously).  However, this strategy is also a “double-edged sword”.

  • Conclusion: activating p53 and inhibiting NF- B at the same time may be a good strategy for preventing or treating cancer.

Classes of compounds that simultaneously activate p53 and inhibit NF=κB 

“Several compounds that have been shown to activate p53 while inhibiting nuclear factor- B (NF-κB) are depicted here. Activating p53 promotes cell-cycle arrest and apoptosis, whereas inhibiting NF-κB decreases cell proliferation, cell invasion and cell survival, thereby promoting tumour regression. —”

“The p53 and nuclear factor-κB (NF-κB) pathways play crucial roles in human cancer, in which inactivation of p53 and hyperactivation of NF-κB is a common occurrence.  Activation of p53 and inhibition of NF-κB promotes apoptosis.  Although drugs are being designed to selectively activate p53 or inhibit NF-κB, there is no concerted effort yet to deliberately make drugs that can simultaneously do both.  Recent results suggest that a surprising selection of small molecules have this desirable dual activity.  In this Review we describe the principles behind such dual activities, describe the current candidate molecules and suggest mechanisms and approaches to their further development.”

Reference:  2011 Inflammation and p53 – A Tale of Two Stresses  “Numerous observations indicate a strong link between chronic inflammation and cancer". This link is supported by substantial experimental evidence indicating mutual negative regulation of NF-κB, the major regulator of inflammation, and p53, the major tumor suppressor.  

  • This antagonistic relationship reflects the opposite principles of the physiological responses driven by these transcription factors, which act as sensors and mediators of intrinsic and extrinsic cell stresses, respectively.  

  • Constitutive activation of NF-κB, the underlying cause of chronic inflammation, is a common acquired characteristic of tumors.  A variety of experimental methods have been used to demonstrate that constitutive activation of NF-κB reduces the tumor suppressor activity of p53, thereby creating permissive conditions for dominant oncogene-mediated transformation.  

  • Loss of p53 activity is also a characteristic of the majority of tumors and results in unleashed inflammatory responses due to loss of p53-mediated NF-κB suppression.  

  • On the other hand, in natural or pharmacological situations of enforced p53 activation, NF-κB activity, inflammation, and immune responses are reduced, resulting in different pathologies.  It is likely that the chronic inflammation that is commonly acquired in various tissues of older mammals leads to general suppression of p53 function, which would explain the increased risk of cancer observed in aging animals and humans.  Although the molecular mechanisms underlying reciprocal negative regulation of p53 and NF-κB remain to be deciphered, this phenomenon has important implications for pharmacological prevention of cancer and aging and for new approaches to control inflammation.”

 

Parthenolides inhibit the Inflammasome directly and also inhibit NF-κB  

There are many of these sesquiterpine that inhibit the NF-lab pathway and half a dozen that also inhibit the NLRP3 Inflammasome as well. Examples include the Parthenolide, derived from the Feverfew plant. Arglabin, derived from the Kazakh tree also is a sesquiterpine.

Here are two illustrations of how these natural products (and Bay 11-7082) work on inhibiting NF-kB signaling and also work on inhibiting the NLRP3 Inflammasome.

Tanacetum Parthenium (Feverfew) 

  • Parthenolide binds to and inhibits IκB kinase complex (IKK)β.

  • Parthenolide inhibits prostaglandine synthetase.

  • Parthenolide reduces human neutrophil oxidative burst activity.

​Conclusions on inhibiting the Inflammasome directly and inhibiting NF-κB directly:

It is now clear that inhibition if NF-κB is clearly a good target for preventing aging and reducing cancer risk.  However most NF-κB inhibitors do not also directly inhibit Inflammasomes.  Parthenolides are unique molecules in that they directly inhibit NF-κB activation by Toll-like receptors (TLRs), but also directly inhibit Inflammasomes by inhibiting Caspace activation and P2X7 receptor mediated potassium efflux from the cell.  

For this reason, Parthenolides and synthetic analogs may end up being very effective chemoprevention compounds for cancer and for aging.

Nrf2 and NF-κB crosstalk – why broccoli prevents cancer

Nrf2 is the key transcription factor that turns on most of the antioxidant enzyme genes (HO-1, SOD,1, NQ01), the genes involving glutathione synthesis (GCLM, GCLC, GCS, GSR), the genes involving NADPH synthesis (G6PD, malice enzyme), and free radical detoxification genes (GPX2, peroxiredoxin, and other enzymes that directly inactivate oxidants or electrophiles (GSTs, UGTs, etc.). 

Recent research has shown that there is considerable crosstalk between the Nrf2 pathway and several other critical stress sensing pathways, the most important ones being p53, Notch1, and NF-κB. 

 * As a consequence, most phytochemicals that activate Nrf2, such as the isothiocyanates found in broccoli, Brussel sprouts, cabbage, cauliflower, and watercress also suppress NF-κB.  The opposite also appears to be true – most anti-inflammatory compounds that inhibit NF-κB also activate the Nrf2 pathway.