Rosacea: Alzheimer’s of the Face

Is Rosacea Caused by Amyloid LL-37, as Alzheimer’s Is Caused by Anti-microbial Abeta?
A recent article in PLoS One (Thanks Daniel!) suggests that the amyloid beta (Abeta) proteins that aggregate to form fibrous plaques in the brain tissue of Alzheimer victims, function as typical defensive anti-microbial peptides (AMPs), similar to the LL-37 cathelicidin implicated in facial tissue in rosacea.  The structural and functional similarities of Abeta and LL-37 suggest to me that Alzheimer’s and rosacea may also be similar in initiation and treatment.  Let’s compare amyloids and AMPs.

[The figure shows a model protein (from ref.) used to examine stain binding to amyloids.  The stains appear to bind to aromatic amino acids spaced evenly between adjacent proteins, but adjacent basic amino acids (blue) are spaced the same way and provide sites for heparin binding.]

Amyloids:

• Amyloid proteins/peptides align into stacks and fibers
• Stacked beta sheets bind amyloid stains: Congo Red, Thioflavin-T
• Fibers form on anionic polymers: heparin, DNA
• Short amyloid stacks are toxic to cells
• Proteases produce multiple sizes of amyloid peptides

Anti-microbial Peptides:

• AMPS typically contain heparin-binding domains -- basic peptides/ plus charge
• Some AMPs, e.g. LL-37, form fibers on DNA, heparin (stain with amyloid stains)
• Toxic to cell membranes
• Kallikrein stimulated by gut flora migrates to face and clips LL-37 to a smaller peptide that binds to host DNA and stimulates the TLR receptor to produce inflammation
• Stomach pepsin hydrolyzes dietary proteins into anti-microbial peptides (heparin is secreted by mast cells onto to the intestinal surface to protect from any amyloid-like effects)
• Defensins, cathelicidins and other AMPs are under transcriptional control of vitamin D receptor

Abeta Is Anti-microbial Like LL-37

Amyloid beta is the well-known source of the fibrous plaques forming brain lesions in Alzheimer’s disease.  The normal function of Abeta has not been firmly established.  The recent article shows data to support Abeta as an anti-microbial peptide comparable to LL-37 against several pathogenic bacteria and yeast.  Knock-out mice deprived of a gene corresponding to Abeta are susceptible to bacterial infections.  The anti-microbial activity present in extracts from Alzheimer’s disease brains was inactivated by anti-Abeta antibodies.

Implications of Abeta as an AMP Like LL-37

The similarities between AMPs and amyloid peptides suggest some implications for both Alzheimer’s disease and rosacea.  Vitamin D is a hormone that binds to a cytoplasmic receptor and the vitD/receptor complex then acts as a transcription factor that controls the expression of defensins in the intestines, LL-37 in facial skin and perhaps Abeta in brains.

Amyloids form fibers on a scaffolding of heparan sulfate (HS).  There is usually an excess of HS on the surface of cells and the HS is rapidly recycled back into cells.  During inflammation, mast cells release heparin, short fragments of HS, that should also inhibit amyloid fiber formation on HS.   Chronic inflammation, however, reduces HS production and may set the stage for amyloid fiber formation.  HS metabolism of the brain may be vitally important to the development of Alzheimer’s disease, especially since the increasing chronic inflammation of aging people should deplete brain HS.

LL-37 forms complexes with DNA from damaged host cells in rosacea skin.  The LL-37/DNA complexes trigger TLRs and inflammation.  LL-37 may normally bind to cell surface HS and chronic inflammation of the skin may cause the shift to pathogenic autoinflammation.  Topical application or perhaps low dose IV heparin may be effective in disrupting the autoinflammation due to LL-37.  Part of the toxicity of LL-37 in the skin may be due to amyloid like structures that could form with inadequate HS and overabundant LL-37 production.  Vitamin D metabolism should also be very important, since LL-37 synthesis is controlled by vitamin D.  This is consistent with the benefits that some rosaceans observe with high doses of vitamin D3 supplements.

references:
Soscia SJ, Kirby JE, Washicosky KJ, Tucker SM, Ingelsson M, Hyman B, Burton MA, Goldstein LE, Duong S, Tanzi RE, Moir RD.  The Alzheimer's disease-associated amyloid beta-protein is an antimicrobial peptide.  PLoS One. 2010 Mar 3;5(3):e9505.

Abedini A, Tracz SM, Cho JH, Raleigh DP.  Characterization of the heparin binding site in the N-terminus of human pro-islet amyloid polypeptide: implications for amyloid formation.  Biochemistry. 2006 Aug 1;45(30):9228-37.

Biancalana M, Makabe K, Koide A, Koide S. Molecular mechanism of thioflavin-T binding to the surface of beta-rich peptide self-assemblies.  J Mol Biol. 2009 Jan 30;385(4):1052-63. Epub 2008 Nov 14.

Rosacea, Brain Cooling and Niacin Flush

Other players include:  Cathelicidins, Prostaglandins, Cryptic Bacteria, Nerves, Gut

What does it take to make your face red?  Excessive solar exposure can lead to apoptosis of skin cells overloaded with DNA damage and trigger inflammation: vasodilation, recruitment of neutrophils, swelling, etc.  Similarly, a local infection can cause inflammation and the accumulation of neutrophils (see The Inner Life/Extravasation for slide show), lymphocytes, etc., that is observed as pus.  These are general responses that occur in skin anywhere, but the face also blushes in response to emotional cues and flushes with exercise.  Rosacea seems to involve all of these reactions to produce a variety of symptoms of wide severity.  Here I try to provide an overview of the complex physiological interactions involved in rosacea.

Rosacea is Persistent Vasodilation of the Face with Accumulation of Neutrophils

The nervous and circulatory systems of the face are unique and provide numerous triggers for inflammation.  Emotional blushing is a common trait among those who progress to rosacea, even though this type of vasodilation is not easily observed with some facial characteristics.  Thus, many rosaceans claim to have never flushed before their first outbreak, but tests of skin circulation indicate that these individuals had skin types that prohibited display of the blushing.  The face is also adapted to control brain temperature, so changes in body temperature, physical activity, etc. can also trigger flushing.

Facial Blood Circulation to Cool the Brain

The cooling of the blood as it traverses the facial skin is used to cool the brain during extensive exercise or in warm environments.  This unique adaptation also means that control of facial vasodilation can potentially be disrupted in disease and cause symptoms of pathology.  In rosacea,  the brain cooling response is disturbed (see reference below), resulting in persistent vasodilation and suggesting that the unique control of inflammation in the face is why rosacea is limited to the face.  The pattern of blood circulation in the face, however, only roughly approximates the inflammation pattern in rosacea.

Nerves to the Face

The face receives sensory branching from the trigeminal nerve.  The enervation pattern of the branches matches emotional blushing, but they also appear to approximate the pattern of reddening in rosacea.  It makes sense that rosacea involves nerve-triggered dilation of the blood vessels of the face.  One contrast between emotional blushing and rosacea is that emotional blushing does not lead to the offloading of lymphocytes, whereas rosacea produces localization of neutrophils that exacerbate and prolong inflammation.

Cathelicidin, Vitamin D Receptor, DNA Complexes, Autoinflammation

A major component of the innate immune system is the group of basic antimicrobial peptides, cathelicidins.  Cathelicidins are effective against bacteria and they are produced during inflammation and are partially controlled by the vitamin D receptor acting as a transcription factor.  Thus, part of the action of vitamin D in providing protection against disease is by enhancing cathelicidin production.  Cathelicidin action in the skin parallels the control of intestinal villi development by defensins, that are also basic antimicrobial peptides under the control of vitamin D.  Cathelicidins also form complexes with host DNA from damaged cells.  These cathelicin/DNA complexes bind to toll-like receptors (TLRs) and trigger inflammation.  This reaction has been associated with psoriasis and may explain how neutrophil damage can perpetuate inflammation in rosacea.

Niacin Flushing Implicates Arrestins

The unique circulatory system of the face also makes it susceptible to flushing with niacin, a.k.a. nicotinic acid or vitamin B3.  Niacin is cheaper and much more effective at raising HDL and lowering triglycerides and LDL than statins, but is not fully utilized because it also produces intense facial flushes.  A recent article (below) has demonstrated that the lipid benefits can be separated from the flushing and implicated beta-arrestin 1 activation by niacin binding to GPR109A (G-protein-coupled receptor) as the triggering event.  Arrestin, which is involved in clathrin-mediated endocytosis, activates phospholipase A2 that in turn releases arachidonic acid (ARA) from phospholipids.  The ARA (that got into the phospholipids as the omega-6 fatty acid in vegetable oils) is converted by COX-2 into the inflammatory prostaglandin D2.  This prostaglandin is what stimulates vasodilation.  It is possible to produce chemicals that will stimulate the lipid metabolism alterations of niacin, without producing the arrestin activation and inflammation.  Aspirin can be used to inhibit COX-2 and other parts of NFkB-mediated inflammation and eliminate the niacin flush.  It is also interesting that the modified lipid metabolism of schizophrenics also eliminates niacin flushing.  Salicylic acid, the same as the acetylsalicylic acid of Aspirin without the acetate, is also used in some topical applications to quiet the symptoms of rosacea.  Arrestin activation may be involved in rosacea.

Gut Flora, Biofilms and Cryptic Bacteria

The gut is probably involved in most cases of rosacea and bacteria are also implicated by the modification of rosacea symptoms by antibiotics.  This area has not been explored, but I suspect that gut flora controlled by diet, as well as pathogenic biofilms and cryptic bacteria, e.g. Clamydia pneumoneae, in facial tissue are involved in varying degrees in the panoply of pathologies called collectively, rosacea.  Since the bacteria in contact with the gut determine the development of the lymphocytes in the lining of the gut, e.g. Tregs vs. T cells that fight infections, pathogenic gut biofilms may disrupt the normal function of the immune system and support rosacea.  Die off and release of cell wall endotoxin from cryptic bacteria could explain the paradoxical inflammation in response to many treatments that are normally anti-inflammatory.  I have discussed in another article potential approaches to strip off biofilms.

Treatment with Anti-Inflammatory Diet

The Anti-Inflammatory Diet (AID) and Lifestyle that I advocate on this blog would seem to be a natural cure for rosacea.  It should eliminate the inflammatory background that supports rosacea and was probably essential for its development.  This diet also eliminates acne, which is directly related to the accumulation of lymphocytes to make pus.  Inflammation is also needed for the offloading of neutrophils that exacerbate inflammation in rosacea.  Vitamin D is instrumental in cathelicidin production to eliminate cryptic bacteria. 

In most cases of rosacea, the AID should be helpful.  Eliminating dietary sources of inflammation, especially vegetable oils (the source of omega-6 fatty acids that are converted into inflammatory prostaglandins), should reduce rosacea symptoms.

In advanced, severe cases, however, it appears that maintenance of the suppression of the response to cryptic bacteria is required to prevent endotoxin-based inflammation.  Thus, most treatments that decrease inflammation, e.g. omega-3 oils, vitamin D3, Vagal maneuvers, can paradoxically produce elevated inflammation.  These treatments may also inadvertantly contribute to inflammation by upsetting pathogenic interactions between bacteria and intestinal cells.  I have discussed these paradoxical ramifications in another article.

references:
Brinnel H, Friedel J, Caputa M, Cabanac M, Grosshans E.  1989.  Rosacea: disturbed defense against brain overheating.  Arch Dermatol Res. 281(1):66-72.
Walters RW, Shukla AK, Kovacs JJ, Violin JD, DeWire SM, Lam CM, Chen JR, Muehlbauer MJ, Whalen EJ, Lefkowitz RJ.  2009.  Beta-Arrestin1 mediates nicotinic acid-induced flushing, but not its antilipolytic effect, in mice.  J Clin Invest. 119(5):1312-21.

Psoriasis, IL-17, Cathelicidin, TLRs, NFkB, Inflammation and Heparin Therapy

Host DNA Released by Keratinocyte Apoptosis Binds LL-37 and Activates Dendrocytes

Psoriasis is an inflammation of the skin that leads to overproduction of keratinocytes resulting in a thick crust.  Skin inflammation, in this case, is considered a result of autoimmunity, but an autoantigen has not been identified.  It is more likely that psoriasis results from an autoinflammatory condition, in which inflammation produces a complex of self molecules that mimic bacterial DNA and trigger TLR/NFkB inflammation signaling.  And of course, if this is going to be interesting, it has to involve heparin.

Vitamin D Binds to a Transcription Factor Receptor that Controls Antimicrobial Peptides
A significant component of the innate immune system is a group of antimicrobial peptide  (defensins, cathelicidins, e.g. LL-37).  These short polypeptides owe their natural antibiotic activity to numerous basic (positively charged, arginine and lysine) amino acids.  The transcription factor that controls the expression of these peptides is the vitamin D receptor.  Thus, various forms of vitamin D influence the amount of antimicrobial peptides produced in the mouth, skin and crypts of the intestinal villi.  Oral vitamin D3 would be expected to directly improve defensin production in the gut and LL-37 production in the skin.

IL-17 Stimulates Skin Inflammation and LL-37 Production
A specific group of lymphocytes, called T helper 17 cells, produce IL-17.  These Th17 cells accumulate in some sites of inflammation, such as psoriasis and their secretion of IL-17 is associated with ongoing inflammation and may contribute to LL-37 production, as well as apoptosis of keratinocytes in the thickening skin of psoriasis plaques.
http://www.ncbi.nlm.nih.gov/pubmed/19623255?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discovery_PMC&linkpos=2&log$=citedinpmcarticles&logdbfrom=pubmed

Th17 Cells Are Produced in the Gut in Response to Segmented Bacteria
One of my readers brought to my attention an article that shows that one of the hundreds of species of gut bacteria, segmented filamentous baceria, stimulates the gut to develop T helper 17 cells that subsequently migrate to sites of inflammation.
http://www.medpagetoday.com/Gastroenterology/InflammatoryBowelDisease/16472
This emphasizes the link between the gut and inflammatory diseases and parallels other examples of gut influence on disease, such as the ability of Helicobacter pylori to affect asthma or parasitic worms to tame Crohn’s disease, allergies and asthma.

Inflammation Lowers Heparan Sulfate Production and Spreads LL-37
One of my students induced inflammation in cells in vitro and showed by quantitative PCR that genes involved in heparan sulfate proteoglycan production are selectively silenced.  This observation explains in part the loss of heparan sulfate in kidneys and intestines that contributes to the leakiness of these organs in response to inflammation and the partial repair of these organs by heparin treatment.  Decrease of heparan sulfate that normally coats cells and binds antimicrobial peptides, such as LL-37, would explain the enhanced movement of LL-37 in psoriatic skin.

LL-37 Binds to Host DNA and Triggers Toll-Like Receptors
DNA is released from keratinocytes in psoriatic skin and this host DNA binds the antimicrobial peptide cathelicidin LL-37.  The LL-37/DNA complex mimics bacterial DNA and triggers the Toll-like receptors (TLR) on the surface of immune cells, dendrocytes, to activate NFkB, the transcription factor controlling inflammation.
http://www.ncbi.nlm.nih.gov/pubmed/19050268?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.Pubmed_Discovery_RA&linkpos=1&log$=relatedarticles&logdbfrom=pubmed

Heparin Treats Psoriasis
It seemed obvious to me that the heparin binding domains (Look at all the basic amino acids in blue in the illustration of LL-37.) of LL-37 were involved in DNA binding and the reason the LL-37 was binding to host DNA, was that heparan sulfate had been depleted as a result of local inflammation.  It also seemed obvious that topical heparin should eliminate psoriasis plaques.  So I did a Google search of psoriasis + topical heparin and got a hit on a 1991 patent application that claims a broad applicability for heparin use in curing symptoms of a wide variety of diseases, including psoriasis.
http://www.patentstorm.us/patents/5037810/description.html
The only topical form of heparin that I know of is Lipactin (available in Canada and Europe?), a treatment for coldsores, which makes sense because herpes viruses use heparan sulfate to infect cells.

Biofilm Transformation, Helicobacter, Klebsiella

Helicobacter pylori causes stomach cancer, but it feeds on hydrogen gas produced by Klebsiella pneumoniae in gut biofilms. DNA released by biofilm bacteria not only transfers antibiotic resistance, but it also provides protection against host antibacterial peptides, such a cathelicidins and defensins.

Exploding Labs

When I was working on host/pathogen interactions and plant disease resistance, I also became familiar with research on the formation of the plant equivalent of cancer, crown galls, and symbiotic bacterial nitrogen fixation. I mention this, because this also exposed me to the free-living bacterial nitrogen fixing system in Klebsiella and to the memorable urban legion of exploding labs. As the story goes, as bacteria convert atmospheric nitrogen gas into ammonia, nitrogen fixation, they use high energy electrons, e.g. from ferrodoxin, and lots of ATP, but they also produce hydrogen gas. In labs where they are researching nitrogen fixation, the excess hydrogen gas would accumulate on the ceiling until... boom! Now those labs are properly vented.

Helicobacter Uses Hydrogen as an Energy Source

Helicobacter pylori is considered the most common bacterial pathogen of humans and is the primary cause of ulcers and stomach cancer. H. pylori lives in the stomach by neutralizing stomach acid with ammonia. Another interesting ability of this bacterium is its ability to use hydrogen dissolved in circulating blood as an energy source. The high energy electrons from molecular hydrogen are transported to its electron transport chain, and the energy is used in membrane transport and ATP production. The circulating hydrogen is produced by gut bacteria.

Klebsiella Is not just a Soil Bacterium, Gut Gases

Klebsiella pneumonia is a lung pathogen and it also forms gut biofilms. Presence in the gut and the ability to produce hydrogen gas has some implications for hydrogen utilizing bacteria like H. pylori. Clearly, the stomach of someone with an abundant source of hydrogen fuel in their blood is a better target for H. pylori colonization. This explains why even at age 50, individuals who were exclusively breastfed have a lower incidence of H. pylori and stomach cancer, since even a single bottle of formula can shift an infant to adult, i.e. Klebsiella gut flora.

Klebsiella Needs Carbs to Produce Hydrogen

K. pneumoniae has been associated with Crohn’s Disease and Ankylosing Spondylitis. It grows in gut biofilms and produces pullulanase, an enzyme that can utilize the branched glucosides left over from the action of amylase on plant starch. So K.p. has an untapped food source and it needs lots of ATP to produce hydrogen gas. The nitrogenase needed for nitrogen fixation and hydrogen production is very sensitive to oxygen, so this means that K.p. needs a partially anaerobic environment and must get its energy from fermentation. Fermentation yields much less ATP than respiration using oxygen, which means that K.p. can only produce hydrogen with lots of glucose from starch.

Low Carb Diet Cures Crohn’s Disease

It turns out that the antigen causing Crohn’s disease is the pullulanse (with collagen mimetics.) As you should expect, it has a basic triplet. Eating a low carb diet reduces the flareups of Crohn’s disease, presumably by starving out the K.p.. It is interesting that nitrogenase is the antigen involved in Ankylosing Spondylitis.

Biofilms Promote Transformation and Antibiotic Resistance

Just as a footnote to the benefit of K.p. as a citizen of a biofilm community, H.p. should also live in those biofilms, since that is the source of the hydrogen it uses. Biofilms also stimulate the exchange of DNA, because the quorum sensing chemical signals trigger the release of DNA. The DNA is a component in the matrix that binds bacteria in the biofilm and can work in conjunction with bacterial acidic polysaccharides and host heparan sulfate. These acidic polymers tend to bind the basic antimicrobial peptides, e.g. defensins and cathecidins produced as a major non-adaptive defense against bacteria. Thus, the release of DNA triggered by quorum sensing, builds matrix, facilitates DNA transformation that is the foundation for the spread of antibiotic resistance in gut biofilms and provides resistance against antimicrobial peptides.