Could seborrhoeic dermatitis be implicated in the pathogenesis of parkinsonism?

Parkinson's disease and skin

Parkinson's disease is associated with a variety of dermatologic disorders and the study of skin may provide insights into pathophysiological mechanisms underlying this common neurodegenerative disorder. Skin disorders in patients with Parkinson's disease can be divided into two major groups: 1) non-iatrogenic disorders, including melanoma, seborrheic dermatitis, sweating disorders, bullous pemphigoid, and rosacea, and 2) iatrogenic disorders related either to systemic side effects of antiparkinsonian medications or to the delivery system of antiparkinsonian therapy, including primarily carbidopa/levodopa, rotigotine and other dopamine agonists, amantadine, catechol-O-methyl transferase inhibitors, subcutaneous apomorphine, levodopa/carbidopa intestinal gel, and deep brain stimulation. Recent advances in our understanding of the role of α-synuclein in peripheral tissues, including the skin, and research based on induced pluripotent stem cells derived from skin fibroblasts have made skin an important target for the study of Parkinson's disease pathogenesis, drug discovery, novel stem cell therapies, and diagnostics.

Parkinson's disease pathogenesis, evolution and alternative pathways: A review

Sporadic Parkinson's disease (PD) is one of the most common neurodegenerative diseases of the elderly. In the scientific literature, surveys aiming to investigate the potential diagnostic biomarkers for PD have focused on skin and intestinal tissue biopsies, whereas more recent studies have reported an association between PD and skin disorders, such as seborrheic dermatitis and rosacea. In addition, a connection between PD and Crohn's disease has been established. These data suggest the hypothesis of a possible link between the gastrointestinal tract and skin and the development of PD. In fact, the nervous system, gastrointestinal tract and skin are analogous in their embryological development and, therefore, have molecular networks and pathogenic pathways in common. Based on these data, it may be assumed that the gastrointestinal tract and skin might be implicated in the pathogenesis of PD. The evolutionary hypothesis might also be a useful tool for further investigations into the overlap across neurological, gastrointestinal and skin disorders.

Peripheral aetiopathogenic drivers and mediators of Parkinson's disease and co-morbidities: role of gastrointestinal microbiota

We seek an aetiopathogenic model for the spectrum of Parkinson's disease (PD), functional bowel disease, depression and cognitive impairment. The adopted concept is that systemic immuno-inflammatory processes mediate neuro-inflammation. The model would be based on phenotype, exposome (including gastrointestinal microbiome), milieu (immuno-inflammatory and metabolome), human genetics and their interactions. It would enable a patient's position, to be understood in terms of drivers, perpetuators and mediators, and a future position, with and without intervention, predicted. Even the cardinal facets of PD may have different drivers: halting one may allow escape down subordinate pathways. Peptic ulceration is prodromal to PD. In our randomised placebo-controlled trial, hypokinesia improved over the year following biopsy-proven Helicobacter pylori eradication and rigidity worsened. This was independent of any (stable, long t½) antiparkinsonian medication. There are pointers to an autoimmune process: for example, surveillance-confirmed hypokinesia effect was indication specific. During surveillance, successive antimicrobial courses, other than for Helicobacter, were associated with cumulative increase in rigidity. Exhibiting laxatives appeared to stem the overall temporal increase, despite antiparkinsonian medication, in rigidity. Thus, intestinal dysbiosis may be a major source of bystander neuronal damage. There are biological gradients of objective measures of PD facets on circulating inflammatory markers and leucocyte subset counts. Moreover, lactulose hydrogen breath test positivity for small-intestinal bacterial overgrowth (present in two thirds of PD patients) is associated with the same subsets: higher natural killer and total CD4+ counts and lower neutrophils. With greater aetiopathogenic understanding, relatively low cost and on-the-shelf medication could have a major impact. A new generation of animal models, based on the gut microbiome, is envisaged.

Blood profile holds clues to role of infection in a premonitory state for idiopathic parkinsonism and of gastrointestinal infection in established disease

The two-stage neuroinflammatory process, containment and progression, proposed to underlie neurodegeneration may predicate on systemic inflammation arising from the gastrointestinal tract. Helicobacter infection has been described as one switch in the pathogenic-circuitry of idiopathic parkinsonism (IP): eradication modifies disease progression and marked deterioration accompanies eradication-failure. Moreover, serum Helicobacter-antibody-profile predicts presence, severity and progression of IP. Slow gastrointestinal-transit precedes IP-diagnosis and becomes increasingly-apparent after, predisposing to small-intestinal bacterial-overgrowth (SIBO). Although IP is well-described as a systemic illness with a long prodrome, there has been no comprehensive overview of the blood profile. Here, it is examined in relation to Helicobacter status and lactulose-hydrogen-breath-testing for SIBO.

A robust finding of reduced lymphocyte count in 126 IP-probands and 79 spouses (without clinically-definite IP), compared with that in 381 controls (p < 0.001 in each case), was not explained by Helicobacter-status or breath-hydrogen. This complements a previous report that spouses were 'down-the-pathway' to 'clinically-definite' disease. In 205 other controls without clinically-definite IP, there were strong associations between sporadic cardinal features and immunoglobulin class concentration, not explained by Helicobacter-status. Premonitory states for idiopathic parkinsonism associated with relative lymphopenia, higher serum immunoglobulin concentrations and evidence of enteric-nervous-system damage may prove viral in origin.

Although only 8% of the above 79 spouses were urea-breath-test-positive for Helicobacter, all 8 spouses with clinically-definite IP were (p < 0.0001). Transmission of a 'primer' to a Helicobacter-colonised recipient might result in progression to the diagnostic threshold.

Twenty-five percent of the 126 probands were seropositive for anti-nuclear autoantibody. In 20 probands, monitored before and serially after anti-Helicobacter therapy, seropositivity marked a severe hypokinetic response (p = 0.03). It may alert to continuing infection, even at low-density. Hyperhomocysteinemia is a risk factor for dementia and depression. Serum homocysteine exceeded the target in 43% of the 126 IP-probands. It was partially explained by serum B12 (12% variance, p < 0.001), but not by Helicobacter-status (gastric-atrophy uncommon in IP) or levodopa treatment. Immune-inflammatory activation increases homocysteine production. Since an estimated 60% of probands are hydrogen-breath-test positive, SIBO, with its increased bacterial utilisation of B12, is a likely cause. Thus, two prognostic indicators in established IP fit with involvement of Helicobacter and SIBO.

Role of inflammation in gastrointestinal tract in aetiology and pathogenesis of idiopathic parkinsonism

Idiopathic parkinsonism (IP) is a common disorder, conventionally regarded as neurodegenerative. Its cardinal features, poverty and slowness of movement, muscle rigidity, postural abnormality and a characteristic tremor, are associated with loss of dopaminergic neurones in the substantia nigra of the brain. Genetic factors explain only a minority of cases, and a common toxic environmental insult remains elusive. We propose that IP is a systemic disorder resulting from a ubiquitous peripheral infection, and that only the tip of the iceberg comes to diagnosis. There is evidence for inflammatory/immune activation peripherally and in the brain. We have used statistical modelling to explore links with non-specific and specific systemic markers of inflammation/infection in IP probands, and explore whether their partners and siblings have a frank or pre-presentation parkinsonian state. Critical to this approach is continuous objective measures of the facets of IP. Hypotheses on causality and mechanism are based on the statistical models. There is pathological and clinical evidence for direct involvement of the gastrointestinal tract in IP. The candidacy of Helicobacter pylori infection as a trigger event or driving infection is relatively high. We have found that eliminating infection in late parkinsonism with cachexia, a stage usually considered intractable, can result in a U-turn. However, eradication therapy may not provide a complete solution. Persistence of antibody against cytotoxin-associated antigen (CagA), increases the predicted probability of being labelled as having parkinsonism. Evidence for autoimmunity and immunocompromise is used to build schemes for the natural history. We conclude that current classifications of neuropsychiatric disease may not prove the best with respect to defining sub-clinical disease, prophylaxis or halting progression.

Seborrheic dermatitis, increased sebum excretion, and Parkinson's disease: a survey of (im)possible links

The concept of skin as a mirror of parkinsonism, dates back at the beginning of the last century. Since then, much evidence has been accumulated supporting a causal association between the neurological disturbance and changes detectable on areas of the integument with the richest sebaceous gland supply, namely seborrheic dermatitis and/or seborrhea. However, the many persisting sources of perplexity weighing on some general aspects of the skin condition itself (lack of standardized diagnostic criteria, high variability of estimates of prevalence, and controversies on etiology and pathomechanisms) must have to date hampered assessment of the real nature, and significance (if any) of the links observed. The three major pathogenical pathways so far conceived in this context will be critically reviewed on the basis of evidences provided in the literature.

Neurophysiological correlate of clinical signs in Parkinson's disease

Clinical diagnosis of Parkinson's disease (PD) is not always coincident with pathological findings. A better characterization of the disease from the results of studies in various areas of neuroscience can help in improving the rate of diagnostic certainty. Neurophysiology is among the techniques with better chances to furnish specific diagnostic cues on motor aspects of the disease. Neurophysiology provides quantifiable data using non-invasive, relatively inexpensive, methods. Neurophysiological tests can be applied with no previous preparation, and repeated many times without dangerous consequences. To be rewarding, however, neurophysiological examination should be done in close cooperation between the clinician who detects relevant specific signs, and the neurophysiologist who devises the most demonstrative methods to document those signs. In this review, we describe the neurophysiological correlate of symptoms and signs in patients with PD, and particularly their pathophysiological meaning, with special focus on those that could be more helpful to the neurologists in establishing differences with respect to other diseases presenting with parkinsonism.

Parkinsonism: differential age-trend in Helicobacter pylori antibody

BACKGROUND

Parkinsonism is associated with prodromal peptic ulceration. Dopamine antagonists provoke experimental ulcer, dopaminergic agents protect, and might inhibit growth of Helicobacter pylori.

OBJECTIVE

To describe the relationship between H. pylori serology and parkinsonism.

METHODS

Serum H. pylori anti-urease-IgG antibody was measured in 105 people with (idiopathic) parkinsonism, 210 without, from same locality. None had received specific eradication therapy.

RESULTS

Controls showed a birth-cohort effect: antibody titre rose from 30 to 90 years (P < 0. 001). Parkinsonism obliterated this (disease status. age interaction, P < 0.05), the differential age trend not being attributable to social class. Those with diagnosed parkinsonism were more likely to be seropositive (odds ratio 2.04 (95% CI: 1.04, 4.22) P < 0.04) before 72.5 years. Overall, titre fell (P=0.01) by 5 (1, 9)% per unit increase in a global, 30-point rating (median 14 (interquartile range 10.5, 17)) of disease severity. No individual category of anti-parkinsonian medication (92% taking) had a differential lowering effect.

CONCLUSIONS

Higher prevalence of seropositivity in parkinsonism, before 8th decade, may be due to host susceptibility/reaction, or, conversely, infection with particular H. pylori strain(s) lowering dopaminergic status. Absence of a birth cohort effect in parkinsonism, despite similar social class representation, may be consequent on eradication, spontaneous (gastric atrophy) or by anti-parkinsonian medication.

Association of circulating TNF-alpha and IL-6 with ageing and parkinsonism

INTRODUCTION

We propose that the increase in TNF-alpha and IL-6 in the brain in idiopathic parkinsonism is in response to a peripheral immune/ inflammatory process, so ubiquitous as to be responsible for the resemblance between ageing and parkinsonism.

METHODS

Circulating cytokine was measured in 78 subjects with idiopathic parkinsonism and 140 without, aged 30 to 90 years, all obeying inclusion/exclusion criteria.

RESULTS

Serum TNF-alpha increased (P<0.0001) by 1.37 (95% CI 0.75, 2.00)% x y(-1), IL-6 by 2.63 (1.75, 3.52) (P<0.0005). TNF-alpha appeared elevated in parkinsonians whose postural and psychomotor responses were abnormal, being suppressed where they were normal: trends which contrasted with those in controls (P = 0.015 and 0.05, respectively). Parkinsonism appeared (P = 0.08) to have an effect on IL-6, equivalent to that of >10 years of ageing (28(-3, 69)%), but was not immediately related to between-subject differences in performance.

CONCLUSION

Ageing and pathogenetic insult may be confounded, age being a progression, not a risk, factor.

Parkinsonism: siblings share Helicobacter pylori seropositivity and facets of syndrome

OBJECTIVE

Given a history of peptic ulcer is more frequent in parkinsonism, to investigate the role of Helicobacter pylori in its pathogenesis and of cross-infection in familial aggregation.

METHODS

Facets of parkinsonism were quantified in 33 elderly subjects with idiopathic parkinsonism and in their 39 siblings with double the number of controls, all obeying inclusion/exclusion criteria. Specific-IgG antibody was assayed.

RESULTS

Siblings, compared with controls, had brady/hypokinesia of gait (P< or =0.002), bradykinesia of hands (P = 0.01), abnormal posture (P = 0.001), rigidity (P < 0.001) and seborrhoea/seborrhoeic dermatitis (P = 0.02). Both parkinsonians and siblings differed from controls in the odds of being H. pylori seropositive [odds ratios 3.04 (95% C.I.: 1.22, 7.63) and 2.94 (1.26, 6.86) respectively, P < 0.02], seropositivity being found in 0.70 of sufferers.

CONCLUSION

Familial transmission of chronic infection plus part of syndrome links Helicobacter with causality. Seropositivity not being universal throughout parkinsonism, consequent on gastric atrophy +/- sporadic antibiotic exposure, might explain less aggressive disease in older sufferers.

Cortisol is higher in parkinsonism and associated with gait deficit

INTRODUCTION

We propose an active pathogenic mechanism, involving circulating cortisol, in parkinsonism.

MATERIALS AND METHODS

Serum cortisol was measured in 96 subjects with idiopathic parkinsonism, 170 without, and in 17 spouses and 36 siblings of elderly sufferers with double the number of controls, all obeying inclusion/exclusion criteria.

RESULTS

Cortisol, adjusted for sampling time, was greater (17%, on average, P<0.001) in parkinsonians, but not in relatives. The central cortisol lowering effect of anti-muscarinics was seen (P=0.025). Selegiline may attenuate the disease, and parkinsonism is less frequent in tobacco smokers. Selegiline was associated with a lower cortisol (P=0.03): chronic smoking appeared (P=0.08) to be, irrespective of parkinsonism. Bowel stasis has been implicated in the pathogenesis: cortisol was higher in parkinsonians requiring laxatives (P=0.05). In controls, cortisol was lower, the longer the stride (P=0.02): in parkinsonians, this relationship was numerically reversed. A similar (P=0.01) group performance interaction was seen for deterioration, over 4 years, in gait.

CONCLUSION

Cortisol is doing harm or mirroring something which is. A common pathway for neuronal protection/rescue emerges.

Association between Malassezia furfur colonization and seborrhoeic dermatitis in AIDS patients

A total of 180 HIV-positive patients were assessed for seborrhoeic dermatitis (SD) and colonization with Malassezia species. Diseased skin of patients with seborrhoeic dermatitis were sampled selectively for Malassezia. In patients without SD, uninvolved skin was sampled. The prevalence of SD was 19%. Of the 34 SD patients, 16 were positive for Malassezia. Of the 146 patients without SD, only 27 were culture positive for Malassezia. Analysis of the largest HIV-positive patient population studied thus far yielded only a weak correlation between SD and Malassezia colonization.