Publications

Many, if not all, chronic medical, neurodegenerative and neuroprogressive illnesses are characterised by chronic immune activation, oxidative and nitrosative stress (O&NS) and systemic inflammation. These factors, notably elevated pro-inflammatory cytokines, activate indoleamine 2,3-dioxygenase (IDO) leading to an upregulated tryptophan catabolite (TRYCAT) pathway of tryptophan degradation in the periphery and in the brain. In such conditions the TRYCAT pathway becomes the predominant system for tryptophan degradation in all body compartments. In this paper we review the pathways whereby TRYCATs may play a role in neuro-inflammatory and neuroprogressive disease. Thus chronic activation of the TRYCAT pathway leads to the production of a range of neuroactive, neuroprotective and neurotoxic TRYCATs. Some TRYCATs such as quinolinic acid act as potent neurotoxins which inhibit ATP production by mitochondria, provoke increases in O&NS, disrupt neuron glial communication and blood brain barrier integrity, induce apoptosis of glial cells, directly damage neurons and function as a N-methyl D-aspartate (NMDA) receptor agonist. Other TRYCATs such as kynurenic acid function as antagonists of NMDA, - amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainate receptors and act to regulate levels of glutamate and dopamine. The neuroprotective functions of this TRYCAT are likely exercised via engagement with alpha7 nicotinic acetylcholine and aryl hydrocarbon receptors but the neuroprotective effects stemming from elevated kynurenic acid levels come at the price of severely compromised neurocognitive function and emotional processing. Other TRYCATS also possess neurotoxic or neuroprotective properties via pro-oxidant and antioxidant effects. Here we discuss the involvement of the abovementioned TRYCAT pathways in schizophrenia, Alzheimer's disease and chronic fatigue syndrome. Keywords: Schizophrenia, chronic fatigue, inflammation, immune, oxidative and nitrosative stress, leaky gut.

In the last decades convergent findings from several lines of evidence has revealed a robust association between major depressive disorder (MDD) and inflammatory pathways. Despite this, the translation of these findings into new and better treatments for MDD has not occurred. The objective of this study is to comprehensively review what is already known with reasonable certainty on inflammatory pathways in MDD, to clarify some points that have been insufficiently studied and to discuss the implications of these findings for future studies targeting inflammatory pathways as a therapeutic tool for individuals with MDD.

Cognitive dysfunction in major depressive disorder (MDD) encompasses several domains, including but not limited to executive function, verbal memory, and attention. Furthermore, cognitive dysfunction is a frequent residual manifestation in depression and may persist during the remitted phase. Cognitive deficits may also impede functional recovery, including workforce performance, in patients with MDD. The overarching aims of this opinion article are to critically evaluate the effects of available antidepressants as well as novel therapeutic targets on neurocognitive dysfunction in MDD. Conventional antidepressant drugs mitigate cognitive dysfunction in some people with MDD. However, a significant proportion of MDD patients continue to experience significant cognitive impairment. Two multicenter randomized controlled trials (RCTs) reported that vortioxetine, a multimodal antidepressant, has significant precognitive effects in MDD unrelated to mood improvement. Lisdexamfetamine dimesylate was shown to alleviate executive dysfunction in an RCT of adults after full or partial remission of MDD. Preliminary evidence also indicates that erythropoietin may alleviate cognitive dysfunction in MDD. Several other novel agents may be repurposed as cognitive enhancers for MDD treatment, including minocycline, insulin, antidiabetic agents, angiotensin-converting enzyme inhibitors, S-adenosyl methionine, acetyl-L-carnitine, alpha lipoic acid, omega-3 fatty acids, melatonin, modafinil, galantamine, scopolamine, N-acetylcysteine, curcumin, statins, and coenzyme Q10. The management of cognitive dysfunction remains an unmet need in the treatment of MDD. However, it is hoped that the development of novel therapeutic targets will contribute to 'cognitive remission', which may aid functional recovery in MDD.

This systematic review aimed to investigate immune-inflammatory and hypothalamic-pituitary-adrenal (HPA) axis biomarkers in individuals with non-specific low back pain (NSLBP) compared to healthy control. The search was performed in five databases until 4 November 2021. Two reviewers independently conducted screenings, data extraction, risk of bias, and methodological quality assessment of 14 unique studies. All studies reported the source of the fluid analyzed: nine studies used serum, two used plasma, one used serum and plasma, and two studies used salivary cortisol. We found preliminary and limited evidence (only one study for each biomarker) of increased levels in growth differentiation factor 15 (GDF-15), interleukin-23 (IL-23), transforming growth factor-beta (TGF-β), and soluble tumor necrosis factor receptor 1 (sTNF-R1) in NSLBP. Inconsistent and limited evidence was identified for interleukin-10 (IL-10). Although C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) levels appear to increase in NSLBP, only one study per each biomarker reported statistically significant differences. Interleukin-1 beta (IL-1β), interleukin-17 (IL-17), interferon gamma (IFN-γ), and high-sensitivity CRP (hsCRP) showed no significant differences. Regarding cortisol, one study showed a significant increase and another a significant decrease. More robust evidence between GDF-15, IL-23, TGF-β, and sTNF-R1 with NSLBP is needed. Moreover, contrary to the findings reported in previous studies, when comparing results exclusively with healthy control, insufficient robust evidence for IL-6, TNF-α, and CRP was found in NSLBP. In addition, cortisol response (HPA-related biomarker) showed a dysregulated functioning in NSLBP, with incongruent evidence regarding its directionality. Therefore, our effort is to find adjusted evidence to conclude which immune-inflammatory and HPA axis biomarkers are altered in NSLBP and how much their levels are affected. https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020176153, identifier CRD42020176153.