Arthritis induced in rats with non-immunogenic adjuvants as models for rheumatoid arthritis

Rat models are useful for studies of the pathogenesis of rheumatoid arthritis (RA) since rats are extraordinarily sensitive to induction of arthritis with adjuvants. Injection of not only the classical complete Freund's adjuvant but also mineral oil without mycobacteria and pure adjuvants such as pristane and squalene, induce severe arthritis in many rat strains. Models like pristane-induced arthritis in rats are optimal models for RA since they fulfill the RA criteria including a chronic relapsing disease course. Arthritogenic adjuvants like pristane, avridine, squalene and mineral oil are not immunogenic since they do not contain major histocompatibility complex (MHC) binding peptides. Nevertheless, the diseases are MHC-associated and dependent on the activation of alphabetaTCR (T-cell receptor)-expressing T cells. However, it has not been possible to link the immune response to joint antigens or other endogenous components although immunization with various cartilage proteins induce arthritis but with different pathogeneses. To unravel the mechanisms behind adjuvant-induced arthritis, a disease-oriented genetic approach is optimal. Several loci that control onset of arthritis, severity and chronicity of the disease have been identified in genetic crosses and most of these have been confirmed in congenic strains. In addition, many of these loci are found in other autoimmune models in the rat as well as associated with arthritis in mice and humans

Pathogenesis of arthritis in rats : Genetic factors and inducing molecules

Rheumatoid Arthritis (RA) is a chronic joint disease for which there is presently no cure, possibly because rational design of therapy is hindered by lack of knowledge of disease mechanisms (pathogenesis), and disease causing genetic and inducing factors (etiology). In this thesis, etiopathogenetic clues were sought in experimental arthritis, induced in different rat strains using both specific and nonspecific triggers of the immune system, i.e. antigens and adjuvants, respectively. Injection of incomplete Freund's adjuvant oil (IFA) triggered joint inflammation, which was associated with expression of mRNA for the proinflammatory cytokines TNF-a and IFN-y. However, no arthritis developed when an antigen was added to IFA. This inhibition appeared to correlate with activation of antigen-specific T cells, since mRNA for the T cell cytokines IL-2 and IL-4 were expressed. Thus, joint inflammation appears to develop as a consequence of inflammation triggered in the absence of targets for adaptive immune responses. The generality of this disease principle was fortified, since many structurally different adjuvants could induce joint inflammation, including defined microbial triggers of innate defence, such as lipopolysaccharide and ß-glucan. Several hydrocarbons were also arthritogenic, and the pathogenic capacity of linear alkanes could be determined at the level of single atom differences in structure. Interestingly, the endogenous lipid and cholesterol precursor squalene could also induce a T cell-mediated arthritis. The role of pathogenic T cells remains elusive in adjuvant arthritis. They may be autoagressive, in which case arthritogenic joint antigens constitute possible targets. Cartilage oligomeric matrix protein (COMP) is presented as one such candidate, since it could induce autoimmune joint inflammation, as can collagen type II in the same rat strain. Both these forms of autoimmune arthritis were associated with a type 1 cytokine profile, while the type 2 cytokine IL-4 was produced in a resistant strain, depending on genes outside the major histocompatibility complex (MHC). Chromosomal non-MHC regions which determine susceptibility were identified in adjuvant arthritis triggered by IFA, i.e. oil-induced arthritis (OIA). These loci may be of general importance in experimental autoimmunity, since IFA is commonly used in combination with different autoantigens to induce autoimmune conditions, such as arthritis, encephalomyelitis, thyroiditis and uveoretinitis. More importantly, the susceptibility genes within these loci may give leads to putative autoimmune diseases in humans, including RA. Key words: arthritis, adjuvants, autoimmunity, MHC, genetics, rat, cytokines ISBN 91-628-2840-

Evidence of Unrecognized Indoor Exposure to Toxic Chlorophenols and Odorous Chloroanisoles in Denmark, Finland, and Norway

Production and use of chlorophenols (CPs) are being phased out around the globe, but with considerable lag in some highlypopulated countries. The process could be incentivized by leading countries sharing their experiences on problems thatoccurred, including the built environment. We previously reported that Swedish industry and authorities promoted CPs,including pentachlorophenol (PCP), as wood preservatives in buildings for decades. Yet, Swedish indoor research did notrecognize exposure to the hazardous CPs and their odor potent derivatives, the chloroanisoles (CAs), which smell like moldand still evolve from legacy preservatives in damp building structures. We hypothesized that the toxic CPs and odorous CAscould be key players for health and odor problems not only in Sweden but also in the neighboring Nordic countries. We foundno reports in scientific medical literature of CPs being used in buildings in these countries. However, grey literature shows thatCPs were indeed used, even during building booms, in house exteriors, constructions, and interiors, from the 1950s up to thelate 1970s (Denmark) and even the 1990s (Finland and Norway). One application of CPs was in houses erected on dampness-prone house foundations, conditions ideal for formation of odorous CAs through microbial methylation. Furthermore, oursearches suggest that these problematic chemicals played hitherto unrecognized key roles when indoor air research evolved.Thus, odor became an important aspect of the “sick building syndrome” in Denmark and an early warning sign of health risksin Finland, as asthma and allergy were attributed to “dampness and mold.” None of the countries addressed the possible linksbetween odor and health effects and exposure to CAs and CPs. In conclusion, our results suggest that unrecognized indoorexposure to toxic CPs and odorous CAs has mislead Nordic indoor air research for decades

Investigating the presence of mold in wood treated with chlorophenol

A common moisture-related problem in Sweden and other countries, is mold odor indoors. The general perception is that mold odor indicates hazardous hidden mold. However, some grey literature studies indicate that the source of mold odor might not be substantial amounts of mold, but rather chloroanisoles (CAs) which are biomethylated from chlorophenols (CPs) in moist conditions. Products containing CPs were commonly used world-wide as wood preservatives in the 1960-70s and problems with indoor mold odor have been reported in buildings where such products have been used. In Sweden, one of the main uses of CPs in buildings was in wooden constructions exposed to big moisture loads, such as sill plates and crawl space ceilings. Here we aimed to determine the potential presence and level of mold growth on wood treated with CPs in one school building with reported odor problems built in the stated time period. Odorous wooden samples were taken and analyzed for mold growth. No mold was detected by the naked eye, but some growth was seen using a microscope. We presently investigate more schools and samples, but so far our results question that mold odor depends on substantial amounts of mold

Overcrowding and Hazardous Dwelling Condition Characteristics: A Systematic Search and Scoping Review of Relevance for Health

Crowding in dwellings is an important public health issue. We hypothesize that overcrowding may cause indirect health effects by adversely affecting the dwelling itself, for example, by increasing dampness leading to mold. We therefore performed a systematic search and a scoping review on overcrowding leading to dwelling condition characteristics of relevance for health. A literature search was performed using the PubMed and Scopus databases up to 5 March 2021. The search yielded 100 records with relevant information. We found that overcrowding is defined in numerous ways and often address “socially deprived” populations. Six studies report associations of overcrowding with at least one dwelling condition characteristic, namely lead, cadmium, microorganism distribution, dust mite and cockroach allergens in dust, cockroach infestation, peeling paint, and mold. One of the studies reports associations between several characteristics, e.g., association of mold with cleanliness and rodent infestation, and points out the common use of pesticides. Additional characteristics were extracted from the remaining 94 records, without data on statistical associations with overcrowding. Our review suggests that multiple potentially hazardous dwelling condition characteristics often coincide in overcrowded dwellings. The epidemiological attribution of health effects to any characteristic is therefore difficult. Causal relationships are even more difficult to establish, as overcrowding is also associated with a range of social and other circumstances that may affect health. The complexity should be considered by scientists and practitioners dealing with overcrowding in dwellings

The Endogenous Adjuvant Squalene Can Induce a Chronic T-Cell-Mediated Arthritis in Rats

Squalene is a cholesterol precursor, which stimulates the immune system nonspecifically. We demonstrate that one intradermal injection of this adjuvant lipid can induce joint-specific inflammation in arthritis-prone DA rats. Histopathological and immunohistochemical analyses revealed erosion of bone and cartilage, and that development of polyarthritis coincided with infiltration of αβ(+) T cells. Depletion of these cells with anti-αβ TcR monoclonal antibody (R73) resulted in complete recovery, whereas anti-CD8 and anti-γδ TcR injections were ineffective. The apparent dependence on CD4(+) T cells suggested a role for genes within the major histocompatibility complex (MHC), and this was concluded from comparative studies of MHC congenic rat strains, in which DA.1H rats were less susceptible than DA rats. Furthermore, LEW.1AV1 and PVG.1AV1 rats with MHC identical to DA rats were arthritis-resistant, demonstrating that non-MHC genes also determine susceptibility. Some of these genetic influences could be linked to previously described arthritis susceptibility loci in an F2 intercross between DA and LEW.1AV1 rats (ie, Cia3, Oia2 and Cia5). Interestingly, some F2 hybrid rats developed chronic arthritis, a phenotype not apparent in the parental inbred strains. Our demonstration that an autoadjuvant can trigger chronic, immune-mediated joint-specific inflammation may give clues to the pathogenesis of rheumatoid arthritis, and it raises new questions concerning the role of endogenous molecules with adjuvant properties in chronic inflammatory diseases

Chloroanisoles and Chlorophenols Explain Mold Odor but Their Impact on the Swedish Population Is Attributed to Dampness and Mold

We recently reported that mold odor may be explained by chloroanisoles (CAs) formed by microbial biotransformation of chlorophenols (CPs) in legacy wood preservatives. Here we examine psychophysical aspects of CAs and trace their historic origins in buildings. Our exposure of healthy volunteers shows that 2,4,6-triCA is often perceived as unpleasant, characterized as musty or moldy and is detected at 13 ng/m3 or lower. Similar concentrations are reported in buildings with odor complaints. Scrutiny of written records reveal that new building construction methods were introduced in the 1950s, namely crawlspaces and concrete slabs on the ground. These constructions were prone to dampness and attack from wood decay fungi, prompting chemical companies and authorities to advocate preservatives against rot. Simultaneously, CPs became household chemicals used for example in indoor paints. When large-scale odor problems evolved, the authorities that once approved the preservatives attributed the odor to hidden mold, with no evidence that substantial microbial biomass was necessary for odor formation. Thereby the public remained unaware of problematic exposure to CPs and CAs. We conclude that the introduction of inappropriate designs of house foundations and CP-based preservatives once ignited and still provide impetus for indoor air research on “dampness and mold”

Mold Odor from Wood Treated with Chlorophenols despite Mold Growth That Can Only Be Seen Using a Microscope

We previously reported that indoor odorous chloroanisoles (CAs) are still being emitted due to microbial methylation of hazardous chlorophenols (CPs) present in legacy wood preservatives. Meanwhile, Swedish researchers reported that this malodor, described since the early 1970s, is caused by hazardous mold. Here, we examined to what extent CP-treated wood contains mold and if mold correlates with perceived odor. We found no studies in PubMed or Web of Science addressing this question. Further, we investigated two schools built in the 1960s with odor originating from crawlspaces. No visible mold was evident in the crawlspaces or on the surfaces of treated wood samples. Using a microscope, varying amounts of mold growth were detected on the samples, all containing both CP(s) and CA(s). Some samples smelled, and the odor correlated with the amount of mold growth. We conclude that superficial microscopic mold on treated wood suffices produced the odor. Further, we argue that CPs rather than mold could explain the health effects reported in epidemiological studies that use mold odor as an indicator of hazardous exposure