The Microbiome in Bronchial Biopsies from Smokers and Ex-Smokers with Stable COPD - A Metatranscriptomic Approach

Current knowledge about the respiratory microbiome is mainly based on 16S ribosomal RNA gene sequencing. Newer sequencing approaches, such as metatranscriptomics, offer the technical ability to measure the viable microbiome response to environmental conditions such as smoking as well as to explore its functional role by investigating host-microbiome interactions. However, knowledge about its feasibility in respiratory microbiome research, especially in lung biopsies, is still very limited. RNA sequencing was performed in bronchial biopsies from clinically stable smokers (n = 5) and ex-smokers (n = 6) with COPD not using (inhaled) steroids. The Trinity assembler was used to assemble non-human reads in order to allow unbiased taxonomical and microbial transcriptional analyses. Subsequently, host-microbiome interactions were analyzed based on associations with host transcriptomic data. Ultra-low levels of microbial mass (0.009%) were identified in the RNA-seq data. Overall, no differences were identified in microbiome diversity or transcriptional profiles of microbial communities or individual microbes between COPD smokers and ex-smokers in the initial test dataset as well as a larger replication dataset. We identified an upregulated host gene set, related to the simultaneous presence of Bradyrhizobium, Roseomonas, Brevibacterium.spp., which were related to PERK-mediated unfolded protein response (UPR) and expression of the microRNA-155-5p. Our results show that metatranscriptomic profiling in bronchial biopsy samples from stable COPD patients yields ultra-low levels of microbial mass. Further, this study illustrates the potential of using transcriptional profiling of the host and microbiome to gain more insight into their interaction in the airways.

Association between melanoma and dermal mast cell prevalence in sun-unexposed skin

BACKGROUND

Both exposure to intermittent intense sunlight during childhood and ultraviolet (UV) radiation-induced immunomodulation have been directly associated with melanoma development. In mice, the prevalence of dermal mast cells determines susceptibility to UVB-induced systemic suppression of contact hypersensitivity responses and thus may affect immunological responses to melanoma antigens.

OBJECTIVES

To determine the relevance of murine studies of dermal mast cell prevalence to human melanoma pathogenesis.

METHODS

The prevalence of mast cells was examined in sun-unexposed buttock skin of 45 melanoma patients and 68 control volunteers who had no history of skin cancer development. Buttock skin was studied because mast cell prevalence is stable with ageing and the confounding effects of environmental UV exposure are minimized.

RESULTS

Using tissue immunostaining, the buttock skin from melanoma patients had a significantly higher dermal mast cell prevalence (mean +/- SEM 38 +/- 2 mast cells mm(-2)) than controls (32 +/- 2 mast cells mm(-2)) (P = 0.02). Analysis by binary logistic regression showed that the association between mast cell prevalence and melanoma outcome was not significantly altered by skin phototype.

CONCLUSIONS

The immunomodulatory effects of mast cell products in UV-irradiated skin may contribute significantly to the initiation and development of human cutaneous malignant melanoma.

The effect of ultraviolet radiation exposure on the prevalence of mast cells in human skin

BACKGROUND

Dermal mast cells have been implicated as important effector cells in innate immunity, hypersensitivity responses and ultraviolet (UV)B-induced suppression of cell-mediated immune responses to contact allergens. Humans, like mouse strains, display variations in dermal mast cell prevalence. The factors determining these differences are yet to be fully elucidated. In mice, expression of the receptor for stem cell factor, c-kit, on dermal mast cells correlates with prevalence.

OBJECTIVES

To evaluate dermal mast cell prevalence and mast cell c-kit expression in non-sun-exposed and sun-exposed skin in the same donor.

METHODS

In 14 subjects, biopsies of skin (4 mm) were sampled from the skin sites of buttock, inner arm, shoulder and back of hand skin and dermal mast cell prevalence quantified. Non-sun-exposed buttock and chronically sun-exposed hand skin were evaluated for mast cell expression of c-kit and elastin content, a feature of photoageing and surrogate marker of UV exposure.

RESULTS

The prevalence of dermal mast cells was significantly higher in hand skin than in the three other anatomically different skin sites. Significant correlations were observed in hand but not buttock skin between increasing dermal mast cell densities, extent of elastin content in the papillary dermis and age of the subject. Cellular expression of c-kit correlated with mast cell prevalence in hand skin. However, no relationship was observed in hand skin between c-kit expression, elastin content and age.

CONCLUSIONS

The prevalence of mast cells in human skin is altered by factors that are intrinsic (mechanisms regulating c-kit expression) and extrinsic (chronic sun exposure), and the fact that the associations of mast cell prevalence with age is explained by the latter being a correlate of cumulative sun exposure.

Tea tree oil reduces the swelling associated with the efferent phase of a contact hypersensitivity response

OBJECTIVE

To examine the anti-inflammatory activities of tea tree oil (TTO) in vivo.

METHODS

Mice were sensitized to a chemical hapten, trinitrochlorobenzene, on their ventral skin and 7 days later challenged (or re-exposed) on their dorsal skin with the same hapten.

RESULTS

TTO applied 30 min before or up to 7 h after to the same dorsal site as hapten challenge caused a significant reduction in skin swelling after 24 h. TTO reduced oedema but not the influx of inflammatory cells. This finding was supported by the inability of TTO to suppress TNFalpha-induced E-selectin expression by human umbilical vein endothelial cells. TTO did not suppress irritant- or ultraviolet B-induced oedema.

CONCLUSION

Topical TTO, specifically the TTO components, terpinen-4-ol and alpha-terpineol can regulate the oedema associated with the efferent phase of a contact hypersensitivity response.

cis-Urocanic acid stimulates neuropeptide release from peripheral sensory nerves

Previous studies using an antibody to cis-urocanic acid and mast-cell-depleted mice implicated both cis-urocanic acid and mast cells in the mechanisms by which ultraviolet B light suppresses systemic contact hypersensitivity responses in mice. In the absence of a direct stimulatory effect of cis-urocanic acid on connective tissue mast cells, an indirect association was investigated. A blister induced in the rat hind footpad was used to examine the effects of slowly perfused cis-urocanic acid on cutaneous blood flow. cis-Urocanic acid but not trans-urocanic acid increased microvascular flow by a mechanism largely dependent on the combined activity of the neuropeptides, substance P and calcitonin gene-related peptide. Perfusion of cis-urocanic acid over the base of blisters induced in sensory-neuropeptide-depleted rats did not have any stimulatory effect above that seen with perfusion of cis-urocanic acid together with neuropeptide receptor antagonists in control rats. There was a small direct effect of cis-urocanic acid on microvascular blood flow. As both substance P and calcitonin gene-related peptide could directly degranulate connective tissue mast cells, this study suggests that cis-urocanic acid indirectly activates mast cells via its effects on peripheral terminals of unmyelinated primary afferent sensory nerves. cis-Urocanic-acid-induced neuropeptides may also contribute to ultraviolet-B-induced cutaneous inflammation and alterations to Langerhans cell activity.

Sunlight, immunosuppression and skin cancer: role of histamine and mast cells

1. The development into tumours of skin cells transformed by ultraviolet (UV) B radiation of wavelengths 290-320 nm is enhanced by the ability of UVB to suppress an immune response that would otherwise destroy them. Ultraviolet B-induced immunomodulation may be by multiple mechanisms, but generally manifests in an antigen-presenting cell defect and an altered cytokine environment in the draining lymph nodes. 2. Immune responses to microbial or self-antigens may be dysfunctional by similar mechanisms following UVB exposure. 3. Earliest-acting intermediates in the initiation of UVB-induced immunosuppression are the UVB absorbers (photoreceptors) of the skin, notably DNA resulting in immunoregulatory cytokine production, and trans-urocanic acid (UCA), which, upon isomerization to its cis isomer, signals downstream immunosuppressive events. 4. In mice, dermal mast cells are critical to UVB-induced systemic immunomodulation. In mice, there is a functional link as well as a linear relationship between the prevalence of histamine-staining dermal mast cells and the log of the dose of UVB required for 50% immunosuppression. Studies with histamine receptor antagonists support histamine as the main' product of mast cells involved. Histamine acts in large part via a prostanoid-dependent pathway. 5. Approximately 50% of humans and greater than 90% of patients with non-melanoma skin cancer are UVB susceptible for suppression of a contact hypersensitivity response. Neither cytokine polymorphisms nor UVB-induced levels of cis-UCA in irradiated skin have been linked to UVB susceptibility. Patients with basal cell carcinomas (BCC) have an increased dermal mast cell prevalence in non-sun-exposed buttock skin. We propose that mast cells function in humans, as in mice, by initiating immunosuppression and, thereby, allowing a permissive environment for BCC development.

Communications: high dermal mast cell prevalence is a predisposing factor for basal cell carcinoma in humans

Ultraviolet B radiation (280-320 nm) can initiate skin cancer as well as suppress the immune system, thereby preventing the rejection of ultraviolet-B-induced tumors. Recently we reported that there was not only a correlation but also a functional link between dermal mast cell prevalence and susceptibility to ultraviolet-B-induced systemic immunosuppression in multiple strains of mice. In this study, we investigated whether increased dermal mast cell prevalence is a significant predisposing factor for basal cell carcinoma development in humans. In 21 Danes with a history of basal cell carcinoma and 20 control subjects of similar age, sex, skin phototype, and recreational sun exposure over the past 12 mo, dermal mast cell prevalence was quantified on non-sun-exposed buttock skin. We investigated this skin site in order to avoid any changes in mast cell prevalence caused by sun exposure and assumed that the prevalence of mast cells in buttock skin correlated with that at sun-exposed sites at critical times in the development of basal cell carcinomas. Patients with a history of basal cell carcinoma had a significantly higher median dermal mast cell prevalence than control subjects (p = 0.01, Mann-Whitney U ). No correlation was observed between dermal mast cell prevalence and age of basal cell carcinoma patients and control subjects. These results suggest that increased dermal mast cell prevalence is a predisposing factor for basal cell carcinoma development in humans. We hypothesize that mast cells function in humans, as in mice, by initiating immunosuppression and thereby allowing a permissive environment for basal cell carcinoma development.

Mast cells in UV-B-induced immunosuppression

Degranulating dermal mast cells in UV-B-irradiated skin have been implicated for many years in the mechanisms of irradiation erythema. There is now considerable evidence that dermal mast cells are important to the processes by which both UV-B radiation and cis-urocanic acid (cis-UCA) suppress immune responses to sensitizing antigens applied to non-irradiated/non-cis-UCA-exposed sites. Mast-cell-depleted mice are resistant to the immunosuppressive effects of UV-B radiation and cis-UCA for 'systemic' immunomodulation. However, these mice gain responsiveness if the dorsal skin is reconstituted six weeks prior to irradiation or cis-UCA administration at that site with cultured bone-marrow-derived mast cells from +/+ mice. The molecular triggers for initiating mast-cell degranulation are being actively sought. Evidence suggests that histamine, and not tumour necrosis factor alpha, is the major mast-cell product that signals altered immune responses to sensitizing antigens applied to non-irradiated, non-cis-UCA-exposed sites. Histamine may have multiple roles, but experiments with indomethacin administered to mice have shown that one process involves induction of prostanoid production.

Ultraviolet B-induced suppression of immune responses in interleukin-4-/- mice: relationship to dermal mast cells

Ultraviolet B radiation is immunosuppressive by multiple mechanisms. In interleukin-4-/- mice, ultraviolet B radiation was not able to suppress delayed-type hypersensitivity or contact hypersensitivity responses when the sensitizing antigen was applied to nonirradiated sites. In contrast, ultraviolet B significantly suppressed contact hypersensitivity responses to haptens applied to irradiated sites in interleukin-4-/- mice. In mast cell depleted Wf/Wf mice, ultraviolet B radiation also significantly suppressed contact hypersensitivity responses to sensitizing antigens applied to irradiated but not to unirradiated sites. In both interleukin-4-/- mice and Wf/Wf mice, the mast cell product, histamine, was immunosuppressive implicating mast cells as the dysfunctional cell in interleukin-4-/- mice. The prevalence of dermal mast cells was similar in wild-type and interleukin-4-/- mice. Dermal mast cells of interleukin-4-/- mice, however, express very low levels of c-kit and did not significantly degranulate in response to ultraviolet B. Ultraviolet radiation induced significant and similar levels of serum interleukin-10 in wild-type and interleukin-4-/- mice. We conclude that interleukin-4 indirectly affects ultraviolet B suppression of contact hypersensitivity and delayed-type hypersensitivity responses to sensitizing antigens applied at sites other than those irradiated by providing a critical differentiative signal for dermal mast cells. This study further emphasizes the central role of mast cells in the initial processes by which ultraviolet B radiation is immunomodulatory for immune responses to sensitizing antigens applied to nonirradiated sites.

A critical role for dermal mast cells in cis-urocanic acid-induced systemic suppression of contact hypersensitivity responses in mice

Many studies have implicated cis-urocanic acid (cis-UCA) in UVB-induced immunomodulation. The strongest evidence came from studies in mice whereby a cis-UCA antibody blocked UVB-induced suppression of delayed-type hypersensitivity responses. Furthermore, in several studies, the cis-UCA antibody at least partially reversed UVB suppression of contact hypersensitivity responses. Previous reports suggested that cis-UCA was immunomodulatory through its effects on keratinocytes, Langerhans cells, fibroblasts, T lymphocytes, natural killer cells and monocytes/macrophages. As dermal mast cells were recently demonstrated to be critical to UVB-induced systemic suppression of certain delayed-type and contact hypersensitivity responses, we investigated whether they were involved in the processes by which cis-UCA was immunomodulatory. Not only was there a correlation between dermal mast cell prevalence and the degree of susceptibility of different strains of mice to the immunomodulatory effects of cis-UCA, there was also a functional link. Mast cell-depleted Wf/Wf mice were rendered susceptible to immunomodulation by cis-UCA injected subcutaneously only after their dorsal skin had been reconstituted with bone marrow-derived mast cell precursors. These studies suggest that mast cells are critical to the processes by which cis-UCA suppresses systemic contact hypersensitivity responses to the hapten, trinitrochlorobenzene, in mice.

Age-related changes in dermal mast cell prevalence in BALB/c mice: functional importance and correlation with dermal mast cell expression of Kit

Differences in dermal mast cell prevalence for adult mice of different strains have been reported previously. In this study, the dermal mast cell prevalence for BALB/c and C57BL/6 mice at 6 weeks of age was similar but as BALB/c mice matured from 6 to 10 weeks of age, their dermal mast cell prevalence halved. In contrast, there was no significant difference in the dermal mast cell prevalence of 6- and 10-week-old C57BL/6 mice. These differences determined the degree of susceptibility of BALB/c and C57BL/6 mice of different ages to UVB (UV radiation of wavelength 280-320 nm)-induced systemic immunosuppression. Expression of the receptor for stem cell factor, Kit protein, was examined on mast cells under conditions in which the dermal mast cell prevalence varied. A significant correlation was observed between Kit expression by mast cells from adult BALB/c, DBA/2 and C57BL/6 mice and dermal mast cell prevalence. In BALB/c mice, mast cell Kit expression decreased as the mice matured from 6 to 10 weeks of age and correlated with the reduction in dermal mast cell numbers. Kit levels on dermal mast cells from C57BL/6 mice were consistently higher than on mast cells from BALB/c mice although significant reductions in Kit were also measured with ageing from 6 to 10 weeks. We hypothesize that regardless of the extent of Kit expression, the dermal mast cell populations were maximally expanded in C57BL/6 mice. We suggest that BALB/c mice of 6 and 10 weeks of age are useful hosts in which to quantitatively evaluate mast cell involvement in a range of functional assays involving skin.

TNF modulates susceptibility to UVB-induced systemic immunomodulation in mice by effects on dermal mast cell prevalence

The mechanisms by which UV radiation is immunosuppressive are controversial, but there is growing evidence that processes of UVB-induced suppression of the immune response towards a sensitizing antigen are different if this antigen is applied to irradiated compared with non-irradiated sites. Consistent with this is our recent observation (Hart et al., J. Exp. Med. 1998. 187: 2045-2053) that the prevalence of dermal mast cells determines the extent of susceptibility of different mouse strains to UVB-induced systemic, but not local, immunosuppression. Using C57BL/6 and BALB/c mice exposed to low and high doses of UVB, respectively, in the presence of a polyclonal anti-TNF antibody, we found that TNF is directly involved as a mediator in the suppression by UVB of local immune responses. To determine whether TNF indirectly regulates UVB-induced systemic immunomodulation by altering the prevalence of dermal mast cells, dermal mast cell numbers in gene-targeted mice deficient in TNF or TNF receptors (p55/p75-/- mice) were quantified by video image analysis. A reduced dermal mast cell prevalence in these mice correlated with decreased susceptibility for systemic immunosuppression caused by UVB. We hypothesize that TNF is one molecule that controls dermal mast cell prevalence by as yet unknown mechanisms. However, it is the mediators released from mast cells upon UVB-induced degranulation, which do not include TNF, that directly signal suppressive events relevant to systemic immunosuppression.

Dermal mast cells determine susceptibility to ultraviolet B-induced systemic suppression of contact hypersensitivity responses in mice

Different strains of mice have varying susceptibilities to ultraviolet radiation (UV) of wavelength 280-320 nm (UVB) for 50% suppression of systemic contact hypersensitivity (CHS) responses. Prevalence of histamine-staining dermal mast cells in different strains of mice (C57BL/ 6J, DBA/2, BALB/c) correlated directly with their susceptibility to UVB-induced systemic immunosuppression. BALB/c mice carrying Uvs1, a major locus for susceptibility to UV-induced immunosuppression, contained greater numbers of dermal mast cells than BALB/c mice of the same parental origin. Strains of mice that were differentiated on their susceptibility to UVB-induced downregulation of systemic CHS responses were similar in their susceptibility to histamine-induced immunomodulation. Histamine, but not UVB irradiation, decreased systemic CHS responses in mast cell-depleted mice (W f/W f). Reconstitution of the dorsal skin of W f/W f mice with bone marrow-derived mast cell precursors from nonmutant mice rendered the mice susceptible to UVB irradiation for systemic suppression of CHS responses. UVB irradiation did not suppress delayed type hypersensitivity responses to allogeneic spleen cells in W f/W f mice. In contrast, UV irradiation suppressed CHS responses in W f/W f mice when hapten was applied to the irradiated site. This study demonstrates that dermal mast cells are necessary for the induction of systemic suppression of CHS responses by UVB radiation, and suggests that mast cell- derived histamine is one component of this UVB-induced systemic immunosuppression.

Immunocytochemical assay for oestrogen receptor in fine needle aspirates of breast cancer by video image analysis

Assessment of heterogeneity in oestrogen receptor (ER) expression aims to improve prediction of prognosis and treatment assignment in breast cancer. Current assessments are performed manually and are subjective. Automated image analysis as described here objectively quantitates ER in breast cancer nuclei obtained by needle aspiration. ER was visualised by ERICA with diaminobenzidine (DAB) substrate. Various indices of ER positivity were derived from the integrated density and average density measurements of nuclear DAB. Each index was compensated for background staining by non-specific antibody binding and endogenous peroxidase activity. Total nuclear ER content (integrated optical density of stain) was strongly associated with the biopsy ER concentration determined by saturation analysis of radioligand binding (DCC), P less than 0.005. Nuclear ER concentration by image analysis (mean optical density of stain) was not associated with the DCC measurement of ER concentration, P greater than 0.05. This was attributed to technical artefacts of cytocentrifugation. Using threshold values of 5% positive cells and 10 fmol mg-1 concordance of assignment of ER status by image analysis with the DCC assay was 91%, sensitivity was 89% and specificity 100%. It was concluded that image analysis is an appropriate, easy and economic method for determining the nuclear ER status of aspirated cancer cells. Image analysis has the potential to become a powerful diagnostic tool in the assessment of hormone receptor status of breast cancer patients.