Shirley B. Russell

Preterm low birth weight and periodontal disease among African Americans

African Americans consistently experience higher rates of preterm and low birth weight (LBW) deliveries than do whites. LBW and preterm infants are more likely to die before their first birthday and survivors may suffer from a number of health problems. Therefore, identification of modifiable risk factors for preterm deliveries and LBW has considerable public health significance. Pregnant womens poor periodontal healtlh is emerging as one such factor. Maternal clinical periodontal status and bacteriologic and immunologic profiles related to periodontal disease have been associateted with risk of fetal growth and preterm LBW, and periodontal treatment during pregnancy has reduced the incidence of preterm deliveries. This article reviews the literature on the above association and presents data from a previously published prospective study of predominantly African Americans to show that preterm LBW deliveries are associated with higher midtrimester maternal serum antibody levels against Porphyromonas gingivalis.

Chemokine and chemokine receptor expression in keloid and normal fibroblasts

Keloids are benign collagenous tumors that occur during dermal wound healing in genetically predisposed individuals. The lesions are characterized by over‐proliferation of fibroblasts, some leukocyte infiltration, and prolonged high rates of collagen synthesis. To determine whether leukocyte chemoattractants or chemokines are participating in this disease process, immunohistochemical staining for the CXC chemokine, MGSA/GROα, and its receptor, CXCR2, was performed on tissue from keloids, hypertrophic scars and normal skin. Immunoreactive MGSA/GROα was not observed in hypertrophic scars or normal dermis, but was present in some myofibroblasts and lymphocytes in nodular areas of the keloid samples. This staining positively correlated with the degree of inflammatory infiltrate in the lesions. Keloids, but not hypertrophic scars or normal dermis, also exhibited intensive immunoreactivity for the CXCR2 receptor in endothelial cells and inflammatory infiltrates with occasional staining of myofibroblasts. In contrast, cultured fibroblasts from either keloids or normal skin did not express detectable amounts of mRNA for MGSA/GRO or CXCR2, although interleukin‐1 strongly induced MGSA/GRO mRNA in both cell types. Interleukin‐1 induction of MGSA/GRO was inhibited by glucocorticoid in normal and keloid fibroblasts, and the effect was more pronounced in keloid fibroblasts. This event was not correlated with inhibition of nuclear activation of NF‐κB, AP‐1 or Sp1, and might therefore be mediated by another mechanism such as decreased mRNA stability or transcriptional repression through the glucocorticoid response element in the MGSA/GRO promoter. Data from in vitro wounding experiments with cultured normal and keloid fibroblasts indicate that there were no significant differences in MGSA/GRO or CXCR2 receptor levels between normal and keloid fibroblasts. We also show that cultured keloid fibroblasts exhibit a delayed wound healing response. We postulate that the inflammatory component is important in development of keloid lesions and chemotactic cytokines may participate in this process.

Fibroblast heterogeneity in glucocorticoid regulation of collagen metabolism: Genetic or epigenetic?

SummaryCultured fibroblasts derived from normal human dermis show a consistent 62% inhibition of collagen synthesis by hydrocortisone, whereas cultures derived from keloids average only 30% inhibition and show a much larger strain to strain variation ranging from 75% inhibition to 49% stimulation. Examination of fibroblast clones indicates that this high variation among keloid strains is not due to differences in the proportion of normal and keloid cells in the mass culture populations. Small but significant differences in the effect of hydrocortisone on collagen deposition are also seen among these clonal populations, but are not related to the type of tissue from which cultures were derived. Two to three-fold differences among clones derived from a single individual were observed, possibly suggesting functional heterogeneity of dermal fibroblasts with regard to collagen metabolism under control conditions and in response to hydrocortisone. However, this variation among clones may simply reflect differences in clonal growth, inasmuch as both collagen synthesis and deposition, and the effect of hydrocortisone on these processes, are strongly affected by population density.

Variation in Prolyl Hydroxylase Activity of Keloid-Derived and Normal Human Fibroblasts in Response to Hydrocortisone and Ascorbic Acid

The effects of ascorbic acid and hydrocortisone on activity of prolyl hydroxylase in fibroblasts from keloid and normal human dermis were investigated and compared to the effects of these agents on collagen synthesis. Prolyl hydroxylase activity in normal fibroblasts grown to confluency in 1.5 microM hydrocortisone was approximately half that of cells grown without the steroid. The concentration of hydrocortisone effective in reducing enzyme activity was the same as that for reducing the rate of collagen synthesis; a half-maximal effect on both parameters was achieved at 10(-7) M. Hydrocortisone lowered enzyme activity through most of the culture cycle. Fibroblasts derived from keloids were significantly less subject to hydrocortisone-mediated reduction of prolyl hydroxylase activity and rate of collagen synthesis. This difference between keloid and normal cells was dependent on the simultaneous presence of ascorbic acid and hydrocortisone. These data suggest that the defect in wound healing that results in keloid formation is associated with a change in a regulatory mechanism that controls the rate of collagen synthesis and is sensitive to physiological levels of hydrocortisone. Continuous culture of fibroblasts in medium supplemented with ascorbic acid also lowered prolyl hydroxylase activity. Unlike the effect of hydrocortisone, growth in ascorbate increased the rate of collagen synthesis and affected keloid and normal strains equally.

Pleiotropic Effects of Immune Responses Explain Variation in the Prevalence of Fibroproliferative Diseases.

Many diseases are differentially distributed among human populations. Differential selection on genetic variants in ancestral environments that coincidentally predispose to disease can be an underlying cause of these unequal prevalence patterns. Selected genes may be pleiotropic, affecting multiple phenotypes and resulting in more than one disease or trait. Patterns of pleiotropy may be helpful in understanding the underlying causes of an array of conditions in a population. For example, several fibroproliferative diseases are more prevalent and severe in populations of sub-Saharan ancestry. We propose that this disparity is due to selection for an enhanced Th2 response that confers resistance to helminthic infections, and concurrently increases susceptibility to fibrosis due to the profibrotic action of Th2 cytokines. Many studies on selection of Th2-related genes for host resistance to helminths have been reported, but the pleiotropic impact of this selection on the distribution of fibrotic disorders has not been explicitly investigated. We discuss the disproportionate occurrence of fibroproliferative diseases in individuals of African ancestry and provide evidence that adaptation of the immune system has shaped the genetic structure of these human populations in ways that alter the distribution of multiple fibroproliferative diseases.

Evidence of selection as a cause for racial disparities in fibroproliferative disease

Fibroproliferative diseases are common complex traits featuring scarring and overgrowth of connective tissue which vary widely in presentation because they affect many organ systems. Most fibroproliferative diseases are more prevalent in African-derived populations than in European populations, leading to pronounced health disparities. It is hypothesized that the increased prevalence of these diseases in African-derived populations is due to selection for pro-fibrotic alleles that are protective against helminth infections. We constructed a genetic risk score (GRS) of fibroproliferative disease risk-increasing alleles using 147 linkage disequilibrium-pruned variants identified through genome-wide association studies of seven fibroproliferative diseases with large African-European prevalence disparities. A comparison of the fibroproliferative disease GRS between 1000 Genomes Phase 3 populations detected a higher mean GRS in AFR (mean = 148 risk alleles) than EUR (mean = 136 risk alleles; T-test p-value = 1.75x10-123). To test whether differences in GRS burden are systematic and may be due to selection, we employed the quantitative trait loci (QTL) sign test. The QTL sign test result indicates that population differences in risk-increasing allele burdens at these fibroproliferative disease variants are systematic and support a model featuring selective pressure (p-value = 0.011). These observations were replicated in an independent sample and were more statistically significant (T-test p-value = 7.26x10-237, sign test p-value = 0.015). This evidence supports the role of selective pressure acting to increase frequency of fibroproliferative alleles in populations of African relative to European ancestry populations.

Assay of prolyl hydroxylase in cultured fibroblast monolayers

Abstract Prolyl hydroxylase may be assayed in cultured cell monolayers after a cold acetone treatment or air-drying. Enzyme activity of dried cells is stable when cell monolayers are stored frozen and desiccated, thus permitting simultaneous assay of cells harvested at different times, e.g., on different days of a culture cycle. Uniformity of cell monolayers permits use of separate dishes for assay of protein or DNA to determine specific enzyme activity. This procedure greatly facilitates harvesting and assay of cells for a variety of biochemical measurements.