High-throughput quantitation of SARS-CoV-2 antibodies in a single-dilution homogeneous assay

SARS-CoV-2 emerged in late 2019 and has since spread around the world, causing a pandemic of the respiratory disease COVID-19. Detecting antibodies against the virus is an essential tool for tracking infections and developing vaccines. Such tests, primarily utilizing the enzyme-linked immunosorbent assay (ELISA) principle, can be either qualitative (reporting positive/negative results) or quantitative (reporting a value representing the quantity of specific antibodies). Quantitation is vital for determining stability or decline of antibody titers in convalescence, efficacy of different vaccination regimens, and detection of asymptomatic infections. Quantitation typically requires two-step ELISA testing, in which samples are first screened in a qualitative assay and positive samples are subsequently analyzed as a dilution series. To overcome the throughput limitations of this approach, we developed a simpler and faster system that is highly automatable and achieves quantitation in a single-dilution screening format with sensitivity and specificity comparable to those of ELISA.

Problematic alcohol use associates with sodium channel and clathrin linker 1 (SCLT1) in trauma-exposed populations

Excessive alcohol use is extremely prevalent in the United States, particularly among trauma-exposed individuals. While several studies have examined genetic influences on alcohol use and related problems, this has not been studied in the context of trauma-exposed populations. We report results from a genome-wide association study of alcohol consumption and associated problems as measured by the alcohol use disorders identification test (AUDIT) in a trauma-exposed cohort. Results indicate a genome-wide significant association between total AUDIT score and rs1433375 [N = 1036, P = 2.61 × 10^-8 (dominant model), P = 7.76 × 10^-8 (additive model)], an intergenic single-nucleotide polymorphism located 323 kb upstream of the sodium channel and clathrin linker 1 (SCLT1) at 4q28. rs1433375 was also significant in a meta-analysis of two similar, but independent, cohorts (N = 1394, P = 0.0004), the Marine Resiliency Study and Systems Biology PTSD Biomarkers Consortium. Functional analysis indicated that rs1433375 was associated with SCLT1 gene expression and cortical-cerebellar functional connectivity measured via resting state functional magnetic resonance imaging. Together, findings suggest a role for sodium channel regulation and cerebellar functioning in alcohol use behavior. Identifying mechanisms underlying risk for problematic alcohol use in trauma-exposed populations is critical for future treatment and prevention efforts.

A genome-wide identified risk variant for PTSD is a methylation quantitative trait locus and confers decreased cortical activation to fearful faces

Genetic factors appear to be highly relevant to predicting differential risk for the development of post-traumatic stress disorder (PTSD). In a discovery sample, we conducted a genome-wide association study (GWAS) for PTSD using a small military cohort (Systems Biology PTSD Biomarkers Consortium; SBPBC, N = 147) that was designed as a case-controlled sample of highly exposed, recently returning veterans with and without combat-related PTSD. A genome-wide significant single nucleotide polymorphism (SNP), rs717947, at chromosome 4p15 (N = 147, β = 31.34, P = 1.28 × 10(-8) ) was found to associate with the gold-standard diagnostic measure for PTSD (the Clinician Administered PTSD Scale). We conducted replication and follow-up studies in an external sample, a larger urban community cohort (Grady Trauma Project, GTP, N = 2006), to determine the robustness and putative functionality of this risk variant. In the GTP replication sample, SNP rs717947 associated with PTSD diagnosis in females (N = 2006, P = 0.005), but not males. SNP rs717947 was also found to be a methylation quantitative trait locus (meQTL) in the GTP replication sample (N = 157, P = 0.002). Further, the risk allele of rs717947 was associated with decreased medial and dorsolateral cortical activation to fearful faces (N = 53, P < 0.05) in the GTP replication sample. These data identify a genome-wide significant polymorphism conferring risk for PTSD, which was associated with differential epigenetic regulation and with differential cortical responses to fear in a replication sample. These results may provide new insight into understanding genetic and epigenetic regulation of PTSD and intermediate phenotypes that contribute to this disorder.

DNA extracted from saliva for methylation studies of psychiatric traits: evidence tissue specificity and relatedness to brain

DNA methylation has become increasingly recognized in the etiology of psychiatric disorders. Because brain tissue is not accessible in living humans, epigenetic studies are most often conducted in blood. Saliva is often collected for genotyping studies but is rarely used to examine DNA methylation because the proportion of epithelial cells and leukocytes varies extensively between individuals. The goal of this study was to evaluate whether saliva DNA is informative for studies of psychiatric disorders. DNA methylation (HumanMethylation450 BeadChip) was assessed in saliva and blood samples from 64 adult African Americans. Analyses were conducted using linear regression adjusted for appropriate covariates, including estimated cellular proportions. DNA methylation from brain tissues (cerebellum, frontal cortex, entorhinal cortex, and superior temporal gyrus) was obtained from a publically available dataset. Saliva and blood methylation was clearly distinguishable though there was positive correlation overall. There was little correlation in CpG sites within relevant candidate genes. Correlated CpG sites were more likely to occur in areas of low CpG density (i.e., CpG shores and open seas). There was more variability in CpG sites from saliva than blood, which may reflect its heterogeneity. Finally, DNA methylation in saliva appeared more similar to patterns from each of the brain regions examined overall than methylation in blood. Thus, this study provides a framework for using DNA methylation from saliva and suggests that DNA methylation of saliva may offer distinct opportunities for epidemiological and longitudinal studies of psychiatric traits.

Cross-cultural gene- environment interactions in depression, post-traumatic stress disorder, and the cortisol awakening response: FKBP5 polymorphisms and childhood trauma in South Asia

Despite increased attention to global mental health, psychiatric genetic research has been dominated by studies in high-income countries, especially with populations of European descent. The objective of this study was to assess single nucleotide polymorphisms (SNPs) in the FKBP5 gene in a population living in South Asia. Among adults in Nepal, depression was assessed with the Beck Depression Inventory (BDI), post-traumatic stress disorder (PTSD) with the PTSD Checklist-Civilian Version (PCL-C), and childhood maltreatment with the Childhood Trauma Questionnaire (CTQ). FKBP5 SNPs were genotyped for 682 participants. Cortisol awakening response (CAR) was assessed in a subsample of 118 participants over 3 days. The FKBP5 tag-SNP rs9296158 showed a main effect on depressive symptoms (p = 0.03). Interaction of rs9296158 and childhood maltreatment predicted adult depressive symptoms (p = 0.02) but not PTSD. Childhood maltreatment associated with endocrine response in individuals homozygous for the A allele, demonstrated by a negative CAR and overall hypocortisolaemia in the rs9296158 AA genotype and childhood maltreatment group (p < 0.001). This study replicated findings related to FKBP5 and depression but not PTSD. Gene-environment studies should take differences in prevalence and cultural significance of phenotypes and exposures into account when interpreting cross-cultural findings.

Early intervention following trauma may mitigate genetic risk for PTSD in civilians: a pilot prospective emergency department study

BACKGROUND

Civilian posttraumatic stress disorder (PTSD) and combat PTSD are major public health concerns. Although a number of psychosocial risk factors have been identified related to PTSD risk, there are no accepted, robust biological predictors that identify who will develop PTSD or who will respond to early intervention following trauma. We wished to examine whether genetic risk for PTSD can be mitigated with an early intervention.

METHOD

65 emergency department patients recruited in 2009-2010 at Grady Memorial Hospital in Atlanta, Georgia, who met criterion A of DSM-IV PTSD received either 3 sessions of an exposure intervention, beginning in the emergency department shortly after trauma exposure or assessment only. PTSD symptoms were assessed 4 and 12 weeks after trauma exposure. A composite additive risk score was derived from polymorphisms in 10 previously identified genes associated with stress-response (ADCYAP1R1, COMT, CRHR1, DBH, DRD2, FAAH, FKBP5, NPY, NTRK2, and PCLO), and gene x treatment effects were examined. The intervention included 3 sessions of imaginal exposure to the trauma memory and additional exposure homework. The primary outcome measure was the PTSD Symptom Scale-Interview Version or DSM-IV-based PTSD diagnosis in patients related to genotype and treatment group.

RESULTS

A gene x intervention x time effect was detected for individual polymorphisms, in particular the PACAP receptor, ADCYAP1R1, as well as with a combined genotype risk score created from independent SNP markers. Subjects who did not receive treatment had higher symptoms than those who received intervention. Furthermore, subjects with the "risk" genotypes who did not receive intervention had higher PTSD symptoms compared to those with the "low-risk" or "resilience" genotypes or those who received intervention. Additionally, PTSD symptoms correlated with level of genetic risk at week 12 (P < .005) in the assessment-only group, but with no relationship in the intervention group, even after controlling for age, sex, race, education, income, and childhood trauma. Using logistic regression, the number of risk alleles was significantly associated with likelihood of PTSD diagnosis at week 12 (P < .05).

CONCLUSIONS

This pilot prospective study suggests that combined genetic variants may serve to predict those most at risk for developing PTSD following trauma. A psychotherapeutic intervention initiated in the emergency department within hours of the trauma may mitigate this risk. The role of genetic predictors of risk and resilience should be further evaluated in larger, prospective intervention and prevention trials.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00895518.

Follow-up and extension of a prior genome-wide association study of posttraumatic stress disorder: gene × environment associations and structural magnetic resonance imaging in a highly traumatized African-American civilian population

Follow-up and Extension of a Prior Genome-wide Association Study of Posttraumatic Stress Disorder: Gene × Environment Associations and Structural Magnetic Resonance Imaging in a Highly Traumatized African-American Civilian Population

Methylation quantitative trait loci (meQTLs) are consistently detected across ancestry, developmental stage, and tissue type

Background

Individual genotypes at specific loci can result in different patterns of DNA methylation. These methylation quantitative trait loci (meQTLs) influence methylation across extended genomic regions and may underlie direct SNP associations or gene-environment interactions. We hypothesized that the detection of meQTLs varies with ancestral population, developmental stage, and tissue type. We explored this by analyzing seven datasets that varied by ancestry (African American vs. Caucasian), developmental stage (neonate vs. adult), and tissue type (blood vs. four regions of postmortem brain) with genome-wide DNA methylation and SNP data. We tested for meQTLs by constructing linear regression models of methylation levels at each CpG site on SNP genotypes within 50 kb under an additive model controlling for multiple tests.

Results

Most meQTLs mapped to intronic regions, although a limited number appeared to occur in synonymous or nonsynonymous coding SNPs. We saw significant overlap of meQTLs between ancestral groups, developmental stages, and tissue types, with the highest rates of overlap within the four brain regions. Compared with a random group of SNPs with comparable frequencies, meQTLs were more likely to be 1) represented among the most associated SNPs in the WTCCC bipolar disorder results and 2) located in microRNA binding sites.

Conclusions

These data give us insight into how SNPs impact gene regulation and support the notion that peripheral blood may be a reliable correlate of physiological processes in other tissues.

Accounting for population stratification in DNA methylation studies

DNA methylation is an important epigenetic mechanism that has been linked to complex diseases and is of great interest to researchers as a potential link between genome, environment, and disease. As the scale of DNA methylation association studies approaches that of genome-wide association studies, issues such as population stratification will need to be addressed. It is well-documented that failure to adjust for population stratification can lead to false positives in genetic association studies, but population stratification is often unaccounted for in DNA methylation studies. Here, we propose several approaches to correct for population stratification using principal components (PCs) from different subsets of genome-wide methylation data. We first illustrate the potential for confounding due to population stratification by demonstrating widespread associations between DNA methylation and race in 388 individuals (365 African American and 23 Caucasian). We subsequently evaluate the performance of our PC-based approaches and other methods in adjusting for confounding due to population stratification. Our simulations show that (1) all of the methods considered are effective at removing inflation due to population stratification, and (2) maximum power can be obtained with single-nucleotide polymorphism (SNP)-based PCs, followed by methylation-based PCs, which outperform both surrogate variable analysis and genomic control. Among our different approaches to computing methylation-based PCs, we find that PCs based on CpG sites chosen for their potential to proxy nearby SNPs can provide a powerful and computationally efficient approach to adjust for population stratification in DNA methylation studies when genome-wide SNP data are unavailable.

Inhibition of fear is differentially associated with cycling estrogen levels in women

BACKGROUND

Although the prevalence of posttraumatic stress disorder (PTSD) is twice as high in women as it is in men, the role of estrogen in the risk for PTSD is not well understood. Deficits in fear inhibition and impaired safety signal learning may be biomarkers for PTSD. We examined menstrual cycle phase and serum estradiol levels in naturally cycling women while they were undergoing a novel conditioned inhibition procedure that measured their ability to discriminate between cues representing danger versus safety and to inhibit fear in the presence of safety cues.

METHODS

Sample 1 included healthy participants in whom we compared inhibition of fearpotentiated startle during the follicular (lower estrogen) and luteal (higher estrogen) phases of the menstrual cycle. We used the same paradigm in a traumatized clinical population (sample 2) in whom we compared low versus high estradiol levels.

RESULTS

In both samples, we found that lower estrogen in cycling women was associated with impaired fear inhibition.

LIMITATIONS

In the clinical sample, the low estradiol group was on average older than the high estradiol group owing to the random recruitment approach; we did not exclude participants based on hormonal status or menopause.

CONCLUSION

Our results suggest that the lower estrogen state during normal menstrual cycling may contribute to risk for anxiety disorders through dysregulated fear responses.

Differential Genetic and Epigenetic Regulation of catechol-O-methyltransferase is Associated with Impaired Fear Inhibition in Posttraumatic Stress Disorder

The catechol-O-methyltransferase (COMT) enzyme is critical for the catabolic regulation of synaptic dopamine, resulting in altered cortical functioning. The COMT Val¹⁵⁸Met polymorphism has been implicated in human mental illness, with Met/Met homozygotes associated with increased susceptibility to posttraumatic stress disorder (PTSD). Our primary objective was to examine the intermediate phenotype of fear inhibition in PTSD stratified by COMT genotype (Met/Met, Val/Met, and Val/Val) and differential gene regulation via methylation status at CpG sites in the COMT promoter region. More specifically, we examined the potential interaction of COMT genotype and PTSD diagnosis on fear-potentiated startle during fear conditioning and extinction and COMT DNA methylation levels (as determined using genomic DNA isolated from whole blood). Participants were recruited from medical and gynecological clinics of an urban hospital in Atlanta, GA, USA. We found that individuals with the Met/Met genotype demonstrated higher fear-potentiated startle to the CS− (safety signal) and during extinction of the CS+ (danger signal) compared to Val/Met and Val/Val genotypes. The PTSD+ Met/Met genotype group had the greatest impairment in fear inhibition to the CS− (p = 0.006), compared to Val carriers. In addition, the Met/Met genotype was associated with DNA methylation at four CpG sites, two of which were associated with impaired fear inhibition to the safety signal. These results suggest that multiple differential mechanisms for regulating COMT function – at the level of protein structure via the Val¹⁵⁸Met genotype and at the level of gene regulation via differential methylation – are associated with impaired fear inhibition in PTSD.

Sex dependent influence of a functional polymorphism in steroid 5-α-reductase type 2 (SRD5A2) on post-traumatic stress symptoms

A non-synonymous, single nucleotide polymorphism (SNP) in the gene coding for steroid 5-α-reductase type 2 (SRD5A2) is associated with reduced conversion of testosterone to dihydrotestosterone (DHT). Because SRD5A2 participates in the regulation of testosterone and cortisol metabolism, hormones shown to be dysregulated in patients with PTSD, we examined whether the V89L variant (rs523349) influences risk for post-traumatic stress disorder (PTSD). Study participants (N = 1,443) were traumatized African-American patients of low socioeconomic status with high rates of lifetime trauma exposure recruited from the primary care clinics of a large, urban hospital. PTSD symptoms were measured with the post-traumatic stress symptom scale (PSS). Subjects were genotyped for the V89L variant (rs523349) of SRD5A2. We initially found a significant sex-dependent effect of genotype in male but not female subjects on symptoms. Associations with PTSD symptoms were confirmed using a separate internal replication sample with identical methods of data analysis, followed by pooled analysis of the combined samples (N = 1,443, sex × genotype interaction P < 0.002; males: n = 536, P < 0.001). These data support the hypothesis that functional variation within SRD5A2 influences, in a sex-specific way, the severity of post-traumatic stress symptoms and risk for diagnosis of PTSD.

FKBP5 and attention bias for threat: associations with hippocampal function and shape

IMPORTANCE

The FKBP5 gene product regulates glucocorticoid receptor (GR) sensitivity and hypothalamic-pituitary-adrenal axis functioning and has been associated with many stress-related psychiatric disorders. The study of intermediate phenotypes, such as emotion-processing biases and their neural substrates, provides a way to clarify the mechanisms by which FKBP5 dysregulation mediates risk for psychiatric disorders.

OBJECTIVE

To examine whether allelic variations for a putatively functional single-nucleotide polymorphism associated with FKBP5 gene regulation (rs1360780) would relate differentially to attention bias for threat. this was measured through behavioral response on a dot probe task and hippocampal activation during task performance. Morphologic substrates of differential hippocampal response were also measured.

DESIGN

Cross-sectional study conducted from 2010 to 2012 examining associations between genotype, behavioral response, and neural response (using functional magnetic resonance imaging [fMRI]) on the dot probe; voxel-based morphometry and global and local shape analyses were used to measure structural differences in hippocampi between genotype groups.

SETTING

Participants were recruited from primary care clinics of a publicly funded hospital in Atlanta, Georgia.

PARTICIPANTS

An African American cohort of adults (N = 103) was separated into 2 groups by genotype: one genotype group included carriers of the rs1360780 T allele, which has been associated with increased risk for posttraumatic stress disorder and affective disorders; the other group did not carry this allele. Behavioral data included both sexes (N = 103); the MRI cohort (n = 36) included only women.

MAIN OUTCOME MEASURES

Behavioral and fMRI (blood oxygen level-dependent) response, voxel-based morphometry, and shape analyses.

RESULTS

Carriers of the rs1360780 T allele showed an attention bias toward threat compared with individuals without this allele (F1,90 = 5.19, P = .02). Carriers of this allele demonstrated corresponding increases in hippocampal activation and differences in morphology; global and local shape analyses revealed alterations in hippocampal shape for TT/TC compared with CC genotype groups.

CONCLUSION

Genetic variants of FKBP5 may be associated with risk for stress-related psychiatric disorders via differential effects on hippocampal structure and function, resulting in altered attention response to perceived threat.

ADCYAP1R1 genotype associates with post-traumatic stress symptoms in highly traumatized African-American females

Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptor (PAC1) play a critical role in biological processes that mediate stress response and have been implicated in psychological outcome following trauma. Our previous work [Ressler et al. (2011); Nature 470:492-497] demonstrated that a variant, rs2267735, in the gene encoding PAC1 (ADCYAP1R1) is associated with post-traumatic stress disorder (PTSD) in a primarily African-American cohort of highly traumatized females. We sought to extend and replicate our previous finding in a similarly trauma-exposed, replicate sample of 1,160 African-American adult male and female patients. Self-reported psychiatric measures were collected, and DNA was obtained for genetic analysis. Using linear regression models to test for association with PTSD symptom severity under an additive (allelic) model, we found a genotype × trauma interaction in females (P < 0.001), but not males (P > 0.1); however, there was no main effect of genotype as in our previous study. The observed interaction suggests a genetic association that increases with the degree of trauma exposure in females only. This interaction remained significant in females, but not males, after controlling for age (P < 0.001), income (P < 0.01), past substance abuse (P < 0.001), depression severity (P = 0.02), or child abuse (P < 0.0005), and all five combined (P = 0.01). No significant effects of genotype (or interactions) were found when modeling depression severity when controlling for comorbid PTSD symptom severity (P > 0.1), demonstrating the relative specificity of this variant for PTSD symptoms. A meta-analysis with the previously reported African-American samples revealed a strong association between PTSD symptom severity and the interaction between trauma and genotype in females (N = 1424, P < 0.0001).

Adcyap1r1 genotype, posttraumatic stress disorder, and depression among women exposed to childhood maltreatment

BACKGROUND

A growing literature indicates that genetic variation, in combination with adverse early life experiences, shapes risk for later mental illness. Recent work also suggests that molecular variation at the ADCYAP1R1 locus is associated with posttraumatic stress disorder (PTSD) in women. We sought to test whether childhood maltreatment (CM) interacts with ADCYAP1R1 genotype to predict PTSD in women.

METHODS

Data were obtained from 495 adult female participants from the Detroit Neighborhood Health Study. Genotyping of rs2267735, an ADCYAP1R1 variant, was conducted via TaqMan assay. PTSD, depression, and CM exposure were assessed via structured interviews. Main and interacting effects of ADCYAP1R1 and CM levels on past month PTSD and posttraumatic stress (PTS) severity were examined using logistic regression and a general linear model, respectively. As a secondary analysis, we also assessed main and interacting effects of ADCYAP1R1 and CM variation on risk of past-month depression diagnosis and symptom severity.

RESULTS

No significant main effects were observed for ADCYAP1R1 genotype on either PTSD/PTS severity. In contrast, a significant ADCYAP1R1 × CM interaction was observed for both past month PTSD and PTS severity, with carriers of the "C" allele showing enhanced risk for these outcomes among women exposed to CM. No significant main or interaction effects were observed for past month depression/depression severity.

CONCLUSIONS

Genetic variation at the ADCYAP1R1 locus interacts with CM to shape risk of later PTSD, but not depression, among women. The molecular mechanisms contributing to this interaction require further investigation.

Family environment and adult resilience: contributions of positive parenting and the oxytocin receptor gene

BACKGROUND

Abundant research shows that childhood adversity increases the risk for adult psychopathology while research on influences of positive family environment on risk for psychopathology is limited. Similarly, a growing body of research examines genetic and gene by environment predictors of psychopathology, yet such research on predictors of resilience is sparse.

OBJECTIVES

We examined the role of positive factors in childhood family environment (CFE) and the OXTR rs53576 genotype in predicting levels of adult resilient coping and positive affect. We also examined whether the relationship between positive factors in the CFEs and adult resilient coping and positive affect varied across OXTR rs53576 genotype.

METHODS

We gathered self-report data on childhood environment, trauma history, and adult resilience and positive affect in a sample of 971 African American adults.

RESULTS

We found that positive CFE was positively associated with higher levels of resilient coping and positive affect in adulthood after controlling for childhood maltreatment, other trauma, and symptoms of posttraumatic stress disorder. We did not find a direct effect of OXTR 53576 on a combined resilient coping/positive-affect-dependent variable, but we did find an interaction of OXTR rs53576 with family environment.

CONCLUSIONS

Our data suggest that even in the face of adversity, positive aspects of the family environment may contribute to resilience. These results highlight the importance of considering protective developmental experiences and the interaction of such experiences with genetic variants in risk and resilience research.

Allele-specific FKBP5 DNA demethylation mediates gene-childhood trauma interactions

Although the fact that genetic predisposition and environmental exposures interact to shape development and function of the human brain and, ultimately, the risk of psychiatric disorders has drawn wide interest, the corresponding molecular mechanisms have not yet been elucidated. We found that a functional polymorphism altering chromatin interaction between the transcription start site and long-range enhancers in the FK506 binding protein 5 (FKBP5) gene, an important regulator of the stress hormone system, increased the risk of developing stress-related psychiatric disorders in adulthood by allele-specific, childhood trauma-dependent DNA demethylation in functional glucocorticoid response elements of FKBP5. This demethylation was linked to increased stress-dependent gene transcription followed by a long-term dysregulation of the stress hormone system and a global effect on the function of immune cells and brain areas associated with stress regulation. This identification of molecular mechanisms of genotype-directed long-term environmental reactivity will be useful for designing more effective treatment strategies for stress-related disorders.

Estrogen levels are associated with extinction deficits in women with posttraumatic stress disorder

BACKGROUND

Women are twice as likely to develop posttraumatic stress disorder (PTSD) than men. As shown in our previous work, the inability to suppress fear responses in safe conditions may be a biomarker for PTSD. Low estrogen in naturally cycling women is associated with deficits in fear extinction. On the basis of these findings, we have now examined the influence of estrogen levels on fear extinction in women with and without PTSD.

METHODS

We measured fear-potentiated startle during fear conditioning and extinction in women. The study sample (N = 81) was recruited from an urban, highly traumatized civilian population at Grady Memorial Hospital in Atlanta, Georgia. We assayed serum estrogen levels and used a median split to divide the sample into high and low estradiol (E(2)) groups. Seventeen of 41 women (41.5%) in the low E(2) group and 15 of 40 women (37.5%) met criteria for PTSD in the high E(2) group.

RESULTS

The results showed that all groups had equivalent levels of fear conditioning. However, we found significant interaction effects between high versus low E(2) groups and PTSD diagnosis [F(1,71) = 4.55, p < .05] on extinction. Among women with low estrogen levels, fear-potentiated startle was higher during extinction in the PTSD group compared with traumatized control women [F(1,38) = 5.04, p < .05]. This effect was absent in the High E(2) group.

CONCLUSION

This study suggests that low estrogen may be a vulnerability factor for development of PTSD in women with trauma histories. Research on the role of estrogen in fear regulation may provide insight into novel treatment strategies for PTSD.

Acute and posttraumatic stress symptoms in a prospective gene x environment study of a university campus shooting

CONTEXT

The serotonin transporter (SLC6A4) has been associated with several stress-related syndromes including posttraumatic stress disorder (PTSD). The ability to detect meaningful associations is largely dependent on reliable measures of preexisting trauma.

OBJECTIVE

To study the association of genetic variants within SLC6A4 with acute and posttraumatic stress symptoms in a civilian cohort with known levels of preexisting trauma and PTSD symptoms collected prior to a shared index traumatic event.

DESIGN

Ongoing longitudinal study.

SETTING

On February 14, 2008, a lone gunman shot multiple people on the campus of Northern Illinois University in DeKalb, Illinois, killing 5 and wounding 21. As part of an ongoing longitudinal study on that campus, a cohort of female undergraduate students, interviewed prior to the shooting, completed follow-up trauma-related measures including PTSD symptom severity (follow-up survey was launched 17 days postshooting; n = 691). To obtain DNA, salivary samples were collected from a subset of the original study population based on willingness to participate (n = 276).

PARTICIPANTS

Two hundred four undergraduate women.

MAIN OUTCOME MEASURES

SLC6A4 polymorphisms STin2, 5-HTTLPR, and rs25531 were genotyped in 235 individuals.

RESULTS

We found that although the STin2 variant and 5-HTTLPR alone did not associate with increased PTSD symptoms, rs25531 and the 5-HTTLPR multimarker genotype (combined 5-HTTLPR and rs25531) were associated with significantly increased acute stress disorder symptoms at 2 to 4 weeks postshooting (n = 161; P < .05). This association remained significant when controlling for race and for level of shooting exposure (n = 123; P < .007). The association was most robust with the 5-HTTLPR multimarker genotype and avoidance symptoms (P = .003).

CONCLUSION

These data suggest that differential function of the serotonin transporter may mediate differential response to a severe trauma. When examined in a relatively homogenous sample with shared trauma and known prior levels of child and adult trauma, the 5-HTTLPR multimarker genotype may serve as a useful predictor of risk for PTSD-related symptoms in the weeks and months following the trauma.

Differential immune system DNA methylation and cytokine regulation in post-traumatic stress disorder

DNA methylation may mediate persistent changes in gene function following chronic stress. To examine this hypothesis, we evaluated African American subjects matched by age and sex, and stratified into four groups by post-traumatic stress disorder (PTSD) diagnosis and history of child abuse. Total Life Stress (TLS) was also assessed in all subjects. We evaluated DNA extracted from peripheral blood using the HumanMethylation27 BeadChip and analyzed both global and site-specific methylation. Methylation levels were examined for association with PTSD, child abuse history, and TLS using a linear mixed model adjusted for age, sex, and chip effects. Global methylation was increased in subjects with PTSD. CpG sites in five genes (TPR, CLEC9A, APC5, ANXA2, and TLR8) were differentially methylated in subjects with PTSD. Additionally, a CpG site in NPFFR2 was associated with TLS after adjustment for multiple testing. Notably, many of these genes have been previously associated with inflammation. Given these results and reports of immune dysregulation associated with trauma history, we compared plasma cytokine levels in these subjects and found IL4, IL2, and TNFα levels associated with PTSD, child abuse, and TLS. Together, these results suggest that psychosocial stress may alter global and gene-specific DNA methylation patterns potentially associated with peripheral immune dysregulation. Our results suggest the need for further research on the role of DNA methylation in stress-related illnesses.

Using polymorphisms in FKBP5 to define biologically distinct subtypes of posttraumatic stress disorder: evidence from endocrine and gene expression studies

CONTEXT

Polymorphisms in the gene encoding the glucocorticoid receptor (GR) regulating co-chaperone FKBP5 have been shown to alter GR sensitivity and are associated with an increased risk to develop posttraumatic stress disorder (PTSD).

OBJECTIVE

To investigate interactions of the FKBP5 single-nucleotide polymorphism rs9296158 and PTSD symptoms on baseline cortisol level, low-dose dexamethasone suppression, and whole-blood gene expression.

DESIGN

Association of FKBP5 genotypes and PTSD symptoms with endocrine measures and genome-wide expression profiles.

SETTING

Waiting rooms of general medical and gynecological clinics of an urban hospital at Emory University.

PARTICIPANTS

The 211 participants were primarily African American (90.05%) and of low socioeconomic status and had high rates of trauma and PTSD.

MAIN OUTCOME MEASURES

Baseline and post-dexamethasone suppression cortisol measures and gene expression levels.

RESULTS

In our endocrine study, we found that only risk allele A carriers of rs9296158 showed GR supersensitivity with PTSD; in contrast, baseline cortisol levels were decreased in PTSD only in patients with the GG genotype. Expression of 183 transcripts was significantly correlated with PTSD symptoms after multiple testing corrections. When adding FKBP5 genotype and its interaction with PTSD symptoms, expression levels of an additional 32 genes were significantly regulated by the interaction term. Within these 32 genes, previously reported PTSD candidates were identified, including FKBP5 and the IL18 and STAT pathways. Significant overrepresentation of steroid hormone transcription factor binding sites within these 32 transcripts was observed, highlighting the fact that the earlier-described genotype and PTSD-dependent differences in GR sensitivity could drive the observed gene expression pattern. Results were validated by reverse transcriptase-polymerase chain reaction and replicated in an independent sample (N = 98).

CONCLUSIONS

These data suggest that the inheritance of GR sensitivity-moderating FKBP5 polymorphisms can determine specific types of hypothalamic-pituitary-adrenal axis dysfunction within PTSD, which are also reflected in gene-expression changes of a subset of GR-responsive genes. Thus, these findings indicate that functional variants in FKBP5 are associated with biologically distinct subtypes of PTSD.

Polymorphisms in CRHR1 and the serotonin transporter loci: gene x gene x environment interactions on depressive symptoms

Gene x environment (G x E) interactions mediating depressive symptoms have been separately identified in the stress-sensitive serotonergic (5-HTTLPR) and corticotropin-releasing hormone (CRHR1) systems. Our objective was to examine whether the effects of child abuse are moderated by gene x gene (G x G) interactions between CRHR1 and 5-HTTLPR polymorphisms. We used an association study examining G x G x E interactions of CRHR1 and 5-HTTLPR polymorphisms and measures of child abuse on adult depressive symptomatology. The participant population (N = 1,392) was African-American, of low socioeconomic status (60% with <$1,000/month family income), and with high rates of childhood and lifetime trauma. Depressive symptoms were measured with Beck Depression Inventory (BDI) and history of Major Depression by Structure Clinical Interview based on DSM-IV (SCID). We first replicated an interaction of child abuse and 5-HTTLPR on lifetime SCID diagnosis of major depression in a subsample (N = 236) of the study population-the largest African-American 5-HTTLPR cohort reported to date. We then extended our previously reported interaction with both a CRHR1 SNP (rs110402) and TCA haplotype interacting with child abuse to predict current symptoms (N = 1,059; P = 0.0089). We found that the 5-HTTLPR S allele interacted with CRHR1 haplotypes and child abuse to predict current depressive symptoms (N = 856, P = 0.016). These data suggest that G x E interactions predictive of depressive symptoms may be differentially sensitive to levels of childhood trauma, and the effects of child abuse are moderated by genetic variation at both the CRHR1 and 5-HTTLPR loci and by their G x G interaction.

CSN-5, a component of the COP9 signalosome complex, regulates the levels of UNC-96 and UNC-98, two components of M-lines in Caenorhabditis elegans muscle

In Caenorhabditis elegans two M-line proteins, UNC-98 and UNC-96, are involved in myofibril assembly and/or maintenance, especially myosin thick filaments. We found that CSN-5, a component of the COP9 signalosome complex, binds to UNC-98 and -96 using the yeast two-hybrid method. These interactions were confirmed by biochemical methods. The CSN-5 protein contains a Mov34 domain. Although one other COP9 signalosome component, CSN-6, also has a Mov34 domain, CSN-6 did not interact with UNC-98 or -96. Anti-CSN-5 antibody colocalized with paramyosin at A-bands in wild type and colocalized with abnormal accumulations of paramyosin found in unc-98, -96, and -15 (encodes paramyosin) mutants. Double knockdown of csn-5 and -6 could slightly suppress the unc-96 mutant phenotype. In the double knockdown of csn-5 and -6, the levels of UNC-98 protein were increased and the levels of UNC-96 protein levels were slightly reduced, suggesting that CSN-5 promotes the degradation of UNC-98 and that CSN-5 stabilizes UNC-96. In unc-15 and unc-96 mutants, CSN-5 protein was reduced, implying the existence of feed back regulation from myofibril proteins to CSN-5 protein levels. Taken together, we found that CSN-5 functions in muscle cells to regulate UNC-98 and -96, two M-line proteins.

A C. elegans homolog of huntingtin-associated protein 1 is expressed in chemosensory neurons and in a number of other somatic cell types

Huntingtin-associated protein 1 (HAP1) is a binding partner for huntingtin, the protein responsible for Huntington's disease. In mammals, HAP1 is mostly found in brain where it is expressed in neurons. Although several functions have been proposed for HAP1, its role has not yet been clearly established. In this paper, we report on the identification of a HAP1 Caenorhabditis elegans homolog called T27A3.1. T27A3.1 shows conservation with rat and human HAP1, as well as with Milton, a Drosophila HAP1 homolog. To determine the cellular expression of T27A3.1 (multiple isoforms; a-e), we generated several transgenic worm lines expressing a fluorescent reporter protein [green fluorescent protein (GFP) and DsRed2] under the control of the promoter for T27A3.1. We have found that T27A3.1 is expressed in many cell types including a subset of chemosensory neurons in the head and tail. These include the amphid chemosensory neurons ASKL and R, ASIL and R, ADFL and ASEL, the phasmid neurons PHBL and R, and the CAN neurons that are required for worm survival.

Association of FKBP5 polymorphisms and childhood abuse with risk of posttraumatic stress disorder symptoms in adults

CONTEXT

In addition to trauma exposure, other factors contribute to risk for development of posttraumatic stress disorder (PTSD) in adulthood. Both genetic and environmental factors are contributory, with child abuse providing significant risk liability.

OBJECTIVE

To increase understanding of genetic and environmental risk factors as well as their interaction in the development of PTSD by gene x environment interactions of child abuse, level of non-child abuse trauma exposure, and genetic polymorphisms at the stress-related gene FKBP5.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study examining genetic and psychological risk factors in 900 nonpsychiatric clinic patients (762 included for all genotype studies) with significant levels of childhood abuse as well as non-child abuse trauma using a verbally presented survey combined with single-nucleotide polymorphism (SNP) genotyping. Participants were primarily urban, low-income, black (>95%) men and women seeking care in the general medical care and obstetrics-gynecology clinics of an urban public hospital in Atlanta, Georgia, between 2005 and 2007.

MAIN OUTCOME MEASURES

Severity of adult PTSD symptomatology, measured with the modified PTSD Symptom Scale, non-child abuse (primarily adult) trauma exposure and child abuse measured using the traumatic events inventory and 8 SNPs spanning the FKBP5 locus.

RESULTS

Level of child abuse and non-child abuse trauma each separately predicted level of adult PTSD symptomatology (mean [SD], PTSD Symptom Scale for no child abuse, 8.03 [10.48] vs > or =2 types of abuse, 20.93 [14.32]; and for no non-child abuse trauma, 3.58 [6.27] vs > or =4 types, 16.74 [12.90]; P < .001). Although FKBP5 SNPs did not directly predict PTSD symptom outcome or interact with level of non-child abuse trauma to predict PTSD symptom severity, 4 SNPs in the FKBP5 locus significantly interacted (rs9296158, rs3800373, rs1360780, and rs9470080; minimum P = .0004) with the severity of child abuse to predict level of adult PTSD symptoms after correcting for multiple testing. This gene x environment interaction remained significant when controlling for depression severity scores, age, sex, levels of non-child abuse trauma exposure, and genetic ancestry. This genetic interaction was also paralleled by FKBP5 genotype-dependent and PTSD-dependent effects on glucocorticoid receptor sensitivity, measured by the dexamethasone suppression test.

CONCLUSIONS

Four SNPs of the FKBP5 gene interacted with severity of child abuse as a predictor of adult PTSD symptoms. There were no main effects of the SNPs on PTSD symptoms and no significant genetic interactions with level of non-child abuse trauma as predictor of adult PTSD symptoms, suggesting a potential gene-childhood environment interaction for adult PTSD.

A novel protein phosphatase is a binding partner for the protein kinase domains of UNC-89 (Obscurin) in Caenorhabditis elegans

Mutation of the Caenorhabditis elegans gene unc-89 results in disorganization of muscle A-bands. unc-89 encodes a giant polypeptide (900 kDa) containing two protein kinase domains, PK1 and PK2. Yeast two-hybrid screening using a portion of UNC-89 including PK2, yielded SCPL-1 (small CTD phosphatase-like-1), which contains a C terminal domain (CTD) phosphatase type domain. In addition to the PK2 domain, interaction with SCPL-1 required the putative autoinhibitory sequence, and immunoglobulin (Ig) and fibronectin type 3 (Fn3) domains lying N-terminal of the kinase domain. SCPL-1 also interacts with PK1, and it similarly requires the kinase domain and upstream Fn3 and Ig domains. Analogous regions from the two other giant kinases of C. elegans, twitchin and TTN-1, failed to interact with SCPL-1. The interaction between SCPL-1 and either Ig-Fn3-PK2 or Fn3-Ig-PK1 was confirmed by biochemical methods. The scpl-1b promoter is expressed in the same set of muscles as unc-89. Antibodies to SCPL-1 localize to the M-line and a portion of the I-band. Bacterially expressed SCPL-1 proteins have phosphatase activity in vitro with properties similar to previously characterized members of the CTD phosphatase family. RNA interference knockdown results in a defect in the function of egg-laying muscles. These studies suggest a new role for the CTD phosphatase family, that is, in muscle giant kinase signaling.

UNC-98 and UNC-96 interact with paramyosin to promote its incorporation into thick filaments of Caenorhabditis elegans

Mutations in unc-96 or -98 cause reduced motility and a characteristic defect in muscle structure: by polarized light microscopy birefringent needles are found at the ends of muscle cells. Anti-paramyosin stains the needles in unc-96 and -98 mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96, and -98 animals. Anti-UNC-98 and anti-paramyosin colocalize in the paramyosin accumulations of missense alleles of unc-15 (encodes paramyosin). Anti-UNC-96 and anti-UNC-98 have diffuse localization within muscles of unc-15 null mutants. By immunoblot, in the absence of paramyosin, UNC-98 is diminished, whereas in paramyosin missense mutants, UNC-98 is increased. unc-98 and -15 or unc-96 and -15 interact genetically either as double heterozygotes or as double homozygotes. By yeast two-hybrid assay and ELISAs using purified proteins, UNC-98 interacts with paramyosin residues 31-693, whereas UNC-96 interacts with a separate region of paramyosin, residues 699-798. The importance of surface charge of this 99 residue region for UNC-96 binding was shown. Paramyosin lacking the C-terminal UNC-96 binding region fails to localize throughout A-bands. We propose a model in which UNC-98 and -96 may act as chaperones to promote the incorporation of paramyosin into thick filaments.

Two LIM domain proteins and UNC-96 link UNC-97/pinch to myosin thick filaments in Caenorhabditis elegans muscle

By yeast two-hybrid screening, we found three novel interactors (UNC-95, LIM-8, and LIM-9) for UNC-97/PINCH in Caenorhabditis elegans. All three proteins contain LIM domains that are required for binding. Among the three interactors, LIM-8 and LIM-9 also bind to UNC-96, a component of sarcomeric M-lines. UNC-96 and LIM-8 also bind to the C-terminal portion of a myosin heavy chain (MHC), MHC A, which resides in the middle of thick filaments in the proximity of M-lines. All interactions identified by yeast two-hybrid assays were confirmed by in vitro binding assays using purified proteins. All three novel UNC-97 interactors are expressed in body wall muscle and by antibodies localize to M-lines. Either a decreased or an increased dosage of UNC-96 results in disorganization of thick filaments. Our previous studies showed that UNC-98, a C2H2 Zn finger protein, acts as a linkage between UNC-97, an integrin-associated protein, and MHC A in myosin thick filaments. In this study, we demonstrate another mechanism by which this linkage occurs: from UNC-97 through LIM-8 or LIM-9/UNC-96 to myosin.

UNC-98 links an integrin-associated complex to thick filaments in Caenorhabditis elegans muscle

Focal adhesions are multiprotein assemblages that link cells to the extracellular matrix. The transmembrane protein, integrin, is a key component of these structures. In vertebrate muscle, focal adhesion-like structures called costameres attach myofibrils at the periphery of muscle cells to the cell membrane. In Caenorhabditis elegans muscle, all the myofibrils are attached to the cell membrane at both dense bodies (Z-disks) and M-lines. Clustered at the base of dense bodies and M-lines, and associated with the cytoplasmic tail of beta-integrin, is a complex of many proteins, including UNC-97 (vertebrate PINCH). Previously, we showed that UNC-97 interacts with UNC-98, a 37-kD protein, containing four C2H2 Zn fingers, that localizes to M-lines. We report that UNC-98 also interacts with the C-terminal portion of a myosin heavy chain. Multiple lines of evidence support a model in which UNC-98 links integrin-associated proteins to myosin in thick filaments at M-lines.

Caenorhabditis elegans UNC-96 is a new component of M-lines that interacts with UNC-98 and paramyosin and is required in adult muscle for assembly and/or maintenance of thick filaments

To gain further insight into the molecular architecture, assembly, and maintenance of the sarcomere, we have carried out a molecular analysis of the UNC-96 protein in the muscle of Caenorhabditis elegans. By polarized light microscopy of body wall muscle, unc-96 mutants display reduced myofibrillar organization and characteristic birefringent "needles." By immunofluorescent staining of known myofibril components, unc-96 mutants show major defects in the organization of M-lines and in the localization of a major thick filament component, paramyosin. In unc-96 mutants, the birefringent needles, which contain both UNC-98 and paramyosin, can be suppressed by starvation or by exposure to reduced temperature. UNC-96 is a novel approximately 47-kDa polypeptide that has no recognizable domains. Antibodies generated to UNC-96 localize the protein to the M-line, a region of the sarcomere in which thick filaments are cross-linked. By genetic and biochemical criteria, UNC-96 interacts with UNC-98, a previously described component of M-lines, and paramyosin. Additionally, UNC-96 copurifies with native thick filaments. A model is presented in which UNC-96 is required in adult muscle to promote thick filament assembly and/or maintenance.

Three new isoforms of Caenorhabditis elegans UNC-89 containing MLCK-like protein kinase domains

In Caenorhabditis elegans, the gene unc-89 is required for A-band organization of striated muscle. In mammals, a likely homolog of UNC-89, called obscurin, has been described and found to be localized at both the M-lines and Z-discs of striated muscle. Here, we show that the coding sequence for unc-89 is larger than originally thought, and that the gene encodes at least four major isoforms: UNC-89-A (original isoform, 732 kDa), UNC-89-B (potentially 900 kDa), and UNC-89-C and UNC-89-D (each 156 kDa). UNC-89-C and -D, except for unique N-terminal tails of eight and 11 residues, respectively, are co-linear with the C terminus of UNC-89-B. The unc-89 complex transcription unit contains at least three promoters: one directing UNC-89-A and -B primarily in body-wall and pharyngeal muscle, one internal promoter directing expression of UNC-89-C primarily in body-wall muscle, and one internal promoter directing expression of UNC-89-D primarily in a few muscle cells of the tail. Isoform-specific RNA interference resulted in a muscle structural phenotype similar to a typical unc-89 mutant, but with varying degrees of severity. Antibodies generated to the interkinase region shared by the UNC-89-B, -C and -D isoforms localize to the middle of A-bands, like previously-described UNC-89 antibodies, and detect proteins on immunoblots consistent with the proposed gene organization and additional isoforms. The three new UNC-89 isoforms contain two protein kinase domains, of the myosin light chain kinase (MLCK) family. UNC-89-B contains two complete protein kinase domains, designated PK1 and PK2. UNC-89-C and -D begin with partial kinase domains, PK1-C and PK1-D. Homology modeling suggests that PK2 is catalytically active, PK1 is inactive, and that PK1-C and PK1-D have similar structures at their N termini that may create sites for interaction with other proteins.

Caenorhabditis elegans UNC-98, a C2H2 Zn finger protein, is a novel partner of UNC-97/PINCH in muscle adhesion complexes

To further understand the assembly and maintenance of the muscle contractile apparatus, we have identified a new protein, UNC-98, in the muscle of Caenorhabditis elegans. unc-98 mutants display reduced motility and a characteristic defect in muscle structure. We show that the major defect in the mutant muscle is in the M-lines and dense bodies (Z-line analogs). Both functionally and compositionally, nematode M-lines and dense bodies are analogous to focal adhesions of nonmuscle cells. UNC-98 is a novel 310-residue polypeptide consisting of four C2H2 Zn fingers and several possible nuclear localization signal and nuclear export signal sequences. By use of UNC-98 antibodies and green fluorescent protein fusions (to full-length UNC-98 and UNC-98 fragments), we have shown that UNC-98 resides at M-lines, muscle cell nuclei, and possibly at dense bodies. Furthermore, we demonstrated that 1) the N-terminal 106 amino acids are both necessary and sufficient for nuclear localization, and 2) the C-terminal (fourth) Zn finger is required for localization to M-lines and dense bodies. UNC-98 interacts with UNC-97, a C. elegans homolog of PINCH. We propose that UNC-98 is both a structural component of muscle focal adhesions and a nuclear protein that influences gene expression.

Titins in C.elegans with unusual features: coiled-coil domains, novel regulation of kinase activity and two new possible elastic regions

We report that there are previously unrecognized proteins in Caenorhabditis elegans that are similar to the giant muscle proteins called titins, and these are encoded by a single approximately 90kb gene. The gene structure was predicted by GeneMark.hmm and then experimentally verified. The Ce titin gene encodes polypeptides of 2.2MDa, 1.2MDa and 301kDa. The 2.2MDa isoform resembles twitchin and UNC-89 in that it contains multiple Ig (56) and FnIII (11) domains, and a single protein kinase domain. In addition, however, the 2.2MDa isoform contains four classes of short, 14-51 residue, repeat motifs arranged mostly in many tandem copies. One of these tandem repeat regions is similar to the PEVK regions of vertebrate and fly titins. As the PEVK region is one of the main elastic elements of the titins and is also composed of short tandem repeats, this suggests that the repeat motifs in the Ce titins may have a similar elastic function. An interesting aspect of the two largest Ce titin isoforms, is that in contrast to other members of the twitchin/titin family, there are multiple regions which are likely to form coiled-coil structure. In transgenic animals, the first approximately 100 residues of the largest isoforms targets to dense bodies, the worm analogs of Z-discs. Anti-Ce titin antibodies show localization to muscle I-bands beginning at the L2-L3 larval stages and this pattern continues into adult muscle. Ce titins may not have a role in early myofibril assembly: (1) Ce titins are too short to span half a sarcomere, and the onset of their expression is well after the initial assembly of thick filaments. (2) Ce titins are not localized to I-bands in embryonic or L1 larval muscle. The Ce titin protein kinase domain is most similar to the kinase domains of the twitchins and projectin. The Ce titin kinase has protein kinase activity in vitro, and this activity is regulated by a novel mechanism.

The C. elegans spe-9 gene encodes a sperm transmembrane protein that contains EGF-like repeats and is required for fertilization

In the nematode worm C. elegans, individuals with mutations in the spe-9 gene produce spermatozoa with wild-type morphology and motility that cannot fertilize oocytes even after contact between gametes. Therefore, disruption of spe-9 function affects either gamete recognition, adhesion, signaling, and/or fusion. The spe-9 gene encodes a sperm transmembrane protein with an extracellular domain that contains ten epidermal growth factor-like repeats. A common feature of proteins that include epidermal growth factor-like motifs is their involvement in extracellular functions such as adhesive and ligand-receptor interactions. Additionally, the overall structure of the predicted SPE-9 protein is similar to that of ligands for the Notch/LIN-12/GLP-1 family of transmembrane receptors. These results suggest that SPE-9 functions in the specialized cell-cell interactions required for fertilization.

Intraocular penetration of topical clindamycin in rabbits. II. Clindamycin phosphate

We have obtained comparative data for the intraocular absorption of topically administered clindamycin hydrochloride hydrate and clindamycin phosphate, made feasible with a new gas chromatographic method of analysis. Results indicated that clindamycin phosphate underwent hydrolysis in the eye, liberating the biologically active clindamycin. However, topical clindamycin hydrochloride produced higher levels (two to six times more) of the antibiotic than those achievable with the phosphates ester in the uvea, aqueous humor, and cornea, presumably due to clindamycin hydrochloride's higher lipid solubility. Based on this data, clindamycin hydrochloride appears to be the preferred form of the antibiotic for topical ocular applications.

Intraocular penetration of topical clindamycin in rabbits

Clindamycin is a recently developed, semisynthetic antibiotic whose spectrum of activity suggests a potential for the treatment of common ocular infections. The upake by various ocular tissues and serum in albino rabbits after topical administration of 0.2% clindamycin hydrochloride was studied. Therapeutic levels were achieved in the cornea, aqueous humor, and iris-ciliary body and persisted for two hours. Peak concentration occurred in the cornea within 15 minutes and in the aqueous humor and the iris-ciliary body at 30 minutes. Freezing of the tissue reduced active clindamycin levels in the cornea by a factor of 2 to 2 1/2 of those determined by fresh tissue analysis but had no apparent effect on aqueous humor and iris-ciliary body. There were, however, no detectable levels in the serum or vitreous humor.