A simple in vitro culture system for tracheal cartilage development.

Semi-circular tracheal cartilage is a critical determinant of maintaining architectural integrity of the respiratory airway. The current effort to understand the morphogenesis of tracheal cartilage is challenged by the lack of appropriate model systems. Here we report an in vitro tracheal cartilage system using embryonic tracheal­lung explants to recapitulate in vivo tracheal cartilage developmental processes. With modifications of a current lung culture protocol, we report a consistent in vitro technique of culturing tracheal cartilage from primitive mouse embryonic foregut for the first time. This tracheal culture system not only induces the formation of tracheal cartilage from the mouse embryonic foregut but also allows for the proper patterning of the developed tracheal cartilage. Furthermore, we show that this culture technique can be applied to culturing other types of cartilage in vertebrae, limbs, and ribs. We believe that this novel application of our in vitro culture system will facilitate the manipulation of cartilage development under various conditions and thus enabling us to advance our current limited knowledge on cartilage biology and development.

Cocaine and sigma-1 receptors modulate HIV infection, chemokine receptors, and the HPA axis in the huPBL-SCID model.

Cocaine is associated with an increased risk for, and progression of, clinical disease associated with human immunodeficiency virus (HIV) infection. A human xenograft model, in which human peripheral blood mononuclear cells were implanted into severe combined immunodeficiency mice (huPBL-SCID) and infected with a HIV reporter virus, was used to investigate the biological interactions between cocaine and HIV infection. Systemic administration of cocaine (5 mg/kg/d) significantly increased the percentage of HIV-infected PBL (two- to threefold) and viral load (100- to 300-fold) in huPBL-SCID mice. Despite the capacity for cocaine to increase corticosterone and adrenocorticotropic hormone levels in control mice, the hypothalamic-pituitary-adrenal axis was suppressed in HIV-infected animals, and corticosterone levels were further decreased when animals were exposed to HIV and cocaine. Activating huPBL in vitro in the presence of 10(-8) M cocaine increased expression of CC chemokine receptor 5 (CCR5) and CXC chemokine receptor 4 (CXCR4) coreceptors. Expression of CCR5 was also increased at early time-points in the huPBL-SCID model following systemic exposure to cocaine (54.1+/-9.4% increase over control, P<0.01). This effect preceded the boost in viral infection and waned as HIV infection progressed. Cocaine has been shown to mediate immunosuppressive effects by activating sigma-1 receptors in immune cells in vitro and in vivo. Consistent with these reports, a selective sigma-1 antagonist, BD1047, blocked the effects of cocaine on HIV replication in the huPBL-SCID mouse. Our results suggest that systemic exposure to cocaine can enhance HIV infection in vivo by activating sigma-1 receptors and by modulating the expression of HIV coreceptors.

Tetrahydrocannabinol suppresses immune function and enhances HIV replication in the huPBL-SCID mouse.

Epidemiologic studies identify marijuana as a potential cofactor in the development and progression of HIV infection. To evaluate this interaction we employed a hybrid model in which human peripheral blood leukocytes (PBL) were implanted into severe combined immunodeficient mice (huPBL-SCID) and infected with an HIV reporter construct in the presence or absence of tetrahydrocannabinol (THC) exposure. Administration of THC alone, in the absence of HIV, decreased CD4 counts and the CD4:CD8 ratio. Co-administration of THC and HIV did not reduce CD4 counts further, but significantly increased the percentage of HIV-infected PBL when compared to saline-treated animals (17+/-4.6% vs. 7+/-1.4%). Quantitative PCR confirmed a 50-fold increase in systemic viral load in THC-treated animals. The CCR5 and CXCR4 chemokine receptors function as coreceptors essential for HIV infection. Administration of THC for 5 days increased the percentage of PBL expressing CCR5 and, to a lesser extent, CXCR4. This effect was lost after 10 days of THC administration, but the number of HIV-infected cells had significantly increased by that time suggesting a role for early upregulation of these coreceptors in the pathogenic effect of THC. Finally, the impact of treatment on the number of human interferon-gamma (IFN-gamma) producing cells was determined by ELISPOT. Both THC and HIV infection independently decreased the number of IFN-gamma producing cells and co-administration produced additive effects. These results suggest that exposure to THC in vivo can suppress immune function, increase HIV coreceptor expression, and act as a cofactor to significantly enhance HIV replication.

Impairment of antimicrobial activity and nitric oxide production in alveolar macrophages from smokers of marijuana and cocaine.

Human alveolar macrophages (AMs) were recovered from the lungs of healthy nonsmokers (NS) or smokers of tobacco (TS), marijuana (MS), or crack cocaine (CS) and challenged in vitro with Staphylococcus aureus. AMs from NS and TS exhibited potent antibacterial activity that correlated with the production of nitric oxide (NO) and induction of NO synthase without the requirement for priming with exogenous cytokines. In contrast, AMs from MS and CS exhibited minimal antibacterial activity and failed to produce NO unless primed with additional cytokines. These results confirm that NO plays a significant role as an effector molecule used by normal human AMs, but this capacity is suppressed in AMs from MS and CS because of a lack of intrinsic cytokine priming.

Evidence of chronic damage to the pulmonary microcirculation in habitual users of alkaloidal ("crack") cocaine.

STUDY OBJECTIVE: To evaluate BAL cells obtained from habitual users of alkaloidal ("crack") cocaine alone or in combination with tobacco, for evidence of cocaine-associated alveolar injury. DESIGN: Prospective cohort study. PATIENTS: A total of 36 healthy men and women (mean age [SD], 37.5 [7.5] years), including 10 cocaine-only smokers (CS), 6 cocaine-plus-tobacco smokers (CTS), 10 tobacco smokers (TS), and 10 nonsmokers (NS), underwent fiberoptic bronchoscopy and BAL. METHODS: Cytospins were prepared from BAL cells and stained with Wright-Giemsa for cell differentials and Gomori's stain for detection of hemosiderin. Endothelin (ET)-1 levels were determined from lavage fluid by enzyme-linked immunosorbent assay. RESULTS: None of the cocaine users reported episodes of hemoptysis or respiratory distress, and routine spirometry findings were within normal limits in all subjects. While there was little effect on total cell numbers or differential counts, the percentages of hemosiderin-positive alveolar macrophages (AMs) were markedly increased in CS (33.8 +/- 8.7% [SEM]) compared to TS and NS (< 2%; p < 0.05). The percentages of hemosiderin-laden AMs were also numerically increased in CTS (11.8 +/- 7.8%), but this value was not statistically significant from that of TS or NS. ET-1 levels were significantly increased in the fluid recovered from CS (6.2 +/- 0.8 pg/mL) when compared to NS (1.2 +/- 0.4 pg/mL) and TS (1.3 +/- 0.2 pg/mL) [p < 0.05], while ET-1 levels were elevated to a lesser extent in CTS (2.5 +/- 0.6 pg/mL). ET-1 levels correlated with the percentage of hemosiderin-positive AMs when CS were analyzed in conjunction with CTS (r = 0.64; p = 0.0004). CONCLUSION: Clinically inapparent alveolar hemorrhage occurs frequently in otherwise healthy crack cocaine smokers and is associated with elevated levels of ET-1, indicative of cocaine-induced pulmonary microvascular injury.

Cocaine enhances human immunodeficiency virus replication in a model of severe combined immunodeficient mice implanted with human peripheral blood leukocytes.

Epidemiologic studies have identified cocaine as a cofactor for development of acquired immunodeficiency syndrome (AIDS). To evaluate this interaction, human peripheral blood leukocytes (PBL) were implanted into severe combined immunodeficient mice and infected with human immunodeficiency virus (HIV) in both the presence and absence of cocaine. Concurrent administration of cocaine resulted in significantly more PBL becoming infected with HIV in vivo (38.85% vs. 18.5%). The number of CD4(+) cells recovered from HIV-infected, cocaine-treated animals was significantly lower than that from mice infected with HIV in the absence of cocaine (6.5 x 10(4) vs. 19 x 10(4)) and was associated with a lower CD4:CD8 ratio and a dramatic increase in virus load. Exposure to cocaine alone did not affect the implantation of PBL, suggesting a specific interaction between cocaine and HIV. This report describes a model for evaluating HIV cofactors and supports cocaine's role in the development and progression of AIDS.