Biomedical subjects

Neal D Hammer

Publications and source records attributed to Neal D Hammer.

5 recordsLinked to original sources

PubMed2006

Developing a structure-function relationship for anionic porphyrazines exhibiting selective anti-tumor activity.

The porphyrazines (pzs) are a class of porphyrin derivatives being studied for their use as optical imaging agents and photodynamic therapy (PDT) anti-tumor agents. A previous study revealed that the anionic pz, 18--of the form H2[pz(An;B4-n)], where A is [S(CH2)3CO2-], B is a fused beta',beta'-diisopropyloxy benzo group, with n=2 (trans)--selectively killed tumor cells, while analogous neutral and positively charged pzs lacked this property. In this report, we compare the properties of a suite of three H2[pz(An;B4-n)] pzs containing the same A and B groups as 18, but differing in their values of n: pzs 4 (n=4) and 11 (n=3), and 18 (n=2, trans) exhibit a progressive variation in charge due to the carboxylates, balance between hydrophobic/hydrophilic character, as well as a progressive variation in the singlet oxygen quantum yield (PhiDelta): PhiDelta (18)>PhiDelta (11)>PhiDelta (4). The biological activity of the pzs was tested in human lung carcinoma (A549) and SV40 transformed embryonic (WI-38 VA13) cell lines. Pzs 4 and 11 exhibited significant toxicity in both tumor and normal cells, while 18 showed selective anti-tumor cell activity in a dose-dependent manner. As the number of net negative charges decreased, the compounds became less toxic to normal cells, and the killing effect observed with these compounds was light independent. These observations indicate that the toxicity may have little to do with singlet oxygen quantum yields, but rather is more dependent on the net number of negative charges a pz contains. The study reported herein presents an example of how the porphyrazines can be easily modified to vary their biological behavior and specifically suggest that anionic porphyrazines pzs with lower n (fewer carboxylates, larger hydrophobic core) are more specific tumor killers, while those with larger n (increased net negative charge) are more potent tumor killers.

Antineoplastic Agents↗

PubMed2005

Charge dependence of cellular uptake and selective antitumor activity of porphyrazines.

Porphyrazines (pzs), or tetraazaporphyrins, can be viewed as porphyrinic macrocycles in which the porphyrin meso (CH) groups are replaced by nitrogen atoms; as such, it can be anticipated that pzs would show similar biocompatibility and biodistribution to those of porphyrins. However, distinctive chemical and physical features of the pzs differentiate them from either the porphyrins or phthalocyanines, in particular making them excellent candidates as optical imaging/therapeutic agents. The novelty of the pzs requires that we first determine how specific structures selectively alter biological function, leading to the development of "rules" that will be used to predict future biologically functional pzs. In the first of these studies, we present here a correlation of pz charge with biocompatibility for a suite of three pzs-neutral, negative, and positive. Confocal fluorescence microscopy and proliferation/viability measurements disclose that the three pzs differ in their toxicity, uptake, and localization in A549 human lung adenocarcinoma cells and WI-38 VA13 normal cells. Interestingly, the negatively charged pz exhibits selective dark toxicity in pulmonary adenocarcinoma cells.

Antineoplastic Agents↗

PubMed2005

Proton pump (H+/K+-ATPase) expression in human laryngeal seromucinous glands.

OBJECTIVE: Recent pilot research suggested that the H+/K+-ATPase (proton pump), which is the target of pharmacotherapy for laryngopharyngeal reflux disease (LPRD), is associated with human laryngeal submucosal glands. The hypothesis of this study is that proton pump is expressed in the human larynx, and is not solely associated with the parietal cells of the stomach. METHODS: Fifteen surgical larynx subjects (27 pathologic specimens) containing seromucinous glands from banked tissue were retrospectively obtained after approval from Human Subjects Committee. Banked human stomach tissue was also obtained for comparative positive and negative controls. Sections were immunostained with two monoclonal antibodies selectively reactive with alpha or beta subunits of the H+/K+-ATPase (proton) pump. RESULTS: In the human larynx, positive staining was seen in 14 of 15 subjects. Twenty-six specimens showed consistent staining in the seromucinous cells and ducts for the alpha subunit, and 23 specimens for the beta subunit. Stomach parietal cells exhibited strongly positive staining for both the alpha and beta subunits of the proton pump. There was no staining in stomach cells that were not morphologically consistent with the parietal cell. CONCLUSION: The H+/K+-ATPase (proton) pump is present in seromucinous cells and ducts in the human larynx, with some variable expression noted. Proton pump involvement in human laryngeal seromucinous glands may explain heightened laryngeal sensitivity in those patients with chronic laryngitis believed to have LPRD. Also, proton pump inhibitor pharmacotherapy may have a site of action in the human larynx, explaining some of the controversies attributable to LPRD. EBM RATING: B-3.

Aged↗

PubMed2004

Nitrosative stress induces DNA strand breaks but not caspase mediated apoptosis in a lung cancer cell line.

BACKGROUND: Key steps crucial to the process of tumor progression are genomic instability and escape from apoptosis. Nitric oxide and its interrelated reactive intermediates (collectively denoted as NOX) have been implicated in DNA damage and mutational events leading to cancer development, while also being implicated in the inhibition of apoptosis through S-nitrosation of key apoptotic enzymes. The purpose of this study was to explore the interrelationship between NOX-mediated DNA strand breaks (DSBs) and apoptosis in cultured tumor cell lines. METHODS: Two well-characterized cell lines were exposed to increasing concentrations of exogenous NOX via donor compounds. Production of NOX was quantified by the Greiss reaction and spectrophotometery, and confirmed by nitrotyrosine immunostaining. DSBs were measured by the alkaline single-cell gel electrophoresis assay (the COMET assay), and correlated with cell viability by the MTT assay. Apoptosis was analyzed both by TUNEL staining and Annexin V/propidium iodine FACS. Finally, caspase enzymatic activity was measured using an in-vitro fluorogenic caspase assay. RESULTS: Increases in DNA strand breaks in our tumor cells, but not in control fibroblasts, correlated with the concentration as well as rate of release of exogenously administered NOX. This increase in DSBs did not correlate with an increase in cell death or apoptosis in our tumor cell line. Finally, this lack of apoptosis was found to correlate with inhibition of caspase activity upon exposure to thiol- but not NONOate-based NOX donor compounds. CONCLUSIONS: Genotoxicity appears to be highly interrelated with both the concentration and kinetic delivery of NOX. Moreover, alterations in cell apoptosis can be seen as a consequence of the explicit mechanisms of NOX delivery. These findings lend credence to the hypothesis that NOX may play an important role in tumor progression, and underscores potential pitfalls which should be considered when developing NOX-based chemotherapeutic agents.

Journal Article↗

PubMed2003

The H+/K+-ATPase (proton) pump is expressed in human laryngeal submucosal glands.

OBJECTIVES/HYPOTHESIS: Diagnosis and treatment of gastroesophageal and laryngopharyngeal reflux disease has significantly increased over recent years. The larynx is highly sensitive to the effects of LPRD and is similarly responsive to proton pump inhibitor pharmacotherapy. The hypothesis of the study was that proton pump activity exists in the human larynx and plays a functional role in normal and/or pathological laryngeal tissue. STUDY DESIGN: Pathological investigation. METHODS: Two fresh human cadaveric larynges (one male and one female larynx) were obtained as part of an exempt protocol from the Human Subjects Committee and were formalin fixed and paraffin embedded. Banked human stomach tissue was also obtained for use as comparative positive and negative control specimens. Sections were immunostained with monoclonal antibodies reactive with both alpha and beta subunits of the H+/K+-ATPase (proton) pump. Specimens were reviewed for staining pattern and intensity. RESULTS: Stomach parietal cells (known to produce gastric acid) exhibited strongly positive staining for both the alpha and beta subunits of the proton pump. There was no staining in stomach cells that were not morphologically consistent with the parietal cell. In the human larynx there were strong focal and identical staining patterns in the serous cells and ducts of the minor seromucinous glands by both alpha and beta monoclonals to the proton pump. There was variable staining in the laryngeal epithelium that was thought to be consistent with artifact staining resulting from tissue processing. CONCLUSION: The H+/K+-ATPase (proton) pump is present in serous cells and ducts of submucosal glands in the human larynx. Proton pump inhibitor pharmacotherapy may have a site of action in seromucinous glands of the human larynx, with possible relevance for patients treated for chronic laryngitis with or without laryngopharyngeal reflux disease.

Adenosine Triphosphatases↗