Anthony T. Vernillo

Blocking Periodontal Disease Progression by Inhibiting Tissue-Destructive Enzymes: A Potential Therapeutic Role for Tetracyclines and Their Chemically-Modified Analogs

Tetracyclines (TCs) have wide therapeutic usage as antimicrobial agents; these drugs (e.g., minocycline, doxycycline) remain useful as adjuncts in periodontal therapy. However, TCs also have non-antimicrobial properties which appear to modulate host response. In that regard, TCs and their chemically-modified analogs (CMTs) have been shown to inhibit the activity of the matrix metalloproteinase (MMP), collagenase. The activity of this enzyme appears crucial in the destruction of the major structural protein of connective tissues, collagen. Such pathologic collagenolysis may be a common denominator in tissue destructive diseases such as rheumatoid and Osteoarthritis, diabetes mellitus, bullous dermatologic diseases, corneal ulcers, and periodontitis. The mechanisms by which TCs affect and, possibly, diminish bone resorption (a key event in the pathogenesis of periodontal and other diseases) are not yet understood. However, a number of possibilities remain open for investigation including the following: TCs may 1) directly inhibit the activity of extracellular collagenase and other MMPs such as gelatinase; 2) prevent the activation of its proenzyme by scavenging reactive oxygen species generated by other cell types (e.g. PMNs, osteoclasts); 3) inhibit the secretion of other collagenolytic enzymes (i.e. lysosomal cathepsins); and 4) directly affect other aspects of osteoclast structure and function. Several recent studies have also addressed the therapeutic potential of TCs and CMTs in periodontal disease. These drugs reduced excessive gingival collagenase activity and severity of periodontal breakdown in rats infected with Porphyromonas gingivalis and in diabetic rats. Furthermore, the latter drug (CMT) was not associated with the emergence of TC-resistant microorganisms. In human clinical trials, low-dose doxycycline therapy substantially reduced collagenase activity in the gingiva and GCF, and prevented the loss of attachment in adult periodontitis. Clearly, the non-antimicrobial properties of TCs have enormous medical and dental therapeutic potential since these drugs can inhibit the activity of MMPs and their degradation of non-osseous and osseous connective tissues. J Periodontol 1993; 64:819-827.

Cathepsin B and L activities in isolated osteoclasts.

Cathepsin B and L activities were examined with chicken osteoclasts isolated by sequential filtration and inhibitors were added to disaggregated rat osteoclasts on cortical bovine bone. Z-Phe-Phe-CHN2, a selective inhibitor of cathepsin L, at 1, 5, and 10 microM, inhibited bone resorption by rat osteoclasts 50, 85, and 100 per cent and, in chicken osteoclasts, cathepsin L activity was comparably inhibited. Cathepsin L in avian osteoclasts was also 25-fold higher than cathepsin B. Chicken osteoclasts treated with Z-Phe-Ala-CHN2, a generalized cysteine proteinase inhibitor, had both cathepsins inhibited to the same extent. Cathepsin L may play a key role in resorption.

Effects of Tetracyclines on Bone Metabolism

The anti-resorptive properties of tetracyclines (TCs) and their non-antimicrobial, chemically modified analogues (CMTs) have enormous therapeutic potential in medicine and dentistry. Osseous destructive diseases associated with excessive mammalian collagenase (matrix metalloproteinase) activity and collagen breakdown include malignancy, arthritis, and periodontitis. However, apart from the significant antimatrix metalloproteinase effects of TCs, TCs/CMTs are also potent inhibitors of osteoclast function (i.e., anti-resorptive). Thus, TCs can affect several parameters of osteoclast function and consequently inhibit bone resorption by (1) altering intracellular calcium concentration and interacting with the putative calcium receptor; (2) decreasing ruffled border area; (3) diminishing acid production; (4) diminishing the secretion of lysosomal cysteine proteinases (cathepsins); (5) inducing cell retraction by affecting podosomes; (6) inhibiting osteoclast gelatinase activity; (7) selectively inhibiting osteoclast ontogeny or development; and (8) inducing apoptosis or programmed cell death of osteoclasts. TCs/CMTs, as anti-resorptive drugs, may act similarly to bisphosphonates and primarily affect osteoclast function.

Feasibility of implementing rapid oral fluid HIV testing in an urban University Dental Clinic: a qualitative study

BackgroundMore than 1 million individuals in the U.S. are infected with HIV; approximately 20% of whom do not know they are infected. Early diagnosis of HIV infection results in earlier access to treatment and reductions in HIV transmission. In 2006, the CDC recommended that health care providers offer routine HIV screening to all adolescent and adult patients, regardless of community seroprevalence or patient lifestyle. Dental providers are uniquely positioned to implement these recommendations using rapid oral fluid HIV screening technology. However, thus far, uptake into dental practice has been very limited.MethodsThe study utilized a qualitative descriptive approach with convenience samples of dental faculty and students. Six in-depth one-on-one interviews were conducted with dental faculty and three focus groups were conducted with fifteen dental students.ResultsResults were fairly consistent and indicated relatively high levels of acceptability. Barriers and facilitators of oral fluid HIV screening were identified in four primary areas: scope of practice/practice enhancement, skills/knowledge/training, patient service/patient reactions and logistical issues.ConclusionsOral fluid HIV screening was described as having benefits for patients, dental practitioners and the public good. Many of the barriers to implementation that were identified in the study could be addressed through training and interdisciplinary collaborations.

Stimulation of collagen and glycosaminoglycan production by phenytoin 5,5-diphenylhydantoin in monolayer cultures of mesenchymal cells derived from embryonic chick sternae

Cultures grown with or without phenytoin (PHT) at a concentration of 5 micrograms/ml from the fifth to the eighth day after plating were labelled with [14C]-proline (0.2 microCi/ml) from the sixth to eighth day. Collagenase digestion indicated that collagen content increased approx. 2-fold after PHT exposure. Increases in sulphated glycosaminoglycan product in response to PHT were approx. 1.5-fold; PHT also stimulated protein production. Both actinomycin D and cycloheximide blocked incorporation of [3H]-leucine, [3H]-proline, and H2(35)SO4 approx. 90 per cent with or without PHT. Continuous sucrose density-gradient fractionation indicated that PHT produced quantitative but not qualitative changes in cellular RNA.

The effect of phenytoin on parathyroid hormone stimulated cAMP activity in cultured murine osteoblasts

Cells were isolated by sequential collagenase digestion from the parietal segments of one day old mice (Swiss albino BNL strain) and characterized for osteoblast parameters by alkaline phosphatase histochemistry and bovine parathyroid hormone (bPTH-(1-34] induced cAMP activity (protein binding assay). Phenytoin (DPH) reduced PTH stimulated cAMP activity nearly 3-fold in the presence and nearly 1.5-fold in the absence of added calcium. In the absence of PTH, DPH exerted no significant effect. Bay-K-8644, a calcium channel activator, appeared to approximate the PTH stimulation of cAMP activity, even in the presence of DPH. This study demonstrates that DPH has a direct effect on PTH stimulated cAMP activity in cultured murine osteoblasts.

Preventive Ethics and Rural Healthcare: Addressing Issues on a Systems Level

The rural hospital and community with its cultural and personal values are uniquely interconnected and distinctly different from the non-rural setting. The unique characteristics of rural healthcare not only shape and influence specific ethical issues but also how healthcare professionals respond to these issues in the provision of care to the community. Cook and Hoas (2008) provide examples of gaps between actual care and the best possible care in their target article, which underscores the complexity of rural healthcare ethical issues and how intractable some ethical conflicts may be to any satisfactory resolution. This commentary offers no precise formulaic solutions towards the resolution of ethical dilemmas but will discuss how preventive ethics as a systems approach may be applied to a rural healthcare setting. In the context of medical error, Cook and Woods (1994) described complex, tightly coupled systems, such as healthcare organizations, as inverted pyramids with a blunt end and a sharp end. Cook and Hoas (2008) describe a patch-work approach in the organizational structure of rural healthcare—one that appears directed only at the sharp end (physicians, patients, and ancillary healthcare staff) and supersedes any systems level approach starting at the blunt end(administrators, managers, and regulators) towards the prevention of ethical dilemmas. Common rural healthcare ethical issues include confidentiality, boundary issues, and the overlapping professional–patient relationship; shared-decision making; the allocation of limited resources and access to quality care; cultural and personal values; truth telling; the patient’s inability to pay for care; and referral to large, specialized and distant medical centers (Nelson et al. 2006; Nelson et al. 2007). For example, dual and overlapping professional–patient relationships means that practicing medicine in a small rural setting generally is equivalent to living and working in the same community. Hence, professionals may be reluctant to record in a patient’s medical chart a potentially stigmatizing diagnosis because it is common for a patient’s relative or friend to be a member of the healthcare professional’s staff, or even the billing clerk who records the diagnoses—it is very challenging to maintain confidentiality (Nelson et al. 2007). There exist only a few qualitative and quantitative studies focusing on the relationship between such rural characteristics and healthcare ethics. Given the dearth of these

The effect of phenytoin on collagenase and gelatinase activities in UMR 106-01 rat osteoblastic osteosarcoma cells.

Phenytoin (PHT), a widely used anticonvulsant, has been shown to inhibit bone resorption in rodent organ cultures. The drug also has complex effects on bone metabolism including chronic clinical symptoms of osteomalacia. However, the precise mechanism of PHT action in bone is still unclear. Neutral collagenases that specifically cleave native collagen have been implicated in the turnover of connective tissue. The effect of PHT was assessed on collagenase and gelatinase activities from UMR 106-01 rat osteoblastic osteosarcoma cells. Semiconfluent cells were treated with PHT (50 and 10 micrograms/ml) in the presence of bovine parathyroid hormone, b-PTH-(1-34), at 10(-7) M for 24, 48, 72 and 96 h. The media were assayed following concentration, APMA activation, and incubation with native or denatured [3H]-methyl collagen substrate (approximately 100,000 dpm) at 27 degrees C for 18 h and 35 degrees C for 2 h, respectively. Enzyme activities were presented as primary counts per minute for each time point and calculated as % activity of PTH at 10(-7) M. Parathyroid hormone (10(-7) M) stimulated collagenase activity (approximately 65-fold) and gelatinase activity (approximately 400-fold). PHT (50 micrograms/ml) reduced the PTH-stimulated collagenase activity by 18-53% and the gelatinase activity by 58-72%. SDS PAGE and fluorography following PHT treatment indicated a PHT-induced partial inhibition of PTH-stimulated degradation to alpha A chains of Type I collagen. Phenytoin may inhibit bone resorption through its action on the transcription, synthesis, and/or secretion of the collagenolytic enzymes, collagenase and gelatinase.

Disclosure of Adverse Clinical Trial Results—Should Legal Immunity Be Granted to Drug Companies?

Liao and colleagues (2009) advance a well structured, incontrovertible argument regarding the rights of human research subjects who voluntarily participate in clinical drug trials — there is a moral duty to disclose all relevant adverse clinical trial results that involve human harms to prospective participants. Furthermore, this duty must supersede the commercial interests of a pharmaceutical company. Their proposal may still be incomplete on balance unless the drug company is also offered legal immunity in the event that a prospective research subject is harmed during a clinical drug trial. Without that additional protection, further development of promising drugs for the public may be hampered — this may have significant repercussions, particularly if a new drug or vaccine is needed in the prevention or treatment of a pandemic disease outbreak (United States Department of Health and Human Services, 2006). If there is full disclosure of all potential adverse clinical trial results, and subjects give their fully informed and voluntary consent, then should a pharmaceutical company still be held liable for harms? A lack of full disclosure or a failure to warn prospective research subjects of all potential adverse clinical results can lead to injury, needless suffering, and even death. Under a legal argument known as pre-emption, however, the United States Food and Drug Administration (US FDA) approval of a drug may absolve companies of any responsibility if that drug later turns out to be dangerous, even if information was concealed from the FDA during the approval process (Gutierrez 2008). Drug companies are thus using pre-emption as a legal defense in a wide variety of law suits. The following cases nonetheless underscore the need for full disclosure and the litigation that results when there is a failure to warn.

Placebos in Clinical Practice and the Power of Suggestion

The use of deceptive placebos in the practice of clinical medicine is ethically justified within certain parameters. Thus, according to the Helsinki Declaration, placebos may be given to research subjects in a clinical trial whose major condition has no known effective treatment (Foddy 2009). It would be ethically impermissible to use a deceptive placebo if there is established therapy. Much research is still needed to elucidate the mechanisms by which a placebo can bring about a beneficial, even life-saving, clinical end result. Nonetheless, a patient’s belief alone in the promise of a cure may be transmuted into significant biochemical and immunological responses, which are indispensable agents of recovery (Cousins 1979). This commentary will underscore the potency of the deceptive placebo by citing its use in the remission of an advanced form of cancer and how the power of suggestion can also have a negative effect on the prognosis of clinical disease. The placebo is the physician who resides within each patient. Respect for autonomy includes a fundamental obligation to ensure those patients, or research subjects, have the right to choose, as well as the right to accept or decline information (Beauchamp and Childress 2001). Forced information, forced choice, and evasive disclosure are inconsistent with this obligation. Any situation in which placebo use involves deliberate deception should be viewed as ethically problematic; the danger to the patient–physician relationship advises against it. If there is a violation to autonomy through the use of a deceptive placebo, however, then what if a far greater good is obtained such that a patient undergoes remission from an otherwise untreatable form of malignancy? The four guiding prima facie principles of autonomy, beneficence, nonmaleficence, and justice are such that no one principle trumps another and each is of equal significance. Efforts must therefore be made to avoid violation of any one of these four principles and to balance all of them. However, all moral norms can be justifiably overridden in some circumstances (Beauchamp and Childress