It is also possible that in an aged or a Th2 environment, viral replication and persistence may be critical for fibrogenesis [76,86] whereas in young or Th1-biased mice, viral replication may be unnecessary for the augmentation or exacerbation of disease [72]. research directions. Keywords:collagen, Epstein-Barr virus, gammaherpesvirus, lung, murine gammaherpesvirus-68, senescence == Idiopathic pulmonary fibrosis: clinical presentation & potential causes == Idiopathic pulmonary fibrosis (IPF) and its histologic presentation, usual interstitial pneumonia (UIP), is a chronic parenchymal disorder of the lungs that is characterized by progressive loss of pulmonary function, probably due to fibroblast hyperplasia and excess collagen deposition destroying normal lung tissue. It is thought to occur after some inciting event causes injury to the alveolar surface and leads to dysregulated Tirbanibulin Mesylate repair. This dysfunctional repair is characterized by loss of type 1 alveolar cells and expansion of type 2 cells [1], induction of proinflammatory cytokines with a Th2 predominance [2], the synthesis of profibrotic factors such as TGF-1 [2,3], alterations in eicosanoid regulation skewing the balance towards leukotriene synthesis and away from prostaglandin synthesis [4,5], decreased plasminogen activation [6], the recruitment of bone marrow-derived fibrocytes [79], the Rabbit Polyclonal to p47 phox occurrence of epithelialmesenchymal transition [1012], fibroblast proliferation, the transformation of these fibroblasts Tirbanibulin Mesylate to -smooth muscle actin producing myofibroblasts [13], and finally, deposition of abundant extracellular matrix. Unfortunately, IPF continues to carry a high morbidity and mortality, with median survival times of 3 years from the time of diagnosis. This is largely due to a lack of effective therapies to halt disease progression. Particular challenges arise when studying IPF owing to the various disease phenotypes exhibited by patients. While the majority of patients present after their fifth decade, they can present in three different ways: chronically with stability over many years; with a steady progression of symptoms and worsening Tirbanibulin Mesylate of lung function; or with a rapid decline in respiratory status over a few weeks with extremely high mortality rates termed an acute exacerbation [14,15]. Unfortunately, we have yet to determine what initiates the fibrotic process, why incidence of fibrosis increases with age [16], or why acute exacerbations occur. Several associations have been found between pulmonary fibrosis and inhaled toxins, chronic aspiration, certain drugs and genetic mutations in telomerase or surfactant protein C (SPC) [1722]; however, these risk factors do not apply to most patients. An intriguing possibility is the hypothesis that occult viral infections act as cofactors in the pathogenesis of pulmonary fibrosis [23]. Most viruses, such as EpsteinBarr virus (EBV), which have been identified as potential culprits are fairly ubiquitous and infect the majority of the population at some point in their lives [24]. Gammaherpesviruses like EBV can alternate between an aggressively replicating lytic phase and a latent phase existing in the epithelial cells of the lung, as well as in B cells and macrophages, and perhaps providing a chronic low level of lung Tirbanibulin Mesylate inflammation [2426]. It is plausible that this chronic inflammation in a host with a genetic susceptibility to dysfunctional repair disrupts the normal healing response, leading to progressive fibrosis. It is also possible that these agents either make the host more susceptible to further injury caused by a separate acute trigger, or something in the host environment, such as stress, coinfections or immunodeficiency, leads to reactivation of the virus to its more aggressive lytic phase, causing an acute deterioration. This article will summarize the emerging evidence from clinical literature for and against the notion that viruses may contribute to some forms of IPF. In addition, data from animal models that support this theory will be explored. Tirbanibulin Mesylate Finally, it will also explore the potential differences that exist in aged and young individuals, which may offer insights into why fibrosis is predominantly a disease of the aged. == Clinical evidence linking viral infections with IPF == == Hepatitis C virus == Several studies have suggested a link between infection with the small, enveloped, positive-sense RNA virus, hepatitis C virus (HCV) [27],.