Activation of senescence in critically ill patients: mechanisms, consequences and therapeutic opportunities

Whereas aging is a whole-organism process, senescence is a cell mechanism that can be triggered by several stimuli. There is increasing evidence that critical conditions activate cell senescence programs irrespective of patient's age. In this review, we briefly describe the basic senescence pathways and the consequences of their activation in critically ill patients. The available evidence suggests a paradigm in which activation of senescence can be beneficial in the short term by rendering cells resistant to apoptosis, but also detrimental in a late phase by inducing a pro-inflammatory and pro-fibrotic state. Senescence can be a therapeutic target. The use of drugs that eliminate senescent cells (senolytics) or the senescence-associated phenotype (senomorphics) will require monitoring of these cell responses and identification of therapeutic windows to improve the outcome of critically ill patients.

Tubulointerstitial nephritis and uveitis syndrome and SARS-CoV-2 infection in an adolescent: just a coincidence in time?

BACKGROUND

Despite recent well-established kidney tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), usually presenting as acute kidney injury (AKI), there are few published cases with SARS-CoV-2-related tubulointerstitial nephritis (TIN). We report an adolescent with TIN and delayed association with uveitis (TINU syndrome), where SARS-CoV-2 spike protein was identified in kidney biopsy.

CASE-DIAGNOSIS/TREATMENT

A 12-year-old girl was assessed for a mild elevation of serum creatinine detected during the evaluation of systemic manifestations including asthenia, anorexia, abdominal pain, vomiting, and weight loss. Data of incomplete proximal tubular dysfunction (hypophosphatemia and hypouricemia with inappropriate urinary losses, low molecular weight proteinuria, and glucosuria) were also associated. Symptoms had initiated after a febrile respiratory infection with no known infectious cause. After 8 weeks, the patient tested positive in PCR for SARS-CoV-2 (Omicron variant). A subsequent percutaneous kidney biopsy revealed TIN and immunofluorescence staining with confocal microscopy detected the presence of SARS-CoV-2 protein S within the kidney interstitium. Steroid therapy was started with gradual tapering. Ten months after onset of clinical manifestations, as serum creatinine remained slightly elevated and kidney ultrasound showed mild bilateral parenchymal cortical thinning, a second percutaneous kidney biopsy was performed, without demonstrating acute inflammation or chronic changes, but SARS-CoV-2 protein S within the kidney tissue was again detected. At that moment, simultaneous routine ophthalmological examination revealed an asymptomatic bilateral anterior uveitis.

CONCLUSIONS

We present a patient who was found to have SARS-CoV-2 in kidney tissue several weeks following onset of TINU syndrome. Although simultaneous infection by SARS-CoV-2 could not be demonstrated at onset of symptoms, since no other etiological cause was identified, we hypothesize that SARS-CoV-2 might have been involved in triggering the patient's illness.

Age-dependent effect of the IFIH1/MDA5 gene variants on the risk of critical COVID-19

MDA5, encoded by the IFIH1gene, is a cytoplasmic sensor of viral RNAs that triggers interferon (IFN) antiviral responses. Common and rare IFIH1 variants have been associated with the risk of type 1 diabetes and other immune-mediated disorders, and with the outcome of viral diseases. Variants associated with reduced IFN expression would increase the risk for severe viral disease. The MDA5/IFN pathway would play a critical role in the response to SARS-CoV-2 infection mediating the extent and severity of COVID-19. Here, we genotyped a cohort of 477 patients with critical ICU COVID-19 (109 death) for three IFIH1 functional variants: rs1990760 (p.Ala946Thr), rs35337543 (splicing variant, intron 8 + 1G > C), and rs35744605 (p.Glu627Stop). The main finding of our study was a significant increased frequency of rs1990760 C-carriers in early-onset patients (< 65 years) (p = 0.01; OR = 1.64, 95%CI = 1.18-2.43). This variant was also increased in critical vs. no-ICU patients and in critical vs. asymptomatic controls. The rs35744605 C variant was associated with increased blood IL6 levels at ICU admission. The rare rs35337543 splicing variant showed a trend toward protection from early-onset critical COVID-19. In conclusion, IFIH1 variants associated with reduced gene expression and lower IFN response might contribute to develop critical COVID-19 with an age-dependent effect.

Transcriptomic clustering of critically ill COVID-19 patients

BACKGROUND

Infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may cause a severe disease, termed coronavirus disease 2019 (COVID-19), with significant mortality. Host responses to this infection, mainly in terms of systemic inflammation, have emerged as key pathogenetic mechanisms and their modulation has shown a mortality benefit.

METHODS

In a cohort of 56 critically ill COVID-19 patients, peripheral blood transcriptomes were obtained at admission to an intensive care unit (ICU) and clustered using an unsupervised algorithm. Differences in gene expression, circulating microRNAs (c-miRNAs) and clinical data between clusters were assessed, and circulating cell populations estimated from sequencing data. A transcriptomic signature was defined and applied to an external cohort to validate the findings.

RESULTS

We identified two transcriptomic clusters characterised by expression of either interferon-related or immune checkpoint genes, respectively. Steroids have cluster-specific effects, decreasing lymphocyte activation in the former but promoting B-cell activation in the latter. These profiles have different ICU outcomes, despite no major clinical differences at ICU admission. A transcriptomic signature was used to identify these clusters in two external validation cohorts (with 50 and 60 patients), yielding similar results.

CONCLUSIONS

These results reveal different underlying pathogenetic mechanisms and illustrate the potential of transcriptomics to identify patient endotypes in severe COVID-19 with the aim to ultimately personalise their therapies.

SARS-CoV-2 Spike Protein in Intestinal Cells of a Patient with Coronavirus Disease 2019 Multisystem Inflammatory Syndrome

A previously healthy 12-year-old boy had severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related multisystem inflammatory syndrome (MIS-C) that was rapidly fatal. Autopsy revealed the presence of a large intracardiac thrombus. SARS-CoV-2 spike protein was detected in intestinal cells, supporting the hypothesis that viral presence in the gut may be related to the immunologic response of MIS-C.

Effects of IFIH1 rs1990760 variants on systemic inflammation and outcome in critically ill COVID-19 patients in an observational translational study

Background:

Variants in IFIH1, a gene coding the cytoplasmatic RNA sensor MDA5, regulate the response to viral infections. We hypothesized that IFIH1 rs199076 variants would modulate host response and outcome after severe COVID-19.

Methods:

Patients admitted to an intensive care unit (ICU) with confirmed COVID-19 were prospectively studied and rs1990760 variants determined. Peripheral blood gene expression, cell populations, and immune mediators were measured. Peripheral blood mononuclear cells from healthy volunteers were exposed to an MDA5 agonist and dexamethasone ex-vivo, and changes in gene expression assessed. ICU discharge and hospital death were modeled using rs1990760 variants and dexamethasone as factors in this cohort and in-silico clinical trials.

Results:

About 227 patients were studied. Patients with the IFIH1 rs1990760 TT variant showed a lower expression of inflammation-related pathways, an anti-inflammatory cell profile, and lower concentrations of pro-inflammatory mediators. Cells with TT variant exposed to an MDA5 agonist showed an increase in IL6 expression after dexamethasone treatment. All patients with the TT variant not treated with steroids survived their ICU stay (hazard ratio [HR]: 2.49, 95% confidence interval [CI]: 1.29–4.79). Patients with a TT variant treated with dexamethasone showed an increased hospital mortality (HR: 2.19, 95% CI: 1.01–4.87) and serum IL-6. In-silico clinical trials supported these findings.

Conclusions:

COVID-19 patients with the IFIH1 rs1990760 TT variant show an attenuated inflammatory response and better outcomes. Dexamethasone may reverse this anti-inflammatory phenotype.

Funding:

Centro de Investigación Biomédica en Red (CB17/06/00021), Instituto de Salud Carlos III (PI19/00184 and PI20/01360), and Fundació La Marató de TV3 (413/C/2021).

Mechanical ventilation promotes lung tumor spread by modulation of cholesterol cell content

Mechanical stretch of cancer cells can alter their invasiveness. During mechanical ventilation, lungs may be exposed to an increased amount of stretch, but the consequences on lung tumors have not been explored. To characterize the influence of mechanical ventilation on the behavior of lung tumors, invasiveness assays and transcriptomic analyses were performed in cancer cell lines cultured in static conditions or under cyclic stretch. Mice harbouring lung melanoma implants were submitted to mechanical ventilation and metastatic spread was assessed. Additional in vivo experiments were performed to determine the mechano-dependent specificity of the response. Incidence of metastases was studied in a cohort of lung cancer patients that received mechanical ventilation compared with a matched group of non-ventilated patients. Stretch increases invasiveness in melanoma B16F10luc2 and lung adenocarcinoma A549 cells. We identified a mechanosensitive upregulation of pathways involved in cholesterol processing in vitro, leading to an increase in PCSK9 and LDLR expression, a decrease in intracellular cholesterol and preservation of cell stiffness. A course of mechanical ventilation in mice harboring melanoma implants increased brain and kidney metastases two weeks later. Blockade of PCSK9 using a monoclonal antibody increased cell cholesterol and stiffness and decreased cell invasiveness in vitro and metastasis in vivo In patients, mechanical ventilation increased PCSK9 abundance in lung tumors and the incidence of metastasis, thus decreasing survival. Our results suggest that mechanical stretch promote invasiveness of cancer cells, which may have clinically relevant consequences. Pharmacological manipulation of cholesterol endocytosis could be a novel therapeutic target in this setting.

Biotrauma during ultra-low tidal volume ventilation and venoarterial extracorporeal membrane oxygenation in cardiogenic shock: a randomized crossover clinical trial

Background

Cardiogenic pulmonary oedema (CPE) may contribute to ventilator-associated lung injury (VALI) in patients with cardiogenic shock. The appropriate ventilatory strategy remains unclear. We aimed to evaluate the impact of ultra-low tidal volume ventilation with tidal volume of 3 ml/kg predicted body weight (PBW) in patients with CPE and veno–arterial extracorporeal membrane oxygenation (V–A ECMO) on lung inflammation compared to conventional ventilation.

Methods

A single-centre randomized crossover trial was performed in the Cardiac Intensive Care Unit (ICU) at a tertiary university hospital. Seventeen adults requiring V–A ECMO and mechanical ventilation due to cardiogenic shock were included from February 2017 to December 2018. Patients were ventilated for two consecutive periods of 24 h with tidal volumes of 6 and 3 ml/kg of PBW, respectively, applied in random order. Primary outcome was the change in proinflammatory mediators in bronchoalveolar lavage fluid (BALF) between both ventilatory strategies.

Results

Ventilation with 3 ml/kg PBW yielded lower driving pressures and end-expiratory lung volumes. Overall, there were no differences in BALF cytokines. Post hoc analyses revealed that patients with high baseline levels of IL-6 showed statistically significant lower levels of IL-6 and IL-8 during ultra-low tidal volume ventilation. This reduction was significantly proportional to the decrease in driving pressure. In contrast, those with lower IL-6 baseline levels showed a significant increase in these biomarkers.

Conclusions

Ultra-low tidal volume ventilation in patients with CPE and V–A ECMO may attenuate inflammation in selected cases. VALI may be driven by an interaction between the individual proinflammatory profile and the mechanical load overimposed by the ventilator.

Trial registration The trial was registered in ClinicalTrials.gov (identifier NCT03041428, Registration date: 2nd February 2017).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00919-0.

Activation of p21 limits acute lung injury and induces early senescence after acid aspiration and mechanical ventilation

The p53/p21 pathway is activated in response to cell stress. However, its role in acute lung injury has not been elucidated. Acute lung injury is associated with disruption of the alveolo-capillary barrier leading to acute respiratory distress syndrome (ARDS). Mechanical ventilation may be necessary to support gas exchange in patients with ARDS, however, high positive airway pressures can cause regional overdistension of alveolar units and aggravate lung injury. Here, we report that acute lung injury and alveolar overstretching activate the p53/p21 pathway to maintain homeostasis and avoid massive cell apoptosis. A systematic pooling of transcriptomic data from animal models of lung injury demonstrates the enrichment of specific p53- and p21-dependent gene signatures and a validated senescence profile. In a clinically relevant, murine model of acid aspiration and mechanical ventilation, we observed changes in the nuclear envelope and the underlying chromatin, DNA damage and activation of the Tp53/p21 pathway. Absence of Cdkn1a decreased the senescent response, but worsened lung injury due to increased cell apoptosis. Conversely, treatment with lopinavir and/or ritonavir led to Cdkn1a overexpression and ameliorated cell apoptosis and lung injury. The activation of these mechanisms was associated with early markers of senescence, including expression of senescence-related genes and increases in senescence-associated heterochromatin foci in alveolar cells. Autopsy samples from lungs of patients with ARDS revealed increased senescence-associated heterochromatin foci. Collectively, these results suggest that acute lung injury activates p53/p21 as an antiapoptotic mechanism to ameliorate damage, but with the side effect of induction of senescence.

Cellular and molecular features of senescence in acute lung injury

A wide range of insults can trigger acute injury in the lungs, which eventually may lead to respiratory failure and death of patients. Current treatment relies mainly on supportive measures and mechanical ventilation. Even so, survivors frequently develop important sequels that compromise quality of life. In the search for new approaches to prevent and treat acute lung injury, many investigations have focused on molecular and cellular pathways which could exert a pathogenic role in this disease. Herein, we review recent findings in the literature suggesting that cellular senescence could be involved in lung injury and discuss the potential use of senotherapies to prevent disease progression.

Preventing loss of mechanosensation by the nuclear membranes of alveolar cells reduces lung injury in mice during mechanical ventilation

The nuclear membrane acts as a mechanosensor that drives cellular responses following changes in the extracellular environment. Mechanically ventilated lungs are exposed to an abnormally high mechanical load that may result in clinically relevant alveolar damage. We report that mechanical ventilation in mice increased the expression of Lamin-A, a major determinant of nuclear membrane stiffness, in alveolar epithelial cells. Lamin-A expression increased and nuclear membrane compliance decreased in human bronchial epithelial cells after a mechanical stretch stimulus and in a murine model of lung injury after positive-pressure ventilation. Reducing Lamin-A maturation by depletion of the protease-encoding gene Zmpste24 preserved alveolar nuclear membrane compliance after mechanical ventilation in mice. Ventilator-induced proapoptotic gene expression changes and lung injury were reduced in mice lacking Zmpste24 compared to wild-type control animals. Similarly, treatment with the human immunodeficiency virus protease inhibitors lopinavir and ritonavir reduced the accumulation of Lamin-A at nuclear membranes and preserved nuclear membrane compliance after mechanical ventilation, mimicking the protective phenotype of Zmpste24^-/- animals. These results show that the pathophysiological response to lung mechanical stretch is sensed by the nuclear membranes of lung alveolar cells, and suggest that protease inhibitors might be effective in preventing ventilator-induced lung injury.

Mechanical stretch modulates cell migration in the lungs

Cell migration is a core process to preserve homeostasis. Release of chemotactic signals induces changes in cell cytoskeleton to facilitate migration. This includes the rearrangement of cytoskeleton, genomic reprogramming and the modification of the surrounding extracellular matrix (ECM) to allow the motion of cells through. In the special case of repair after acute lung injury, cells must migrate while exposed to an increased mechanical stretch caused either by an increased work of breathing or positive-pressure ventilation. Interestingly, the cell response to this increased mechanical load can modify virtually all the mechanisms involved in cell migration. In this review we explore the interplay between stretch and the machinery responsible for cell migration. A translational approach to find new therapies in acute lung injury must take into account these interactions in order to develop effective treatments that promote lung repair.

Proline cis-trans isomerization and its implications for the dimerization of analogues of cyclopeptide stylostatin 1: a combined computational and experimental study

Cis and trans proline conformers are often associated with dramatic changes in the biological function of peptides. A slow equilibrium between cis and trans Ile-Pro amide bond conformers occurs in constrained derivatives of the native marine cyclic heptapeptide stylostatin 1 (cyclo-(NSLAIPF)), a potential anticancer agent. In this work, four cyclopeptides, cyclo-(NSTAIPF), cyclo-(KSTAIPF), cyclo-(RSTAIPF) and cyclo-(DSTAIPF), which are structurally related to stylostatin 1, are experimentally and computationally examined in order to assess the effect of residue mutations on the cis-trans conformational ratio and the apparent capacity to form dimeric aggregates. Primarily, cyclo-(KSTAIPF) and cyclo-(RSTAIPF) showed specific trends in circular dichroism, MALDI-TOF and HPLC purification experiments, which suggests the occurrence of peptide dimerization. Meanwhile, the NMR spectrum of cyclo-(KSTAIPF) indicates that this cyclopeptide exists in the two slow-exchange families of conformations mentioned above. Molecular dynamics simulations combined with quantum mechanical calculations have shed light on the factors governing the cis/trans conformational ratio. In particular, we have found that residue mutations affect the internal hydrogen bond pattern which ultimately tunes the cis/trans conformational ratio and that only trans conformers are capable of aggregating due to the shape complementarity of the two subunits.

[Experience in the management of the HIV patient among the physicians of the Secretaría de Salud]

OBJECTIVE

To determine the experience of the National Health Ministry physicians in the management of HIV-infected patients and in the use of antiretrovirals.

MATERIAL AND METHOD

A descriptive, observational and transversal study was performed, with support from the National AIDS Council from March to May 1998. Self-applicable questionnaires were filled by National Health Ministry physicians with experience in HIV patient clinical care, at the beginning of 5 different meetings on HIV/AIDS in several cities of the country. Statistical analysis included the chi-square test.

RESULTS

One hundred and eighty-one questionnaires were applied. The median of HIV patients attended by physicians was 4 (interval 1-97); 36.5% of the physicians had used antiretrovirals (35.4% prescribed nucleoside analogs and 9.9% protease inhibitors). The most frequently used drugs were AZT and/or ddl (40.3%); 17.7% had administered CD4+ lymphocyte count and 8.8% viral load.

CONCLUSIONS

The proportion of National Health Ministry physicians with experience in VIH patient care was low, as was the use of antiretrovirals. Efforts should be focus on improving care of HIV patients through physician training.

Serum and urine selenium concentrations in patients with cardiovascular diseases and relationship to other nutritional indexes

Serum and urine selenium levels were determined in patients with cardiovascular diseases by hydride generation atomic absorption spectrometry. Mean serum Se concentrations measured in patients with acute myocardial infarction (AMI; n = 32) or with ischemic cardiomyopathy (n = 50) were significantly lower than those determined in control groups. In AMI patients, serum triglyceride levels showed a positive significant correlation with the serum Se concentration (r = 0.59, p < 0.05). This result reinforces the important role of Se as an antioxidant agent in this disease. Mean urine Se concentrations of AMI patients (n = 33) were also significantly lower to those determined in the control group (p < 0. 05). This reaction of the organism contributes to regulate the Se homeostasis to keep the body Se status as high as possible.

Serum and urine selenium concentrations as indicators of body status in patients with diabetes mellitus

Serum and urine selenium levels were determined in patients with diabetes by hydride generation atomic absorption spectrometry. Mean serum selenium concentrations measured in patients with diabetes mellitus (64.9 +/- 22.8 micrograms/l) were significantly lower than those determined in the control group (74.9 +/- 27.3 micrograms/l) (P < 0.05). Mean serum selenium concentrations were not significantly different between the two groups of diabetic patients considered (P > 0.05). Mean urine selenium concentration in diabetic patients (18.8 +/- 10.7 micrograms/l) were not significantly different from those measured in the control group (20.2 +/- 10.1 micrograms/l) (P < 0.05). No significant differences in serum and urine selenium levels were found if related to sex of patients (P > 0.05). Application of linear regression analysis to serum and urine selenium levels and patients' age showed a non-statistically significant correlation (P > 0.05). Given the marked overlap between the two ranges of the populations, the predictive values of serum selenium in diabetic patients are low.

[Zidovudine plus didanosine in HIV infected asymptomatic patients previously treated with zidovudine]

OBJECTIVE

To evaluate if the combination of AZT/ddl offered any advantages in surrogate markers among HIV infected asymptomatic patients previously treated with AZT for at least six months.

METHODS

We used a prospective cohort of 269 asymptomatic HIV patients with CD4+ cell counts between 200 and 500 cells/microL. They were given didanosine (ddl 400 mg/d) in addition to AZT (500 mg/d) and had received AZT monotherapy for an average of 20 months. End points were progression to AIDS, death, or toxicity.

RESULTS

Median CD4+ cell count at the start of the combination therapy was 339 cells/microL which increased at three months to 451 and subsequently declined at 6, 12 and 18 months of followup (medians of 392, 360, 307 cells/microL respectively). Five patients progressed to AIDS, six developed toxicity (myelosuppression, hepatitis or pancreatitis) and 26 had minor side effects that required only dose reduction.

CONCLUSIONS

The addition of ddl to patients with prolonged ZDV monotherapy can be useful. CD4+ T cell counts showed a significant increase at 3 months with a gradual subsequent decline to below baseline at 18 months. Adverse effect of the drugs, although frequent, did not stop therapy in most patients.

Serum selenium levels as indicators of body status in cancer patients and their relationship with other nutritional and biochemical markers

A cross-sectional study of serum selenium levels in patients (n = 59) with different types of cancer from southeastern Spain was carried out using hydride generation atomic absorption spectrometry. The subjects were divided into four groups according to the cancer location (respiratory, digestive, haematological and gynaecological groups). Serum selenium levels in all patients (54.41 +/- 24.80 mg/l) were significantly lower (P < 0.001) than those determined in control groups [healthy subjects from the same area (n = 130) and institutionalized elderly people (n = 93)]. Mean serum selenium concentrations were not significantly different among the four groups considered (P > 0.05). Linear regression analyses performed on serum selenium levels and biochemical markers (total cholesterol, triglycerides, transaminases, uric acid and urea) did not establish any statistically significant correlation (P > 0.05). No significant relationships between serum selenium concentrations and sex or age of patients was observed (P > 0.05). Given the marked overlap between the two ranges of the populations (the means are within approx. 1/2 S.D.) the predictive values of serum selenium are low. Thus, there is indeed a statistical significance between the means, but selenium cannot be used to determine whether or not a patient has cancer disease.